Abstract Gas generator is an essential part of gas generator cycle Liquid Propellant Rocket Engine (LPRE). While designing the Gas Generator (GG), the selection of an unoptimized characteristic length result in an increase in mass flow rate of propellants required to drive turbine. As the exhaust of the gas generator is of little importance in the thrust of the engine, therefore, the specific impulse of the engine decreases with increase in the propellant flow rate to the gas generator. In literature, it is witnessed that researchers have conducted investigation of gas generator performance in terms of variation in mixing ratio or some models have been used to predict the characteristic length; however, it lacks the experimental investigation of gas generator performance in terms of characteristic length. In this paper, an experimental investigation of the gas generator of LPRE is conducted to determine the optimum characteristic length of the gas generator with liquid oxygen and kerosene. Hot tests are conducted with two different types of injectors, namely pressure swirl injector and impinging injectors in a modular water cooled gas generator. The gas generator is tested using six different characteristic lengths (i.e., from 1.75 m up to 9.67 m) for pressure swirl injector and with three different characteristic lengths (i.e., from 1.75 m up to 7.15 m) for impinging injector. The experimental results of hot tests show that the highest characteristic velocity of gas generator is achieved at a characteristic length of 4.27 m. It is demonstrated that a higher characteristic velocity of gas generator is achieved using impinging injector as compared to liquid-liquid pressure swirl coaxial injector at mixing ratio of 0.28 at optimum characteristic length. The effects of increase in mixing ratio with decrease in total mass flow rate on the chamber pressure are also discussed.

中文翻译：

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液体火箭发动机气体发生器的最佳特征长度

摘要 气体发生器是气体发生器循环液体推进剂火箭发动机（LPRE）的重要组成部分。在设计气体发生器 (GG) 时，选择未优化的特征长度会导致驱动涡轮所需的推进剂质量流量增加。由于气体发生器的排气对发动机的推力影响不大，因此，发动机的比冲会随着进入气体发生器的推进剂流量的增加而减小。在文献中，研究人员已经根据混合比的变化对气体发生器的性能进行了研究，或者已经使用一些模型来预测特征长度；然而，它缺乏在特征长度方面的气体发生器性能的实验研究。在本文中，对LPRE的气体发生器进行了实验研究，以确定液氧和煤油气体发生器的最佳特征长度。使用两种不同类型的喷射器进行热测试，即模块化水冷气体发生器中的压力旋流喷射器和冲击喷射器。气体发生器使用六个不同的特征长度（即，从 1.75 m 到 9.67 m）用于压力旋流喷射器，并使用三个不同的特征长度（即，从 1.75 m 到 7.15 m）用于撞击喷射器。热试验的实验结果表明，在4.27 m的特征长度处达到了气体发生器的最高特征速度。结果表明，与液-液压力涡流同轴喷射器相比，在最佳特征长度下混合比为 0.28 时，使用撞击喷射器可以获得更高的气体发生器特征速度。还讨论了混合比的增加与总质量流量的减少对腔室压力的影响。