The Development Of The Constant-volume Boom And Methane Combustion Characteristic

The coal-bed methane commonly was known as the mashgas. Its main composition is methane (CH4) which is flammable and combustible. Due to the characteristics of the confined space of storage warehouse and transportation vehicles, recently, gas leakage led to fire and explosion accidents emerge in endlessly, the potential safety hazard is extremely serious especially in the process of warehouse transformation or construction, and so as the gas transportation. Study the law of methane combustion characteristic in confined space is of great significance to gas safety storage.For our research purpose, we have found a measurement system of gas fuel combustion by means of schlieren system, pressure sensor and high-speed camera. On the basis of the experiment, we have made a profound analysis of the influences of equivalence ratios and initial pressure on combustion characteristics of methane-air mixtures. The results as follows:(1) On the basis of the experiment, we have made a profound analysis of the influences of equivalence ratios on combustion velocities of methane-air mixtures. And there is a critical equivalence ratio with a value of1.1, under this value, the flame propagation speed (2.548m/s), unstretched flame propagation speed (2.767m/s) and laminar burning velocity (0.368m/s) are the highest. The larger equivalence ratio was, the faster velocities would be. While the shift occurred in equivalence ratio of1.1, velocities decreased due to the increase of equivalence ratio.(2) It was shown that, the influences of equivalence ratios on combustion pressure of methane-air mixtures. And there is a critical equivalence ratio with a value of1.1, the value of the pressure firstly increased, and then decreased with increasing equivalence ratios, the maximum (0.703MPa) appearing at the equivalence ratio of1.1.(3)This experiment suggests there is a common influence between initial pressure and combustion pressure. The maximum of combustion pressure is0.73MPa with the initial pressure of1.0arm, while with the initial pressure of1.6atm, which the maximum of combustion pressure is1.42MPa. With the lower initial pressure, the appearing time of maximum value is not changed sharply. Once surpassed the normal pressure (1.0atm) the appearing time of maximum value would be brought forward largely. (4)The stability of the flame firstly decreased, and then increased with increasing equivalence ratios, the worst case occurred in equivalence ratio of1.1. While with the higher initial pressures, the instability of flame was strengthened.