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1.	Andersson, Mats, 1963, et al. (författare) Evaporation of Gasoline-Like and Ethanol-Based Fuels in Hollow-Cone Sprays Investigated by Planar Laser-Induced Fluorescence and Mie Scattering 2011 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; , s. 2011-01-1889- Tidskriftsartikel (refereegranskat)abstract The evaporation of different fuels and fuel components in hollow-cone sprays at conditions similar to those at stratified cold start has been investigated using a combination of planar laser-induced fluorescence (LIF) and Mie scattering. Ketones of different volatility were used as fluorescent tracers for different fuel components in gasoline-like model fuels and ethanol-based fuels. LIF and Mie images were compared to evaluate to what extent various fuel components had evaporated and obtained a spatial distribution different from that of the liquid drops, as a function of fuel temperature and time after start of injection. A selective and sequential evaporation of fuel components of different volatility was found.
2.	Berg, Victor, 1990, et al. (författare) Characterization of Gaseous and Particle Emissions of a Direct Injection Hydrogen Engine at Various Operating Conditions 2023 Ingår i: SAE Technical Papers. - 0148-7191 .- 2688-3627. Konferensbidrag (refereegranskat)abstract This paper investigates the gaseous and particulate emissions of a hydrogen powered direct injection spark ignition engine. Experiments were performed over different engine speeds and loads and with varying air- fuel ratio, start of injection and intake manifold pressure. An IAG FTIR system was used to detect and measure a variety of gaseous emissions, which include standard emissions such as NOX and unburned hydrocarbons as well as some non-standard emissions such as formaldehyde, formic acid, and ammonia. The particle number concentration and size distribution were measured using a DMS 500 fast particle analyzer from Cambustion. Particle composition was investigated using ICP analysis as well as a Sunset OC/EC analyzer to determine the soot content and the presence of any unburned engine oil. The results show that NOX emissions range between 0.1 g/kWh for a λ of 2.5 and 10 g/kWh λ of 1.5. The highest particle concentration was found for low loads and low intake pressures, with peaks values as high as 5*108 n/cc. ICP analysis confirmed that the particles contained traces of engine oil, while the OC/EC analysis showed that 99% of particle matter collected on filters was organic carbon, and <1% soot. The emissions of N2O as well as several other species measured with FTIR was found to be in the single ppm range, and thus not significant.
3.	Bladh, Henrik, et al. (författare) Flame propagation visualization in a spark-ignition engine using laser-induced fluorescence of cool-flame species 2005 Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 16:5, s. 1083-1091 Tidskriftsartikel (refereegranskat)abstract The flame propagation in a spark-ignition engine has been studied using laser-induced fluorescence (LIF) of species formed during the first ignition stage of hydrocarbon combustion. The detected two-dimensional LIF images showed the distribution of unburned regions. For the excitation, two Nd:YAG lasers operating at 355 mn were used for two consecutive measurements within the same engine cycle with adjustable time separation between the pulses. Two ICCD cameras that were synchronized to each of the laser pulses recorded pairs of fluorescence images, i.e. the movement of the flame front could be tracked. It is well known that formaldehyde is excited using a wavelength of 355 nm and a spectral signature of this species was also identified in engine LIF spectra. Programme routines were developed and used for evaluation of the flame propagation velocity from the fluorescence images. This paper presents the potential and the characteristics of the experimental technique as well as the evaluation procedure. The measurements of cool-flame intermediates have also been compared with measurements of fuel-tracer as an indicator of unburned fuel-air mixture. A good agreement between position and shape of the signal areas was obtained at crank angles where both fluorescence signal from cool-flame species excited at 355 nm and added 3-pentanone excited at 266 nm could be detected.
4.	Clasén, Kristoffer, 1992, et al. (författare) High Load Lean SI-Combustion Analysis of DI Methane and Gasoline Using Optical Diagnostics with Endoscope 2021 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Konferensbidrag (refereegranskat)abstract Homogeneous lean spark-ignited combustion is known for its thermodynamic advantages over conventional stoichiometric combustion but remains a challenge due to combustion instability, engine knock and NOx emissions especially at higher engine loads above the naturally aspirated limit. Investigations have shown that lean combustion can partly suppress knock, which is why the concept may be particularly advantageous in high load, boosted operation in downsized engines with high compression ratios. However, the authors have previously shown that this is not true for all cases due to the appearance of a lean load limit, which is defined by the convergence of the knock limit and combustion stability limit. Therefore, further research has been conducted with the alternative and potentially renewable fuel methane which has higher resistance to autoignition compared to gasoline. Operation with a gaseous fuel on high load was achieved by high pressure direct injection and boosting in a single cylinder research engine. To analyse the combustion further, an endoscope allowing optical access to the combustion chamber was utilized to acquire combustion chamber flame images. High load lean operation with methane could confirm the hypothesis that without a knock limit, optimal ignition timing could be maintained resulting in high combustion stability, and the lean load limit mitigated. Instead, limitation was reached due to peak cylinder pressure. Direct injected methane resulted in overall higher combustion stability compared to gasoline. However, methane also provided an overall lower fuel conversion efficiency by 1-2 %-units compared to gasoline. Despite higher combustion stability using methane, the maximum air-dilution could only be marginally extended. Flame images using the endoscope revealed that the flame growth post ignition was prohibited, possibly due to flame quenching, at high turbulence conditions.
5.	Dahlander, Petter, 1967, et al. (författare) Experimental investigation of fuel pressure influence on droplet size and velocity for a gasoline multi-hole direct injection injector spray under vaporizing conditions in a constant pressure chamber 2005 Ingår i: ILASS Americas, 18th Annual Conference on Liquid Atomization and Spray Systems, Irvine, CA, May 2005. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
6.	Dahlander, Petter, 1967, et al. (författare) Experimental investigation of the influence of fuel pressure on the fuel distribution and liquid penetration of a high-pressure gasoline multi-hole direct injection injector spray 2005 Ingår i: 20th ILASS Europe Annual Meeting of the Institute of Liquid Atomization and Spray System, 5th - 7th September 2005, Orleans, France. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
7.	Dahlander, Petter, 1967, et al. (författare) HIGH-SPEED PHOTOGRAPHY AND PHASE DOPPLER ANEMOMETRY MEASUREMENTS OF FLASH-BOILING MULTI-HOLE INJECTOR SPRAYS FOR SPRAY-GUIDED GASOLINE DIRECT INJECTION 2006 Ingår i: 10th International Conference on Liquid Atomization and Spray Systems, ICLASS 2006, August 27-Sept 1, 2006. Konferensbidrag (refereegranskat)
8.	Dahlander, Petter, 1967, et al. (författare) High-Speed Photography of Stratified Combustion in an Optical GDI Engine for Different Triple Injection Strategies 2015 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; Volume 2015-April:April Tidskriftsartikel (refereegranskat)abstract To contribute to knowledge required to meet new emissionrequirements, relationships between multiple injection parameters, degrees of fuel stratification, combustion events, work output and flame luminosity (indicative of particulate abundance) were experimentally investigated using a single-cylinder optical GDI engine. A tested hypothesis was that advancing portions of the massinjected would enhance the fuel-air mixing and thus reduce flame luminescence. An outward-opening piezo actuated fuel injector capable of multiple injections was used to inject the fuel using different triple injection strategies, with various combinations of late and earlier injections leading to various degrees of fuel stratification. Sprays and combustion events were captured using two high-speedcameras and cylinder pressure measurements. The data were analyzed to assess effects of fuel stratification on yellow flame luminescence(assumed to be dominated by soot luminescence), flame propagation, jet flames, pool fires and heat release. The combustion phasing, amount of fuel injected and engine speed were kept constant and theengine was unthrottled for all tested cases. Image sectorization was used to analyze events captured in different parts of the cylinder. The results show that the injection strategy influences fuel spray behaviorand the combustion in terms of both flame luminescence patterns and work output. Injecting some of the fuel earlier results in increased spray liquid penetration, streakier sprays (due to the lower backpressure),and less intense yellow flame luminescence, but alsoreductions in work output. The greater portions of fuel injected close to the ignition results in increased soot luminescence.
9.	Dahlander, Petter, 1967, et al. (författare) Measurements of Time-Resolved Mass Injection Rates for a Multi-Hole and an Outward Opening Piezo GDI Injector 2015 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2015-April:2015-April Tidskriftsartikel (refereegranskat)abstract Time-resolved mass injection rates of an outward opening piezoactuated and a solenoid actuated multi-hole GDI injector were measured to investigate (1) the influence of both hardware and software settings and (2) the influence on the injection rates from a wide range of operational parameters and (3) discuss limitations and issues with this measurement technique. The varied operating parameters were fuel pressure, back-pressure, electrical pulse width,single/double injection and injection frequency. The varied hardware/software parameters were injector protrusion, upstream fuel pressure condition and the cut-off frequency of the software's low-pass filter. Signal quality was found to be dependent on both hardware and software settings, especially the cut-off frequency of the low-passfilter. Measurements with high signal quality were not possible for back-pressures lower than 0.5 MPa. For the smallest possible injections, the piezo-actuated injector was found to be superior since it can inject very small amounts of fuel very accurately with little fuelpressure dependency. For engine realistic back-pressures, the multi-hole injector was found to be back-pressure independent. The piezo injector however was found to be strongly influenced by the back-pressure. The dynamic range was found to be much higher for the piezo injector, and the non-linear flow area was much larger for the multi-hole injector. Both injectors were capable of doubleinjections but the piezo can use shorter dwell times. Effects of upstream fuel pressure fluctuations, especially on the second injection of a double injection, must be carefully taken into account.
