Numerical Simulation And Experimental Study On Microwave Ignition

With the increasingly severe energy and environmental problems,there is an urgent need to speed up the upgrading of industrial technologies for energy conservation and emission reduction of internal combustion engines.Among many new technologies,lean combustion can not only make full use of fuel and reduce the air exchange loss of the engine,but also reduce the emission of pollutants.The general ignition technology faces the problems of misfire,low flame propagation speed,unstable ignition and the like under the lean-burn condition,while the microwave ignition technology can not only greatly improve the combustion stability and combustion efficiency under the lean-burn condition,but also effectively expand the lean-burn limit.Therefore,the research on microwave ignition technology is of great significance to the development of energy saving and emission reduction technology for internal combustion engines.At present,the research on the mechanism of microwave resonant cavity gas discharge is not clear.Microwave ignition is the result of interaction between microwave spark plug resonant cavity discharge and plasma.Based on the microwave spark plug structure and the ionization reaction equation of air discharge,this paper studies the changes of resonant cavity and plasma characteristics in resonant cavity air discharge when microwave signal parameters change.The research results show that the experimental results of the effect of pulsed microwave signals on spark plug discharge are consistent with the numerical simulation results.The range of plasma discharge can be controlled by adjusting the microwave signal parameters.This research not only provides important guiding significance for understanding the coupling mechanism of microwave spark plug plasma discharge and optimization of pulse microwave input signal,but also lays a theoretical research foundation for practical research of microwave discharge ignition.Traditional spark plug ignition only relies on spark arc discharge to ignite combustible mixture,while microwave ignition can also realize combustion and combustion-supporting effect besides microwave discharge.Therefore,microwave ignition is not only suitable for internal combustion engines,but also for thermal power plants,boiler plants and other occasions that need to accelerate the full combustion of fuel and reduce pollutant emissions.According to the characteristics of microwave ignition,the ignition experimental research studies the influence of pulse microwave signal parameter changes on microwave discharge and microwave combustion-supporting from single pulse sequence ignition and double pulse sequence ignition respectively.The results show that the combustion performance of dual-pulse series microwave ignition is better than that of single-pulse series microwave ignition as a whole.Increasing the pulse period or duty cycle can effectively expand the lean burn limit and improve the ignition success rate,while low period and low duty cycle combustion-supporting pulse series have more obvious promotion effect on combustion.Therefore,adjusting the pulse microwave signal parameters can not only optimize the ignition and combustion performance,but also realize the real-time control of the combustion state,providing direction and possibility for the precise controllability of microwave ignition.In addition,the difference in combustion performance of microwave ignition in methane-air and methane-oxygen shows that the combustion state is related to the composition of combustion gas.The comparative combustion experimental results of microwave ignition and traditional ignition show that the combustion performance of microwave ignition is far better than traditional spark ignition.Microwave ignition can realize stable and rapid combustion under the condition of lean burn equivalence ratio,that is,microwave ignition can greatly expand the lean combustion limit while realizing energy saving and emission reduction.Therefore,microwave ignition is a kind of ignition method with great development prospect and future.The simulation and experimental research on microwave discharge and microwave combustion-supporting in this paper provide an important theoretical and experimental research foundation for the practical and industrial development of microwave ignition.