Calculation and analysis by modular modeling for frequency characteristics of a LOX/LH2 rocket engine
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摘要: 为分析某型氢氧火箭发动机频率特性，建立了主、副系统耦合的线性化动态模型：通过一维分布参数模型描述管路特性；采用考虑熵波的绝热流动模型描述燃烧组件特性；推导了转速脉动反馈的传递函数，采用考虑气蚀效应的模型描述泵组件；采取有理近似式表达分布式参数模型和热力组件中的超越函数。在Simulink平台上建立模块化仿真模型，采用扫频法获取频率特性，并利用热试车数据进行验证。结果表明，所开发的模块化仿真库对工程应用十分友好，可用于分析发动机系统低频至中频频率特性；该型发动机在燃气脉动激励下将产生主系统10、165 Hz和副系统124、204 Hz的频率响应；考虑转速脉动反馈计算所得特征频率更加准确；增加泵前管路局部流阻和燃气发生器喷注压降，可提高发动机系统稳定性。Abstract: In order to analyze the frequency characteristics of a LOX/LH2 rocket engine，an engine linearized dynamic model with main and subsidiary systems coupled was developed，including pipelines described by one-dimensional distributed parameter model，combustion components described by adiabatic flow model considering entropy wave and pumps components were described by model considering cavitation.The transcendental functions in thermodynamic component models and distributed parameter models were expressed by rational approximation.After establishing modular simulation model in Simulink，a frequency sweep was conducted to obtain the frequency characteristics，and hot test data was implemented in validation.The result showed that the modular simulation library is user-friendly，and is capable of analyzing the low to medium frequency characteristics of the engine system.Under the excitation of gas pulsation，the engine produced the frequency response of 10 and 165 Hz in main system and 124 and 204 Hz in subsidiary system.The calculated characteristics frequency showed better accuracy while considering the rotation speed feedback.The stability of the engine system was improved while increasing the local resistance of the pipeline before the pump or increasing the pressure drop of the gas generator injection.
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Key words:
- frequency characteristics /
- modular modeling /
- coupled system /
- stability analysis /
- approximate model
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