10.	Dahlander, Petter, 1967, et al. (författare) Multi-hole Injectors for DISI engines: Nozzle Hole Configuration Influence on Spray Formation 2008 Ingår i: SAE World Congress, Detroit, USA, 2008, SAE paper 2008-01-0136. ; , s. 14- Konferensbidrag (refereegranskat)abstract High-pressure multi-hole injectors are one candidate injector type for closed-spaced direct injection (DI) gasoline engines. In such a system, the spark plug must be located close to the spray and, during stratified operation, the spray is ignited very soon after the fuel droplets have been vaporized. Thus there are very high demands on the sprays used in such a system. An additional challenge is the positioning of the spark plug relative to the spray; both consistent ignitability and the absence of liquid fuel droplets must be achieved. Many injector parameters influence spray formation; for example, hole diameter, length to hole diameter ratio, nozzle hole configuration etc. This paper investigates the spray formation and spray induced air movement associated with rotational symmetrical and asymmetrical nozzle hole configurations. Four different nozzles with different hole configurations and umbrella angle were investigated both experimentally and numerically in a heated/ pressurized spray chamber. Their influence on spray formation, spray induced air motion, cross-flow velocity, fuel/air ratio, turbulence and cycle-to-cycle variations were studied. It was found that rotational symmetrical configurations produce non-coherent isolated clouds of fuel. If an asymmetrical configuration is used instead (holes positioned along a horseshoe-shaped arc) then, by choosing the injector configuration carefully, it is easier to obtain a coherent fuel cloud; this also facilitates better control over the conditions at the spark plug, for example the fuel/air ratio, cross-flow velocity and turbulence. Furthermore, asymmetrical nozzles benefit from smaller fuel gradients and enhanced mixing between spray plumes as a result of shorter spray plume distance and improved spray-induced air motion. All the nozzles tested produced partially premixed vapor clouds, with cycle-to-cycle variations. These variations may be an important issue for ignition stability in a closed-spaced combustion system.
11.	Dahlander, Petter, 1967, et al. (författare) Particulates in a GDI Engine and Their Relation to Wall-Film and Mixing Quality 2022 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Konferensbidrag (refereegranskat)abstract This paper investigates how particulates number PN is influenced by fuel wall-film, liner wetting, and the mixing quality for different start of injection timings (SOI). Both experimental data with PN measurements, endoscope images from a high-speed camera from a single-cylinder engine, and CFD simulations were used for the analysis. Engine geometry was a spray-guided system with 300 bar fuel pressure and with single injections. Data was captured for 2000 rpm / 9 bar IMEPn. The results show that fuel film on the piston was only found to significantly increase PN for over-advanced SOI (in our engine geometry, earlier than -310 CAD). This results in luminescence from diffusion burn on the piston surface, which strongly contributes to PN. For an SOI timing of -310 CAD, fuel film on piston reaches a maximum of 3#x00025; of the injected fuel, vaporizes, and no remaining fuel film is found at the time of ignition. Approximately 0.5-1#x00025; of the fuel ends up on the liner. Because of the slower evaporation, the liner film is exposed to scraping by the piston rings late in the compression stroke. For tested SOI timings of -310 CAD and later, all piston film evaporates before combustion, and the mixing quality starts dominating the PN formation. The mixing time has the strongest effect, leading to the reduction in PN with earlier SOI up until -310 CAD. Spray-tumble flow interactions are also shown to have appreciable effects on the mixing quality, and the usefulness of these interactions varies depending on the SOI.
12.	Dahlander, Petter, 1967 (författare) Source Term Model Approaches to Film Cooling Simulations 2001 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Film cooling simulations using Computational Fluid Dynamics (CFD) are very difficult and extremely computer power demanding. This thesis deals with the development of a method to save computer power for these types of simulations. The cooling air is injected using additions to the source terms of the discretised governing equations. Cell lengths up to about one or two cooling hole diameters are used, thereby precluding modelling of the detailed flow around each cooling hole. Three different models for distributing the source terms are evaluated. In the first model, the sources are distributed to only one cell, namely the cell closest to the cooling hole, resulting in a poorly penetrating jet. To obtain better jet penetration and to be able to better control the concentration of coolant at the wall, the second model distributes the sources as a line source. This model produced reasonable results for the heat transfer rate on a film-cooled nozzle guide vane but not for temperature comparisons on multi-row effusion-cooled plates. The results were found to be sensitive to some input parameters. The third model uses limited parts of source term fields, evaluated from the averaged solutions of detailed jet simulations. This model showed the best and most realistic injection of the coolant. Owing to the different qualities of the results, especially for the first and second models, the method should be seen as a ``last way out`` when it is not possible to make detailed 3D simulations of high quality due to a lack of computer power.
13.	Dahlander, Petter, 1967, et al. (författare) Visualization of fuel sprays for stratified cold starts in Gasoline Direct Injection engines 2008 Ingår i: 22:nd European Conference on Liquid Atomization and Spray Systems, 8-10 September, 2008, Como Lake, Italy (ILASS 2008). Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract About 90% of the unburned hydrocarbons (UBHC) emissions from port-fuel injected gasoline engines are emitted during cold starts, before the catalyst reaches the light-off temperature. In Gasoline Direct Injection engines cold starts can be made much cleaner by using modern fuel injectors operating at high fuel pressures and injecting the fuel late during the compression stroke to deliver a stratified charge, thereby enhancing the fuel’s rate of evaporation and reducing wall wetting. The objective of this study was to assess the relative importance of variables that influence the formation and characteristics of the sprays generated in such conditions. For this, a high-speed camera was used to acquire images and measure sprays of fuel injected by an outward-opening piezo-actuated injector into a pressurized spray chamber in which the fuel temperature could be cooled to temperatures as low as 243 K (-30 ºC). The varied parameters were fuel pressure, back-pressure, injection strategy and fuel temperature. For reliable ignition of such sprays a spark plug should be positioned in the vortex they create. The results show that if the fuel pressure is reduced to 5 MPa from the injector’s design pressure of 20 MPa, as it could potentially be during a cold start, the vortex is not created and fuel will not be present at the spark. However, multiple injections and the temperature of the fuel were found to have relatively weak effects on the vortex formation.
14.	Etikyala, Sreelekha, 1991, et al. (författare) Effect of Renewable Fuel Blends on PN and SPN Emissions in a GDI Engine 2020 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Tidskriftsartikel (refereegranskat)abstract To characterize the effects of renewable fuels on particulate emissions from GDI engines, engine experiments were conducted using EN228-compliant gasoline fuel blends containing no oxygenates, 10% ethanol (EtOH), or 22% ethyl tert-butyl ether (ETBE). The experiments were conducted in a single cylinder GDI engine using a 6-hole fuel injector operated at 200 bar injection pressure. Both PN in raw exhaust and solid PN (SPN) were measured at two load points and various start of injection (SOI) timings. Raw PN and SPN results were classified into various size ranges, corresponding to current and future legislations. At early SOI timings, where particulate formation is dominated by diffusion flames on the piston due to liquid film, the oxygenated blends yielded dramatically higher PN and SPN emissions than reference gasoline because of fuel effects. For particulates >23 nm and with optimized SOI timing, the use of oxygenated blends significantly increases SPN and conversely decreases raw PN emissions at low load (4.5 bar IMEP). At high load (9 bar IMEP), overall SPN emissions were significantly higher and there were no clear differences between the blends. Additionally, SPN measurements showed that soot formation and emissions of volatile organic compounds (VOC) depended strongly on blend composition. Finally, adding oxygenates (up to 22%) to gasoline did not reduce emissions of SPN in the size ranges addressed by current regulations.
