Abstract: Abstract: To obtain the influence of gas-liquid flow patterns on spray shape and droplet size distribution in effervescent atomizer, a visual effervescent spray system and a gas-liquid two-phase flow simulation model of atomizer interior and spray field were established, both experimental and simulation methods were used to investigate the spray shapes and droplet distribution characteristics of a visual effervescent atomizer under churn flow and bubbly flow. The structure design together with the structural geometric parameters of the visual effervescent atomizer was carried out on the basis of the relevant research at home and abroad. The gas-liquid flow patterns, the spray shape and parameters were presented in the effervescent spray experiments. The gas-liquid two-phase flow pattern together with its influencing factors, and features of gas-liquid mixing form under churn and bubbly flow in the mixing chamber were experimentally studied by the visual effervescent spray system. The simulation model of gas-liquid two-phase flow in the exit orifice of effervescent atomizer was established. Based on this, characteristics of flow parameters pulsating under different flow patterns at the exit section of the orifice were clarified. The spray shapes of different gas-liquid two-phase flow patterns in the atomizer were experimental studied by the visual effervescent spray system. The characteristics of droplet distribution in the spray field of different flow patterns were studied by simulation method. The variation law of spray shape together with its pulsation characteristics, and the droplet distribution features in the spray field of different gas-liquid two-phase flow patterns were determined clearly. The results show that under churn flow, the pulsation amplitude of gas fraction and its variation in the atomizer exit orifice are relatively small and gas fraction is relatively high. Under bubbly flow, the gas fraction is lower and shows bander oscillating attenuation. The pulsation of the spray shapes is not obvious in the churn flow, and distribution of spray half cone angle is relatively concentrated, while the situations are exactly opposite in the bubbly flow. In churn flow, the proportion of spray half cone angle is more than 70% in the range of 8°-14°, while that of the bubbly flow is less than 40%. The influences of gas-liquid two-phase flow patterns in the atomizer on the droplet collision rate and droplet velocity in the spray field are limited to the vicinity of the orifice. Under churn flow, the droplet size distribution near the exit orifice is more concentrated and the distribution range changes more with the increase of the axial distance, the average droplet diameter is about 4% smaller than that of bubble flow. In the outlet of the nozzle region (axis distance < 40 mm), the standard deviation of droplet diameter of churn flow is more than 30% smaller than that of bubbly flow. The difference in droplet size distribution with different gas-liquid two-phase flow patterns decreases with the increase of the axial distance, under churn flow, the radial extent of the large-sized droplet area is slightly smaller than that of bubbly flow, and the droplet size is significantly larger than that of bubbly flow. The research can provide theoretical and experimental basis for the development of effervescent atomization technology and the reasonable selection of flow patterns for various purpose.