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Numerical Analysis of Combustion Instability in Hybrid Rockets

混合火箭燃烧不稳定性的数值分析

基本信息

批准号：
18J14267
负责人：
KARTHIKEYAN GOUTHAM
金额：
$ 0.38万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for JSPS Fellows
财政年份：
2018
资助国家：
日本
起止时间：
2018-04-25 至 2019-03-31
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18J14267/
关键词：
Hybrid Rocket Combustion Stability Numerical Modeling

项目摘要

A computational model of a hybrid rocket motor has been developed for the purpose of simulation of internal ballistics and transient behavior such as combustion instabilities. The numerical model is validated against experiments for prediction of steady state regression rates. In the unsteady time-dependent simulation, the unsteady convective heat flux is modelled by the application of a temporal boundary layer delay of the steady state form of wall heat flux to the changes in the regression rate. With analogy to a simple non-linear oscillating system, it is shown that such a delay can result in negative damping in the system causing self-excited oscillations. Upon this modelling, an unstable region ensues. At first an oscillating periodic increase in the regression rate and chamber pressure is observed (linear regime), which then proceeds into a non-linear limit cycle. A positive DC shift in the chamber pressure is also observed. The frequencies of different natural modes (including the intrinsic hybrid oscillation mode) predicted by the model are found to be in good agreement with theoretical prediction. Parametric analyses have been carried out with different motor configurations. Their effect on the predicted values of DC shift and RMS amplitude is reported. Comparison against the prediction of non-linear limit cycle amplitude is performed for experimental data in literature, showing good agreement. It is concluded that using such a novel approach, a hybrid rocket motor designer can study the stability characteristics of the motor being designed.

建立了混合动力火箭发动机的计算模型，用于内弹道和燃烧不稳定性等暂态行为的模拟。通过实验对数值模型进行了验证，预测了稳态回归速率。在非定常时变模拟中，非定常对流热流通过采用稳态形式的壁面热流的时间边界层延迟来模拟回归速率的变化。通过对一个简单的非线性振动系统的类比，证明了这种时滞可以导致系统的负阻尼，从而引起自激振荡。在这种模型下，一个不稳定的区域随之而来。首先观察到衰减率和燃烧室压力的周期性振荡增加(线性区域)，然后进入非线性极限环。此外，还观察到了腔室压力的正直流漂移。模型预测的不同固有振型(包括固有混合振型)的频率与理论预测值吻合较好。对不同电机配置进行了参数分析。报道了它们对直流漂移和均方根幅值预测值的影响。将实验数据与文献中预测的非线性极限环幅值进行了比较，结果吻合较好。结果表明，采用这种新的方法可以使混杂火箭发动机设计者研究所设计发动机的稳定性特性。