15.	Etikyala, Sreelekha, 1991, et al. (författare) History Effect on Particulate Emissions in a Gasoline Direct Injection Engine 2021 Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 15:3 Tidskriftsartikel (refereegranskat)abstract Soot formation in internal combustion engines is a combination of complex phenomena. Understanding the formation mechanism that influences particulate emissions can help to make gasoline direct injection (GDI) engines comply with increasingly stringent emission standards. It is generally accepted that the deposition of liquid fuel wall films in the combustion chamber is a significant source of particulate formation in GDI engines. The injection timing, which can help avoid interaction between the pistons and fuel spray, has been identified as the parameter with the greatest influence. Traditionally, the start of injection (SOI) sweeps one can find in the literature are carried out by changing the timing one value at a time. To quantify the influence of SOI, variations in our study were carried out in a novel way using cycle-to-cycle parameter control. Instead of motoring or turning off the engine between different SOI variations, the motor was run continuously with combustion and SOI sweeps carried out online in a series of preprogrammed perfectly deterministic SOI sequences to provide evidence of so-called history effects on particulate number (PN). The variation in SOI produces a change in engine combustion and liquid fuel impingement, leading to a state that acts as a precursor for the next state. The different preprogrammed sequences provided excellent data repeatability between engine runs but very different results, depending on the order in which the SOI timings were set. In-cylinder combustion was visualized with an endoscope connected to a high-speed camera. Two SOI timings were chosen (based on piston deposit level data from stationary measurements) to investigate the history effect of preceding conditions on PN. The results show that the preceding engine states influence PN formation and emission that is established as history effect in the study. The history effect is pronounced and was most noticeable under impinging conditions such as early injection timings like -340 crank angle degrees (CAD). History effect was also found to depend on the duration and SOI of the preceding state. More importantly, the history effect depends on how SOI is varied, which in turn influences PN emissions. In the cycle-to-cycle variation of SOI, PN levels at relatively later injection timing of -250 CAD resulted in similarly high levels at an early injection timing of -340 CAD.
16.	Etikyala, Sreelekha, 1991, et al. (författare) Particulate Emissions in a GDI with an Upstream Fuel Source 2019 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2019-April:April Tidskriftsartikel (refereegranskat)abstract Public health risk and resulting stringent emission regulations for internal combustion engines pose a need for solutions to reduce particle emissions (PN). Current PN control approaches include increasing fuel injection pressure, optimizing spray targeting, multiple injection strategies, and the use of tumble flaps together with gasoline particulate filters (GPF). Experiments were performed using a single-cylinder spark-ignited GDI engine equipped with a custom inlet manifold and a port fuel injector located 500 mm upstream. Particulate emissions were measured during stationary medium/high load operation to evaluate the effect of varying the mass split between the direct and upstream injectors. Mixing quality is improved substantially by upstream injection and can thus be controlled by altering the mass split between the injectors. Additional particulate measurements were performed using a thermodenuder and a catalyst to remove major part of the volatile organic compounds (VOCs) from raw emissions. This made it possible to determine particle numbers (PN) both raw emissions and solid particulates, and the size distribution of the solid particulate emissions. Upstream fuel source was found to reduce PN emissions by almost a factor of 10 under optimal conditions, and significant reductions were achieved even when only 10% of the fuel mass was injected upstream. At a fixed load, as mass percentage from PFI increases, PN decreases. However, the PN reduction due to PFI is load-dependent and can be sensitive to engine speed. Solid PN decreased almost linearly with the PFI mass percentage, independently of engine speed. This implies that upstream injection improved mixing and thus reduced rich zone formation and/or wall-wetting compared to exclusive direct injection.
17.	Etikyala, Sreelekha, 1991, et al. (författare) Soot Sources in Warm-Up Conditions in a GDI Engine 2021 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2021:2021 Konferensbidrag (refereegranskat)abstract Gasoline direct injection (GDI) engines usually emit higher levels of particulates in warm-up conditions of a driving cycle. Thus, sources of soot formation in these conditions were investigated by measuring particulate numbers (PN) emitted from a single-cylinder GDI engine and their sizes. The combustion was also visualized using an endoscope connected to a high-speed camera. Engine coolant and oil temperatures were varied between 15 and 90oC to mimic warm-up conditions. In addition, effects of delaying the start of ignition (SOI) on the emissions in these conditions were examined. Coolant and oil temperatures were varied individually to identify which factor has most effect on PN emissions. While coolant temperature strongly influenced PN with cold oil, the oil temperature insignificantly affected PN at low coolant temperature. These findings indicate that PN emissions are heavily dependent on the engine block's temperature, which is dominated by the coolant. SOI plays a significant role in PN formation because it influences the wall film thickness on the piston top. In the experimental warm-up conditions, injecting fuel at a later SOI was found to decrease PN emissions. Visualization showed no occurrence of diffusion flames at late SOI timings due to the associated reduction in interaction between liquid fuel and the piston. The integrated luminescence from combustion images was found to correlate closely with PN emission measurements. Thus, higher integrated luminescence, indicating higher soot formation due to pool fires on the piston top, was associated with higher PN levels. When coolant and oil temperatures were both varied, PN emissions were found to decline dramatically with increasing temperatures. At lower temperatures, diffusion combustion occurred on the piston due to persistence of a non-vaporized fuel film. At 15oC coolant and oil temperature, this phenomenon was strong, but it gradually declined as the temperature increased. When the temperature reached 60oC, diffusion flames started to disappear, resulting in a dramatic decrease in PN.
18.	Etikyala, Sreelekha, 1991, et al. (författare) Visualization of soot formation in load transients during GDI engine warm-up 2023 Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 24:7, s. 3073-3084 Tidskriftsartikel (refereegranskat)abstract Reducing the emissions of pollutants, and particularly soot particles, from internal combustion engines is one of the greatest challenges faced by car manufacturers. Although modern gasoline direct injection (GDI) engines produce relatively low particulate emissions during steady state operation under near-stoichiometric conditions, they can produce much higher particulate emissions during transients that cause abrupt changes in load, fuel consumption, and the air-to-fuel ratio. Emissions during transients are particularly high when the engine coolant temperature is low, as occurs during engine start-up. Consequently, there is a need to find ways of reducing particulate emissions during load transients. This paper therefore investigates particulate formation during load transients in a single-cylinder GDI engine equipped with an endoscope in the cylinder head. A transient sequence was designed in which the engine load was increased from 4 bar NMEP to a maximum of 12 bar NMEP in 2 s at an engine speed of 2000 rpm. During the transients, the engine’s particulate emissions were measured in terms of particulate number (PN) and images of the combustion process inside the cylinder were captured via the endoscope using a high-speed camera to identify locations where soot formation occurred. Experiments were conducted at a range of coolant temperatures and using different injection strategies to determine how these parameters affect PN emissions. The coolant temperature was found to be the dominant factor governing PN emissions during transients. Luminescence data obtained by analyzing the flame images agreed well with the measured PN emissions during transients. Under all varied parameters in the transients except delayed injection, soot was mainly formed from wall films. For transients with delayed fuel injection, much of the piston film could be avoided but soot formation instead became mixing-dominated. Variation of the air-fuel ratio had little effect on PN emissions during transients. At all coolant temperatures, PN emissions were lowest when using a split injection strategy but delaying the injection timing increased PN emissions even though the endoscope images suggested a lower frequency of diffusion flame formation. No conditions were found under which the PN emissions during transients with low coolant temperatures could be reduced to levels comparable to those seen with warm coolant.
19.	Hemdal, Stina, 1974, et al. (författare) In-cylinder soot imaging and emissions of stratified combustion in a spark-ignited spray-guided direct-injection gasoline engine 2011 Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 12:6, s. 549-563 Tidskriftsartikel (refereegranskat)abstract The combustion in a spark-ignited spray-guided gasoline direct-injection engine operating in a stratified mode has been studied by in-cylinder imaging of the fuel, OH, and soot distributions. Information on the fuel distribution was obtained by laser-induced fluorescence imaging of the aromatic molecules in the gasoline. The OH and soot distributions were simultaneously visualized by detection of the natural emissions at 306nm (OH) and around 530nm (soot) using two intensified charge-coupled device cameras. In addition to the in-cylinder observations, engine-out soot emissions, NO(x), and HC were measured. The engine was operated at a speed of 2000 r/min and an indicated mean effective pressure of 2.5 bar, with a fully open throttle, resulting in a globally lean combustion with a fuel-air equivalence ratio of about 0.25. The gasoline was injected in single or double injections by an outward-opening piezo-actuated injector. The combustion was ignited efficiently at locally fuel-rich conditions. The soot formation and oxidation were investigated for the two injection strategies, each with three injection timings and two fixed ignition timings. The results showed that soot was efficiently formed and oxidized. From the in-cylinder measurements, it could be seen that the soot luminescence intensity quickly rose and then declined, while the combustion temperature was still increasing. Furthermore, the OH intensity was still increasing as the soot luminescence was declining. The soot incandescence peak intensity occurred at a crank angle degree close to 50 per cent mass burned, and the OH* intensity peak arose later, shortly before the maximum soot temperature around top dead centre (TDC). When the injection timing was retarded, with constant ignition timing with respect to injection, it was found that the total soot luminosity increased. In addition, less OH* chemiluminescence was observed during the decrease of the soot incandescence, implying conditions less favourable for efficient soot oxidation in the later part of the combustion for retarded injections. This was confirmed by the engine-out soot emission measurements, which showed increased soot levels as the injection was retarded. It was also found that fuel impinged on the spark plug during the injections, resulting in a persistent jet flame close to the spark plug in the centre of the cylinder, which is believed to contribute to engine-out soot emissions.
