工艺水平对柴油机气道性能的影响

针对某直喷式柴油机在气道稳流试验时,所测不同气缸盖涡流比存在随气门升程的变化曲线相差较大的问题,对标准气道、气门座孔无倒角气道和倾斜气道分别进行了气道稳流试验数值模拟.标准气道模拟结果与试验结果的对比表明,数值模拟所得流量系数和涡流比与试验结果吻合较好,数值模拟具有一定的可信度.气门座孔无倒角气道和倾斜气道2种方案的模拟结果表明,其气道稳流试验所测涡流比变化范围大,是在气缸盖的生产过程中因机加工和铸造等方面的误差较大所致.

Influence of Technological Level on Intake Port Performance of Diesel Engine

To understand the cause of swirl ratio fluctuation among different cylinder heads of DI diesel en- gine, numerical simulation is carried out to study steady-state intake. Steady-state intake simulation has been made on the standard port, tangential port without valve seat chamfer and inclined tangential port. To compare the results of simulation and steady-state flow experimental testing, the same boundary conditions and evalua- tion methods are applied. Comparison shows that flow coefficient and swirl ratio from numerical simulation are consistent with those from testing, and the accuracy of simulation is acceptable. The numerical simulation of tangential port without valve seat chamfer and inclined tangential port indicates that swirl ratio fluctuation among different cylinder heads is caused by inadequate manufacturing accuracy.