Development Of Reduced Kinetic Mechanism And Availability Analysis In Low Temperature Combustion Engine

Low temperature combustion has potential to realize effective and clean working process for engine,which is mainly controlled by chemical kinetic of the fuels.New reduced kinetic models of primary reference fuel?PRF?and toluene reference fuel?TRF?suitable for low temperature combustion engine are developed based on perspective of kinetics analysis.Availability changes are analyzed and effects of boundary conditions on availability proportion are studied using second law analysis method.The present research of primary reference fuel kinetic models is analyzed firstly.On the basis of the existing typical mechanisms,the reaction coefficients are optimized through ignition delay sensitivity analysis under several target conditions,and a reduced PRF kinetic model consisting of 68 elementary reactions are eventually formed.By comparison with ignition delay data of shock tube experiments and main species transformation process of preferred stirred reaction experiments,the reduced model is proved useful in certain working conditions.The detailed toluene kinetic mechanism of Metcalfe is reduced by several reduction methods,such as DRGEP,temperature sensitivity analysis,rate of reaction and reactive path analysis.After that,it is combined with the reduced PRF sub-mechanism,the reduced toluene reference fuel kinetic model consisting of 220 reactions is developed.The modeled results are contrasted with experimental data of shock tube and homogeneous charge compression ignition engine,furthermore the reduced model is compared with the detailed model of Mehl,and result shows that the reduced kinetic model has good prediction ability.Availability analysis model of low temperature combustion engine is developed.Combined with the reduced TRF mechanism and Chemkin pro software,combustion characteristics of temperature,pressure and species mole fractions are calculated,and then processes of thermomechanical availability,chemical availability,work availability and availability destruction are solved.The effects of EGR and its main components on combustion process are studied,and the results show that work availability proportion increases as EGR ratio turns up.N₂ content in EGR has major influence on proportion distribution of availability terms.Meanwhile,the effects of boundary conditions such as intake temperature,intake pressure,equivalence ratio,compression ratio and engine speed on proportion distribution of availability terms are analysed.