对称结构锅炉炉膛内非对称流动机理分析

Mechanism Analysis of Asymmetric Flow in the Boiler Furnace with a Symmetrical Structure

本文对从具有对称结构的锅炉炉膛内流动问题抽象出的二维流动模型进行了数值模拟,探讨在这种对称结构下出现的非对称流动的机理.数值模拟结果表明,无论采用层流模型还是湍流模型,在某些参数范围内,流场的数值结果都出现了非对称现象,在层流模型下,当Re<1500时,计算得到的流场呈对称分布;当Re达到2500时,流场开始不对称;而当Re达到4000时,所获得的流场明显不对称,并且速度值发生振荡.在湍流模型下,Re<4000时,流速时均值呈对称分布;当Re≥8000时,速度时均值不对称,且出现振荡.本文分析表明,对于具有完全对称结构的流动问题,由于内部的原因可能出现非对称的流场,这为分析锅炉炉膛中出现的热偏差机理提供了基础.

The asymmetric flow is presented by the numerical simulation in the boiler furnace with a symmetrical structure. The results show that, whether using laminar model or turbulence model, and the numerical results of the flow in the furnace have asymmetric phenomenon within some range of the parameter. Using the laminar model, when Re of burner nozzle is less than 1500, the velocity field is symmetrical distribution; when Re reached 2500, the velocity field becomes asymmetrical; while Re is larger than 4000, the velocity field in the furnace is totally asymmetrical, the static bifurcation appears and the instantaneous value of velocity is oscillating over time. Using the turbulence model, when Re is less than 4000, the mean speed is symmetrical; When Re is greater than or equal to 8000, the velocity field is asymmetric, and the mean speed is oscillatory. The asymmetrical flow field can be caused in a flow problem with a completely symmetrical structure which provides a basis analysis of the mechanism of thermal deviation in the boiler furnace.