ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2022, Vol. 43 ›› Issue (9): 126018-126018.

• Fluid Mechanics and Flight Mechanics •

### Suppression effect of injection intensity distribution on longitudinal combustion instability

WANG Guangxu1, TAN Yonghua2, ZHUANG Fengchen3, CHEN Jianhua1, YANG Bao'e1, HONG Liu1

1. 1. Key Laboratory for Liquid Rocket Engine Technology, Xi 'an Aerospace Propulsion Institute, Xi 'an 710100, China;
2. Academy of Aerospace Propulsion Technology, Xi 'an 710100, China;
3. Department of Aerospace Science and Technology, Space Engineering University, Beijing 101416, China
• Received:2021-07-08 Revised:2021-07-31 Online:2022-09-15 Published:2021-10-09
• Supported by:
Science and Technology Foundation of Key Liquid Rocket Engine Technology (614270419)

Abstract: Radial injection intensity distribution has been adopted in many liquid rocket engines using storable hypergolic propellants, and has been one of the most important suppression methods of combustion instability for these engines in engineering, except for acoustic damping devices. However, these engines are still confronted with some risk of combustion instability, which means that deep study on its suppression effect is still necessary. With the idea of independent injector, a model combustion chamber with impingement injectors of hypergolic propellant was designed, and experimental study on high frequency longitudinal combustion instability of different injection intensity distribution was conducted. It is found that for the case that droplet evaporation acts as the rate-control process, enhancing the injection intensity of the 'hump zone' can improve the high frequency longitudinal combustion stability, but the improvement effect depends on the relative result of the variation of combustion characteristic length and chamber length. Compared with the case of the short chamber, in the case with long combustion chamber, the relative result of the variation of combustion characteristic length due to the change of injection intensity distribution and combustion chamber length will be smaller, and the corresponding suppression effect will be weakened. Compared with the case of lower pressure chamber, in the case of high pressure chamber, evaporation of propellant droplets will accelerate and mixture efficiency will be improved, which means that the effect of controlling combustion distribution through much bigger droplets in high the intensity zone will be weakened, and suppression effect will be reduced accordingly. For the case with high chamber pressure and long chamber length, high amplitude pressure oscillation is excited for each injector, and distribution of amplitudes has no relation with the injection intensity in hump zone.

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