边界条件对柴油机瞬态工况燃烧特征参数的影响

Influence of Boundary Conditions on Diesel Combustion Parameters under Transient Conditions

为了建立瞬态工况下边界条件与发动机燃烧特征参数、热效率及排放的基本映射关系,在一台增压柴油机上试验研究了以喷射正时和喷油压力作为单一燃烧边界条件与燃烧特征参数及其主要性能参数的影响关系。试验结果表明:喷油正时对瞬态工况下燃烧重心(CA50)和压力升高率峰值(dpmax)的影响较大,二者近乎成线性变化,而喷油压力对CA50的影响相对较小,但热效率和烟度排放对喷油压力却极为敏感;喷油正时和喷油压力所控制的CA50都各有一个合适的区域使发动机的可靠性、热效率、烟度及NOx排放具有良好的平衡关系;dpmax和NOx排放随着ΔCA50的减小成线性增加,而烟度和热效率与ΔCA50的关系因燃烧边界条件的不同而不同。

In order to set up a basic mapping relationship of boundary conditions with the combustion characteristics and performance parameters of diesel engines under transient conditions,the influence of combustion boundary conditions including injection timing and injection pressure,on diesel combustion characteristics and performance parameters had been experimentally analyzed using a heavy-duty turbocharged diesel engine.The results indicate that injection timing has a significant effect on CA50 and dpmax with a quasi-linear change while injection pressure has a less impact on CA50 and a strong impact on thermal efficiency and smoke emission.The optimal trade-off among the reliability,thermal efficiency,smoke and NOxemissions for CA50 controlled by injection timing and injection pressure in a suitable area can be acquired under transient conditions.Besides,the dpmaxand NOx emission would quasi-linearly increase with the decrease ofΔCA50,however,the change of smoke and thermal efficiency withΔCA50is different depending on combustion boundary conditions.