20.	Hemdal, Stina, 1974, et al. (författare) Stratified Cold Start Sprays of Gasoline-Ethanol Blends 2009 Ingår i: SAE SP 2241 SI Combustion and Direct Injection SI Engine TEchnology 2009. - 9780768021370 ; , s. 397-410 Konferensbidrag (refereegranskat)
21.	Hemdal, Stina, 1974, et al. (författare) Stratified cold start sprays of gasoline-ethanol blends 2009 Ingår i: SAE International Journal of Fuels and Lubricants. - : SAE International. - 1946-3952 .- 1946-3960. ; 2:1, s. 683-696 Tidskriftsartikel (refereegranskat)abstract Gasoline and gasoline-ethanol sprays from an outward-opening piezo-injector were studied in a constant volume/pressure chamber using high-speed imaging and phase doppler anemometry (PDA) under stratified cold start conditions corresponding to a vehicle ambient temperature of 243 K (-30 °C/-22 °F); in-cylinder air pressure of 5 bar, air temperature of 350 K (-30 °C/-22 °F) and fuel temperature of 243 K. The effects of varying in-cylinder pressure and temperature, fuel injection pressure and fuel temperature on the formation of gasoline, E75 and pure ethanol sprays were investigated. The results indicate that fuel composition affects spray behaviour, but less than expected. Furthermore, varying the temperature of the fuel or the air surrounding the spray also had minor effects. As expected, the fuel injection pressure was found to have the strongest influence on spray formation under stratified conditions.
22.	Huang, Chen, 1981, et al. (författare) Gasoline Direct Injection - Simulations and Experiments 2011 Ingår i: ILASS2011. The 24th European Conference on Liquid Atomization and Spray Systems, Estoril, Portugal, September, 5-7, 2011. ; , s. 4 pagews- Konferensbidrag (övrigt vetenskapligt/konstnärligt)
23.	Johansen, Lars Christian Riis, 1987, et al. (författare) Analysis of Transient Compressible Gas Jets Using High Speed Schlieren Imaging 2013 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2 Tidskriftsartikel (refereegranskat)abstract Transient compressible gas jets, as encountered in direct injection gas fuel engines, have been examined using schlieren visualization. Helium has been injected into air in a pressure chamber to create the jets examined. The structure of the jets is studied from the mean and coefficient of variation of the penetration length, jet width and jet angle. The quantities are calculated by digital image processing of schlieren images captured with a high-speed camera. Injection pressure and chamber pressure have been varied to determine whether they have an effect on the response variables. Design of experiments methods have been used to develop the scheme employed in performing the experiments. The mean normalized penetration length of the jets is found to scale with injection to chamber pressure ratio and is in agreement with a momentum conserving relation given in the literature. The dispersion of the penetration length has been found to be in agreement with a normal distribution. The Turner model for a jet has been found to be in agreement with the observed jets. The jet has been observed to transition to self-similarity within 20 nozzle diameters. The calculated penetration constant Γ has been observed to vary with the pressure ratio and is smaller than previously reported values. The jet angle approaches a constant value for all cases and has also been found to be in approximate agreement with a normal distribution.
24.	Johansson, Anders, 1985, et al. (författare) Experimental Investigation of Soot in a Spray-Guided Single Cylinder GDI Engine Operating in a Stratified Mode 2013 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 6 Tidskriftsartikel (refereegranskat)abstract Forthcoming reductions in legal limits for emissions of particle matter (PM) from direct injection engines have increased the need for understanding particle distributions in the engines and the factors affecting them. Therefore, in the presented study the influence on PM-emissions of potentially important factors (fuel injection pressure, load, speed and 50% mass fraction burned phasing) on particle mass, number and size distributions were experimentally investigated. The experimental system was a spray-guided, direct injection, single-cylinder research engine operated in stratified charge mode (using gasoline with 10% ethanol as fuel), under five load and speed settings that are appropriate for stratified combustion. The particle distributions obtained from operating the engine in homogeneous combustion and stratified combustion modes were also compared. The particle distributions were measured using a Cambustion DMS500 fast particle analyzer in combination with a Dekati FPS4000 fine particle sampler and a thermodenuder in all tests except the comparison of distributions under stratified and homogeneous combustion conditions. The sampling system was designed to remove as much of the volatile unburned hydrocarbons as possible in order to sample mostly solid particles. Under all of the stratified operating conditions studied, the results indicate that the particle distribution has a characteristic shape with a tail and one large peak. The operating speed significantly affected the size of the largest particles and the quantity of the particles represented by the tail. An almost linear, positive relationship was found between the load and particle number. Increasing the fuel injection pressure reduced particle numbers whereas combustion phasing had no significant observed effects. More particles were generated in stratified combustion mode than in homogeneous mode.
25.	Johansson, Anders, 1985, et al. (författare) Experimental Investigation of the Influence of Boost on Combustion and Particulate Emissions in Optical and Metal SGDI-Engines Operated in Stratified Mode 2016 Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 9:2, s. 807-818 Tidskriftsartikel (refereegranskat)abstract Boosting and stratified operation can be used to increase the fuel efficiency of modern gasoline direct-injected (GDI) engines. In modern downsized GDI engines, boosting is standard to achieve a high power output. However, boosted GDI-engines have mostly been operated in homogenous mode and little is known about the effects of operating a boosted GDI-engine in stratified mode.This study employed optical and metal engines to examine how boosting influences combustion and particulate emission formation in a spray-guided GDI (SGDI), single cylinder research engine. The setup of the optical and metal engines was identical except the optical engine allowed optical access through the piston and cylinder liner.The engines were operated in steady state mode at five different engine operating points representing various loads and speeds. The engines were boosted with compressed air and operated at three levels of boost, as well as atmospheric pressure for comparison. The fuel used was market gasoline (95 RON) blended with 10% ethanol. The spark plug and injector were mounted in parallel with the intake valves. The gas motion induced by the engine head was primarily tumble motion with a small amount of swirl.Results on particulate emissions indicated that nucleation mode particulates increased with increasing boost. In contrast, agglomeration mode particulates decreased with increasing boost pressure. The combustion was found to consist of a yellow flame in the center of the combustion chamber and a pre-mixed blue flame in the perimeter. The optical studies indicated that the flame area decreased with increasing boost.
26.	Johansson, Anders, 1985, et al. (författare) Experimental Investigation on the Influence of Boost on Emissions and Combustion in an SGDI-Engine Operated in Stratified Mode 2015 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2015-September:September Tidskriftsartikel (refereegranskat)abstract Among many techniques used for increasing fuel efficiency of a modern Gasoline Direct-Injected (GDI) engine are boosting and stratified operation. In modern downsized GDI engines, boosting is standard in order to achieve a high power output. Boosted GDI-engines have however mostly been operated in homogenous mode and little is known on the effects of operating a boosted GDI-engine in stratified mode. This paper presents the influence on combustion , standard emissions and particulate size distribution in a Spray-Guided, Gasoline, Direct-Injected (SGDI), single cylinder, research engine operated with various levels of boost .The engine was operated in steady state mode at five engine operating points of various load and speed. The engine was boosted with a Roots blower and operated at four levels of boost as well as atmospheric pressure for comparison. The engine was fueled with market gasoline (95 RON) blended with 10% ethanol. The gas motion induced by the engine head was primarily tumble motion but a small amount of swirl. The spark plug and injector was mounted in parallel with the intake valves. Results indicate that exhaust temperature and NOx emissions decrease with increasing boost . Hydrocarbon emissions increase with increasing boost . The results on particulate emissions indicate that nucleation mode particulates increase with increasing boost . The opposite trend was observed for agglomeration mode particulates which decreased with increasing boost pressure.
27.	Johansson, Anders, 1985, et al. (författare) Measurements of particulate size distribution from a GDI engine using a nafion dryer and a DMS500 without sample dilution 2014 Ingår i: FISITA 2014 World Automotive Congress - Proceedings. Konferensbidrag (refereegranskat)abstract Several types of engine exhaust contain moisture that must be maintained in gaseous state when sampling particulates to prevent potential destruction of the particles or damage to the measurement apparatus. This is normally achieved by diluting the sample in order to reduce the partial pressure, thus avoiding condensation. When measuring size distributions of particulates emitted from a gasoline engine, a dilution ratio of at least 5:1 is recommended. However, in some operating modes (e.g. lean homogenous modes) or measurement locations (e.g. downstream of a particulate filter) this ratio can be too high for high-resolution measurements due to the low levels of particulates. The presented study investigates the potential for using a nafion dryer to remove water from the exhaust instead of diluting the sample. An electrical mobility measurement device, a Cambustion DMS500 mk II, was operated without diluting the exhaust gases but with a nafion dryer to remove water from the exhaust. These dryers are commonly used for measuring particulates in airborne aerosols, but no information has been found in the open literature on their application in engine research. The sampling system was connected to a four cylinder SGDI-engine operating in modes that generate small amount of particulates. Samples were taken in four operating conditions, downstream of the catalyst. Overall losses in the complete system and components of the system were determined by tests with an artificially generated aerosol. Factors such as particulate losses, system performance and sample manipulation are discussed. Particulate size distributions were successfully recorded in operating regimes in which they are difficult to measure with conventional sampling systems using the required dilution. Particulate losses were found to be small in the nafion dryer but large in the heated hose prior to the nafion dryer.
