Study on the evolution law of a low resistance gas diffusion flow field under the condition of constant volume and variable pressure

Conventional gas emission experiments are widely used in outburst prevention and control work, but the system resistance of the test device interferes with the gas emission process of the coal particles themselves. In this paper, the pressure loss characteristics under conventional/low resistance conditions are compared through the developed low-resistance gas emission experimental device, and the pipeline pressure loss simulation and transient emission inversion analysis are carried out by means of Solidworks flow simulation and COMSOL Multiphysics software. It is concluded that in the process of conventional gas emission, the dynamic change of pressure loss is significant, and the fluctuation is up to 20 times, which hinders the emission process of coal particles themselves. The low-resistance diffusion experiment truly restores the gas diffusion process, and the released gas pressure shows a nonlinear upward trend. The velocity change is divided into three stages: initial high speed, lateral diffusion, and reflux and stable low speed. The mechanism includes Bernoulli effect, gas compression effect, and hydrodynamic instability. The Boltzmann model based on COMSOL inversion accurately characterizes the transient attenuation law of the outburst port velocity, and the maximum gas outburst port velocity of 0.5–1 mm coal particles at 2 MPa is 2.39 m/s. In this paper, the evolution law of a low resistance gas diffusion flow field under the condition of constant volume and variable pressure is studied, which provides support for the theoretical research of a gas outburst mechanism and also provides a new technical way for the prediction and prevention of outburst risk.