有声腔燃烧室的声学特性实验

为了掌握声腔对燃烧室声学特性的影响规律，采用冷态实验方法，研究了带有轴向直圆孔声腔的模拟燃烧室的声学特性，其中声腔长度、开口面积比（声腔横截面积除以燃烧室横截面积）和个数均可调节.研究结果表明:燃烧室固有频率随声腔长度的增加而逐渐减小；声腔存在最佳深度，能够抑制一阶切向振型，该最佳深度不受声腔开口面积比影响，略小于1/4一阶切向波长；对抑制一阶切向振型而言，声腔存在最佳开口面积比，在本研究中约为0.17；声腔的分布对燃烧室的声学特性影响较大，相同开口面积比下，声腔个数越多，声波衰减越快. 

Experiment on acoustic characteristic of combustion chamber with acoustic resonators

In order to obtain influence of acoustic resonators on the acoustic characteristic of combustors, a model combustor with axial resonators was investigated experimentally in cold flow tests. The length, area ratio (section area of acoustic resonators divided by section area of combustor) and number of acoustic resonators were changeable in the experiments. It was found that the eigen frequencies of combustor decreased as the length of acoustic resonators increased. The results show that there exists an optimal acoustic resonator length for restraining 1T mode, which is independent from area ratio of acoustic resonators and a little smaller than quarter wave length of 1T mode. For restraining 1T mode, there also exists an optimal area ratio, which is 0.17 in present study. This also indicates that the distribution of acoustic resonators can dramatically affect the acoustic characteristic of a combustor, with acoustic wave decaying faster for more resonators at the same area ratio.