大直径液氧煤油发动机燃烧室结构和隔板型式对声学特性的影响

Effects of Structural Parameters and Baffle Patterns on Acoustic Characteristics of Combustion Chamber for Large Diameter LOX/Kerosene Engine

关键词:  大直径燃烧室  液氧煤油发动机  收敛段  声学特性  隔板型式

Key words:  Large diameter combustion chamber  LOX/kerosene rocket engine  Convergent section  Acoustic characteristics  Baffle pattern

摘要:

随着火箭发射任务轨道高度和载荷质量的提高，发动机推力和燃烧室直径增大，使燃烧室固有声学振型越发复杂。燃烧室收敛段、抗脉动隔板及其结构型式会显著影响燃烧室的声学特性，进而改变发动机的燃烧不稳定性裕度。为了研究燃烧室结构和隔板型式对声学特性的影响，建立了燃烧室声学有限元模型，并通过单喷嘴声学实验验证了仿真模型的准确性。研究了燃烧室收敛段和一周六径隔板对燃烧室声学特性的影响，重点分析了RD-170和F-1发动机不同隔板型式下燃烧室的声学特性，从声压分布的角度分析了其隔板设计的合理性。结果表明：添加收敛段后，燃烧室的1L和1T1L振型的频率分别提高了14%和17%。RD-170发动机的周向隔板位于2R振型速度波腹位置；F-1发动机所采用的两周八径13分区隔板不仅减小了2R振型速度波腹的半径，而且使切向振型的声压极值面积最小。双十字隔板使F-1发动机燃烧室中出现径向振型切向化的趋势。

Abstract:

Due to the increase of orbit height and load quality of launch mission， the engine’s thrust and diameter of combustion chamber increased， which makes its acoustic oscillation modes more and more complicated. Convergent section of combustion chamber， anti-pulsating baffle and its structural patterns could not only significantly affect the chamber’s acoustic characteristics， but also indirectly impact the combustion instability margin. In order to study the effects of structural parameters and baffle patterns on acoustic characteristics， a finite element simulation model of the combustion chamber is established. Firstly， the accuracy of the finite element model is verified by a single nozzle acoustic experiment. On this basis， the influence rules of convergent section of combustion chamber and one hub and six radial baffle are analyzed. The design rationality of baffle patterns for RD-170 and F-1 engine is emphatically investigated in terms of sound pressure distribution. The results show the frequency of 1L and 1T1L mode increases by 14% and 17% ， respectively， when convergent section of combustion chamber is considered. For RD-170 engine， the hub baffle locates at the position of 2R mode acoustic velocity anti-node. For F-1 engine， the 13-compartment baffle could not only reduce the radius of 2R mode acoustic velocity anti-node， but also minimize the area of pressure amplitude in tangential modes. The trend of radial vibration mode changing to tangential vibration mode is observed in F-1 engine’s combustion chamber with double cross baffle.