Volume 40, Number 2, April 2022
|Page(s)||306 - 315|
|Published online||03 June 2022|
A method for numerical simulation of mode transition process of compression system of variable cycle engine based on throttle valve model
School of Power and Energy, Northwestern Polytechnical University, Xi’an 710072, China
In order to study the aerodynamic characteristics of the compression system of a variable-cycle engine during its mode transition, a low-order model was established based on the throttle valve theory to describe the throttle characteristics of the mode selection valve at its different opening degrees. The model was applied to the outlet of a double-bypass variable-cycle fan in the form of characteristic boundary. A 3D low-order hybrid computational model was established for the numerical simulation of flow fields in the mode transition process of the compression system. The calculation accuracy and effectiveness of the throttle valve model were verified by comparing its calculation results with those of the 3D valve model. The simulation method was further applied to the prediction and analysis of the fan performance variation during the single and double bypass mode transitions of the variable-cycle fan. The simulation results show that: the throttle coefficient, which represents the throttle intensity, has something to do only with the flow area ratio of the valve but has nothing to do with its angle. Therefore, the throttle valve model is universal for valves with different motion angles; the throttle valve model can accurately predict the variation trend of the aerodynamic characteristics of the fan in all stages of the mode transition process. Compared with the 3D valve model, the prediction error of the pressure ratio of the fan in all stages is less than 1.93%, and the efficiency error is less than 1.05%. In the valve closing process, the second-stage rotor performance changes more dramatically, and the first-stage rotor performance changes with lag.
为了研究变循环发动机压缩系统模式转换过程中气动特性变化规律，基于节流阀理论，建立了能够描述不同开度下模式选择阀门节流特性的低阶模型。并将该模型以特征边界的形式应用于某双涵道变循环风扇的外涵道出口，建立了用于模式转换过程流场数值仿真的全三维/低阶混合计算模型。通过与全三维阀门建模的计算结果对比，验证了节流阀计算模型的精度和有效性，进一步将此方法用于该变循环风扇单-双涵道模式转换过程风扇性能变化预测及分析，得到以下结论: 表征节流强度的节流阀系数只与阀门流通面积比有关，与阀门角度无关，因此该节流阀模型对于不同运动角度范围的模式选择阀门具有普适性; 节流阀模型方法能够准确地预测模式转换过程中风扇整机及各级气动特性的变化趋势，与阀门三维建模方法相比，对风扇整机及各级压比预测误差不超过1.93%，效率误差不超过1.05%;在阀门关闭的过程中，第二级风扇性能变化更剧烈，第一级风扇性能在阀门开度较大时气动性能基本不变，开度较小时才出现明显变化，存在滞后性。
Key words: variable cycle engine / mode transition / throttle model / numerical simulation
关键字 : 变循环发动机 / 模式转换过程 / 节流阀模型 / 数值仿真
© 2022 Journal of Northwestern Polytechnical University. All rights reserved.
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