28.	Johansson, Anders, 1985, et al. (författare) Reduction of Soot Formation in an Optical Single-Cylinder Gasoline Direct-Injected Engine Operated in Stratified Mode Using 350 Bar Fuel Injection Pressure, Dual-Coil and High-Frequency Ignition Systems 2017 Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 10:3, s. 709-721 Tidskriftsartikel (refereegranskat)abstract The current trend toward more fuel efficient vehicles with lower emission levels has prompted development of new combustion techniques for use in gasoline engines. Stratified combustion has been shown to be a promising approach for increasing the fuel efficiency. However, this technique is hampered by drawbacks such as increased particulate and standard emissions. This study attempts to address the issues of increased emission levels by investigating the influence of high frequency ionizing ignition systems, 350 bar fuel injection pressure and various tumble levels on particulate emissions and combustion characteristics in an optical SGDI engine operated in stratified mode on isooctane. Tests were performed at one engine load of 2.63 bar BMEP and speed of 1200 rpm. Combustion was recorded with two high speed color cameras from bottom and side views using optical filters for OH and soot luminescence. The results indicated that increasing the fuel injection pressure led to faster burn as well as a reduction in soot luminescence. The ionizing ignition system generated faster initial combustion. Increasing the tumble level reduced the soot luminescence at all injection pressures, but the influence was largest at the lowest fuel injection pressure. The combination of an ionizing ignition system and high fuel pressure was most beneficial for lowering soot luminescence.
29.	Khatri, Jayesh, 1993, et al. (författare) Effect of relative humidity on water injection technique in downsized spark ignition engines 2021 Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 22:7, s. 2119-2130 Tidskriftsartikel (refereegranskat)abstract Combustion knock is a major barrier to achieving high thermal efficiency in spark ignition engines. Water injection was recently identified as a potential way of overcoming this barrier. To evaluate its general applicability, experiments were performed on a downsized three-cylinder spark ignition engine, varying the humidity of the intake air, the water injection timing, and the engine speed. The minimum quantity of injected water required to maintain a given load (and thus level of engine performance) was determined under each set of tested conditions. The knock-suppressing effects of water injection were found to be related to changes in the fuel–air mixture’s specific heat ratio (kappa) rather than evaporative cooling, and to therefore depend on the total quantity of water in the cylinder rather than the relative humidity per se. The total quantity of water in the cylinder was also shown to be a key determinant of advancement in combustion phasing and particulate emissions under various conditions.
30.	Khatri, Jayesh, 1993, et al. (författare) Water Injection Benefits in a 3-Cylinder Downsized SI-Engine 2019 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2019-January:January, s. 236-248 Tidskriftsartikel (refereegranskat)abstract With progressing electrification of automotive powertrain and the demand to meet increasingly stringent emission regulations, a combination of electric motor and downsized turbocharged Spark Ignited Engines has been recognized a viable solution. Maximum Power and reduction of tailpipe CO2 need to come from optimizing the IC Engine. However, the increased BMEP (Brake Mean Effective Pressure) and drive for higher compression ratio/thermal efficiency increases the propensity of knocking in Downsized Engines. Engine knock occurs when the unburnt charge auto-ignites before the propagation flame reaches the unburnt charge. Currently, knock is mitigated by retarding the ignition timing. Under high power demand, ignition retard is limited by the exhaust components temperature limit. This is compensated by mixture enrichment – injecting more fuel – which in turn reduces combustion temperature at the cost of increased fuel consumption and Carbon Monoxide (CO) emissions. The potential of Water injection to alleviate these problems has been identified over the last decade – following the trail of same technology used in Aircraft combustion engines. Water Injection suppresses combustion knocking by decreasing the local in-cylinder temperature. During liquid to vapor phase transformation, water requires energy – latent heat of vaporization and the injected water absorbs most of this energy from the mixture, subsequently decreasing its temperature. Addition of adequate water can result in obtaining stoichiometric Air/Fuel Ratio engine operation henceforth leading to both reduced fuel consumption and CO emissions. For this study, a 4-stroke, 1.5 liter, 3-cylinder turbocharged engine with direct fuel injection and port water injection has been operated on 91, 95 and 98 RON Gasoline fuel. An experimental investigation to the effect of water injection on knock mitigation, combustion phasing improvement, required AFR and exhaust gas temperature control has been performed. Full load curves are presented and analyzed for different fuels and different water injection strategies.
31.	Mamikoglu, Mehmet Sarp, 1984, et al. (författare) Impact of Conventional and Electrified Powertrains on Fuel Economy in Various Driving Cycles 2017 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2017-March:March Tidskriftsartikel (refereegranskat)abstract Many technological developments in automobile powertrains have been implemented in order to increase efficiency and comply with emission regulations. Although most of these technologies show promising results in official fuel economy tests, their benefits in real driving conditions and real driving emissions can vary significantly, since driving profiles of many drivers are different than the official driving cycles. Therefore, it is important to assess these technologies under different driving conditions and this paper aims to offer an overall perspective, with a numerical study in simulations. The simulations are carried out on a compact passenger car model with eight powertrain configurations including: a naturally aspirated spark ignition engine, a start-stop system, a downsized engine with a turbocharger, a Miller cycle engine, cylinder deactivation, turbocharged downsized Miller engine, a parallel hybrid electric vehicle powertrain and an electric vehicle powertrain. These are tested in seven driving cycles including the NYCC, FTP75, NEDC, WLTC, US06, HWFET and CADC. The impacts of different technologies on fuel economy and CO₂ emissions are analyzed, with respect to different operating conditions. Results reveal that a combination of certain driving cycles and vehicle configurations have a large influence on fuel consumption and CO₂ emissions. In general, Miller and downsized engines offer some improvements in all cycles while the start-stop system has benefits in city cycles with frequent stops. The HEV and EV configurations offer a substantial improvement compared to conventional technologies in lower speed conditions like city cycles, but their benefits are reduced at cycles including higher speeds.
32.	Mamikoglu, Mehmet Sarp, 1984, et al. (författare) Modelling of Hybrid Electric Vehicle Powertrains - Factors That Impact Accuracy of COâ Emissions 2019 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2019-January:January Tidskriftsartikel (refereegranskat)abstract All Rights Reserved. Modelling is widely used for the development of hybrid electric vehicle (HEV) powertrain technologies, since it can provide accurate prediction of fuel consumption and COâ emissions, for a fraction of the resources required in experiments. For comparison of different technologies or powertrain parameters, the results should be accurate relative to each other, since powertrains are simulated under identical model details and simulation parameters. However, when COâ emissions of a vehicle model are simulated under a driving cycle, significant deviances may occur between actual tests and simulation results, compromising the integrity of simulations. Therefore, this paper investigates the effects of certain modelling and simulation parameters on COâ emission results, for a parallel HEV under three driving cycles (NEDC, WLTC and RTS95 to simulate real driving emissions (RDE)). A sensitivity analysis on battery state of charge levels (SOC), control systems, component data resolutions, warm-up phase, time-step, driver controller behavior and 0D vs 1D simulation parameters is carried out and their effect on COâ emission results are investigated. While any change in one of the parameters may result in either a lower or higher COâ value, their cumulative effect on simulation results may result in significant differences of up to +-15%. Unfortunately, it is not hard to overlook the effect of these parameters and conduct powertrain simulations without taking this into account. By identifying key parameters and quantifying their effect on simulation results, this paper aims to improve the accuracy of HEV powertrain simulations to provide more reliable results.
33.	Marti-Aldaravi, P., et al. (författare) A comparison of non-reactive fuel sprays under realistic but quiescent engine conditions for SGDI 2012 Ingår i: ICLASS 2012 - 12th International Conference on Liquid Atomization and Spray Systems. Konferensbidrag (refereegranskat)abstract A comparative study on the two most commonly found gasoline direct injectors is presented, where a solenoid driven multi-hole (6 horseshoe hole) and piezo driven outward opening injector were evaluated on liquid penetration, spray width and spray structure within a constant volume chamber. These three variables have been investigated for three typical fuels (iso-octane, gasoline 95 and e100 ethanol) at a fixed calorific delivery value of 389.4 J, typical combustion required value for stratified road-load operation. A first series of tests allowed correlating mass flow and injection duration for each injector and fuel. The chemical properties of the three fuels were used to calculate the injection duration for the target calorific value. This energy value was determined previously by tests in a single cylinder research engine at stratified operation. The non-impinging, non-combusting spray was visualized using back-lit high speed photography. The pressure and temperature values set on the chamber correspond to SOI of 20, 30 and 40 CAD bTDC during engine testing at 2000 rpm and an IMEP of 2.5 bar for an overall lean operation of λ = 4. The spray visualization was also carried out at ambient conditions (25°C of temperature and 1 and 6 bar of back pressure). The results show that the penetration length is function of ambient temperature and pressure, fuel and injector type. The solenoid driven multi-hole injector produces longer penetration lengths and at a faster rate than the piezo unit under all test parameters. Moreover, there is greater variance in penetration curves for the fuels tested using the solenoid multi-hole injector compared to the piezo actuated outward opening injector. Despite wall-wetting aspects have not been tested, larger variance in penetration curves for different fuels in the solenoid multi-hole injector indicate that it is less suitable for bi-fuel engines. Thus, spray targeting differences will lead to potential increase in combustion stability (COVimep), increase in emissions and increase in wetting of surfaces i.e. sparks plug, bore or piston.
