| 1. |
- Andersson, Mats, 1963, et al.
(författare)
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Temperature measurements using exciplex fluorescence with TMPD and methylnaphthalene as tracers
- 2008
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Ingår i: Proc. 22nd European Conference on Liquid Atomization and Spray Systems. - 9788890371202 ; , s. ILASS-08-P-19-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Laser-induced exciplex fluorescence has been used to measure the temperature in a spray of a diesel-like fuel. To a model fuel consisting of 70 % n-decane and 30 % 1-methylnaphthalene, TMPD was added in a concentration of 0.2 %. When excited with UV-light TMPD efficiently forms an exciplex with methylnaphthalene fluorescing with a peak intensity at a wavelength around 505 nm at room temperature. When the temperature of the fuel increases the peak position shifts to shorter wavelengths, and the peak reaches a position of 475 nm at 150 ºC. This shift of the fluorescence spectrum can be used to estimate the temperature of the liquid fuel, by measuring the fluorescence light intensity in two different wavelength intervals and evaluate the ratio between them as a function of temperature. The intensity ratio as a function of temperature was evaluated and calibrated, and subsequently used to determine the temperature of the liquid fuel along the spray axis.
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| 2. |
- Ehleskog, Rickard, 1972, et al.
(författare)
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Effects of Multiple Injections on Engine-Out Emission Levels Including Particulate Mass from an HSDI Diesel Engine
- 2007
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Tidskriftsartikel (refereegranskat)abstract
- The effects of multiple injections on engine-out emissionsfrom a high-speed direct injection (HSDI) dieselengine were investigated in a series of experimentsusing a single cylinder research engine.Injection sequences in which the main injection wassplit into two, three and four pulses were tested andthe resulting emissions (NOx, CO HC and particulatematter), torque and cylinder pressures were comparedto those obtained with single injections. Togetherwith the number of injections, the effects ofvarying the dwell time were also investigated. It wasfound that dividing the main injection into two partslowered the engine-out particulate and CO emissionsand increased fuel efficiency. However, it also resultedin increased NOx emissions. Further, usingdouble injections reduced the peak rate of heatrelease (RoHR) and increased RoHR in the laterstages of the combustion without changing the combustionduration, resulting in a more even distributionof RoHR during the combustion, which is believed tobe the main reason for the changes in fuel consumptionand engine-out emission levels. When the numberof injections was increased to three or four and thedwell time was prolonged the RoHR decreased, thecombustion duration increased and the CA50 was retarded.Consequently, NOx emissions were reducedbut the fuel efficiency also declined, and emissions ofparticulate mater, CO and HC rose.
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| 3. |
- Ehleskog, Rickard, 1972, et al.
(författare)
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Soot evolution in multiple injection diesel flames
- 2008
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Tidskriftsartikel (refereegranskat)abstract
- In order to meet future emission regulations, variousnew combustion concepts are being developed, severalof which incorporate advanced diesel injectionstrategies, e.g. multiple injections, offering attractivepotential benefits. In this study the effects of split injectionson soot evolution in diesel flames were investigatedin a series of flame experiments performed usinga high pressure, high temperature (HP/HT) spraychamber and laser-induced incandescence apparatusto measure soot volume fractions. The focus wason split injections with varied dwell times preceded bya short pilot. The results, which were analyzed andcompared to results from engine tests, show that netsoot production can be decreased by applying an appropriatesplit injection strategy.
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| 4. |
- Eismark, Jan, 1962, et al.
(författare)
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Role of formation and transportation of hydroxyl radicals for enhanced late soot oxidation in a low emissions heavy-duty diesel engine.
- 2010
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Ingår i: Thiesel 2010 conference on Thermo-and fluid dynamic processes in Diesel Diesel Engines. - 9788469350096 ; , s. 173-190
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Konferensbidrag (refereegranskat)abstract
- In previous research enhancement of late soot oxidation by increased mixing rates has been identified as an important measure to decrease engine-out soot emissions. Additionally, the availability of oxidants, especially hydroxyl radicals (OH) in the mixing zones, is considered as essential for an effective fuel and soot burn-out process. The objective of this study was to combine experimental and computational methods to identify the role of OH for late soot oxidation. Experimental data from a high pressure/high temperature spray chamber and a heavy-duty single cylinder engine were analysed using combustion CFD. The formation, lifetime and transportation of OH were studied together with other important in-cylinder parameters. The soot formation and oxidation processes were analysed for a dataset of engine results with equal NOx emissions but having a large variation of engine-out soot emissions. The spray chamber experimental set-up includes a flame divider designed to enable studies of the OH history in the leading edge of the flame vortex. The engine combustion CFD results could be compared with CFD analysis of the spray chamber results regarding the behaviour of OH. From this study, it is suggested that the fluctuating interface between the soot leading edge and the important soot oxidant specie OH is influenced by interactions between local turbulent flame movements and the availability of OH. The soot and OH interface was observed to develop smoothly in a strongly re-directed side of a flame as well as on the free side of the same flame. According to experimental observations and analysis of CFD source terms of soot formation and oxidation rates, both the OH radical pool and the soot oxidation reach farther downstream in the flame than the soot formation. The study gave an increased understanding of limiting factors for enhanced late soot oxidation during diesel engine operation.
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| 5. |
- Hemdal, Stina, 1974, et al.
(författare)
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In-cylinder soot imaging and emissions of stratified combustion in a spark-ignited spray-guided direct-injection gasoline engine
- 2011
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 12:6, s. 549-563
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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.
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| 6. |
- Johansson, Monica, 1979, et al.
