Study On Flow Characteristics Of Gas-mist Two Phase Confined Jet

As an important kind of flow, jet is widely used in space flight, power, autocontrol and so on The heat and mass transfer processes that are especially controlledby out-diffusion can be strengthened through the turbulence of jet. Because of the speediness and high effect of reaction in it, gas-mist two-phase jet is greatly used in chemical reaction engineering. As a part of the research of the whole system, the flow characters of two-phase confined jet are stressed in the paper.The theoretical model on calculation of the hydrodynamics parameters is established based on the theoiy of free jet. The integral formulas of momentum and mass diffusion equation are combined to deduce the two-phase jet calculation formulas for the velocity distribution of gas and concentration distribution of droplets. Then the velocity distribution of droplets in the flow field of gas is obtained by single particle dynamics model. The results show that the flow characters of the turbulent jet in confined space are similar with those of free jet. For example, the width of confined jet is proportional to the distance from the noz.zle(be= e x). And the value of ?is almost equal to the value of free jet (0.114). The fluid from the downstream direction of the confined jet is carried away by itself in the jet room and the velocity of gas is decreased by the entrainment of droplets in the jet In addition, the calculation shows that, for the droplets with diameters 5 pm, ~m entrained into the confined jet where velocity is 140m/s, they can be accelerated to the equal velocity with gas in the distance of 10mm. The concentration of droplets in the jet increases in the downstream direction and it is lower in the center than elsewhere. Furthermore, the separation interface that may exist near the exit of jet is discussed.Finally, the experimental results prove that the velocity distribution of droplets,IIwhich are measured by Laser Doppler Anemometry, is accordant with the calculation values and the theoretical model can be successfully used in the simulation of flow field of confined jet. The effects of velocities ofjet, capacity of ullrasouic mist maker and diameters of droplets on hydrodynamic parameters in the flow field are simulated and the results are reasonably analyzed and discussed.