34.	Melaika, Mindaugas, 1986, et al. (författare) 48V Mild-Hybrid Architecture Types, Fuels and Power Levels Needed to Achieve 75g CO2/km 2019 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2019-April:April Tidskriftsartikel (refereegranskat)abstract 48V mild hybrid powertrains are promising technologies for cost-effective compliance with future CO2 emissions standards. Current 48V powertrains with integrated belt starter generators (P0) with downsized engines achieve CO2 emissions of 95 g/km in the NEDC. However, to reach 75 g/km, it may be necessary to combine new 48V powertrain architectures with alternative fuels. Therefore, this paper compares CO2 emissions from different 48V powertrain architectures (P0, P1, P2, P3) with different electric power levels under various driving cycles (NEDC, WLTC, and RTS95). A numerical model of a compact class passenger car with a 48V powertrain was created and experimental fuel consumption maps for engines running on different fuels (gasoline, Diesel, E85, CNG) were used to simulate its CO2 emissions. The simulation results were analysed to determine why specific powertrain combinations were more efficient under certain driving conditions. As expected, the greatest influence on emissions was from powertrain architectures. Increased electric power levels (from 8 kW to 20 kW) allowed more brake energy to be recovered, reducing CO2 emissions by 2 - 16% depending on the driving cycle. The P2 and P3 architectures with even low electric motor power level offered substantially better fuel efficiency (by 19% on average) than a conventional powertrain with a start-stop system, whereas the P0/P1 architectures offered average improvements of only 4% for different power levels and driving cycles. In the P0 and P1 architectures, engine friction severely limited energy recovery during braking and made electric propulsion infeasible due to significantly increased power demands. The P2 and P3 architectures allow the engine to be decoupled from the powertrain and so avoid this problem. Overall, the 48V P2/P3 powertrains allowed for significant improvements in CO2 emissions when used with CNG, E85 or diesel fuel. 75 g/km target value was predicted to be achievable with CNG-fuelled systems under the NEDC and WLTC cycles, and possibly even under RTS95 on a well-to wheel basis when using a renewable fuel such as E85.
35.	Melaika, Mindaugas, 1986, et al. (författare) DI-CNG injector nozzle design influence on SI engine standard emissions and particulates at different injection timings 2022 Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 317 Tidskriftsartikel (refereegranskat)abstract Compressed natural gas direct injection (DI-CNG) systems in spark ignition (SI) internal combustion engines have shown that it can give several benefits compared to CNG port fuel injection systems. However, the DI-CNG injector nozzle head design and gas jet formation may greatly influence engine exhaust gas emissions and performance. Present experimental study investigated the influence of 7 different nozzle head designs of sprayguided DI-CNG injectors on the combustion process, engine performance, standard emissions, and particulate number (PN) when methane fuel was injected at different injection timings (SOI) and injection pressures (18 bar and 50 bar). The nozzle heads had two main design patterns – heads with small multi holes/orifices and heads with larger crevices (swirl or umbrella spray pattern). Naturally aspirated SI engine tests were conducted at part load (6 bar IMEP) and wide-open throttle (WOT) at 2000 rpm engine speed. The results revealed that the difference between the nozzle heads was small when the fuel was injected at an early stage of the intake stroke (310–350 CAD bTDC) either at part load or high load. However, for late injection timing (130–190 CAD bTDC), the design of the DI-CNG injector nozzle head had a large impact on the combustion stability, standard emissions formation and particulates. Multi-hole nozzle heads showed improved CO2, CO, THC, total PN, and slightly higher NOx emissions compared to nozzle heads with larger crevices. For some of the nozzles, the SOI could be retarded more than for other injector head designs at higher injection pressure whilst still ensuring an acceptable engine performance in terms of combustion stability, power output and emissions formation. Overall, 50-bar injection pressure and a late injection timing under WOT conditions achieved higher engine load levels with all injector nozzle types. Images acquired using an optical endoscope technique with a high-speed video camera showed that a yellow flame was present for all nozzle types at a low injection pressure and late SOI. Increasing the injection pressure reduced the injection duration, improved air/fuel mixing which resulted in the reduced byellow flame formation and lower PN for most of the nozzle heads.
36.	Melaika, Mindaugas, 1986, et al. (författare) Experimental Investigation of Methane Direct Injection with Stratified Charge Combustion in Optical SI Single Cylinder Engine 2016 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Tidskriftsartikel (refereegranskat)abstract This paper assesses methane low pressure direct injection with stratified charge in a SI engine to highlight its potential and downsides. Experiments were carried out in a spark ignited single cylinder optical engine with stratified, homogeneous lean and stoichiometric operational mode, with focus on stratified mode. A dual coil ignition system was used in stratified mode in order to achieve sufficient combustion stability. The fuel injection pressure for the methane was 18 bar. Results show that stratified combustion with methane spark ignited direct injection is possible at 18 bar fuel pressure and that the indicated specific fuel consumption in stratified mode was 28% lower compared to the stoichiometric mode. Combustion and emission spectrums during the combustion process were captured with two high-speed video cameras. Combustion images, cylinder pressure data and heat release analysis showed that there are fairly high cycle-to-cycle variations in the combustion. Both blue pre-mixed flame and soot luminescence occurred in the combustion. The occurrence of soot luminescence was also supported by the emission spectrum. Soot formation sources were found to be localized randomly in the bulk flame but not on the piston nor in the vicinity of the spark plug. These findings illustrate the difficulty of achieving proper mixing between air and methane resulting in fairly high cycle-to-cycle variations in the combustion and fuel rich areas which create a source of soot.
37.	Melaika, Mindaugas, 1986, et al. (författare) Methane Direct Injection in an Optical SI Engine - Comparison between Different Combustion Modes 2019 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2019-January:January Tidskriftsartikel (refereegranskat)abstract © 2019 SAE International. All Rights Reserved. Natural gas, biogas, and biomethane are attractive fuels for compressed natural gas (CNG) engines because of their beneficial physical and chemical characteristics. This paper examines three combustion modes - homogeneous stoichiometric, homogeneous lean burn, and stratified combustion - in an optical single cylinder engine with a gas direct injection system operating with an injection pressure of 18 bar. The combustion process in each mode was characterized by indicated parameters, recording combustion images, and analysing combustion chemiluminescence emission spectra. Pure methane, which is the main component of CNG (up to 98%) or biomethane (> 98 %), was used as the fuel. Chemiluminescence emission spectrum analysis showed that OH∗ and CN∗ peaks appeared at their characteristic wavelengths in all three combustion modes. The peak of OH∗ and broadband CO 2 ∗ intensities were strongly dependent on the air/fuel ratio conditions in the cylinder. Lower OH∗ and CO 2 ∗ intensities were observed with lean air/fuel mixtures because under these conditions, more air was present, the combustion reactions were slower, and the cylinder pressure was higher. CN∗ was formed by the spark plasma and was detected over a particularly long period when using a dual coil ignition system. The intensities of the OH∗ and CN∗ signals correlated when using this ignition system. Combustion image analysis showed that the flame had a wrinkled boundary in stoichiometric and lean burn modes and was especially distorted in stratified mode. No yellow soot luminescence was observed during homogeneous combustion. However, the emission spectra and combustion images acquired during stratified combustion showed that soot formation occurred due to the presence of fuel-rich areas with inadequate mixing in the cylinder. The difficulty of maintaining stable fuel injection, achieving proper air/fuel mixing, and ensuring stable flame propagation in lean air/fuel mixtures increased cycle-to-cycle variations. However, the homogeneous lean burn and stratified combustion modes achieved significantly lower indicated specific fuel consumption values than stoichiometric combustion.
