Abstract: On the test bench, single cylinder valve train is taken as the research object, and the sound power of diesel engine frontend is measured by using nearfield sound intensity method when each cylinder distribution mechanism is working. The contribution of single cylinder valve train excitation to diesel engine frontend noise is separated by using two experimental methods, and the accuracy of the two experimental methods is studied. The results show that the four valve units calculated by these two experimental methods cause more frontend noise power levels than the reference value. At 600r/min, the difference is 0.36dB(A), and when the speed increases to 1700r/min, the difference increases to 2.44dB(A). More accurate results can be obtained by the experimental method: the sound power at the front end of the engine when the valve mechanism of a single cylinder is used (4 cases) minus the sound power at the front end of the engine when no valve mechanism is operating. When the excitation force of the gear at the front end decreases, the frontend sound power level decreases roughly in parallel when the singlecylinder valve mechanism is working. When the threecylinder valve mechanism is working at the same time, the frontend sound power level increases at 800r/min, and decreases when the speed increases to 1600r/min.

Key words: diesel engine, valve train, contribution, sound power, vehicle and power

摘要： 在试验台架上，以单缸配气单元为研究对象，通过使用近场声强法测量各缸配气机构工作时柴油机前端的声功率，使用两种实验方法分离出单缸配气单元激励对柴油机前端噪声的贡献度，研究这两种实验方法的准确度。结果表明：这两种实验方法计算出来的四个配气单元引起的前端噪声声功率级都比基准值大，在600r/min时二者相差0.36dB(A)，转速升高到1 700r/min时，差值增加到2.44dB(A)，其中用单缸配气机构工作时前端的声功率(4种情况)减去无配气机构工作时前端的声功率的实验方法更为准确。当前端齿轮激励力减小后，单缸配气机构工作时前端声功率级大致平行减小，三缸配气机构同时工作时前端声功率级在800r/min时增大，转速升高到1 600r/min时减小。

关键词: 柴油机, 配气机构, 贡献度, 声功率, 车辆与动力