液体中心式气液同轴离心喷嘴自激振荡机理研究

Self-pulsation is an important phenomenon that occurs in the gas-liquid coaxial injector. It can cause the pressure and mass flux oscillation at the injector exit, and finally oscillates the atomization and combustion process. So far the self-pulsation has been observed in the gas-liquid shear coaxial injector, the liquid-centered swirl coaxial injector and the gas-centered swirl coaxial injector, but there is yet no scientific consensus on the self-pulsation mechanism. The present work will focus on the self-pulsation in liquid-centered swirl coaxial injector, and extract the the self-pulsation characteristics. Then the effects of injector geometry and operation condition on the self-pulsation characteristics are investigated. The correlation between the self-pulsation and the acoustic characteristics of the swirl coaxial injector, and the correlation between the self-pulsation and the fluid instability are analysed to find the oscillation source. Then the critical operation condition is obtained through a large number of experiments, and the flow field of the sprays with and without self-pulsation are compared to find the excitation of self-pulsation. Finally, an “annular gas flow-conical liquid film-central air core” fluid oscillator model is proposed to investigate the response characteristics. The simulation of the gas-liquid flow field in the recess chamber is also conducted to investigate the delay feedback characteristics of the interaction between the annular gas flow, the conical liquid film and the central gas core. And the correlation between the shedding vortex and the self-pulsation is also investigated.

自激振荡是发生在喷嘴中的一个重要物理现象，会引起的喷嘴出口压力和流量的振荡，从而会造成雾化和燃烧过程的振荡。目前在同轴直流式喷嘴、液体中心式气液同轴离心喷嘴和气体中心式同轴离心喷嘴中均发现了自激振荡，但是对自激振荡的产生机理还没有统一的认识。本项目拟针对液体中心式气液同轴离心喷嘴的自激振荡现象，提取自激振荡特性参数，研究自激振荡特性随喷嘴结构和工况参数的变化规律。分析自激振荡与喷嘴声学特性及喷嘴内部流动不稳定的相关性，找到自激振荡的振荡源。在此基础上，获取自激振荡产生的临界条件，对比有无自激振荡的喷雾流场，找到自激振荡发生的前兆。最后建立“环缝气体-锥形液膜-中心气核”流动振荡器模型，分析流动振荡器对外部扰动的响应特性。开展缩进室内部的气液两相流动数值仿真，分析环缝气体/锥形液膜/中心气核三者相互作用的时滞反馈特性，研究脱落涡与自激振荡之间的相关性。

自激振荡是发生在喷嘴中的一个重要物理现象，会引起喷嘴出口压力和流量的振荡，从而会造成雾化和燃烧过程的振荡。目前在同轴直流式喷嘴、液体中心式气液同轴离心喷嘴和气体中心式同轴离心喷嘴中均发现了自激振荡，但是对自激振荡的产生机理还没有统一的认识。针对上述问题，本项目对自激振荡现象与发展规律、结构参数对自激振荡的影响规律以及自激振荡的产生机理开展研究。.在第一方面研究内容中：提出了自激振荡的拍摄和捕捉方法；提出了自激振荡特性参数的提取方法；研究了自激振荡的起振过程和喷嘴工况参数对自激振荡的影响。.在第二方面研究内容中：研究了喷嘴缩进长度、环缝宽度和喷嘴出口壁面厚度等三个结构参数对自激振荡特性参数的影响规律。.在第三方面研究内容中：研究了喷嘴内部流场结构，分析了自激振荡过程中喷嘴内部扰动的传递机制和缩进室内部的流动模态。.受本项目资助发表的学术论文共6篇，其中SCI收录3篇，EI收录1篇，国内会议2篇。.通过上述研究，项目全面完成了研究计划内容，达到了预期目标。项目预算经费28万元，决算4.7829万元，经费执行率17.1%。