38.	Melaika, Mindaugas, 1986, et al. (författare) Particulates from a CNG DI SI Engine during Warm-Up 2021 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2021:2021 Konferensbidrag (refereegranskat)abstract To assist efforts reducing harmful emissions from internal combustion engines, particulate formation was investigated in a compressed natural gas (CNG) Direct Injection single-cylinder SI engine in warm-up conditions. This involved tests at low engine speed and load, with selected engine coolant temperatures ranging from 15 to 90 °C, and use of a gasoline direct injection (GDI) system as a standard reference system. Total particulate number (PN), their size distribution, standard emissions, fuel consumption and rate of heat release were analyzed, and an endoscope with high-speed video imaging was used to observe combustion luminescence and soot formation-related phenomena. The results show that PN was strongly influenced by changes in coolant water temperature in both the CNG DI and GDI systems. However, the CNG DI engine generated 1 to 2 orders of magnitude lower PN than the GDI system at all tested temperatures. The PN decreased in both systems when the coolant temperature increased. The results also show that PN was sensitive to a broader engine coolant temperature range in the GDI system. However, PN was around two orders of magnitude higher at the lowest coolant temperature (15 °C) than at the highest temperature (90 °C) in the CNG DI system. In homogeneous CNG combustion (unlike gasoline combustion) high-speed video images revealed no diffusion or yellow flame anywhere in the cylinder, even at the lowest coolant temperature. Thus, no soot formation location could be determined from the images in CNG cases. Overall, engine measurements showed that the CNG DI engine emitted lower standard emissions (CO2, CO, HC, NOx) and PN than the GDI system across the experimental range of engine coolant temperatures.
39.	Melaika, Mindaugas, 1986, et al. (författare) Spark ignition engine performance, standard emissions and particulates using GDI, PFI-CNG and DI-CNG systems 2021 Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 293 Tidskriftsartikel (refereegranskat)abstract Gaseous fuels, e.g., natural gas, biogas, have several advantages over liquid fuels owing to their favorable physical and chemical properties, e.g., lower carbon numbers in the fuel composition and no issues regarding fuel evaporation. The present study investigated compressed natural gas (CNG) port fuel injection (PFI) and direct injection (DI) systems compared to gasoline direct injection (GDI) cases in a spark ignition (SI) naturally aspirated single cylinder engine at stoichiometric conditions. The tests included usual engine working points – from 4.5 bar IMEP to 9 bar IMEP engine load at different engine speeds – from 1500 rpm to 2500 rpm. The main aim was to investigate how gaseous fuels can improve the SI engine efficiency, reduce standard emissions and particulates, and explain the benefits of a natural gas DI system versus standard gas PFI and GDI systems. Analysis of the results showed that the rate of heat release of natural gas was lower than that of gasoline fuel. However, the stable combustion process of DI-CNG gave additional benefits, e.g., increased turbulence in the cylinder, which increased the combustion rate and affected the exhaust gas formation. The highest engine efficiency was achieved with the same natural gas DI system. The highest iSHC, iSCO, iSCO2 and iSNOx emissions reduction achieved at low and part load conditions with DI-CNG compared to GDI combustion. Particulates formation was lower with the gaseous fuel compared to gasoline. Additional benefits of lower particulate numbers among three injection systems were observed with DI-CNG combustion.
40.	Skogsberg, Mikael, 1975, et al. (författare) An experimental study of mixture preparation and combustion in an optical engine using a piezo-actuated injector 2007 Ingår i: Direkteinspritzung im Ottomotor IV. - 9783816927167 ; , s. 143-159 Konferensbidrag (refereegranskat)
41.	Skogsberg, Mikael, 1975, et al. (författare) Effects of injector parameters on mixture formation for multi-hole nozzles in a spray-guided gasoline di engine 2005 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Konferensbidrag (refereegranskat)abstract This paper focuses on ways of improving the spray formation from spray-guided multi-hole gasoline direct injection injectors. Work has been done both experimentally using laser diagnostic tools and numerically using Computational Fluid Dynamics. Laser Induced Exciplex Fluorescence (LIEF) measurements in a constant pressure spray chamber and optical engine measurements have shown that injectors with 6-hole nozzles and 50-degree umbrella angles are unsuitable for stratified combustion because they produce steep air-fuel ratio gradients and create a spray with overly-deep liquid fuel penetration as well as presence of liquid fuel around the spark plug. In order to study injector performance, numerical calculations using the AVL FIRE™ CFD code were performed. The numerical results indicate that by increasing the injector umbrella angle, the extent of piston wall wetting can be decreased. Also, changing the pattern of holes in the nozzle changes the spray pattern, enabling its optimization with respect to ignition and flame propagation. Furthermore, PDA and Direct Imaging experiments showed that increasing the l/d ratio by reducing the hole diameter resulted in a decrease in the mean droplet sizes (D32). The spray angle was found to increase with decreasing l/d ratios. It has also been shown that by choosing a suitable l/d ratio it is possible to control the local AFR and cross-flow velocity at the spark plug. Copyright © 2005 SAE International.
42.	Skogsberg, Mikael, 1975, et al. (författare) Fuel distribution visualization from an air-assisted injector in a spray chamber 2004 Ingår i: Comodia 2004, Yokohama, 2-5 aug 2004. Konferensbidrag (refereegranskat)abstract Optical measurements have been performed to visualize the fuel distribution from an air-assisted GDI injector in a constant volume spray chamber. In the air-assisted injector, fuel droplet breakup occurs as the droplets are accelerated by the expanded air flow passing out through the injector nozzle. The injector design allows for two distinct modes of operation: stratified (low load) and homogenous (full load). Therefore, measurements were taken at back-pressure and temperature settings corresponding to both low and full loads, to investigate the influence of these variables on fuel distribution, droplet sizes and velocities in the two modes.Results from PDA measurements show that most of the droplet break-up occurs inside the nozzle. Downstream of the nozzle, rates of break-up and evaporation are low. The cause of the low breakup and evaporation rates downstream of the nozzle is believed to be the low relative velocity between the liquid fuel and the surrounding cold air jet.The fuel distribution has been visualized qualitatively by simultaneous MIE and LIF measurements with two intensified digital cameras in combination with a 266 nm YAG-laser.
43.	Skogsberg, Mikael, 1975, et al. (författare) Spray shape and atimization quality of an outward-opening piezo gasoline DI injector 2007 Ingår i: SAE. Konferensbidrag (refereegranskat)
44.	Skogsberg, Mikael, 1975, et al. (författare) Spray shape and atomization quality of an outward-opening piezo gasoline di injector 2007 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Tidskriftsartikel (refereegranskat)abstract The spray formation and consequent atomization of an outward opening piezo-electric gasoline DI injector have been experimentally investigated in a constant pressure spray chamber. The sizes and velocities of the droplets and the resulting spray shape were evaluated, under different boundary conditions, using Planar Mie scattering and Planar Laser-induced Fluorescence (PLIF) in combination with Phase Doppler Anemometry (PDA) analyses and high-speed video photography. The use of piezo-electric actuation for gasoline DI injectors provides an additional means to control the atomization and spray shape that is not available with solenoid-driven injectors such as swirling and multi-hole type injectors. For instance, with piezo injectors up to four injections per cycle are possible, and the fuel flow rate can be controlled by adjusting needle lift. The captured high-speed video images show that a hollow-cone spray forms as the fuel exits the outward-opening nozzle. Shortly after the start of injection, the momentum exchange with the surrounding air creates a recirculation zone at the leading edge of the spray. The images also show that the position and size of this recirculation zone depends on the chamber back pressure and that it too can be controlled by the injection timing. In addition, the PDA analysis shows that the creation of the recirculation zone, with a fuel pressure of 20 MPa, results in good atomization, slow-moving droplets, and helps guide fuel to the spark plug in stratified charge operation. The effects of flash boiling on the injector's sprays were also investigated. The results indicate that flash boiling affects the spray shape less than when multi-hole injectors are used. Furthermore, it has been shown that the use of multiple injections per cycle can decrease the spray penetration and provide an extended window of ignitable mixture at the spark plug.
45.	Skogsberg, Mikael, 1975, et al. (författare) Studies of the effect of injector parameters on mixture formation for multi-hole nozzles in a spray-guided 2005 Ingår i: SAE World Congress 2005. Konferensbidrag (refereegranskat)abstract This paper focuses on ways of improving the spray formation from spray-guided multi-hole gasoline direct injection injectors. Work has been done both experimentally using laser diagnostic tools as well as numerically using Computational Fluid Dynamics (CFD).Laser Induced Exciplex Fluorescence (LIEF) measurements in a constant pressure spray chamber and optical engine measurements has shown that a 6-hole nozzle with a 50 degree umbrella angle has steep air-fuel ratio gradients and too long liquid fuel penetration as well as presence of liquid fuel at the spark plug location, making it unsuitable for stratified combustion. In order to improve the injector performance, numerical calculations using the AVL FIRE CFD code have been performed. The numerical results indicate that by increasing the injector umbrella angle, the piston wall wetting can be decreased. Also, by optimizing the spray pattern through a change of the nozzle hole arrangement, the conditions for ignition and flame propagation can be improved. Furthermore, it was found experimentally by the use of PDA and Direct Imaging that an increase of the l/d ratio through a reduction of the hole diameter resulted in a decrease of the mean droplet sizes (D32). The spray angle was found to increase with decreasing l/d. It has also been shown that by choosing a suitable l/d it is possible to control the local AFR and cross-flow velocity at the spark plug.
