| 1. |
- Berntsson, Andreas, 1978, et al.
(författare)
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A LIF-study of OH in the Negative Valve Overlap of a Spark-assisted HCCI Combustion Engine
- 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
- Future requirements for emission reduction from combustionengines in ground vehicles might be met byusing the HCCI combustion concept. In this study,negative valve overlap (NVO) and low lift, short duration,camshaft profiles, were used to initiate HCCIcombustion by increasing the internal exhaust gas recirculation(EGR) and thus retaining sufficient thermalenergy for chemical reactions to occur when a pilot injectionwas introduced prior to TDC, during the NVO.One of the crucial parameters to control in HCCI combustionis the combustion phasing and one way of doingthis is to vary the relative ratio of fuel injected inpilot and main injections. The combustion phasing isalso influenced by the total amount of fuel supplied tothe engine, the combustion phasing is thus affectedwhen the load is changed. This study focuses on thereactions that occur in the highly diluted environmentduring the NVO when load and pilot to main ratio arechanged.To monitor these reactions, planar laser-induced fluorescence(PLIF) from OH radicals was analyzed ina series of experiments with an optical single-cylinderengine, since these radicals are known to be associatedwith high temperature reactions. A series of experimentswas also performed using a multi-cylinderengine with varied NVO timings, which showed thatthe combustion phasing was influenced by both theratio between the pilot and main injection amountsand the total amount of fuel. Data acquired from correspondingoptical analysis showed the occurrenceof OH radicals (and thus high temperature reactions)during the NVO in all tested operating conditions. Theresults also indicate that the extent of the high temperaturereactions was influenced by both varied parameters,since decreasing the relative amount of the pilotinjection and/or increasing the total amount of fuel ledto larger amounts of OH radicals.
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| 2. |
- Lindgren, Ronny, 1976, et al.
(författare)
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Modeling gasoline spray-wall interactions and comparison to experimental data
- 2004
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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 a gasoline spray impinging on a heated surface were investigated under simulated engine conditions in an earlier study. The data from the experimental investigation have now been compared to results obtained from Computational Fluid Dynamic (CFD) simulations generated using several different numerical models for spray-wall impingement found in the literature. It was found that the models based on single-drop experiments do not predict the outcome of spray impingement well in some respects. Their major drawback was that the predicted diameter distributions of the reflected drops in the secondary spray were shifted downwards from the measured drop size distributions. The tested models predicted the normal velocity component relative to the wall well. However, they were less good at capturing the tangential velocity component relative to the wall. Since the models did not capture the velocities in the tangential direction correctly, the spread of the secondary spray above the wall was under-predicted.
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| 3. |
- Larsson, Monica, 1979, et al.
(författare)
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Combustion of Fischer-Tropsch, RME and Conventional Fuels in a Heavy-Duty 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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Konferensbidrag (refereegranskat)abstract
- This investigation includes a comparison of two Fischer-Tropsch (FT) fuels derived from natural gas and a Rapeseed Methyl Ester (RME) fuel with Swedish low sulfur Diesel in terms of emissions levels, fuel consumption and combustion parameters. The engine used in the study was an AVL single cylinder heavy-duty engine, equipped with a cylinder head of a Volvo D12 engine. Two loads (25% and 100%) were investigated at a constant engine speed of 1200 rpm. The engine was calibrated to operate in different levels of EGR and with variable injections timings. A design of experiments was constructed to investigate the effects of these variables, and to identify optimal settings. The results showed that the soot emissions yielded by FT and RME fuels are up to 40 and 80 percent lower than those yielded by the Swedish Diesel. In addition the FT fuel gave slightly lower, and the RME significant higher NOx emissions than the Swedish Diesel. Due to the low heating value of the RME fuel, the fuel consumption was increased by 10% compared with the Swedish Diesel. The fuel consumption with the FT fuel, which has a similar heating value to conventional fuels, was not significantly different from that obtained with the Diesel.
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| 4. |
- Beatrice, Carlo, et al.
