Investigation On Combustion Process And Propulsive Performance Of Rotating Detonation Engine

On the background of the engineering application of rotating detonation engine(RDE),the flowfield structure and propagation characteristics of rotating detonation waves(RDWs)in the combustion chamber and the effects of plume flowfield on the engine’s propulsive performance are investigated through theoretical analysis,numerical simulations and experimental investigations.The influence factors that affect the propagation mode of the RDWs under premixed multi-injector injection conditions are analyzed.Compared to the ideal injection model,the contact area between high-temperature detonation products and fresh premixed gas under premixed multi-injector injection condition is larger,and the pre-burning phenomena is more obvious.When the heat released by pre-burning has been accumulated to a certain extent,new detonation waves can be induced and the propagation mode in the combustion chamber will change.The mode-transition phenomena occurs more easily when the exit width of the injectors is smaller.With a constant injection pressure of the premixed gas,the number of RDWs is basically proportional to the chamber perimeter.As the mass flow rate of the premixed gas increases,the number of RDWs in the combustion chamber increases.When the equivalence ratio of the premixed gas is too small,it is hard to induce new detonation waves.The flowfields and propagation characteristics of RDWs within annular RDEs and hollow RDEs under non-premixed conditions are investigated.In both two types of RDEs,the RDW can introduce pressure perturbations in the plenums,making the injection pressure in the plenums increase.This effect is more obvious for annular RDEs.The pressure in the combustion chamber increases when the RDW is propagating,and the axial velocity decreases,which can enhance the mixing quality of the propellants.As the mass flow rate increases,the number of RDWs in the combustion chamber increases.The injection structure has important effects on the propagation of the RDWs.Under the same operating condition,the number of RDWs in the combustion chamber decreases as the air throat width increases.Keeping the total hydrogen injection area constant,the propagation velocity decreases as the number of injectors decreases.The mixing quality is better when air is injected radially and hydrogen is injected axially,and the engine thrust is larger.Under non-premixed conditions,some propellants flow out of the combustion chamber without being burned due to the imperfect mixing,resulting a performance loss,which is more obvious in hollow RDEs.The propulsive performance of hollow RDEs has obvious decrease compared to annular RDEs.By attaching a Laval nozzle to the hollow RDE,the thrust can be increased and is more stable.As the contration ratio of the Laval nozzle increases,the height of the RDW decreases,and the engine’s thrust increases.The plume flowfields of annular RDEs and hollow RDEs and their effects on the propulsive performance are investigated.The thrust calculation formula considering the effects of endfaces is derived.There are spiral pressure waves developing radially outwards in the plume flowfields.For annular RDEs,there is a negative pressure region near the endface of the inner cylinder under high environment pressure condition,making the average thrust of the engine decrease;and the pressure distribution on the endface of the outer wall is unsteady,making the total thrust of the engine to fluctuate.The effects mentioned above is small under low environment pressure condition,which can be neglected.For hollow RDEs,the errors brought by using the thrust calculation method without considering endface effects is obviously smaller than the annular RDEs,but the unsteadiness of the engine’s thrust is still underestimated.