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Viewing 1 to 7 of 7
2013-04-08
Journal Article
2013-01-0865
Amin Maghbouli, Sina Shafee, Rahim Khoshbakhti Saray, Wenming Yang, Vahid Hosseini, Hui An
Dual-fuel diesel-natural gas (NG) engine exhibits higher power density and lower specific emissions compared to dedicated diesel engines. However, high intake temperatures, high compression ratios, combined with high engine loads may lead to engine knock. This is potentially a limiting factor on engine downsizing and getting higher power. In the present study, the combustion process under knocking conditions has been investigated in a dual-fuel diesel-NG engine. A comprehensive multi-dimensional simulation framework was generated by integrating the CHEMKIN chemistry solver into the KIVA-3V code. A detailed chemical kinetics mechanism was used for n-heptane and methane as diesel and NG surrogates. Combination of detailed chemical kinetics and detailed fluid dynamics calculation enabled the model to take into account the characteristics of most pronounced knock type in dual-fuel engines, so called end-gas knock.
2010-10-25
Technical Paper
2010-01-2168
Vahid Hosseini, W Neill, Hongsheng Guo, Cosmin Emil Dumitrescu, Wallace Chippior, Craig Fairbridge, Ken Mitchell
The effects of cetane number, aromatics content and 90% distillation temperature (T90) on HCCI combustion were investigated using a fuel matrix designed by the Fuels for Advanced Combustion Engines (FACE) Working Group of the Coordinating Research Council (CRC). The experiments were conducted in a single-cylinder, variable compression ratio, Cooperative Fuel Research (CFR) engine. The fuels were atomized and partially vaporized in the intake manifold. The engine was operated at a relative air/fuel ratio of 1.2, 60% exhaust gas recirculation (EGR) and 900 rpm. The compression ratio was varied over the range of 9:1 to 15:1 to optimize the combustion phasing for each fuel, keeping other operating parameters constant. The results show that cetane number and T90 distillation temperature significantly affected the combustion phasing. Cetane number was clearly found to have the strongest effect.
2009-04-20
Technical Paper
2009-01-1107
Vahid Hosseini, W. Stuart Neill, Wallace L. Chippior
Homogeneous Charge Compression Ignition (HCCI) combustion characteristics of dual-stage autoignition fuels were examined over the speed range of 600 to 1700 rpm using a Cooperative Fuels Research (CFR) engine. A fuel vaporizer was used to preheat and partially vaporize the fuel inside the intake plenum. The air and fuel were well-mixed prior to entering the cylinder. Since low temperature heat release (LTHR) is known to be an important factor that affects HCCI combustion of fuels that exhibit dual-stage autoignition behavior, a detailed heat release analyses were performed on both time and crank angle bases. At the lower and upper speeds, the operating ranges were compared as a function of air/fuel ratio (AFR) and exhaust gas recirculation (EGR) from the knocking to misfiring limits. The AFR-EGR operating region was more limited at 1700 rpm than at 900 rpm for the commercial ULSD fuel. Combustion stability was problematic at higher engine speeds.
2008-04-14
Technical Paper
2008-01-0049
Vahid Hosseini, M. David Checkel
Although HCCI engines promise low NOx emissions with high efficiency, they suffer from a narrow operating range between knock and misfire because they lack a direct means of controlling combustion timing. A series of previous studies showed that reformer gas, (RG, defined as a mixture of light gases dominated by hydrogen and carbon monoxide), can be used to control combustion timing without changing mixture dilution, (λ or EGR) which control engine load. The effect of RG blending on combustion timing was found to be mainly related to the difference in auto-ignition characteristics between the RG and base fuel. The practical effectiveness of RG depends on local production using a fuel processor that consumes the same base fuel as the engine and efficiently produces high-hydrogen RG as a blending additive.
2007-04-16
Technical Paper
2007-01-0206
Vahid Hosseini, M. David Checkel
Homogeneous Charge Compression Ignition (HCCI) combustion offers high fuel efficiency and some emissions benefits. However, it is difficult to control and stabilize combustion over a significant operating range because the critical compression ratio and intake temperature at which HCCI combustion can be achieved vary with operating conditions such as speed and load as well as with fuel octane number. Replacing part of the base fuel with reformer gas, (which can be produced from the base hydrocarbon fuel), alters HCCI combustion characteristics in varying ways depending on the replacement fraction and the base fuel auto-ignition characteristics. Because fuel injection quantities and ratios can be altered on a cycle-by-cycle basis during operation, injecting a variable blend of reformer gas and base fuel offers a potential HCCI combustion control mechanism.
2007-04-16
Technical Paper
2007-01-0208
Vahid Hosseini, M. David Checkel
Homogeneous Charge Compression Ignition (HCCI) engines offer high fuel efficiency and some emissions benefits. However, it is difficult to control and stabilize combustion over a sufficient operating range because the critical compression ratio and intake temperature at which HCCI combustion can be achieved varies with operating conditions such as speed and load as well as with fuel octane number. Replacing part of the base fuel with reformer gas, (which can be produced from the base hydrocarbon fuel), alters HCCI combustion characteristics in varying ways depending on the replacement fraction and the base fuel auto-ignition characteristics. Injecting a blend of reformer gas and base fuel offers a potential HCCI combustion control mechanism because fuel injection quantities and ratios can be altered on a cycle-by-cycle basis.
2006-10-16
Technical Paper
2006-01-3247
Vahid Hosseini, M. David Checkel
This paper describes use of reformer gas (RG) to alter and control combustion in a CNG-fueled HCCI engine. Experimental work used a mixture of simulated RG (75% H2 and 25% CO) to supplement base CNG fueling in a CFR engine upgraded to achieve high compression ratios. RG was used to improve the engine's operating performance and to control combustion onset in experiments conducted at three different compression ratios. A combination of high compression ratio (18.5) and high intake temperature (140°C) was observed to be appropriate to run the CNG-fueled CFR engine in HCCI mode. RG replacement of CNG altered combustion characteristics and expanded the operating range on the lean side. Use of RG decreased knock severity and reduced NOx emission. At constant relative air/fuel ratio (λ) it advanced combustion timing, moving the maximum cylinder pressure earlier in the cycle and increasing maximum pressure.
Viewing 1 to 7 of 7