46.	Tripathy, Srinibas, 1991, et al. (författare) 1D-3D CFD Investigations to Improve the Performance of Two-Stroke Camless Engine 2024 Ingår i: SAE Technical Papers. - 0148-7191 .- 2688-3627. Konferensbidrag (refereegranskat)abstract The transportation sector still depends on conventional engines in many countries as the alternative technologies are not mature enough to reduce carbon footprints in society. The four-stroke diesel engines, primarily used for heavy-duty applications, need either high intake boosting or a large bore to produce higher torque and power output. There is an alternative where a four-stroke engine operated in two-stroke mode with the help of a fully flexible variable valve actuation (VVA) system can achieve similar power density without raising the intake boosting or engine size. A fully flexible VVA is required to control the valve events (lift, timing, and durations) independently so that the four-stroke events can be completed in one cycle. In this study, 1D-3D CFD coupled simulations were performed to develop a gas exchange process for better air entrapment in the cylinder and evacuate the exhaust products simultaneously. The intake and exhaust valve closing timings were optimized based on the engine torque. The in-cylinder fresh charge mostly leaves the cylinder through exhaust ports during the gas exchange process even if the valve timings were optimized. Hence, a new design was proposed in which different deflectors (rectangular and semi-circular) were placed near the intake valve seats with the hope of achieving better air entrapment in the cylinder. The deflectors prevented the intake charge particles from being shot-circuited through the exhaust port and helped the charge particles to trap in the cylinder. The semi-circular deflector showed a more promising technique than the rectangular deflector and achieved a 45% higher torque improvement than the baseline design without a deflector.
47.	Wärnberg, Jonas, 1978, et al. (författare) Ignitability of hollow cone gasoline/gasoline-ethanol sprays 2009 Ingår i: 18. Aachener Kolloquium, Fahrzeug- und Motorentechnik. ; 1, s. 413-450 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Powering vehicles by a fuel-blend of ethanol and gasoline (E85) is being considered as one of various possible ways to decrease fossil carbon dioxide emissions. There is great potential to both improve power and increase energy conversion efficiency using such blends in combination with direct injection by modern outward-opening piezo-actuated injectors. However, cold starts when using mixtures with high ethanol contents are problematic. This report presents results of ongoing observations of sprays from a piezo-injector under conditions similar to those that would be encountered in-cylinder during cold starts at -30°C (243 K) ambient temperatures.Sprays of several fuels (gasoline, E75 and neat ethanol) have been monitored in a constant pressure, constant temperature spray chamber by both laser-induced fluorescence, to obtain understanding of the fuel vaporization process, and particle image velocimetry to map flow velocities and vortex formation inside the sprays and fuel clouds formed by their atomisation. In addition, the ignitability of the ethanol fuel sprays has been evaluated using focused laser light to obtain indications of the likelihood that similar sprays could be ignited in a real engine.As expected, under the test conditions ethanol evaporates more slowly than the lighter components of gasoline. In experiments at various temperatures, with constant air density, the vortex structure inside ethanol fuel clouds varied substantially between cycles, but remained similar. The clouds consistently formed toroid shapes in which two counter-rotating vortices developed, and the first traces of vapour appeared at the centres of these vortices. In addition, the laser ignition tests showed that under possible in-cylinder conditions with a fairly high compression ratio (~12:1) it would be possible to ignite a stratified neat ethanol spray.
48.	Yamaguchi, Akichika, et al. (författare) Air Motion Induced by Ultra-High Injection Pressure Sprays for Gasoline Direct Injection Engines 2020 Ingår i: SAE International Journal of Fuels and Lubricants. - : SAE International. - 1946-3952 .- 1946-3960. ; 13:3, s. 223-235 Tidskriftsartikel (refereegranskat)abstract The fuel injection pressures used in gasoline direct injection (GDI) engines have increased in recent years to improve fuel efficiency and reduce emissions. Current GDI engines use injection pressures of up to 350 bar, and there is evidence that even higher fuel injection pressures could yield further improvements in atomization. Higher injection pressures could also improve mixture formation by increasing the spray velocity; however, the research with higher injection pressures over 1000 bar is limited due to a limit of mechanical components. This manuscript summarizes experimental investigations into the effect of injection pressure, injection mass, and nozzle shape on spray-induced air motion with ultrahigh injection pressure over 1000 bar. Fuel sprays were generated at a range of injection pressures with different injection masses and nozzle geometries, and Particle Image Velocimetry (PIV) was performed using a Charge-coupled device (CCD) camera and an Nd:YAG (neodymium-doped yttrium aluminium garnet) laser to characterize the vector fields in the surrounding air and the rate of air entrainment into the sprays. Sprays generated with higher injection pressures and injection masses induced stronger large-scale air motion: an injection pressure of 1500 bar with an injection mass of only 5 mg caused almost the same amount of air entrainment as an injection pressure of 200 bar with an injection mass of 27 mg. However, the spray-induced air motion dissipated within 5 ms after the end of injection (EOI) in all cases. The air entrainment rate was also increased by using a divergent nozzle rather than a convergent one. Interactions between the spray and the surrounding air are thus strengthened by using a high injection pressure and a divergent nozzle.
49.	Yamaguchi, Akichika, 1988, et al. (författare) Spray Behaviors and Gasoline Direct Injection Engine Performance Using Ultrahigh Injection Pressures up to 1500 Bar 2021 Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 15:1 Tidskriftsartikel (refereegranskat)abstract High fuel injection pressure systems for Gasoline Direct Injection (GDI) engines have become widely used in passenger car engines to reduce emissions of particulates and pollutant gases. Current commercial systems operate at pressures of up to 450 bar, but several studies have examined the use of injection pressures above 600 bar, and some have even used pressures around 1500 bar. These works revealed that high injection pressures have numerous benefits including reduced particulate emissions, but there is still a need for more data on the possible benefits of injection pressures above 1000 bar. This article presents spray and engine data from a comprehensive study using several measurement techniques in a spray chamber and optical and metal engines. Shadowgraph imaging and Phase Doppler Interferometry (PDI) were used in a constant volume chamber to interpret spray behavior. Particle Image Velocimetry (PIV) was used to capture near-nozzle air entrainment. Optical engine experiments were performed to visualize the spray's position relative to the piston at different start of injection (SOI) timings. A single-cylinder GDI engine was used to investigate the effects of injection pressure on emissions and combustion characteristics. The spray tests showed that high-pressure sprays tend to exhibit better atomization and create more air entrainment, accelerating evaporation and mixing. However, high pressures also cause high spray tip penetration due to the high spray velocity, potentially causing wall film formation. At commonly used SOI timings, the benefits of high-pressure injection are relatively insignificant. The improvements in combustion stability and emissions of hydrocarbon (HC) and particulates are greater when the SOI timing is advanced (≈340°bTDC) or retarded (later than 180°bTDC). Wall film occurs at advanced SOI timing for all injection pressures, but high injection pressures significantly reduce particle number (PN) emissions by affecting wall film formation. At late SOI timings, high injection pressures yield acceptable combustion stability and emissions because they shorten the injection and promote mixing. These results suggest that high-pressure sprays allow HC and PN emissions to be greatly reduced and increase flexibility with respect to injection timing without sacrificing engine performance or increasing other emissions. Fuel consumption is also improved, but the effect is more significant when the injection pressure is 1000 bar.
50.	Yamaguchi, Akichika, et al. (författare) Spray Characterization of Gasoline Direct Injection Sprays under Fuel Injection Pressures up to 150 MPa with Different Nozzle Geometries 2019 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2019-January:january Tidskriftsartikel (refereegranskat)abstract Maximum fuel injection pressures for GDI engines is expected to increase due to positive effects on emissions and engine-efficiency. Current GDI injectors have maximum operating pressures of 35 MPa, but higher injection pressures have yielded promising reductions in particle number (PN) and improved combustion stability. However, the mechanisms responsible for these effects are poorly understood, and there have been few studies on fuel sprays formed at high injection pressures. This paper summarizes experimental studies on the properties of sprays formed at high injection pressures. The results of these experiments can be used as inputs for CFD simulations and studies on combustion behavior, emissions formation, and combustion system design. The experiments were conducted using an injection rate meter and optical methods in a constant volume spray chamber. Injection rate measurements were performed to determine the injectors' flow characteristics. Spray imaging was performed using a high-speed video camera. Several spray properties such as the liquid spray penetration, spray plume angle, and the spray breakup point were determined as functions of the fuel injection pressure and injected fuel mass by image post-processing. The impact of fuel pressure on spray droplet size was also investigated using two-component Phase Doppler Interferometry. Piezoelectric injectors for diesel engines were used with modified nozzles that produce sprays resembling those generated in gasoline engines. Experiments were performed with fuel injection pressures ranging from 20 to 150 MPa, and chamber pressures of 0.1 and 0.6 MPa. In addition, four different nozzles with three different nozzle configurations and either 6 or 10 holes were used to determine how hole geometry affects spray formation. The study's key findings are that increasing the fuel injection pressure advances spray breakup and creates smaller droplets, improving mixture formation and accelerating evaporation. The nozzle type and the ambient pressure both significantly affect aspects of spray behavior such as spray tip development.

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