Study Of Initial Little Species Mechanism And Steady Condition Calibration On Engine Performance

Our country is facing the problem of energy conservation and environmental protection.China's energy efficiency is still lower than the world average with the growth of consumption.The pressure to reduce emissions is even higher compared to energy saving.The best way to solve these problems is look for new alternative fuels and optimize the combustion mode at the same time.Because both NOx and soot formation depends on high local temperatures,low temperature combustion strategies have drawn extensive attention.When the peak temperature is reduced to 2000?or below,the initial concentration in the inlet mixture of NOx seems to have a significant effect on ignition delays,phasing time and cool flame heat release.It will occur even if the concentration is only dozens of ppm,which is possible due to EGR.In order to gain more understanding in the chemical aspect of initial NOx and control of auto-ignition in HCCI engine,n-heptane,iso-octane,toluene,ethanol and their binary or ternary mixtures were chosen as surrogate fuel.From both experiments and modeling results,the different blending effect between NOx and linear alkanes,branched alkanes,aromatics was studied.Since natural gas is the only fossil fuel to rise in usage.The influence of NOx and the steady state calibration of methane are discussed separately.The computing results show that the key reactions of NO and HO₂\RO₂ to these fuel are similar,but the effects on each fuels are different.For n-heptane and iso-octane,The NO+RO₂ reactions are less important or influential than the reaction between NO and HO₂ when the fundamentality in methane and ethanol is just the opposite.Finally a detailed kinetic mechanism composed out of n-heptane,iso-octane,toluene,ethanol and NOx sub-mechanism has been developed based on the analysis.The mechanism has been validated against experimental dataes,the results demonstrate that this mechanism can explain the low temperature chemical kinetics of hydrocarbon-NOx and the ignition delay,phase time,conversion of NO-NO₂ are described well.