结冰风洞试验段水滴分布特性分析

喷雾系统是结冰风洞的主要组成部分,在结冰风洞试验段直接进行不同状态粒子分布特性的测量,会耗费巨大的成本。为此,本文提出一种采用实验测试和数值计算相结合的手段研究结冰风洞试验段水滴分布特性的方法。通过搭建独立的喷雾粒子试验系统,得到喷嘴出口处的粒子分布特性,在此基础上,采用数值方法计算不同水滴在风洞内的运动及传质传热过程,得到不同水滴蒸发之后的直径,进而获得试验段粒子的分布特性。采用该方法对典型雾化状态下3m×2m结冰风洞试验段粒子分布特性进行了研究,对比了空气湿度的影响。研究发现:(1)喷嘴出口处的初始喷雾粒子与试验段的水滴均保持近似正态的分布,试验段的水滴平均直径(MVD)与初始MVD接近,蒸发不能引起明显的MVD变化;(2)虽然空气湿度越小,水滴蒸发量越大,但湿度为100%时试验段水滴的 MVD比湿度为70%时小。研究成果为结冰风洞喷雾系统设计和调试提供了较好的技术基础。

Analysis of water droplets distribution in the test section of an icing wind tunnel

The spray system is the main component of an icing wind tunnel.It costs a lot to measure water droplets characteristics directly in the test section of an icing wind tunnel.In this paper,a means,including both experimental and numerical method,of studying the droplet dis-tribution in the icing wind tunnel test section is proposed.The droplet distribution characteristics at the nozzle exit are obtained by setting up an independent experimental system based on which the numerical method is used to calculate the movement and mass/heat transfer process of differ-ent droplets in the wind tunnel.Then the diameter and mass fraction of different droplets after e-vaporation can be obtained.The distribution characteristics of droplets in an icing wind tunnel with 3m×2m test section under typical conditions are investigated,and the effects of air humidi-ty is explored.The results show that:(1)the droplets at the nozzle exit and in the test section are in an approximate normal distribution,the MVD in the test section is close to the initial value at the nozzle exit,and evaporation does not cause a significant change in MVD.(2 )generally speaking,the smaller the absolute humidity is,the greater the evaporation of water droplets is. Though,when the absolute humidity is 100%,the MVD of droplets in the test section is smaller than that when the humidity is 70%.The research results can provide a good technical basis for the design and use of an icing wind tunnel.