基于数值定容弹方法的燃烧室声学特性研究

Investigation on Acoustic Characteristic of Thruster with Numerical Constant-Volume Bomb Method

为确定给定构型燃烧室最容易激发的声学振型,提出了能够实现大幅值非特定频率的"数值定容弹"模型。圆柱体内声学振型频率的预测值与理论结果偏差在7%以内。对姿轨控发动机推力室进行了数值定容弹激励,给出了推力室压力分布的时空演化,获得了多声学模态压力振荡及其最容易激发的声学振型。进一步研究了收缩比对推力室声学特性的影响。结果表明:随着收缩比增大,一阶和二阶切向声学振型的幅值增加,但对应的频率基本保持不变;而一阶纵向和一切-一纵声学振型的幅值减小,但对应的频率增大,当收缩比较大时,一阶纵向和一切-一纵声学振型消失。可见,与短粗构型相比,细长推力室构型有利于抑制切向声学振型。

In order to determine the most inspirable acoustic mode for a thrust chamber with given configuration,a＂numerical constant-volume bomb＂model was developed,which can achieve an artificial disturbance with high amplitude and non-specified frequency. Compared with the theoretical acoustic eigen-frequencies,the error of the predicted acoustic eigen-frequencies for a cylinder based on this model are less than 7%. The apogee attitude and orbit control thruster was stimulated by the numerical constant-volume bomb. The spatial and temporal evolution of pressure distribution in it were presented,and the pressure oscillations characterized by several acoustic modes were excited. Therefore the most inspirable acoustic mode was obtained. Furthermore,the effects of the contraction ratio of thrust chamber on the acoustic characteristic were investigated. With an increase of the contraction ratio,the amplitudes of the first tangential mode and the second tangential mode increase,while those of the first longitudinal mode and the mixed first tangential-first longitudinal mode decrease and they even do not appear any more when contraction ratio is larger. The frequencies of the first tangential mode and the second tangential mode keep constant while those of the first longitudinal mode and the mixed first tangential-first longitudinal mode increase as the contraction ratio increases. Compared with stumpy chamber,the slender chamber is helpful to restrain the tangential acoustic modes.