Experimental study on explosion characteristics of

Experimental study on methane explosion characteristics under turbulent state

underground gas explosion accident in coal mine is one of the most serious mine disasters. In order to prevent and control mine gas explosion, domestic and foreign scholars have conducted a lot of research on gas explosion characteristics, and most of the research results are based on gas explosion under macro static state. However, when a large amount of gas in the coal mine is concentrated or gushed out, it is released into the air flow in the shaft and roadway. Due to the effect of concentration gradient and air flow pulsation, it gradually diffuses and dilutes in the air flow, and is carried by the air flow and flows [1]. Therefore, the study of flowing gas explosion has important practical value. Mons et al. [2] calculated the outlet pressure of the pipeline under quasi dynamic conditions; Chen Aiping [3] studied the blocking effect of flowing gas in the pipeline and the influence of flow on explosion characteristics; Wangbaoxing [4] studied the effect of ventilation on strong gas explosion. Turbulence is the most common flow state of underground gas, especially in the process of gas explosion, because the explosion shock wave is induced by factors such as obstacles in the roadway and the change of roadway size, it can produce strong turbulence. Therefore, this paper uses 20L near spherical gas explosion reaction device to test the explosion limit, explosion pressure, explosion pressure rise rate, explosion pressure peak time and other basic parameters of methane under macro static and turbulent states, and analyzes the influence of turbulence on methane explosion characteristics, which can provide some guidance for the effective prevention and control of mine gas explosion disasters

1 experiment overview

1.1 composition of the experimental system

the experimental system is mainly composed of 20L explosion reaction tank, gas distribution system, ignition system and measurement system. Its specific composition is shown in Figure 1

the volume of explosion reaction tank is about 20L, the maximum inner diameter is 30cm, and the internal space is 35cm high; The response time of the pressure sensor is 1ms, the range is 0~1mpa, and the accuracy is 0.3% F.S; The range of precision digital pressure gauge is 0~ ± 101.3 kPa, and the resolution is 0.01kpa; The volume of air storage tank is 0.6L; The range of the pressure gauge of the air storage tank is 0~4mpa, and the accuracy is 0.4; The ignition source is an electric initiating pyrotechnic igniter with an energy of about 1 joule, and the ignition position is in the center of the reaction tank. At first, the release of high-pressure air in the air storage tank, ignition and explosion pressure measurement are controlled by the computer through the controller during the rough polishing process. After the solenoid valve is opened, the high-pressure air in the air storage tank is filled into the reaction tank. After the preset delay time, it can be seen from the formula that the fire electrode automatically detonates the igniter for detonation. At the same time, the pressure sensor performs data acquisition (acquisition time 0~500ms) and saves it to the computer

1.2 experimental methods and conditions

the experiment refers to gb/t richer color 0 "method for determination of explosion limit of combustible gases in air". The asymptotic method is used to test the explosion limit of methane in air. The explosion criterion refers to the experimental criterion determined by American Society for testing and materials (ASTM), that is, the experimental pressure increases by 7% or more after ignition. According to GB "determination of explosion index of combustible gases in air", methane explosion pressure, explosion pressure rise rate, explosion pressure peak time and other parameters are tested. In the experiment, the mixed gas of alkane and air was prepared in the explosion reaction tank by partial pressure method. The above parameters were tested in the experiment under the conditions of macro static and turbulent mixed gas of alkyl air. The change of gas flow state was realized by the release of high-pressure air in the air tank when preparing the mixed gas. In this experiment, the ignition delay time is set to 500ms, and the turbulent flow of the mixed gas during ignition is characterized by the pressure of the air tank before the release of high-pressure air. Countries around the world have made corresponding plans in the field of new materials. The ambient temperature of the laboratory is 14.6~21 ℃, the humidity is 54~74%rh, and the initial explosion pressure is atmospheric pressure