支板/凹腔组合稳焰器耦合机制研究

Coupling Mechanism of Strut/Cavity Combined Flame Stabilizer

关键词:  火箭基组合循环发动机  火焰稳定  回流区  旋涡结构  质量输运

Key words:  Rocket based combined cycle engine  Flame stabilization  Recirculation zone  Eddy structure  Mass transport

摘要:

针对典型火箭基组合循环（Rocket Based Combined Cycle，RBCC）发动机高效稳定燃烧问题，对模型燃烧室支板/凹腔组合稳焰器进行了三维数值模拟，并结合局部流动特性、燃烧释热规律、流场旋涡结构以及质量输运特性，分析了飞行马赫数6.0条件下支板/凹腔组合稳焰性能以及耦合作用机制。研究发现：凹腔稳焰能力受凹腔与主流燃气之间的质量输运特性影响；而引入支板后，支板尾缘的螺旋上升式旋涡结构使得燃料由支板回流区向凹腔回流区转移，燃料在回流区内的停留时间增加，掺混效果增强，凹腔内局部释热增加。在不同旋涡结构的作用下，凹腔与主流间质量交换率约占来流空气流量的10%~20%。较优的旋涡结构和质量输运特性将使稳焰区燃温提升9%，燃烧效率提升超过10%。因此，支板/凹腔组合稳焰器稳焰性能由局部旋涡结构和燃气质量输运特性共同影响。当支板/凹腔间距缩短时，支板/凹腔组合稳焰器耦合作用更强，燃烧稳焰性能更佳。

Abstract:

Aiming at the problem of efficient and stable combustion of a typical Rocket Based Combined Cycle （RBCC） engine， three-dimensional numerical simulation of strut/cavity combined flame stabilizer in the model combustion chamber was carried out. Based on local flow characteristics， regularities of heat release， eddy structure and mass transport characteristics， the flame stabilization performance and coupling mechanism of the strut/cavity flame stabilizer under the flight Mach number 6.0 were analyzed. The study shows that flame stabilization performance of the cavity is affected by the mass transport characteristics between cavity and main flow. However， with the addition of strut， the spiraling eddy structure at the trailing edge of the strut makes the fuel transfer from the recirculation zone of strut to that of cavity. Then the residence time of fuel in the recirculation zone increases， mixing efficiency is enhanced and local heat release increases in cavity. Under the action of different eddy structure， the mass exchange rate between cavity and main flow accounts for about 10% to 20% of the incoming air flow. Better structure of eddy and characteristics of mass transport will increase combustion temperature by 9% in flame stabilization zone and increase combustion efficiency by more than 10%.Therefore， the flame stabilization performance of the strut/cavity combined flame stabilizer is affected by local eddy structure and gas mass transport characteristics. When the distance between the strut and cavity is shortened， the coupling effect between them is stronger and the performance of combustion and flame stabilization is better.