The Study On Flow Field Characteristics Of The Combined Nozzle

Different nozzles which are placed in a certain way constitute the combined nozzle. The gas humidification and wet steam source will need to use combined nozzle. The flow field of the combined nozzle is very complex because that the different nozzles influence each other. Current research on this issue is still relatively small, so the study on combined nozzle flow field has great significance. The study is developed by the ways of theoretical analysis, numerical analysis and experiments. The goal of the study are revealing flow field structure of combined nozzle, realizing the flow characteristics of combined nozzle in free space and in confined cross-flow, and exploring the mechanism of atomization flow field interference.Experimental system was designed and built to study the flow field characteristics of 4 pressure nozzles and combined nozzles in free space. The outlet diameters of nozzles are 0.21mm,0.28mm,0.38mm,0.46mm. The experimental results show that droplet velocity decrease rapidly when the droplet leaves the nozzle exit in short distance, then it slowly reduces to stable value. The spray droplets average diameter increases with the increases of outlet diameters of nozzles and decreases with the increase of atomization pressure. Combined nozzle spray droplet velocity is larger than that of a nozzle, the average particle size is smaller than that of single nozzle. Both of them are along with the change of relative spray axial distance same as the single nozzle. The spray droplet size range of combined nozzle is larger than that of single nozzle. The nozzle spacing has little effect on spray droplet average diameter. When nozzle angle increases moderately, spray droplet average diameter can decrease significantly. Combined nozzle droplet average diameter decreases with the increase of the spray pressure.The flow field characteristics of 4 pressure nozzles in a rectangular channel are investigated experimentally. The dimension of the rectangular channel is 150mm×150mm×1000mm, and the air velocity in the rectangular channel is 10 m/s. This paper presents the influence of injection angle, nozzle placement and nozzle combination on the flow field. The experimental results show that the non-impinging distance increases with the injection angle; the average D32 in downstream spray is 10% lower than that in no stream, and the particle size range is slightly expanded in downstream spray. The average D32 in counter-current spray is 70μm lager than that in no stream, and the particle size range is expanded 3-4 times in counter-current spray. The narrow range of size distribution can be expanded through counter-current spray or downstream spray. The atomization quality of double nozzles in confined cross-flow is related to flow ratio of gas-liquid. The results provide some reference for gas conditioning.The 2D and 3D simulation of the single nozzle spray flow field has been done based on the experimental data by using CFD software and DPM model. After simulating the spray flow field in confined cross-flow, the influence of air velocity on spray droplet diameter and velocity are discussed. The result shows that droplet size decreases with the increase of air velocity. There is a linear relationship between the average speed of spray droplets and air velocity. The non-impinging distance increases with the increase of air velocity. The 3D simulation of the combined nozzle spray flow field has been done, and the result shows that the DPM model is not right when the grid size is not small enough.