【摘要】 以某重型柴油机为研究对象，通过仿真计算，探究了燃烧室结构和喷孔锥角对发动机燃烧过程的影响，提出了提高柴油机热效率的技术方案.结果表明：通过减小凹坑半径及凹坑深度提高压缩比可以减少缸内过稀区，在压缩比提高和缸内空间利用率提高的共同作用下，热效率提高了0.8%；随着燃烧室凹坑边缘直径增大，进入燃烧室挤流区燃油增多，热效率先升高后降低，凹坑边缘直径为97 mm时热效率最高；随着喉口直径减小，燃油达到壁面距离缩短，挤流区当量比增大，油耗先降低后升高，喉口直径为69 mm时油耗最低.当进入挤流区燃油过少时，可以通过增大凹坑边缘直径及减小喉口直径改善混合气分布，提高热效率.喷孔锥角也是影响混合气分布的重要因素，改变燃烧室结构后需要优化喷孔锥角以获得最佳热效率.采用凹坑边缘直径为97 mm、喉口直径为69 mm的燃烧室方案以及144°的喷孔锥角，热效率相比原机提高1.8%.更多还原

【Abstract】 A numerical simulation study is conducted to explore the influence of combustion chamber structure and nozzle angle on the combustion process of a heavy-duty diesel engine,and a scheme to improve the diesel engine thermal efficiency is proposed. Results show that increasing the compression ratio by reducing piston cup radius and piston cup depth can reduce the lean zone in the cylinder. With the increase in the compression ratio and the utilization rate of in-cylinder space,the thermal efficiency increases by 0.8%. More fuel enters the top of the combustion chamber,and the thermal efficiency increases first and then starts to drop with the increasing piston cup diameter(edge). When the piston cup diameter(edge) is 97 mm,the thermal efficiency is the highest. The distance between the fuel and the wall is shortened,the equivalent ratio in the squeeze zone increases,and the brake specific fuel consumption decreases first and then starts to increase with the decreasing contracted throat diameter. When the contracted throat diameter is 69 mm,the brake specific fuel consumption is the lowest. When there is little fuel entering the top of the combustion chamber,a bigger piston cup diameter(edge) and a smaller contracted throat diameter can make a more reasonable distribution of the fuel-air mixture,and the thermal efficiency will increase. The nozzle cone angle is also an important factor affecting the mixture distribution. After changing the combustion chamber structure,it is necessary to optimize the nozzle cone angle to obtain the best thermal efficiency. When the piston cup diameter(edge) is 97 mm,the contracted throat diameter is 69 mm,and the nozzle cone angle is 144°,the thermal efficiency will increase by 1.8%.更多还原