隔板喷嘴对燃烧室切向声学模态作用研究

Effects of Baffled Injectors on TransverseAcoustic Mode in a Combustor

关键词:  隔板喷嘴  燃烧不稳定性  理论模型  声导纳  切向声学振荡模态

Key words:  Baffled injectors  Combustion instability  Theoretical model  Acoustic admittance  Transverse acoustic mode

摘要:

隔板喷嘴通过改变燃烧室声学特性，在抑制火箭发动机高频燃烧不稳定性方面具有重要作用。然而，目前并没有合适的理论模型，来预测隔板喷嘴对燃烧室声学特性的作用规律。为了获得隔板喷嘴对燃烧室内切向声学振荡模态作用的理论模型，通过理论推导隔板喷嘴声导纳，利用分离变量法结合实验验证，研究了径向隔板喷嘴间隙、数量及长度对燃烧室一阶切向声学振荡模态的影响。结果表明，存在最佳隔板喷嘴间隙，对燃烧室内一阶切向声学振荡模态抑制效果最佳；随着隔板喷嘴数量或长度的增加，燃烧室内一阶切向声学振荡模态频率和幅值均呈现下降趋势，且弱化了隔板喷嘴间隙的作用效果。该模型为隔板喷嘴研究奠定了一定的理论基础，研究结果为火箭发动机隔板喷嘴设计提供指导。

Abstract:

Baffled injectors have played an important role in suppressing high-frequency combustion instability in liquid rocket engines by changing acoustic characteristics of the combustion chamber. However，no appropriate model can successfully predict effects of baffled injectors on acoustic characteristics of a combustion chamber. In order to obtain the theoretical model of effects of baffled injectors on the transverse acoustic mode of the combustion chamber，the acoustic admittance of baffled injectors was deduced theoretically. Effects of gap，number and length of baffled injectors on the first transverse mode of the combustion chamber were studied by means of separation variable method and experiment. Results show that the maximum suppression effects on the first transverse acoustic mode occurs at a certain gap. The frequency and amplitude of the first transverse acoustic mode decrease with increasing the number and length of baffled injectors. Furthermore，suppression effects of gap are weakened with the increasing of number or length of baffled injectors. This model lays a theoretical foundation for the study of baffled injectors，and results offer some guidance to the design of baffled injectors in liquid rocket engines.