Experimental Research And Kinetics Analysis On Ignition Characteristics Of Ethylene Under Pt Catalysis

Catalytic combustion,as a new combustion technology,has important significance in fuel ignition and flame stabilization.Based on the experimental system of rapid compressor,the ignition characteristics of ethylene under Pt catalysis are studied quantitatively,which provides theoretical basis for low temperature ignition technology of engine.Firstly,based on the rapid compressor system of measuring medium and low temperature,the PT catalytic drying and suspension device is designed,and a reliable catalytic combustion system of the compressor is established.The suspension characteristics of the catalyst were studied,and the experimental flow of Pt catalytic combustion was developed in the lower settlement rate.Secondly,through the above-mentioned test system,the equivalent ratio of 0.5-1.5,the temperature of the upper and the dead center is 847K-975K,the pressure of the top stop point is 3.5MPa-5.30MPa,and the ignition delay time of ethylene with and without catalyst is measured.The results show that the initial pressure will affect the active surface area of catalyst when the gas is distributed,and the surface area of catalyst increases with the increase of initial pressure.With the increase of pressure,the ignition delay time decreases greatly with the increase of initial pressure,and the ignition delay time decreases greatly with the increase of catalyst active surface area under the same working condition.At the same Pt catalyst quantity,the initial pressure and experimental temperature are certain,the temperature and pressure of the upper and the end points decrease with the increase of the equivalence ratio,while in the same equivalence ratio and the same initial pressure,with the rise of the temperature of the top dead center,the ignition delay time is shortened,and then under the same working conditions,The ignition delay time of ethylene with catalyst addition is shorter than that without catalyst,and the ignition delay time increases with the temperature decreasing.Then,the simulation analysis of the kinetic model of gas chemical reaction was carried out in CHEMKIN Pro 17.0.The USC-II mech model and Aramco mech 2.0 model are selected to simulate the ignition delay time of ethylene gas combustion in different equivalence ratio,different top and end point temperature and different top and end point pressure.The comparison with experimental data shows that USC-II model can predict the ignition delay time of ethylene gas combustion well.In the aspect of catalytic combustion,the mechanism of 0.5-1.5,847K-975K,3.5MPa-5.30MPa of the upper and dead center pressure is verified by modifying the existing surface catalytic reaction mechanism.The results show that the modified surface catalytic model can better predict the catalytic combustion of ethylene.The operating range of ethylene,and further analyzes the ignition characteristics of ethylene at medium and low temperature through chemical dynamics simulation,sensitivity analysis and main path analysis.The results show that the change of ignition delay time of ethylene at medium and low temperature is based on the change of reaction path,at higher temperature,The unit reaction of ethylene gas phase reaction plays a leading role in all reactions.At low temperature,the reaction path changes,and the C₂H₄+HO₂=CH₂OCH₂+OH mechanism is weakened,while the corresponding C₂H₄（1S）=C₂H₄（2S）,C₂H₄+Pt（S）=C₂H₄（1S）is the main promoting reaction.This is because the surface reaction of adsorption is relatively high at low temperature.C₂H₄（1S）and C₂H₄（2S）adsorbed by Pt provide support for ethylene dehydrogenation and cracking reaction on the surface.For the gas phase reactions such as C₂H₄+HO₂=CH₂OCH₂+OH,the influence of system temperature is inhibited.Secondly,Pt catalyst can promote ignition delay time at different temperatures,but its mechanism is different.At low temperature,the catalyst mainly adsorbs ethylene and promotes ethylene surface reaction.Meanwhile,catalyst also participates in the third phase reaction to promote ignition.At high temperature,Pt adsorbs O₂ and promotes O₂to decompose into free radical O（S）,and desorbs to form a strong free radical o in the environment,which promotes the ignition of high temperature gas phase.In the process of medium temperature,the third part participated in the reaction to the maximum,and on Pt surface,ethylene fuel adsorption and O₂ adsorption process were carried out simultaneously,forming the surface competition and promoting the ignition.