Numerical Simulation Of Diesel Combustion Process In Low Temperature Environment

The dynamic performance of diesel engine becomes poor at low temperature environment.Especially in high latitude areas,the winter temperature here is particularly low,which causes the decrease of power output.It is significantly meaningful to investigate the diesel combustion process under low temperature and research the influence of ambient temperature on the diesel engine performance.Besides traditional methodology,the numerical simulation by computer software is also commonly used to study combustion process.In this paper,three-dimensional numerical modeling of engine combustion process is introduced.The mechanism of turbulence model, atomization model and combustion model are explained in detail.By adopting 3-dimensional CFD software FIRE(developed by AVL Co.,Ltd, Austria),The combustion process with different temperature parameters, such as,intake air temperature,fuel temperature and cylinder wall temperature is simulated.The combustion characteristics,including temperature and fuel distribution within cylinder as well as heat release rate is obtained.The results indicate:(1) The intake air temperature has the greatest effect on the combustion.If the intake air temperature decreases,the fuel evaporating rate slows down,the fuel penetration distance becomes shorter,the fuel jet impingement weakens.In addition,the ignition time is delayed;the in-cylinder pressure and temperature decreases;the emission of NO_x and soot are obviously reduced. (2) The influence of fuel temperature and intake air temperature on combustion process is indicated by fuel jet penetration distance.The lower the fuel temperature,the longer the fuel jet penetration distance,the more frequently the fuel impingement happens.(3) The decreasing of cylinder wall temperature enlarges the heat transfer from charge to cylinder wall,which delays combustion timing,as a result,the temperature and pressure within cylinder decreases.As a result,the decrease of ambient temperature causes the decrease of in-cylinder pressure and in-cylinder temperature,the indicated work and power output of the engine decline,and the dynamic performance becomes worse,to maintain its original power output,the fuel supply will be corrected,the lower the ambient temperature,the more the fuel supply be needed。...