基于液滴高压蒸发理论的变时滞燃烧室动力学建模与研究

Modeling and research on variable time lag combustion chamber dynamics based on droplet high-pressure evaporation theory

为实现燃烧室组件的精确建模及其动力学特性的仿真研究,以零维时滞燃烧室模型为基础,考虑燃烧室内喷射、雾化、蒸发、混合、化学反应过程,采用针栓喷注器SMD(Sauter Mean Diameter,索特尔平均直径)经验关联式以及液滴高压蒸发理论对液氧/甲烷推进剂组合的燃烧时滞进行求解,建立了基于液滴高压蒸发理论的变时滞燃烧室模型。基于1 kg/s级推力室开展热试车验证了变时滞燃烧室模型的准确性,结果表明:所建立的变时滞燃烧室模型可以较为准确地预测燃烧室的压力以及温度动态响应过程,与试验结果相比,稳态压力以及温度误差均在6%以内,压力参数动态响应时间的误差在14%以内,仿真结果具有较高的精度。基于变时滞燃烧室模型开展仿真研究,研究发现:液氧液滴初始粒径以及燃烧室温度作为影响液氧液滴寿命的主要因素,主导着液氧时滞的变化;变时滞模型可以根据工况参数动态计算推进剂燃烧时滞,启动初期喷注器雾化效果较差,液滴最大粒径达到800μm,且燃烧室温度低,进而导致燃烧时滞偏大,最大达到了1100 ms,约为稳定工作状态下燃烧时滞的40倍。本文所建立的变时滞燃烧室模型可根据工况参数对燃烧时滞进行动态计算,相较于传统时滞模型,其燃烧时滞的变化趋势更符合发动机实际工作过程,同时其室压的响应时间、稳态值也更接近实验值,该模型未来可为实际发动机时序设计等提供仿真支撑。

A variable time lag combustion chamber dynamic model was established which considered the processes of injection,atomization,evaporation,mixing,and combustion in the combustion chamber.The liquid oxygen/methane propellant combination combustion time lag was solved using an empirical correlation formula of the pintle injector SMD(Sauter Mean Diameter)and the droplet high-pressure evaporation theory.Based on the zero-dimensional time lag combustion chamber model and liquid oxygen time lag,the variable time lag dynamic combustion chamber model based on the liquid droplets high-pressure evaporation theory was established.Hot test was carried out on a 1 kg/s level thrust chamber to verify the accuracy of the established model.The results show that the established model can accurately predict the combustion chamber pressure and temperature dynam⁃ic response process.Compared with the experimental results,the errors of steady-state pressure and temperature are within 6%,and the pressure dynamic response time error is also within 14%.The results have high accuracy.Based on the established model,simulation research was conducted,and it is found that the liquid oxygen initial droplet size and the chamber temperature are the main factors affecting the lifetime of liquid oxygen droplets,which dominate the variation of liquid oxygen time lag.Due to the fact that the time lag of the established model is calculated based on the spray combustion process,the atomization effect of the injector is poor during start-up,and the maximum droplet size reaches 800μm.And the chamber temperature is also low,resulting a maximum combustion time lag of nearly 1100 ms,which is about 40 times the time lag in steady-state operation.The vari⁃able lag model established can dynamically calculate the combustion lag based on operating parameters.Com⁃pared with the traditional time lag model,the combustion lagchanging trend in this model can more accurately re⁃flect the actual engine working process.Additionally,the response time and steady-state values of chamber pres⁃sure are closer to experimental values.In the future,this model can provide simulation support for the design of actual engine timing,etc.