用混合燃烧模型研究缸内直喷醇类燃料发动机的燃烧

通过引入湍流燃烧延迟系数，将单步不可逆反应模型和漩涡破碎燃烧模型结合在一起，建立了一个新的混合燃烧模型．利用混合燃烧模型对一台采用火花点火、缸内直喷、周向分层燃烧系统的醇类燃料发动机的燃烧过程进行了三维数值模拟，计算所得的缸内压力和燃烧放热速率与实验结果吻合良好．模拟结果表明，在缸内直喷醇类燃料发动机中，混合气能稳定地实现由浓到稀的周向分层，醇类燃料高的汽化潜热导致混合气温度较低，燃烧过程中预混燃烧与扩散燃烧并存，燃烧速率非常快．

Numerical Investigation on Combustion Process in a Spark-Ignited Direct-Injection Alcohol Engine via Hybrid Combustion Model

A new hybrid combustion model, combining a single-step irreversible combustion reaction with eddy breakup (EBU) model by introducing a delay coefficient of turbulent combustion, is established. Three-dimensional numerical simulation of the combustion process in an alcohol engine, with a new type of spark-ignited direct-injection circularly stratified-charge combustion system, is carried out. The computed pressure and heat release data coincide with the experimental results well. The simulation results show that the stratification concentration from rich to lean of air-fuel mixture downstream along the direction of air swirl motion can be formed stably in the alcohol engine. The higher latent heat of evaporation of alcohol fuels results in a lower air-fuel mixture temperature. The premixed and diffusive stages coexist during the combustion process, and the combustion proceeds very stably and rapidly.