Study On The Influence Of Hydrogen Ratio On The Propagation Characteristics Of Kerosene-air Rotating Detonation Wav

Detonation has the characteristics of high thermal cycle efficiency,high energy release density and high heat release rate.Rotating detonation engine(RDE)is a new engine based on detonation combustion,which generates thrust by forming one or more rotating detonation waves propagating along the circumferential direction in a annular combustion chamber.However,in the RDE with normal temperature kerosene and air as working substance,if the diameter of kerosene droplets after atomization is too large or the mixing characteristics with air are poor,it will lead to decoupling and extinguishing.By adding highly reactive gaseous fuel such as hydrogen in the fuel,the probability of successful initiation and the stability of detonation wave propagation can be greatly increased.Therefore,numerical simulation and experimental research are adopted in this paper to study the propagation characteristics of hydrogen-kerosene-air RDE.The main work is as follows:Two-dimensional numerical simulation of internal flow field of hydrogen-kerosene-air RDE was carried out.The effects of mass flow rate and proportion of hydrogen on the propagation characteristics and modes of rotating detonation wave were analyzed,and the gasliquid non-uniformity in gas-liquid two-phase detonation was explored.Numerical results show that the detonation wave has three propagation modes,namely single wave mode,single wave mode caused by double wave collision and double wave mode caused by double wave collision,under the successful detonation condition.The double wave mode is easily generated by increasing mass flow rate and hydrogen proportion.The weak shock wave generated during the initial ignition collides with the detonation wave and transmits it.A hot spot is induced by the transmitted shock wave near the slow-burning area and forms a new detonation wave.After a series of collisions,transmitting,and enhancing processes,a stable single wave mode or double wave mode is finally formed.When the detonation wave stabilizes,the internal flow field during the stable propagation of rotating detonation wave in the combustion chamber can be divided into slow-burning area,combustion-rich area,oxygen-rich area and filling area due to the mal-distribution of gas and liquid in the combustion chamber.Numerical simulation of the influence of different injection structures on hydrogenkerosene-air RDE was carried out,and the propagation characteristics of rotating detonation engine with different injection structures of inlet nozzle and different proportion of hydrogen were studied.The interaction between different nozzle structures and combustor was analyzed.The results show that when the proportion of hydrogen in fuel is increased to 29.8%,the rotating detonation wave propagates in double wave mode when the cross-sectional area of the nozzle outlet is small.The detonation wave and reflected shock wave will compress the airflow at the nozzle outlet,thus affecting the nozzle inlet process.The flow states in the inlet nozzle can be divided into three states: reflux caused by detonation wave,no reflux but affected by detonation wave and not affected by detonation wave.The RDE experiments of hydrogen fuel and hydrogen-kerosene mixture fuel were carried out.The RDE ignition initiation process and self-sustaining propagation stage of rotating detonation wave of two different fuels were studied,and the propagation characteristics of rotating detonation wave under different equivalent ratio and different proportion of hydrogen were analyzed.The results show that it takes tens of milliseconds from the ignition signal to the pressure signal collected by PCB.After the initial detonation wave of hydrogen-kerosene-air RDE propagate into the combustion chamber,the pressure signal is weaker and weaker,finally decoupling.A stable self-sustaining detonation wave is formed after the decoupling and reinitiation process repeated several times in the combustor.In hydrogen-air RDE,when the equivalent ratio is reduced to 0.56,detonation and deflagration coexist in the combustion chamber.In hydrogen-kerosene-air RDE detonation velocity deficit is higher.When the proportion of hydrogen is relatively low,detonation and deflagration coexist in the combustion chamber.When the proportion of hydrogen is higher,the rotating detonation wave propagating frequency will increase at a certain moment in a sudden.