Research On Isolator Of Ramjet Rotating Detonation Engine

Ramjet rotating detonation engine(RRDE)is a new type of propulsion device based on detonation combustion.When RRDE works,the air trapped in the intake port is used as the oxidant to organize the fuel for rotating detonation combustion after entering the combustor.It has the advantages of fast heat release,small entropy increase and high thermal cycle efficiency,so it has a broad application prospect.In order to suppress the influence of unsteady pressure disturbance on the upstream steady inlet in rotating detonation combustor,the inlet and combustor are usually connected by isolator,but the research on RRDE isolator is relatively less at present.In this paper,the research on RRDE isolator is carried out by means of numerical simulation and experiment.Firstly,the numerical simulation of the whole flow field of the gas-liquid two-phase isolator and combustor with liquid kerosene fuel was carried out.The results show that a forward oblique shock wave will be induced to the upstream flow field of the fuel after rotary detonation combustion.For the injection scheme of the inner wall of the fuel,the forward oblique shock wave has limited influence on the flow field of the isolator,and the air flow maintains supersonic throughout the isolator.The forward nozzle position can improve the mixing efficiency of the fuel.For the strut injection scheme,the introduction of the strut will cause an end normal shock wave in the upstream of the isolation section,and the forward oblique shock wave moves upstream and intersects with the end normal shock wave,resulting in greater flow loss;the fuel mixing efficiency of the strut injection scheme is better than that of the inner wall injection scheme;the forward displacement of the strut position is easy to cause the flame to propagate forward,which makes the detonation wave unable to propagate by itself.Then the anti pressure characteristics of the conventional isolation section,concave isolation section,S-ring isolation section and diaphragm isolation section are studied.It is found that for the conventional isolation section,the forward oblique shock wave will form shock string in the expansion section,and the first shock wave surface of the shock string is not completely perpendicular to the axis of the isolation section;the relative total pressure loss will be improved by changing the expansion parameters or expansion form of the conventional isolation section.For the cavity isolation section,the concave cavity can weaken the forward oblique shock wave,and its anti pressure capability is better than that of the conventional isolation section;when there is a middle interlayer,the relative total pressure loss of the isolation section is limited and not affected by the arrangement parameters of the ring joint;when there is no middle interlayer,the relative total pressure loss of the isolation section decreases obviously,and is in direct proportion to the depth of the cavity.For the S-ring isolation section,the forward oblique shock wave is effectively suppressed in the annular channel of the isolation section without shock disturbance to the straight circular channel.The total pressure recovery of the isolation section of S-type circular ring is better than that of the conventional isolation section and concave section under the same calculation conditions.For the partition isolation section,compared with the conventional isolation section,the introduction of diaphragm can improve the total pressure recovery of the flow field,but the staggered arrangement of the diaphragm will cause the flow field disorder,which can affect the upstream intake branch pipe and the downstream combustion chamber.Finally,RRDE direct connection test was carried out based on the S-shaped circular ring isolator.Under all test conditions,no high-frequency dynamic pressure signal was collected in the straight circular channel of the S-shaped circular ring isolator.The results show that the Sshaped circular ring isolator has good anti back pressure ability.Through the analysis of propagation mode of detonation wave,it is found that the complex phenomena such as double wave collision,single / double wave transition,steering and so on occur frequently in the process of detonation wave propagation.The results show that the lower limit of reactant equivalence ratio increases with the increase of air injection annular gap width,and intermittent detonation and end detonation appear in the test,which can be improved by increasing the equivalence ratio.