燃烧室声腔结构对固体火箭发动机热声振荡影响的实验研究

The thermo-acoustic instability combustion in the combustion chamber of solid rocket motor will cause serious damage to normal operation of the motor. In order to deeply understand the influence mechanism of thermo-acoustic instability, a plane burner thermo-acoustic experimental device was designed based on the subscale solid rocket motor. The effects of chemical equivalence ratio and chamber structure on thermo-acoustic oscillation were studied by multi-working condition tests. For the combustion chamber with 920 mm length and 150 mm inner diameter without simulated grain, the amplitude of thermo-acoustic oscillation first increases and then decreases with the increase of chemical equivalence ratio. The amplitude can reach the maximum value 35.4 Pa when ϕ= 1.31.For the combustion chamber with simulated grain, with the change of chemical equivalence ratio, thermo-acoustic instability mode conversion phenomena appears in the combustion chamber:thermo-acoustic instability changes from first-order thermo-acoustic instability to second-order thermo-acoustic instability. The influence of grain inner diameter on the frequency and amplitude of two unstable modes was compared and analyzed. The damping effect of grain structure on thermo-acoustic oscillation was further analyzed by measuring the pressure attenuation coefficient. It is found that the damping effect of grain structure on thermo-acoustic oscillation decreases with the increase of grain inner diameter. The results show that during the working process of motor, with the regression of burning surface, the inner diameter of the grain becomes larger and the damping effect becomes smaller, resulting in the reduction stability of the motor at the end of working process, and the combustion instability is more likely to occur.