Research On Laminar Combustion Characteristics Of Hydrogen-ethanol Premixed Gas Under High Pressure

In response to the concern about energy issues in the"14th Five-Year Plan"and to achieve my country’s"carbon neutral"aspirations,hydrogen,as one of the cleanest energy sources,is currently a hotspot in energy research.However,due to the excessively fast flame propagation speed in the combustion process of hydrogen in an internal combustion engine,the application defect of the hydrogen internal combustion engine cannot stabilize the output power.Blending ethanol with hydrogen is one of the important measures to improve the combustion characteristics of hydrogen.At present,the research on the combustion characteristics of hydrogen-ethanol premixed gas has not been in-depth.This thesis systematically studies the laminar combustion characteristics of hydrogen-ethanol premixed gas.The constant pressure method is used to study different initial pressures,different fuel ratios and different equivalent ratios,and to carry out the study of the laminar combustion characteristics of hydrogen-ethanol premixed gas.At the same time,the Chemkin software is used to simulate the chemical reaction kinetic characteristics of hydrogen-ethanol premixed gas.First,the composition and experimental methods of the constant volume incendiary bomb test platform are introduced.Through the schlieren system and high-speed camera,the visualization of the combustion process is realized,and the laminar combustion characteristics of hydrogen-ethanol premixed gas are summarized through data analysis.The constant volume incendiary bomb test platform includes the bomb body,ignition system,data acquisition system,and gas emission and supply system.It uses a high-speed camera to receive the light path converted by the schlieren system,and records the change process of the spherical flame front in the bomb.Through Halcon software to identify the flame front,calculate the spherical flame area,and then calculate the stretching flame propagation speed,and use the nonlinear extrapolation method to derive the non-stretch flame propagation speed,and further analyze the markstein length and laminar burning velocity,etc.Changes in laminar combustion characteristic parameters.Secondly,the laminar combustion characteristics of hydrogen-ethanol premixed gas under different environmental pressures,different fuel ratios and different equivalent ratios were systematically studied.Including the change of the pressure change in the combustion bomb during the combustion process,the stretching flame propagation speed,the laminar combustion speed and other laminar combustion characteristic parameters,and the analysis of the flame propagation law under different working conditions.The results show that the increase of the initial pressure increases the pressure peak in the combustion bomb during the combustion process,and the heat loss decreases.That is,the increase of the initial pressure reduces the energy release during the combustion process and suppresses the flame propagation speed.At the same time,as the equivalence ratio increases,the pressure peak increases,and the premixed gas under rich combustion reduces the energy release.The laminar combustion speed of the premixed gas is first increased and then decreased with the increase in the equivalence ratio.The peak value of the hydrogen-depleted gas is atφ=1.2 and the peak value of the hydrogen-rich gas is atφ=1.3,indicating the stratification of the hydrogen-ethanol premixed gas The peak point of the flow combustion rate will shift to the higher equivalence ratio as the proportion of hydrogen increases.Although the increase in the initial pressure does not affect the change of the peak point,it will reduce the laminar combustion speed and inhibit the burning process of hydrogen-ethanol premixed gas.Finally,the combustion of gas is simulated by Chemkin software,and the laminar combustion characteristics of premixed gas are analyzed from the perspective of chemical reaction kinetics.The results show that the increase in the equivalence ratio promotes the reaction rate of the fuel,but when the equivalence ratio is too high,the chemical reaction rate of the fuel will be inhibited.As the equivalence ratio increases,the adiabatic flame temperature also increases first and then decreases,and the adiabatic flame temperature of hydrogen-rich gas fluctuates more greatly because hydrogen can release more energy when the proportion of hydrogen in the premixed gas is large.However,the initial pressure does not affect the change in the mole fraction of the combustion reactants and products of the premixed gas,but the total mole fraction of CO,H₂O,CO₂ and residual gas is lower than the stoichiometric ratio due to insufficient supply of reactants in the lean and rich phases The total mole fraction of unburned gas.The increase in the proportion of hydrogen and the increase in the laminar combustion speed are due to the increase in the mole fraction of H radicals during the combustion process.Therefore,the increase in the initial pressure will reduce the mole fraction of H radicals,thereby affecting the laminar combustion speed.