Characteristic Research On Integrated-regulation Flow Path Of Ramjet In Wide Speed Range

Hypersonic technology is a commanding high point in the field of aerospace technology,hypersonic vehicle in wide speed range is the key to the next step of research,ramjet in wide speed range is the core foundation of its propulsion system.In this dissertation,a ramjet with integrated-regulation flow path in wide speed range,which is able to break the performance boundary of fixed-geometry ramjet,has been proposed.The performance evaluation,numerical simulations and ground tests have been carried out for the following aspects:In order to extend the speed range,the design of ramjet with integrated-regulation flow path in wide speed range is proposed.Based on the results obtained from thermodynamic cycle analysis,the possibility that ramjet with integrated-regulation flow path maintains high performance in wide speed range is verified and the design method of geometric matching between the inlet and combustor is provided.Unsteady numerical calculations equipped with dynamic mesh method have been carried out to study the aerodynamic performance of a supersonic inlet with a translating cowl.It is found that the aerodynamic performances of the inlet at different flight Mach numbers have different variation trends due to the different moving directions of cowl,and the critical internal contraction ratios for inlet passage have been obtained.The inlet with translating cowl has three types of buzz.The unbalance between the inlet capture capability and flux capability is the cause of the inlet buzz.The geometric regulation forces the transition of buzz mode.The path of the large-size separation's leading edge on the external compression wall and the variation of inlet drag are provided.Unsteady numerical calculations have been carried out to study the motion characteristics of shock train affacted by the dynamic background waves.The dynamic evolution of background waves in supersonic inlet/isolator with translating cowl is given.Under the influence of the dynamic background waves,the shock train has three motion forms: abrupt motion cross the shock attachment point on the wall,oscillation around separation and steady movement.The motion of the shock train has obvious path dependence characteristic,when the direction of cowl changes.The frequency of shock train forced oscillation is approximately equal to the one of backpressure at the isolator exit.The increase of backpressure ratio at the isolator exit would intensify the forced oscillation of shock train.A configuration of smooth supersonic combustor is proposed.Numerical calculations and ground direct-connection experiments have been carried out to study the performance of variable-geometry combustors with different structures.It is discovered that the length of heat release increases with the augment of combustor expansion ratio.Compared with the deflected combustor,the thrust augmentation of smooth combustor is larger,and the smaller the deflection angle of the combustor,the larger the thrust augmentation.Numerical calculations have been carried out to study the performance of a ramjet with integrated-regulation flow path in wide speed range.The variation trend of combustor expansion ratio and aerodynamic performance of the matching inlet are given.The specific impulse of a ramjet with integrated-regulation flow path in wide speed range is obtained from numerical results.The integrated-regulation flow path extends the speed range.Further optimization of the geometric matching rules between the inlet and combustor can effectively improve the performance of ramjet.