Experimental study of shock pressure and erosion characteristics of high‐pressure gas–liquid two‐phase jet: Exploration for improving coalbed methane extraction efficiency

Abstract Coalbed methane extraction promotes energy exploitation and alleviates the greenhouse effect. This study aimed to analyze the technical potential of a high‐pressure gas–liquid two‐phase jet in increasing coalbed permeability and promoting coalbed methane extraction. A well‐designed experimental setup was used to investigate the erosion characteristics of a high‐pressure gas–liquid two‐phase jet. Through the shock pressure monitoring and erosion tests of the jet, the effects of pump pressure, mixer structure, and nozzle structure on the shock pressure and rock‐breaking performance were studied, and the rock‐breaking mechanism of the high‐pressure gas–liquid two‐phase jet was examined. The results showed that the nonuniformity of mixing and the expansibility of high‐pressure gas continually alters high‐pressure gas–liquid two‐phase jets between single and multiple streams, which makes the jet show obvious pulse effects and considerably improves the rock‐breaking performance. Furthermore, reasonable air pump pressure and water pump pressure settings significantly increase the shock area, whereas the maximum shock pressure only decreases slightly. Although the shock pressure of a high‐pressure gas–liquid two‐phase jet decreases with the increase in air pump pressure, its shock efficiency first increases and then decreases with the increase in air pump pressure. To improve the erosion efficiency of a high‐pressure gas–liquid two‐phase jet, the settings of the air pump pressure and water pump pressure is crucial, but the optimal air pump pressure differs for different water pump pressures. Additionally, the greater the angle between the gas and liquid inlets, the greater the energy loss of the fluid during the mixing. Finally, the rock‐breaking performance showed that the optimal nozzle structure is the single‐cone nozzle.