Laminar Flame Characteristics Research Of Methane-oxygen-water Mixture Based On Constant Volume Combustion Bomb

With the rapid consumption of petroleum resources and the increase of environmental pollution,people need to develop and use clean alternative fuels and develop new combustion technologies.Natural gas has become the most promising alternative fuel with its abundant reserves,clean combustion and high safety.Oxygen steam combustion technology has attracted much attention due to its high-efficiency and near-zero emissions.In order to study the laminar flame characteristics of methane under oxygen/steam conditions,a multi-functional constant volume combustion experimental system was built,which combined with the schlieren-image technology to test the premixed laminar burning velocity of methane under oxygen/steam conditions.It provides basic data and theoretical support for combustion technology of CH₄ burning under O₂/H₂O conditions.The multi-functional constant volume combustion experimental system mainly includes constant volume combustion bomb,intake/exhaust system,ignition system,temperature control heating system and flame image acquisition system.The inlet systems and the temperature control heating system can regulate the intake of the gas and the high-concentration water vapor at different initial temperatures.By changing the initial conditions such as preheating temperature and equivalence ratio of the mixture,and setting the high water vapor dilution concentration,the laminar combustion flame images of methane under high temperature and high humidity pure oxygen atmosphere are obtained by the constant volume combustion test bench.And then,the flame image processing program on MATLAB is used to calculate the flame image.Finally,the laminar burning velocity of methane-oxygen-water vapor premixed gas and its variation with initial temperature and equivalence ratio are obtained.The accuracy of the test bench and measurement method was verified by measuring the laminar flame velocity under methane air conditions.The initial temperature of the methane-oxygen-steam premixed combustion experiment is 400 K and 450 K.The water vapor dilution concentration is 0.64.And the equivalent ratio is from 0.7 to 1.3.The equivalence ratio has a great influence on the tensile flame propagation speed,the non-stretching flame propagation velocity and the laminar burning velocity.When the equivalence ratio is less than 1.1,the tensile flame propagation velocity,the unstretched flame propagation velocity and the laminar combustion velocity are increased with the increase of the equivalence ratio,and reaches the maximum when the equivalence ratio is 1.1.After the equivalence ratio is greater than 1.1,these burning speeds are reduced with the further increase of equivalence ratio.And the increase of temperature also has a significant effect on the burning rate.The Markstein length is positive.It is increased with the increase of the equivalence ratio.The increase of temperature has little effect on the Markstein length.