(författare)
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Experimental Assessment on Exploiting Low Carbon Ethanol Fuel in a Light-Duty Dual-Fuel Compression Ignition Engine
- 2020
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 10:20
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Tidskriftsartikel (refereegranskat)abstract
- Compression ignition (CI) engines are widely used in modern society, but they are also recognized as a significative source of harmful and human hazard emissions such as particulate matter (PM) and nitrogen oxides (NOx). Moreover, the combustion of fossil fuels is related to the growing amount of greenhouse gas (GHG) emissions, such as carbon dioxide (CO2). Stringent emission regulatory programs, the transition to cleaner and more advanced powertrains and the use of lower carbon fuels are driving forces for the improvement of diesel engines in terms of overall efficiency and engine-out emissions. Ethanol, a light alcohol and lower carbon fuel, is a promising alternative fuel applicable in the dual-fuel (DF) combustion mode to mitigate CO2 and also engine-out PM emissions. In this context, this work aims to assess the maximum fuel substitution ratio (FSR) and the impact on CO2 and PM emissions of different nozzle holes number injectors, 7 and 9, in the DF operating mode. The analysis was conducted within engine working constraints and considered the influence on maximum FSR of calibration parameters, such as combustion phasing, rail pressure, injection pattern and exhaust gas recirculation (EGR). The experimental tests were carried out on a single-cylinder light-duty CI engine with ethanol introduced via port fuel injection (PFI) and direct injection of diesel in two operating points, 1500 and 2000 rpm and at 5 and 8 bar of brake mean effective pressure (BMEP), respectively. Noise and the coefficient of variation in indicated mean effective pressure (COVIMEP) limits have been chosen as practical constraints. In particular, the experimental analysis assesses for each parameter or their combination the highest ethanol fraction that can be injected. To discriminate the effect on ethanol fraction and the combustion process of each parameter, a one-at-a-time-factor approach was used. The results show that, in both operating points, the EGR reduces the maximum ethanol fraction injectable; nevertheless, the ethanol addition leads to outstanding improvement in terms of engine-out PM. The adoption of a 9 hole diesel injector, for lower load, allows reaching a higher fraction of ethanol in all test conditions with an improvement in combustion noise, on average 3 dBA, while near-zero PM emissions and a reduction can be noticed, on the average of 1 g/kWh, and CO2 compared with the fewer nozzle holes case. Increasing the load insensitivity to different holes number was observed.
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| 5. |
- Eismark, Jan, 1962, et al.
(författare)
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Reduced soot emissions by piston bowl-shape guided late cycle oxidation in low-swirl heavy-duty diesel engine combustion
- 2018
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Ingår i: SIA POWERTRAIN ROUEN 2018 The New Compression Ignition Engine, Electrification and Sustainable Fuels for Passenger Cars and Commercial Vehicles. ; , s. 265-276
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Konferensbidrag (refereegranskat)abstract
- Reduced soot emissions by piston bowl-shape guided late cycle oxidation in low-swirl heavy-duty diesel engine combustion. Late cycle soot oxidation in heavy-duty diesel engine low-swirl combustion was investigated using single-cylinder engine and spray-chamber experiments supported by engine combustion computational fluid dynamics (CFD) simulations. The in-cylinder flow situation during interaction between adjacent flames (flame-flame event) was shown to have a large impact on the combustion late in the cycle. In order to modify the flame-flame flow-situation, a new piston bowl shape having wave-shaped protrusions (waves) for guiding of the near-wall flow, was developed. This resulted in a significant reduction of soot emissions and also increased fuel efficiency. The waves were observed to enhance the late cycle mixing which manifested as an increased apparent rate of heat release after the end of injection. Combustion simulations were used to show that the increased mixing was driven by the enhanced intensity of side-vortices leading to the creation of a radial mixing zone. This radial mixing zone extended further into the centre of the piston bowl where unused ambient gas is available, which promotes oxidation. This flame-interaction effect was isolated and further studied using an optical spray-chamber with a two-hole fuel injector nozzle and a wall interaction. Finally, the influence of bowl geometry on the flow field was investigated and coupled to observed late cycle soot oxidation efficiency.
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| 6. |
- Eismark, Jan, 1962, et al.
(författare)
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Role of late soot oxidation for low emission combustion in a diffusion-controlled, High-EGR, heavy duty diesel engine
- 2009
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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
- Soot formation and oxidation are complex and competing processes during diesel combustion. The balance between the two processes and their history determines engine-out soot values. Besides the efforts to lower soot formation with measures to influence the flame lift-off distance for example or to use HCCI-combustion, enhancement of late soot oxidation is of equal importance for low-λ diffusion-controlled low emissions combustion with EGR. The purpose of this study is to investigate soot oxidation in a heavy duty diesel engine by statistical analysis of engine data and in-cylinder endoscopic high speed photography together with CFD simulations with a main focus on large scale in-cylinder gas motion. Results from CFD simulations using a detailed soot model were used to reveal details about the soot oxidation. A particular objective of the present study was to investigate the importance of enhancing soot oxidation after End of Injection (EOI) when temperature and NOx formation rapidly decreases. Geometrical measures to control flame propagation and different flame interactions were investigated. Such measures contribute to conserve available kinetic energy until late in the combustion period in an efficient way. Based on this combustion strategy it is possible to reach near zero engine-out soot emissions. Copyright © 2009 SAE International.
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| 7. |
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| 8. |
- Husberg, Tobias, 1975, et al.
