Numerical simulation of thermoacoustic instability in Rijke tube

放置状态及变参数对热声不稳定工作特性分析

¹ AVIC Xi'an Flight Automic Control Research Institute, Xi'an 710076, China
² School of Power and Energy, Northwestern Polytechnical University, Xi'an 710072, China

Received: 21 October 2020

Abstract

The influence of three different states on the thermoacoustic instability characteristics of Rijke tube was compared in order to reseach the influencing factors of thermoacoustic oscillation by using the Rijke tube model with stack as the heat source. The thermoacoustic oscillations are numerically simulated from the start-up to the saturation state, and the effects of the temperature on the dynamic viscosity and the thermal conductivity are compared. The results show gravity has a greater influence than the thermoacoustic oscillation caused by thermal buoyancy, and it is related to the inner balance of the tube after the gravity and the temperature gradient caused by the protrusion and the temperature gradient caused by the reduction of the amplitude dissipation. For the comprehensive comparison of the two variable parameters, it is found that when the viscosity coefficient changes with temperature and the thermal conductivity is a fixed value, both of them decrease by 49.5% with the temperature change rate. This result far exceeds the viscosity coefficient itself influences.

摘要

为了进一步研究热声振荡机理影响因素，针对以恒温板叠为热源的四分之三波长Rijke管模型，通过对比3种不同放置态对Rijke管内热声不稳定特性的影响，采用CFD方法对管内的热声振荡进行了从起振到饱和状态全过程的数值模拟，并对加入温度对动力黏性系数和导热系数的变参数影响进行对比考察。结果表明，重力比热浮力所导致的热声振荡影响大，且无重力时压力过渡段的凸起现象与温度梯度所导致的饱和后减小振幅耗散来达到管内平衡现象有关。对于2种变参数综合比较发现，当黏性系数随温度变化且导热系数为定值的幅值相比两者均随温度变化倍率净缩小49.5%，这一结果远远超过黏性系数自身带来的影响。