为了提高某商用车柴油机的燃油经济性，首先建立缸内三维燃烧模拟模型，然后根据模拟结果制作活塞，开展压缩比和燃烧室形状对柴油机燃油经济性影响的试验研究。结果表明：对于不同类型的燃烧室形状，油耗对油嘴凸出高度的敏感度不同；在循环压力峰值不变的约束下，仅提高压缩比而不提高燃烧室的放热速率，无法提高燃油经济性，而提高压缩比耦合改进燃烧室形状，缩短燃烧持续期，可以有效降低油耗；提高压缩比的同时提高循环压力峰值，可有效降低油耗，且高压缩比燃烧室可在降低油耗和控制NO_x排放之间获得更好的平衡。试验测试验证了模拟研究结果，高压缩比燃烧室CR18.6的有效燃油消耗率相比基础燃烧室CR16.8降低，其中1 300 r/min全负荷工况有效燃油消耗率降低1.42%，同时NO_x排放降低4.58%。

In order to improve the fuel economy of commercial vehicle diesel engine, three-dimensional simulation model of in-cylinder combustion was built to study the effects of compression ratio and combustion chamber shape on fuel economy. Then pistons were manufactured and tested according to the simulation results. The results show that the fuel economy of different chamber shapes has different sensitivity to nozzle tip protrusion. Under the constant cycle pressure peak, the fuel economy will not improve only by increasing the compression ratio without increasing the heat release rate of chamber, and the fuel consumption will reduce by increasing compression ratio coupling with optimizing the chamber shape to shorten the combustion duration. Increasing the compression ratio can reduce fuel consumption effectively by combining with increasing the cycle pressure peak, and a high compression ratio chamber can achieve a better balance between fuel consumption reduction and NO_x emission control. The experimental measurement verifies the simulation. The BSFC of CR18.6 chamber with a high compression ratio is lower than that of CR16.8 base chamber. The BSFC and NO_xemission of CR18.6 reduce by 1.42% and 4.58% respectively at full load of 1 300 r/min.