Experimental Study On The Characteristics Of Air-water Two-phase Flow Through Helical Channel In Single Screw Expander Prototype

The single screw expander is a kind of power generation, it can use low temperature heat source to obtain relatively high power generation efficiency. In the project of recycling of waste heat resources, the single screw expander has a good perspective application. At present, the study of single screw expander mainly focus on processing and performance, lack of the study on the characteristics of air-water two-phase flow through helical channel in the single screw expander. But it is one of the important factors that affect the work efficiency. Therefore, we proposed to study on the characteristics of air-water two-phase flow through helical channel in the single screw expander.In the experiments, we processed out two kinds of the size of the transparent screw using organic glass which diameter is 117 mm and 155 mm respectively. The channel in the screw is a kind of three-dimensional helical channel which cross-section shape is irregular, the two phase flow through helical channel are water and air.By using high speed camera and the backlight imaging methods, we obtained the image of flow pattern in the screw channel. We analyze the characteristics of different flow patterns under different working conditions or different round angle location. The experimental results show that the screw channel mainly exist the bubbly flow, intermittent flow and annular flow; The characteristics of various flow patterns affected by working conditions and round angle position, even under the same conditions, the characteristics of flow patterns in different round angle position is not the same. According to the experimental observation results, we made the flow pattern map under three round angle, then analyzed the flow pattern transitions boundaries between bubbly flow with intermittent flow, annular flow with intermittent flow.Due to the pressure drop of gas-liquid two-phase flow and pressure fluctuation information can reflect the condition of the two-phase flow in the channel, studying the characteristics of these parameters is great significance for monitoring and controlling of two-phase flow. It is also help to the design and operation of two-phase flow system. Therefore, we proposed to study on pressure drop of gas-liquid two-phase flow in the inlet and outlet. Then we analyze the characteristics of the probability density function and power spectrum distribution of differential pressure fluctuation signal under different flow patterns, these researches are help for improving the efficiency of single screw expander system.