突变截面燃烧室声腔纵向振荡频率规律分析

将药柱贴壁浇注的固体火箭发动机燃烧室简化为中间管型药两端容腔的形式,建立了突变截面H型声腔的物理模型,求解了此种声腔纵向振频的理论解和有限元解,以对称声腔与非对称声腔为对象,分析了一些关键几何尺寸对纵向声振频率变化的影响规律.计算结果表明,声振频率受装药长度与燃烧室长度的比值、装药内外径比值以及药柱浇注位置的共同影响.从合理的装药装填率考虑,初始振荡频率小于圆柱型声腔的振频,并随燃面退移连续增大.

Analysis on acoustic longitudinal oscillation frequency in combustion chamber with sudden change sections

Combustion chamber with case bonded propellant,often used in solid rocket motors,can be simplified into an "H" type sudden change section configuration with tube grain in the middle and cavities connected at both head end and aft end.In the paper,a physical model of "H" acoustic cavities was established;then the longitudinal frequency was calculated by theoretic and finite element model(FEM) methods.Symmetrical and unsymmetrical "H" acoustic cavities were used separately to investigate the influences of geometrical parameters on the oscillation frequency.The results indicate that the ratio of the length of grain to combustion chamber,the ratio of inner-outer grain radius and grain position have cooperative effects on the frequency.Considering the reasonable volumetric loading fraction of the grain,it is concluded that oscillation frequency,which is smaller than that in cylindrical cavity at beginning,increases continuously with burning surface regression.