气雾两相受限射流特性的研究

Study on Flow Characteristics of Gas-mist Two Phase Confined Jet

本文采用自由射流理论研究了有限空间中气雾两相射流的流动特性 ,考虑雾相的存在对气相流速的作用 ,并由此推出了受限气雾两相流气速分布和雾相浓度分布计算方法 ,结果表明雾滴的卷入对气流的流动起到了阻滞作用 ,使其流速减小 ,在此基础上对受限射流在排出口附近存在的分离面进行了讨论 ,并采用单颗粒动力学模型求解了雾滴的速度分布 ,得知当雾滴的直径dp =5 μm ,在距喷嘴出口 30mm的地方将雾滴加入到出口气速u0 =140m/s的气相射流中时 ,雾滴在 15mm左右的距离内就能被加速到与气流等速 ,最后经过实验论证得知模型计算值与实验值吻合较好 ,该模型能较好的体现有限空间中的气雾两相射流特性。

The theory of free jet is used to get the flow parameters of gas mist two phase confined jet. Integral momentum formula and mass diffusion equation are combined to deduce the calculation formulas for the velocity distribution of gas and the concentration distribution of droplets in two phase jet. The results show that the immixture of droplets reduces the velocity of gas. Furthermore, the separation interface that may exist near the exit of jet is discussed and the velocity distribution of droplets is obtained by single droplet dynamics model. The calculation makes clear that when the droplets with diameter of 5μm are mixed into the confined jet with velocity of 140m/s at the nozzle exit, they can be accelerated to the velocity equal to that of gas in the distance of 15mm. The experiments also show that the velocity of droplets, measured by laser doppler anemometry, is accordant with the calculated values and the radial profiles of axial velocity are still self similar in confined jet.