Study On Influence Of Initial Temperature And Pressure On Gas Explosion Characteristics

The feature of gas explosion is instantaneity,complexity and destructive.Gas explosion is the result of joint action of many factors,which initial temperature,initial pressure,gas concentration,oxygen content and so on all have great influence on.In order to explore the influence of initial temperature and pressure on gas explosion characteristics,in this paper,on the basis of theoretical analysis,gas explosion characteristics was experimentally studied under the condition of different initial temperature and initial pressure,and was numerically simulated from two aspects of chemical kinetics and fluid dynamic.Based on the thermal explosion theory and the chain reaction theory,the process of gas explosion was analyzed,in particular,the development of initial ignition stage was emphatically analyzed and the ignition condition of gas explosion is presented.On this basis,the influence of initial temperature and pressure on gas explosion reaction rate,explosion characterization parameters and explosion limit were analyzed.Explosion experiments at different gas concentrations show that the optimum gas concentration under the experimental conditions is 10.1%.Using the special environment 20L explosion characteristics test system,experimental study was carried out under different initial temperature at the optimum gas concentration.The experimental results show that:in the experimental temperature range(25??200?),with the increase of initial temperature,the maximum explosion pressure of gas explosion reduced exponentially,the maximum pressure rise rate increases slightly,and the ignition delay time is shortened.Researches of gas explosion limits under the conditions of different initial temperature and initial pressure show that in the experimental temperature(25??200?)and pressure(0.1Ma?1.0MPa)range,as the initial temperature and/or initial pressure rise,the gas upper explosion limit increases,and the lower explosion limit is reduced,that is,gas explosion limit range is widened.The upper explosion limit increases exponentially with increasing initial temperature and initial pressure,while the lower explosion limit is reduced exponentially with increasing initial temperature and linearly with increasing initial pressure.The coupling effect of initial temperature and initial pressure on gas explosion limits is much more significant than the single factor influence,and higher than that of both influences.The experimental values of maximum explosion pressure and explosion limit are in good consistency with theoretical ones,and experimental changing trend of the two parameters with initial temperature or initial pressure is consistent with the theoretical one.Reference to the concept of risk and fuzzy evaluation method,a preliminary assessment method of gas explosion risk was proposed.CHEMKIN and FLUENT package were used in numerical simulation study of gas explosion process.Main element reactions of gas explosion are determined by the sensitive analysis of temperature and free radicals concentration.The development process of gas explosion in confined spaces reappeared through the analysis of explosion flow field.Within the simulated temperature range(298K to 1173K),explosion temperature rises with elevated initial temperature,but increases in temperature are all around 2400K compared to the initial temperature.While the maximum explosion pressure is lower at higher initial temperature,and simulation values are in good consistency with experimental ones.Simulation values of the maximum explosion pressure are slightly higher than experimental ones,yet the difference between the two ones is gradually narrowed with the rise of initial temperature.Moreover,reaction time is shortened as initial temperature rises.When the initial pressure increases,change of flame speed is not obvious in the early reaction stage,while in the late stage,the flame speed is faster at higher initial pressure,so in the whole reaction process,the average flame speed accelerates and the reaction time is shorten.With the same rising value of initial pressure,higher initial temperatures larger rise amplitude of blast temperature.With the same increasing value of initial temperature,higher initial pressures lower decrease amplitude of the maximum explosion pressure.Therefore,the risk of gas explosion increases when the initial temperature and initial pressure rise at the same time.