Experimental and theoretical study on the break phenomenon of self-pulsation for liquid-centered swirl coaxial injectors

• Published in: Journal of Zhejiang University. A. Science Vol. 23; no. 2; pp. 140 - 155
• Main Authors: Cao, Peng-jin, Bai, Xiao, Li, Qing-lian, Cheng, Peng
• Format: Journal Article
• Language: English
• Published: Hangzhou Zhejiang University Press 01.02.2022; Springer Nature B.V; Science and Technology on Scramjet Laboratory,College of Aerospace Science and Engineering,National University of Defense Technology,Changsha 410073,China
• Subjects: Chambers; Civil Engineering; Classical and Continuum Physics; Energy transfer; Engineering; High speed cameras; Industrial Chemistry/Chemical Engineering; Injectors; Liquid phases; Liquid sheets; Mechanical Engineering; Pressure effects; Research Article; Self pulsation; Theoretical analysis; Theoretical model of self-pulsation; 压力特性; Break phenomenon; Liquid-centered swirl coaxial (LCSC) injector; 液体中心式气液同轴离心式喷嘴; Pressure oscillation characteristics; 间断现象; 自激振荡理论模型; 缩进; Recess
• ISSN: 1673-565X; 1862-1775
• DOI: 10.1631/jzus.A2100222

Experimental observations together with theoretical analysis were conducted to investigate the break phenomenon and the corresponding mechanisms of self-pulsation for a liquid-centered swirl coaxial injector with recess number of RN=1. Instantaneous spray images were obtained based on background light imaging technology with a high-speed camera. By dynamic analysis of the flow process of the liquid sheet in the recess chamber, a 1D self-pulsation theoretical model was established, and the self-sustaining mechanisms of self-pulsation were analyzed in depth. The results show that the increase of the momentum flux ratio will lead to the occurrence of the break phenomenon of self-pulsation for the injector with a larger recess length, and the frequency and intensity of self-pulsation before and after the break phenomenon differ significantly. The flow dynamics in the recess chamber sequentially transform from a periodic expansion-dominated flow to a stable flow, and then develop to a periodic contraction-dominated flow during the break process of self-pulsation. With the occurrence of self-pulsation before the break phenomenon, the liquid sheet has little effect on the pressure disturbance in the recess chamber. In contrast, with the occurrence of self-pulsation after the break phenomenon, the pressure disturbance is obviously affected by the liquid sheet. Based on the theoretical analysis model of self-pulsation, the self-pulsation frequency can be predicted. Furthermore, the self-sustaining mechanism of self-pulsation before and after the break phenomenon is preliminarily confirmed. The energy transfer between the gas- and liquid-phase is an important factor for maintaining the self-pulsation process.