Abstract
Abstract: Air lift pump is widely applied in oil and ore exploitation, due to its simple structure, high practicability and other prominent advantages. However, the pump is not fully applied because of its low efficiency. To investigate the lift performance of air-lift pump intensively, a theoretical analysis was carried out to and a theoretical model of air-lift for different inlet methods was established in present paper. At the same time, to test the theoretical model and better understand its operating principle, in this paper, the performance of air lift pump was investigated by changing air inlet area and pore distribution pattern in the air lift pump facility. In the experiment, the air, supplied from air compressor, was injected into the riser pipe by nozzle, in order to drive the liquid to move upward in the pipe. Air and water were separated from the gas-liquid separation tank in the top of the riser pipe, and the separated water dropped into the water measuring tank (bucket). In the experimental test, stopwatch recorded the working time of air lift pump, and electronic scale weighed the water from the bucket. The air nozzle selected 3 kinds of injection areas, i.e. 25, 50 and 100 mm2, and for each injection area, 3 injection methods were adopted. Various submergence ratios (0.4-0.9) were investigated, while the range of the air flow rate was from 0 to 16.0 m3/h. For each air injection method and submergence ratio, the air flow rate varied, the corresponding flow rate of water was measured, and the promoting efficiency was calculated. We used high-speed camera to capture the flow regime in the tube to deeply discuss the relationship between air lift capacity and the two-phase flow characteristics. By analyzing the experimental data, the results are obtained as follows: Firstly, for the air injection method of 7 mm square nozzle, with the increase of air flow rate, the fluid flow rate of pump increases quickly, and then rises slowly, and the efficiency of pump goes up rapidly to the peak, and then decreases continuously. With the submergence ratio increasing, the peak of promoting efficiency becomes bigger, and the corresponding air flow rate is smaller. Secondly, for the submergence ratio of 0.5, when the air injection area is 25 mm2, the liquid volume flow rate is significantly higher than other areas of nozzle. For the different air injection areas, the smaller area will cause higher pipeline pressure, which helps to lift liquid but decrease promoting efficiency of pump. For the same air injection area, there is little difference in the pump performance with different pore distribution patterns. Thirdly, in the gas-liquid two-phase flow of riser pipe, we observe 4 kinds of flow patterns, i.e. bubbly, slug, churning, and annular flow. In the bubbly and slug flow, there is little noise in the experiment, but in the churning and annular flow, the noise increases gradually. Near the slug flow, the promoting efficiency reaches the highest point, and the stability is good. In the annular flow, the promoting efficiency reaches the lowest point, and the stability is bad. Finally, the experimental results are compared with the theoretical values, while the experimental results agreed well with the theoretical analysis results in present paper, and the model could predict the liquid flow rate of air-lift pump better in a certain range. Near the slug flow, the theoretical model preferably predicts the performance characteristics of air lift pump, and the calculation results have a good agreement with experimental results. In the other flow patterns, the experimental data and the simulation results have some deviation. The cause is that the theoretical model adopts the slip ration formula of Griffith and Wallis, which is only suitable for the slug flow. In the follow-up work, the theoretical model should be improved. In a word, this study provides an important reference for deeply understanding the performance characteristics of air lift pump.
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