基于三维CFD的RBCC发动机建模方法

Modeling method of RBCC engine based on three-dimensional CFD

RBCC发动机可多模态工作,能适应宽广的飞行包线,因而其火箭尾流剪切作用变化强烈、流道截面变化大,喷油规律复杂,给发动机建模与控制研究带来困难。针对RBCC发动机的地面直连实验构型,采用三维CFD计算分析RBCC流场特点,研究发动机状态变量特征,并基于CFD计算结合拟合法的建模思路,建立了RBCC状态空间模型,模型的计算结果与三维CFD的计算结果有较好的吻合度,均方差满足要求。研究表明,在一定范围内增加计算特征数据点个数,可提高建模精度,但当计算特征数据点的个数超过20时,继续增加点的个数对精度的提高非常有限。

RBCC engine can operate at multi-modes（ （ inject-,ramjet,scramjet and rocket as well） ） and adapt to a wide flight envelope,which is mainly resulted from the shearing action between the primary rocket plume and inlet air varies drastically. The cross-section along the flow path varies a lot for mounting the rocket,stabling the burning and accelerating the gases, and meanwhile the fuel is injected changing in both the amounts and the positions as well according to the operating mode. The complex driving-forces result in the difficulties to develop the performance model and to control RBCC.Based on the ground test configuration of RB-CC engine,the characteristics of flow field and state variables of RBCC engine were studied by using three-dimensional CFD,and then a state variable model with the method of CFD and linear fitting was developed.It is shown that the state variable model matches up with CFD calculations. Studies also show that modeling accuracy can be improved by increasing the data points till 20.