Numberical Study On The Soot And NO_x Emission Of Gasoline Compression Ignition Of Low Temperature Combustion

Gasoline compression ignition of low temperature combustion (LTC) is an advanced combustion concept, which has a great potential on reducing soot and NO_x emissions. At high load, soot emission of gasoline compression ignition on LTC is relative higher, so exploring the laws of soot and NO_x emission has very important significance on realizing clean combustion. So that, in the current work, three-dimensional numerical simulations was used to simulate a gasoline compression ignition of LTC engine, meanwhile the formation and evolution process were analyzed.In the current work, KIVA internal combustion engine simulated program and CHEMKIN chemical reaction kinetics software were coupled to establish a three dimensional numerical simulation model, and then simulated the operating conditions of different injection timing and different EGR to study the effect of different timing and different EGR on gasoline LTC combustion, soot and NO_x emission. Results indicated that, in-cylinder pressure curve, heat release rate curve, the predictions of soot and NO_x emission agree quite well the experimental results in different injection timing or different EGR, which Verify the reliability of the three dimensional numerical simulation model. Increasing the EGR rate can effectively reduce soot and NO_x emission. Which injection timing lags behind, in-cylinder soot generation rate increase, while soot oxidation rate increase faster at the same time, so soot emission slightly reduced, but will NO_x emission increased.Base on the previous work, study the effect of fuel properties and components on gasoline LTC combustion numerical simulation. The results indicated that, changing three components fuel of n-heptane, isooctane and toluene to tow components fuel of n-heptane and isooctane, fuel ignition delay period become longer, and soot emission simulation result is almost zero emission, but NO_x emission almost not change. So we can see that toluene has great effect on soot emission numerical simulation. Compare to three components of physical properties of fuel, single isooctane property of fuel can reduce soot emission and increase combustion temperature. Soot generation position change from combustion chamber wall to combustion chamber pit. Fuel properties and components have great effect on gasoline LTC combustion and emission.