基于数值模拟的某柴油机燃烧室优化研究

A Study on Optimization of Diesel Engine Combustion Chamber Based on Numerical Simulation

用AVL FIRE软件建立了柴油机喷雾燃烧过程研究的计算模型,根据模型分析了燃烧室关键特征对经济性和排放的影响,并设计了燃烧室优化方案。研究发现,在A100工况,优化方案改善了油气混合状况,提高了空气利用率,并加速了燃烧后期速度,使得经济性得到提高,同时NO_x排放也有所增加;而在部分负荷A25工况,优化方案降低了燃烧室碗底的流动速度,减少了壁面传热损失,经济性得到提高,同时NO_x排放也有所降低。发动机台架试验结果表明,相对于原始方案,优化方案的外特性油耗平均降低了约2.0g/(kW·h);ESC循环加权油耗降低了2.2g/(kW·h),且加权NO_x比排放相当。

The calculation model of spray and combustion of a diesel engine was established by the AVL FIRE software.Based on the model,the influence of the key characteristics of combustion chamber on fuel economy and emissions was analyzed,and the optimization of combustion chamber was developed.The study shows that at full load and speed A,the optimized scheme improves the fuel-air mixture,increases the air utilization rate and accelerates the post-combustion speed.Thus improving the fuel economy and increasing the NO x emissions.At the 25%load of speed A,the optimized scheme reduces the air flow rate at the bottom of the combustion chamber bowl thereby reducing the wall heat transfer loss.This allows to have higher fuel economy with a reduction of NO x emissions.The engine experiment indicates that compared with original scheme,the fuel consumption of the optimized scheme is reduced by 2.0 g/(kW·h)or so under full load operating conditions,the ESC 13 modes weighed fuel consumption is cut down by 2.2 g/(kW·h),and the weighted NO x emissions are also equivalent.