Narankhuu Jamsran

A Study on the Autoignition Characteristics of DME–LPG Dual Fuel in the HCCI Engine

This study investigated the potential increase of engine power through the mixture of dimethyl ether (DME) and liquefied petroleum gas (LPG) with homogeneous charge compression ignition combustion. The effects of mixing ratio of DME/LPG at a constant intake temperature were confirmed experimentally in a single-cylinder diesel engine. A numerical analysis was conducted through the detailed chemical kinetics by using CHEMKIN-PRO for the mixing model of DME and n-butane to clarify the underlying mechanism of autoignition, while considering the gas mixture heat loss to the cylinder wall to compare with the experiment. The results show that the increased amount of LPG reduces the low-temperature heat release and activates the high-temperature heat release, which increases in-cylinder pressure. Therefore, it has potential to raise the indicated mean effective pressure when mixing ratio was adjusted appropriately. Also, thermal efficiency was increased to 51.2% at the mixing ratio of 0.6. Finally, engine out emissions including total hydrocarbon increased a small amount and carbon monoxide was decreased to almost zero when the mixing ratio of DME decreased until the combustible zone. Numerical results agreed with the experiment, indicating weakened low-temperature oxidation from the increase of the n-butane amount.

Numerical study of the effects of exhaust gas recirculation stratification on reducing the rate of pressure rise in dimethyl ether homogeneous charge compression ignition combustion

This work investigates the potential of in-cylinder exhaust gas recirculation stratification for reducing the rate of pressure rise in dimethyl ether homogeneous charge compression ignition engines and its coupling with both thermal stratification and fuel stratification. Numerical analyses were performed using a five-zone version of the CHEMKIN-II kinetics rate code and the kinetic mechanics of dimethyl ether. The effects of inert components were used to represent the presence of exhaust gas recirculation in calculations. Three cases of exhaust gas recirculation stratification were tested in terms of both thermal stratification and fuel stratification at a fixed initial temperature, fixed initial pressure and fixed fuelling rate at bottom dead centre. In order to explore the appropriate stratification of exhaust gas recirculation, the exhaust gas recirculation width (defined as the difference between the exhaust gas recirculation ratios in zone 1 and zone 5 in the five-zone model) which we employed was from 0% to 30%. The case of exhaust gas recirculation homogeneity (called case 1), in which the exhaust gas recirculation width is 0%, was examined. In case 2, exhaust gas recirculation is located densely in a hot zone for combination with thermal stratification or in a fuel-rich zone for combination with fuel stratification. The last case (case 3) was the inverse of case 2. Ringing was reduced to an acceptable level in the case of fuel stratification with an appropriate exhaust gas recirculation distribution, which slowed the rapid burning during the compression stroke.

Potential of fuel stratification for reducing pressure rise rate in HCCI engines fueled with DME/n-Butane

This study investigated the effect on reducing the pressure rise rate(PRR) in HCCI Engine by the variation of mixing ratio in the pre-mixture of DME and n-Butane that has different auto-ignition characteristics. In addition to measure of gas pressure in the engine cylinder, chemiluminescence image using the optical accessible engine and numerical analysis with multi-zones model were used to assess the combustion at each local area in the combustion chamber. The maximum PRR changes depending on mixing condition of DME and n-Butane. When DME is stratified and n-Butane is distributed uniformly, maximum PRR becomes lowest which is about 0.25MPa/ms and it corresponds to 5deg. retarding of CA50.

Potential of Fuel Stratification for Reducing Pressure Rise Rate in HCCI Engines Fueled With DME/n-Butane

We investigated the efficacy of fuel stratification in a pre-mixture of Di-methyl ether and n-Butane, which have different auto-ignition characteristics, for reducing the pressure rise rate of homogeneous charge compression ignition engines. A new chemical reaction model was created by mixing DME and n-Butane and compared to existing chemical reaction models to verify the effects. The rate of maximum pressure rise depends on mixture ratio. When DME was charged with stratification and n-butane was charged with homogeneity, the maximum pressure rise rate was the lowest. The calculations were performed using the SENKIN application of CHEMKIN-II.