A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front o...A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front of a blunt body into a conical shock, and the lateral jets work to protect the spike tip from overheating and to push the conical shock away from the blunt body when a pitching angle exists during flight. Experiments are conducted in a hypersonic wind tunnel at a nominal Mach number of 6. It is demonstrated that the shock/shock interaction on the blunt body is avoided due to injection and the peak pressure at the reattachment point is reduced by 70% under a 4° attack angle.展开更多
The paper focuses on the triple jets interaction with a hypersonic external flow on a revolution body. The experimental model is a ogive-cylinder body with three supersonic nozzles, which are aligned along the flow di...The paper focuses on the triple jets interaction with a hypersonic external flow on a revolution body. The experimental model is a ogive-cylinder body with three supersonic nozzles, which are aligned along the flow direction. The freestream Mach numbers are 5 and 6. The spatial and surface flow characteristics are illustrated by the schlieren photographs and the typical pressure distribution. The results show that there are multi-wave system, separation, reattachment, multi-peak pressure, high-pressure and low-pressure zone boundaries obvious distinction in tri-jets interference flowfield. The present paper also analyzes how do the pressure ratio, the angle of attack, and Mach number effect on tri-jets interaction characteristics.展开更多
Aimed at the problem of store separation from internal cavity,this paper innovatively puts forward a separation scheme of using lateral jet to assist store safe separation.The jet ensures that the store is continuousl...Aimed at the problem of store separation from internal cavity,this paper innovatively puts forward a separation scheme of using lateral jet to assist store safe separation.The jet ensures that the store is continuously subjected to down head moment during separation,so as to ensure safe separation.The wind tunnel free drop test technique with lateral jet is established,which can ensure that there is no support interference in the motion process of the store and more truly simulate the motion of the store.The feasibility of the new separation scheme is proved by wind tunnel test.The test shows that the new scheme can also change the more dangerous state into a safe state.Through the analysis of the test data,the pitching moment coefficients of the store under different pressures in the high-pressure cylinder are obtained,and the effects of aircraft and cavity on the pitching moment of the store are obtained.The 3 stages of store passing through cavity shock wave are found.The results show that the lateral jet provides the store with continuous head down moment,and makes the store overcome the head up moment caused by the shock wave in front of the cavity,so as to ensure the safety of separation.展开更多
Raindrop impact erosion has been observed since early days of aviation,and can be catastrophic for exposed materials during supersonic flight.A single impact waterjet apparatus is established for mimicking drop impact...Raindrop impact erosion has been observed since early days of aviation,and can be catastrophic for exposed materials during supersonic flight.A single impact waterjet apparatus is established for mimicking drop impacts at the velocities between 350 m/s and 620 m/s.Carbon Fiber Reinforced Polymer(CFRP)laminates with three different surface morphologies and specimen thicknesses are tested here.A central region with no visible damage has been noticed,surrounded by a"failure ring"with common damage patterns including resin removal,matrix cracking,fiber breakage and mass fiber loss.Asymmetric features are presented in the"failure ring"whose whole scope extends larger along the longitudinal direction than the transverse direction of the top layer.The mechanism of the resin removal is related to fiber-matrix debonding,and its onset and propagation can be facilitated by initial surface asperities with the shear action of the lateral jetting.In cases of multiple impact,good surface quality can slow down the evolution of resin removal and fiber exposure on the CFRP surface,reducing the erosion speed and delaying the occurrence of structural damages in the subsequent impacts.Rayleigh wave dominates the occurrence of matrix cracking on the CFRP surface,and subsequently,results in material loss and peeling of the top-layer because of lateral flow.With the increase of the specimen thickness,both the interlaminar and intralaminar failures decrease as the impact damage mechanism changes from plate bending stress to the reflection of stress waves.展开更多
基金the National Natural Science Foundation of China (10632090)the National Aerodynamic Pre-Research Foundation (513130401)
文摘A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front of a blunt body into a conical shock, and the lateral jets work to protect the spike tip from overheating and to push the conical shock away from the blunt body when a pitching angle exists during flight. Experiments are conducted in a hypersonic wind tunnel at a nominal Mach number of 6. It is demonstrated that the shock/shock interaction on the blunt body is avoided due to injection and the peak pressure at the reattachment point is reduced by 70% under a 4° attack angle.
文摘The paper focuses on the triple jets interaction with a hypersonic external flow on a revolution body. The experimental model is a ogive-cylinder body with three supersonic nozzles, which are aligned along the flow direction. The freestream Mach numbers are 5 and 6. The spatial and surface flow characteristics are illustrated by the schlieren photographs and the typical pressure distribution. The results show that there are multi-wave system, separation, reattachment, multi-peak pressure, high-pressure and low-pressure zone boundaries obvious distinction in tri-jets interference flowfield. The present paper also analyzes how do the pressure ratio, the angle of attack, and Mach number effect on tri-jets interaction characteristics.
基金supported by the National Natural Science Foundation of China(Nos.U21B2054,11772317)supported by the Open Fund of Key Laboratory of Icing and Anti/Deicing,China(No.IADL20200408).
文摘Aimed at the problem of store separation from internal cavity,this paper innovatively puts forward a separation scheme of using lateral jet to assist store safe separation.The jet ensures that the store is continuously subjected to down head moment during separation,so as to ensure safe separation.The wind tunnel free drop test technique with lateral jet is established,which can ensure that there is no support interference in the motion process of the store and more truly simulate the motion of the store.The feasibility of the new separation scheme is proved by wind tunnel test.The test shows that the new scheme can also change the more dangerous state into a safe state.Through the analysis of the test data,the pitching moment coefficients of the store under different pressures in the high-pressure cylinder are obtained,and the effects of aircraft and cavity on the pitching moment of the store are obtained.The 3 stages of store passing through cavity shock wave are found.The results show that the lateral jet provides the store with continuous head down moment,and makes the store overcome the head up moment caused by the shock wave in front of the cavity,so as to ensure the safety of separation.
基金supported by the National Natural Science Foundation of China(Nos.11832015,12072289 and 12172304).
文摘Raindrop impact erosion has been observed since early days of aviation,and can be catastrophic for exposed materials during supersonic flight.A single impact waterjet apparatus is established for mimicking drop impacts at the velocities between 350 m/s and 620 m/s.Carbon Fiber Reinforced Polymer(CFRP)laminates with three different surface morphologies and specimen thicknesses are tested here.A central region with no visible damage has been noticed,surrounded by a"failure ring"with common damage patterns including resin removal,matrix cracking,fiber breakage and mass fiber loss.Asymmetric features are presented in the"failure ring"whose whole scope extends larger along the longitudinal direction than the transverse direction of the top layer.The mechanism of the resin removal is related to fiber-matrix debonding,and its onset and propagation can be facilitated by initial surface asperities with the shear action of the lateral jetting.In cases of multiple impact,good surface quality can slow down the evolution of resin removal and fiber exposure on the CFRP surface,reducing the erosion speed and delaying the occurrence of structural damages in the subsequent impacts.Rayleigh wave dominates the occurrence of matrix cracking on the CFRP surface,and subsequently,results in material loss and peeling of the top-layer because of lateral flow.With the increase of the specimen thickness,both the interlaminar and intralaminar failures decrease as the impact damage mechanism changes from plate bending stress to the reflection of stress waves.
