Investigations On Two-phase Fuel Detonation Transition Characteristics And Its Application In Rotating Detonation Engine

Rotating detonation engine is one of the new propulsion devices which use the detonation process as the energy conversion mode.Compared with the traditional engine,the RDE has a more compact structure and higher thermal cycle efficiency.It attracts more and more attentions recently.At present,most investigations focus on the gas-fuel RDE.Liquid fuel has higher density specific impulse.With the same volume of fuel,it can produce a greater impulse.Therefore,this paper studies two-phase fuel detonation transition characteristics and its application in Rotating Detonation Engine through experimental and numerical simulation approaches.The deflagration to detonation transition(DDT)process is experimentally studied with gasoline and air mixture.The flame and pressure signals are measured to analyze the DDT time and distance.It was found that the addition of oxygen concentration in air reduces the DDT distance and time significantly,however,it has little effect on the formation phase of detonation wave.The higher of the oxygen concentration,the faster of the detonation velocity,the smaller of the induction time and the induction distance.The hydrogen peroxide solution was added to the gasoline and the mixture was successfully detonated,but it has little effect on detonation transition characteristics.Gasoline and hydrogen mixed fuel was successfully detonated.With the increase of the hydrogen mass flow rate,the DDT time decreased and the velocity of the initially formed detonation wave was increased.Numerical simulation of the DDT in detonation tube.The numerical simulation reveals that there are two forms of the onset of detonation.,one is that the local hot spots resulting from the mach stem which was generated by the shock reflection from the wall or the obstacles,The other is that strong shock wave constantly catch up with the fire front and spread together.Increasing the volume fraction of oxygen can reduce the DDT distance and time.However,the initial deflagration develops to detonation immediately when the volume fraction of oxygen is greater than 40%.With the same equivalence ratio,a significant reduction in DDT time and distance is achieved with the addition of hydrogen in the octane.And a shortest DDT time and distance are obtained when the volume fraction of hydrogen is 20%.The experiments of liquid-fuelled RDE was carried out by using gasoline.The results show that the detonable equivalence ratios of RDE ranges from 0.75 to 1.8.The direct initiation of the detonation wave in the annular chamber was never achieved by the pre-detonation tube.The detonation wave issued from the pre-detonation tube decays gradually,and a rich oxygen air are required to the formation of detonation wave.There is a transition from single-wave mode to double-wave mode during the operation of RDE,and the detonation engine operates steadily with two waves in the annular chamber.