(författare)
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Analysis of advanced multiple injection strategies in a heavy-duty diesel engine using optical measurements and CFD-simulations
- 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 emissions legislation for Diesel engines and reduce their CO 2 emissions it is necessary to improve diesel combustion by reducing the emissions it generates, while maintaining high efficiency and low fuel consumption. Advanced injection strategies offer possible ways to improve the trade-offs between NOx, PM and fuel consumption. In particular, use of high EGR levels ( > 40%) together with multiple injection strategies provides possibilities to reduce both engine-out NOx and soot emissions. Comparisons of optical engine measurements with CFD simulations enable detailed analysis of such combustion concepts. Thus, CFD simulations are important aids to understanding combustion phenomena, but the models used need to be able to model cases with advanced injection strategies. Thus, in the study presented here, engine tests were performed with settings selected to simplify CFD simulation, with long dwell times between the injections and only injection changes between engine settings in test cases presented in this paper. The key to reducing both soot and NOx emissions by applying pilot injections is that the pilot injected fuel should not ignite before sufficient mixing/lean-out has occurred. Hence, substantial heat releases prior to the main injection must be prevented. Thus, high EGR levels are needed to increase the bulk gas mass and reduce the temperature so that there is sufficient time for the pilot injections to mix and become locally lean before ignition. Copyright © 2008 SAE International.
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| 9. |
- Jia, Zhiqin, 1983, et al.
(författare)
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Experimental investigation into the combustion characteristics of a methanol-Diesel heavy duty engine operated in RCCI mode
- 2018
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 226, s. 745-753
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Tidskriftsartikel (refereegranskat)abstract
- This study examines combustion in a dual-fuel methanol-Diesel heavy duty engine using three different methanol injection configurations: port injection into the intake manifold; direct injection during the intake stroke (DI_E) and direct injection during the compression stroke (DI_L). The latter two methanol direct injection configurations were used in the attempt to reduce HC and CO emissions, which were considerably high in the port-injected high-octane fuel RCCI combustion. Engine experiments were performed using a double Diesel injection strategy with two pilot Diesel injections (PI1 and PI2) and a constant engine speed of 1500 rpm. The effects of three parameters – the PI1 and PI2 injection timings, and the PI2/PI1 duration ratio – were investigated at 5 bar IMEP for the three methanol injection configurations. The onset of unstable combustion and excessive combustion phasing advancement imposed lower or upper limits on the sweeps over the studied parameters. The DI_L configuration achieved lower net indicated thermal efficiencies than the other two methanol injection configurations. The influences of the methanol injection pressure and methanol substitution percentage (MSP) were also investigated for the DI_L configuration at 5 bar IMEP, revealing that the combustion process was relatively insensitive to the methanol injection pressure but was adversely affected by increasing the MSP. Finally, the port and DI_L configurations were tested at various loads. Neither configuration offered any advantage over pure Diesel combustion in terms of net indicated thermal efficiency nor emissions of HC and CO, but both offered lower greenhouse gas emissions at all load points. However, only the methanol port injection configuration achieved ultra-low NO x and soot emissions at 12 bar IMEP.
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| 10. |
- Saccullo, Michael, 1984, et al.
(författare)
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Dual Fuel Methanol and Diesel Direct Injection HD Single Cylinder Engine Tests
- 2018
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2018-April
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Tidskriftsartikel (refereegranskat)abstract
- Laws concerning emissions from heavy duty (HD) internal combustion engines are becoming increasingly stringent. New engine technologies are needed to satisfy these new requirements and to reduce fossil fuel dependency. One way to achieve both objectives can be to partially replace fossil fuels with alternatives that are sustainable with respect to emissions of greenhouse gases, particulates and nitrogen oxides (NOx). A suitable candidate is methanol. The aim of the study presented here was to investigate the possible advantages of combusting methanol in a heavy duty Diesel engine. Those are, among others, lower particulate emissions and thereby bypassing the NOx-soot trade-off. Because of methanol's poor auto-ignition properties, Diesel was used as an igniting sources and both fuels were separately direct injected. Therefore, two separate standard common rail Diesel injection systems were used together with a newly designed cylinder head and adapted injection nozzles. This study serves as a proof-of-concept, demonstrating that methanol can successfully be used in a high pressure Diesel injection system. Additionally, the combustion properties of the dual fuel system were compared to those of pure Diesel with the same dual injection strategy. Methanol offered comparable combustion efficiencies to conventional Diesel with lower NOx and significantly lower soot emissions. A design of experiments study was performed to characterize the methanol-diesel system's behavior in detail at a single speed-load point. A sweet spot analysis showed potential for optimizing the given setup towards even higher indicated gross efficiency with very low soot and low NOx.
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