变循环发动机前可调面积涵道引射器的通流计算方法

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

关键词:  前VABI  通流计算  流线曲率法  变循环  一体化设计

Key words:  Forward VABI  Throughflow calculation  Streamline curve method  Variable cycle  Integrated design

摘要:

为了实现变循环涡扇发动机压缩系统的快速一体化气动设计，研究了变循环特征部件在一体化通流计算中的实现途径，针对其中的关键部件前可调面积涵道引射器(前VABI)，结合其工作机理和流线曲率法通流计算方法的特点，提出了一种通流模拟的思路，发展了不同应用条件下的计算方法，并基于汇流环管流动模型对计算方法的合理性和准确性进行了校验。计算结果显示，在不发生流动堵塞的情况下，前VABI的轴向调节和俯仰调节方式对变循环压缩系统中第一、二外涵道匹配工作特性的影响较小，匹配流量的最大误差小于0.2%，在计算中采用俯仰调节可以准确地模拟轴向调节时的真实特性。在通流计算中，当第一外涵道气流总压高于第二外涵道较多(核心机驱动风扇级增压比大)时，前VABI尾缘的通流计算站应该合理设置，以避免计算模型对流通能力的附加限制。前VABI的通流计算方法对第一、二外涵道流量匹配特性的计算误差小于1%(与CFD结果相比)，能够满足变循环压缩系统初始方案设计的需求。

Abstract:

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.