REGR成分对船用LNG发动机燃烧与排放特性的影响模拟

Simulation on Effects of REGR Composition on Combustion and Emission Characteristics of Marine LNG Engine

利用三维计算流体力学(Computational Fluid Dynamics,CFD)仿真软件CONVERGE,建立船用点燃式液化天燃气(Liquefied Natural Gas,LNG)发动机的三维仿真模型,探究废气重整再循环(Reformed Exhaust Gas Recirculation,REGR)成分及REGR率对LNG发动机燃烧与排放特性的影响。研究结果表明:在相同的REGR率下,随着REGR重整气中H_2含量的提高,使得着火时刻提前且发动机缸内燃烧速度加快,缸内最高燃烧爆发压力提升、NOx排放量增加,磁氢化合物排放量和CO排放量受REGR重整气成分和缸内流体共同作用呈先增加后减少的趋势。掺烧相同REGR重整气时,随着REGR率的提高,着火时刻提前且燃烧速率加快,升压率提高导致缸内最高压力提升,船舶排放尾气中NOx排放量和CO排放量提高,HC排放呈现先减后增的趋势。

A 3D Computational Fluicl Dynamics（ CFD） model is built with CONVERGE and used to explore the effects of Reformed Exhaust Gas Recirculation（ REGR） components and REGR ratio on the combustion and exhaust emission characteristics of marine spark ignition Liquefied Natural Gas（ LNG） engine. The experiments show that under given REGR ratio,the increase of H2 content in the reformed gas will result in earlier ignition,higher speed of in-cylinder combustion and higher maximum in-cylinder pressure. The emission of NOxalso increases as the H2 content goes higher. The combined effect of the REGE reformed gas components and the fluid in the cylinder makes the emissions of HC and CO to increase at first and then decrease. For same REGR reformed gas,higher REGR ratio results in earlier ignition,higher speed of combustion,improved rate of pressure rise and higher maximum in-cylinder pressure. The emissions of NOxand CO in the exhaust go up as the ratio increases. The emission of HC decreases first and then increases. The promotion effect of H2 on the combustion process is greater than that of CO.