涡流比对双燃料发动机燃烧过程影响的数值分析

A Numerical Simulation of Swirl Rate Effect on the Combustion of A Dual Fuel Engine

利用数值模拟的方法研究了涡流比对柴油引燃天然气发动机燃烧速率的影响。计算软件为经过修改的KIVA Ⅲ程序 ,计算对象为具有深盆形燃烧室的发动机。研究表明 ,当涡流比从 0依次增加到 2 5、5时 ,虽然缸内平均湍流强度增加 ,但最高湍流区湍流强度先升后降 ;由于燃烧速率赖于当地的湍流强度 ,而不是缸内的平均湍流强度 ,所以燃烧速率并不是一直随涡流比增大而增大。

A multidimensional numerical simulation is carried out to study the effect of swirl rate on burning rate of a diesel-natural gas dual-fuel engine with deep bowl combustion chamber using modified KIVA-Ⅲ code.The results show that:(1)when swirl rate increases form 0 to 2.5 and 5,the turbulence intensity in highest turbulence zone first increases then decreases,although the mean turbulence intensity increases;(2)the burning rate is proportional to the turbulent intensity in the burning region,therefore it does not always increases when swirl rate rise.In addition,by comparing two different injection styles,the ways of improving combustion by swirl of mixture are discussed.