Numerical Investigation On The Flow Field And Combustion Performance Of Two Phase Rotating Detonation Wave Fueled By N-hepatne And Air

Different from traditional deflaration combustion,detonation combustion is a combustion form similar to the constant volume combustion process.Under the same total pressure of inlet air,the combustion products of detonation combustion have higher pressure than those of deflagration combustion.The detonation combustor based on detonation combustion has higher cycle efficiency than the conventional combustor based on deflagration combustion.Among them,the rotating detonation chamber has stable thrust,wide inlet range and continuous operation with just one ignition due to its inherent propagation characteristics.Rotating detonation chamber is gradually becoming a research hotspot recently.Besides,compared with gases fuel,liquid fuel has the characteristics of high storage safety and high energy density.Therefore,the rotating detonation combustor with liquid fuel has a huge application prospect.Before designing a two-phase rotating detonation chamber,it is necessary to conduct a systematic research on the characteristic parameters of two-phase rotating detonation waves,such as detonation flow field characteristics and combustor propulsion performance.It is worth noting that although the research on two-phase rotating detonation has been widely carried out,there are some shortcomings in the research,such as the unclear interaction between detonation wave and droplet,and the research on the chemical reaction process in detonation flow field has not been carried out.Based on the key issues in the current research of two-phase rotating detonation,this paper conducted a numerical simulation study of the formation process,propagation characteristics,and combustion chamber performance of two-phase rotating detonation wave fuled by n-heptane/air without considering the surface cooling problems of the combustion chamber wall.The main research work are as follow:(1)In this paper,the mixing problem of fuel and oxidizer in the two-phase rotating detonation combustor is studied firstly.By comparing the distribution of droplet diameter and the mixing efficiency of fuel and oxidizer at different axial positions,the effects of the combustor head structure and the number of fuel injectors on the mixing efficiency of fuel and oxidizer are studied.After that,by changing the back pressure to simulate the uneven pressure distribution in the real detonation flow field,the influence of the back pressure on the mixing efficiency of fuel and oxidant is further investigated.Finally,by comparing the mixing process under different fuel injection pressures,the fuel injection scheme that can satisfy the stable propagation of two-phase rotating detonation wave is determined.It is found that compared with the structure of axial air injection along the combustor,the radial air injection along the combustor has a more obvious reflux zone at the expansion section of Laval nozzle.The flow direction of n-heptane droplet and air jet changes to axial flow when flowing through this area under the influence of the reflux zone.The mixing efficiency of fuel and oxidizer increases rapidly under the influence of the reflux area.(2)After obtaining a reasonable inlet structure,the propagation process of two-phase rotating detonation wave is simulated in a two-dimensional computational domain.The flow field structure of two-phase rotating detonation wave,the interaction relationship between detonation wave and droplets and the detailed chemical reaction process in the fuel filling area are investigared in this paper.On this basis,the effects of initial droplet diameter and the total temperature of inlet air on the characteristic parameters of detonation wave are studied.It is found that the propagation velocity of the detonation wave and the detonated fuel fraction decrease with the increase of the initial diameter of the droplet.In the fuel filling area,the intermediate species R’O2H of low temperature chemical reaction(LTC)has a significant effect on the change of chemical explosion mode in the undetonated mixture.(3)After obtaining the basic flow field characteristics of the two-phase rotating detonation wave,this paper carried out a three-dimensional numerical simulation to investigate the propagation characteristics of the non-premixed two-phase rotating detonation wave.The development process of two-phase rotating detonation wave under the condition of high inlet pressure and inlet temperature are analyzed.Among them,the characteristics of the flow field on the inner and outer walls of the unpremixed rotary detonation combustion chamber are also compared.Besides,in order to explore the stable working range of the two-phase rotating detonation chamber,the influence of the mass flow rate and equivalence ratio on the formation process and the stability of the detonation wave are relatively analyzed.It is found that when the detonation wave propagates stably,the pressure on the outer wall of the combustion chamber is higher than that on the inner wall.The increase of the mass flow rate of inlet air will increase the velocity of the oxidizer and lead to the increase of the mixing efficiency of the fuel and oxidizer,and eventually lead to the increase of the detonation pressure.Under the condition of different equivalence ratios of combustor,the development processes of detonation wave are obviously different.When the equivalence ratio gradually increases from 0.8 to 1.2,the formation time of detonation wave gradually decreases with the increase of the equivalence ratio.With the further increase of the equivalence ratio,the time required for the formation of stable detonation increases again.