In order to calculate the sound field in the cylinder more accurately, acoustic reflection coefficient of combustion chamber wall, as an important parameter of boundary conditions, should be calculated separately. The acoustic reflection coefficients of different structures and their application were analyzed, and the expression of cylindrical structure of three-media reflect coefficient was derived based on the actual situation of combustion process. The three-media reflect coefficient was discussed under different conditions, and it was confirmed that the range of cylindrical structure reflection coefficient was 0.977-1.0. The effects of different reflection coefficients were calculated with the help of the wave equation which can describe the cylinder pressure fluctuation. The results show that when the wave frequency in the combustion chamber is below 10 000 Hz, the reflection coefficient of the cylindrical structure can more accurately describe cylinder pressure fluctuations.%为了对气缸中的声场进行更加准确的计算,燃烧室壁面声学反射系数作为重要参数,需要单独讨论.分析不同结构的声反射系数及其应用范围,结合内燃机燃烧过程的实际情况,推导出柱面结构下的3层介质反射系数表达式,对不同参数条件下的3层结构反射系数进行计算讨论,确认了柱面结构反射系数的取值范围为0.977～1.0.结合能够描述缸内压力波动变化情况的波动方程,分别计算了不同反射系数对压力波动的影响,结果表明,在燃烧室内声学波动频率约为10 000 Hz以下时,采用柱面结构反射系数能够更加准确地描述缸内的压力波动.
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