Research On Complex Wave And Flame Propagation Characteristics Of Internal Combustion Wave Rotor

The internal wave rotor combustor,as a new conceptual combustion apparatus,possesses the advantages of wave rotor pre-pressurization and efficient constant volume combustion,which improve the performance of various kinds of engines and machinery significantly.It compresses the airflow by pressure wave,shock wave and other unstable complex wave systems which generate under special circumstances and thus implement pre-pressurization.At the same time,it can realize the constant volume combustion of high efficiency of thermal cycle by using the detonation mode.This thesis takes the internal wave rotor combustor as the research object and studies the complex wave of the wave rotor combustor as well as the flame propagation with experiment and numerical methods,at the same time,the different blockage ratio of spoiler and different mixed gas filling speed and different nitrogen dilution mixed gas effecting on the wave and flame propagation characteristics.The main research results are as follows:(1)In view of the simulation of the combustion process,Using direct relational graph(DGR),quasi steady state hypothesis(QSSA)and sensitivity analysis method,a simplified mechanism for the reaction including 23 components with 55 steps is established.Compared the ignition delay time,flame propagation speed and concentration of combustion process with the detailed mechanism,which is verified that the simplified mechanism can be well applied to ethylene combustion process simulation.(2)Through the analysis of structure and working process of internal combustion wave rotor,three kinds of simplified calculation model of the internal combustion wave rotor including single channel two-dimensional internal combustion wave rotor model,full channel two-dimensional internal combustion wave rotor model and full channel three-dimensional internal combustion wave rotor model was established.Then,according to the flow and combustion characteristics of the internal combustion wave rotor,the calculation method for the simulation of the working process of the internal combustion wave rotor is determined.(3)A detailed analysis of the interaction process of wave and flame of single channel two-dimensional internal combustion wave rotor was done,which generally divided into three stages: one is the wave leads flame spread,two is waves hit the end wall and act flame front,the three is wave to hit the end wall and catch up with the flame front.Joining the spoiler,wave and flame in the first stage realize coupling.With spoiler blockage ratio increase,wave and flame coupling time and distance are reduced.When the nitrogen dilution reaches 0.8,the flame and wave can’t realize coupling in the first stage because the intensity of the combustion process is weakened.A detailed analysis of the interaction process of wave and flame of the whole channel two-dimensional internal combustion wave rotor was done.Considering the mixed gas filling process,wave and flame quickly coupled together,then the detonation wave spread in the rotor channel.To be spread to the fuel and air interface,wave and flame appeared decoupling.After that,wave impact wall and reflection.The flame continues to spread forward until the premixed gas is depleted in the channel.The increase of gas filling speed is more conducive to the pressurization process.However,when the speed of mixture filling is too large,there will be a mixed gas overflow channel.After that,increasing the speed of mixing gas will not benefit the subsequent ignition process.A detailed analysis of the interaction process of wave and flame of the whole channel three-dimensional internal combustion wave rotor was done.Under this model,the wave and flame can’t be coupled but the average velocity of flame propagation in the whole process reaches 106.6m/s.The fast combustion mode is realized.When the exhaust seal plate is opened,the high temperature and high-pressure gas in the rotor channel will be discharged outward.A series of expansion waves will appear.The expansion wave propagating into the channel can reduce the pressure and temperature in the channel,which is conducive to the filling process of the next working cycle.(4)The simplify internal combustion wave rotor experimental system was carried out,by which the pressure gain and flame propagation characteristic was researched with different blockage ratio.The results show that there is a spoiler can greatly improve the strength of pressure wave in the rotor channel.At the same time as the spoiler blockage ratio increase the average flame propagation speed increase.The maximum average flame propagation speed can be obtained at Br=38.91%.