小排量增压天然气发动机的燃烧特性

Combustion characteristic of a downsized turbocharged compressed natural gas engine

为在不影响发动机性能指标的前提下,减少尾气中的二氧化碳和其他气体污染物排放,开发了一款由小型增压汽油发动机经过二次开发而成的压缩天然气(CNG)气道喷射(PFI)点燃式发动机。定量分析了小型增压天然气发动机的燃料性能优势,降低爆震强度,优化了压缩比,提高了燃烧效率。爆发压强控制在12 MPa以下,最大扭矩为180 Nm;在转速为3 000 r/min时,该天然气发动机的扭矩与原型机处于同一水平。当采用优化后的压缩比应用于CNG模式时,有效热效率达到了38%。因此,与汽油相比,CNG模式能够令二氧化碳排放减少24.2%,里程燃油成本节省46.4%。

A turbocharged spark-ignition engine with port fuel injection(PFI)was developed suing compressed natural gas(CNG)based on a secondary development for a downsizing gasoline engine to reduce both vehicle tailpipe CO2emissions and other exhaust gas emissions without compromising driving performance.This paper quantified the advantage of fuel performance characteristics of the downsized CNG engine with reduced knock sensitivity,optimized compression ratio,and improved combustion efficiency.While peak cylinder pressure was controlled below12MPa,peak torque180Nm,same level as gasoline variant,was realized from3000r/min.With adapted compression ratio for CNG operation,effective combustion efficiency is over38%,which is even higher than turbocharged gasoline direct injection(TGDI)version.Therefore,compared to gasoline application,operation with CNG will lead to24.2%of CO2emission reduction as well as46.4%of mileage-specific fuel cost saving.