(författare)
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NOx and soot emissions trends for RME, SME and PME fuels using engine and spray experiments in combination with simulations
- 2013
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 106, s. 293-302
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Tidskriftsartikel (refereegranskat)abstract
- This study includes engine tests with neat FAME fuels and blends of 7% and 30% of RME in European Diesel, EN590 (non FAME added). The study was also completed with spray studies and numerical simulations for a deeper understanding of the engine results.The engine was operated at four operational points (A25, B50, B75 and C100) taken from the European Stationary Cycle, ESC cycle. The A25 case was also extended to achieve information how the soot emissions varies with the operational parameters; start of injection (SOI), NOx level (regulated by EGR) and needle opening pressure (NOP). The spray studies were performed in a high temperature/high pressure spray chamber at relevant conditions. For the numerical simulations the KIVA 3-V code was used with detailed chemical kinetics.The results shows that the neat FAME fuels lower the soot emissions by up to 90% compared with Diesel fuel. Moreover, even low blend ratios lowers the soot emissions significantly. Among the FAME fuels, combustion with PME had the lowest amount of soot emissions due to its lowest amount of di-and tri-unsaturated fatty acids (i.e. less double bonds) in comparison with SME and RME.The NOx emissions were increased for the neat FAME fuels in relation the Diesel fuel. The increase in NOx emissions for the neat FAME fuels is due to the higher flame temperature for the FAME fuels which could be a result of the oxygen content which causes a lower equivalence ratio (phi), i.e. leaner local reacting mixture.The A25 operational case showed that the most important factor to decrease soot emissions for Diesel fuel was NOP, while for the FAME fuels SOI had the greatest impact. Further, at constant level of NOx emissions for the included fuels it was observed that the FAME fuels still reduced the soot emissions significantly.The study shows that FAME fuels and Diesel blends with FAME fuels, can be a tool to meet future emission legislation, since low soot emissions levels can be reached for low NOx emissions and the fact that FAME fuels are renewable, the global warming impact is lower than for Diesel.
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| 7. |
- Kösters, Anne, 1983, et al.
(författare)
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Diesel sprays – modeling and validation
- 2011
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Ingår i: ILASS 2011 Estoril, Portugal.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spray formation and combustion are highly complex processes, which have already been subjects of intense modeling efforts. If fuel is injected in gas a two-phase flow is generated, and several models have been developed to describe the gas and liquid phases, the models chosen are of course important for the results. Also, the way a model is implemented is important, especially regarding the treatment of the liquid core break-up process. It is not possible to estimate a single droplet size distribution for the whole spray, hence a spray model should generate a local droplet size distribution in the spray. However, the commonly applied models for primary and secondary break-up are not able to do this and often the spray model implementations are unstable and strongly grid size dependent. In the work presented here, the VSB2 spray model, developed by Volvo Technology Corporation, was implemented in OpenFOAM. The results obtained from VSB2 spray simulations are compared with data from experiments performed at Chalmers.
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| 8. |
- Lif, Anna, 1962, et al.
(författare)
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Optical studies of spray development and combustion of water-in-diesel emulsion and microemulsion fuels
- 2010
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 89:1, s. 122-132
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Tidskriftsartikel (refereegranskat)abstract
- Physical properties, spray behaviour and combustion characteristics of a water-in-diesel emulsion, a water-in-diesel microemulsion and a conventional diesel fuel were investigated. The size of the drops, in the water-containing fuels, was measured by NMR diffusometry. Spray development and combustion were studied by optical methods in an optically accessed combustion vessel at conditions similar to those in a diesel engine. High speed shadowgraphs were employed to measure break-up, droplets penetration, vapour penetration and start of combustion. Combustion duration, flame temperature and relative soot concentration were determined by emission-based methods. Differences in spray behaviour suggest an enhanced atomisation for the water-containing fuels compared to regular diesel fuel. Moreover, reduced soot concentrations and flame temperature with increased combustion duration were noticed for the water-in-diesel fuels than for the regular diesel fuel.
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| 9. |
- Lima Ochoterena, Raul, 1978, et al.
(författare)
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Determination of soot size and concentration in optically dense sprays by optical methods
- 2006
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Ingår i: 10th Conference on Combustion Generated Nanoparticles, 2006. Zurich, 21st -23rd August.
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Konferensbidrag (refereegranskat)abstract
- The understanding of the formation and oxidation of soot is of interest to become able to reduce the emission of soot particles to the atmosphere from direct injection engines. A possible path to study the formation of soot in diesel sprays is by laser-based optical methods, having the potential for high temporal and spatial resolution; moreover they can be combined to obtain information of soot at any given instant from the start of combustion. Laser Induced Incandescence (LII), Elastic Light Scattering (ELS) and Light Extinction (LE) have been widely used for soot studies [1]. Soot particle size and concentration can be measured simultaneously combining LII, ELS and LE, the combination of these three techniques has proven to be functional when used to measure soot in optically thin flames in atmospheric conditions [2] and exhaust gases [3]. Optically dense systems such as diesel spray combustion, and the diagnostic of soot in them, require special attention to the LII signal because of its strong non-linear dependence on the laser fluence. Moreover particular concern must be given to the enhanced conductive heat transfer term in the LII interpretation due to the high pressure inside the combustion chamber at which diesel engines are usually operated [4]. This paper presents a method to measure particle size and particle concentration in optically dense sprays in conditions similar to those prevailing in real direct injection engines. For this purpose a non-linear compensation method to approximate the laser intensity across optically dense sprays was developed together with a new non-continuum heat transfer model for the LII signal.
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| 10. |
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