Throughflow Calculation Method of Variable Cycle Engine Forward Variable Area Bypass Injector

To design a variable cycle compression system's components in a rapid and integrated way, an integrated throughflow calculation platform was built and methods of simulating the variable cycle character components were researched. For the critical forward variable area bypass injector (VABI), a throughflow model was newly built by considering its working principles and the characteristic of streamline curve throughflow method. Different calculation schemes were developed for various application situations. The rationality of the model and accuracy of the numerical method was verified by CFD results. The simulation results show that when the flow is not choked, the way of adjusting forward VABI, axial or pitching, has little effect on matching characteristics of first and second bypass. The maximum difference in mass flow is less than 0.2%. So axial adjustment of forward VABI can be accurately simulated by pitching adjustment in throughflow calculation, which is readily programmed by streamline curvature method. In order to avoid additional mass flow limits attached by the calculation model when the total pressure of first bypass flow is much higher than that of second bypass flow, i.e. the pressure ratio of core-driven fan stage upstream of first bypass is large, the profile of quosi-orthogonal at forward VABI trailing edge should be carefully determined. The mass flows calculated by the new throughflow method for both first and second bypass are within error of 1% when compared to CFD results. The new throughflow method can meet the needs of variable cycle compression systems' preliminary design.