Shock waves can significantly affect the film cooling for supersonic flow and shock waves may have different influence when impinging in different regions.The present study numerically compared the results of shock wa...Shock waves can significantly affect the film cooling for supersonic flow and shock waves may have different influence when impinging in different regions.The present study numerically compared the results of shock wave impinging in three different regions and analyzed the effect of impinging region.The shock wave generators were located at x/s=5,25,45 with 4°,7°and 10°shock wave incidence.The mainstream Mach number was 3.2 and the coolant Mach number was 1.2 or 1.5.The numerical results illustrated that the shock wave impinged in the further upstream region led to a larger high-pressure region and a larger vortex in the boundary layer.Moreover,placing the shock wave generator upstream resulted in the lower mass fraction of coolant in the downstream region.The velocity in the upstream part of the cooling layer was lower than the midstream and downstream part,which resulted in the less ability to resist the shock wave impingement.Therefore,the upstream impingement deteriorated the cooling performance to a greater extent.The study also manifested that the stronger shock wave had a larger effect on supersonic film cooling.Increasing the coolant inlet Mach number can increase the blowing ratio and reduce the mixing,which was of benefit to improve cooling effect.展开更多
The Euler equations for two dimensional, steady, isentropic, and inviscid flow are considered. All the elementary waves are classified into incoming and outgoing waves under the assumption that there is a singular po...The Euler equations for two dimensional, steady, isentropic, and inviscid flow are considered. All the elementary waves are classified into incoming and outgoing waves under the assumption that there is a singular point in the configuration of the solution.The interactions of at most two incoming waves are dealt with in this paper, and all six kinds of configurations for the solutions are obtained. They are the Mach reflection (one kind), the shock wave S transmits contact discontinuity J (two kinds), the overtaking of two incoming shock waves (two kinds), and the collision of two incoming shock waves (one kind). 展开更多
The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film cool...The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film cooling.The results indicate that without shock-wave impingement and with helium as the coolant,segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection,especially at larger coolant Mach numbers.However,with nitrogen as the coolant,the cooling effect of the segmented-injection system is very close to that of the single-injection system.Mixing at the impinging region is enhanced significantly when there is an incident shock wave.When the shock wave impinges between the two coolant inlets,segmented cooling-stream injection improves film cooling effectiveness in the midstream and downstream regions more than single injection because only part of the cooling stream undergoes the enhanced mixing effect of the shock wave.The advantage of segmented injection is reduced when the impinging region is behind the second coolant inlet.The further downstream the impinging region,the smaller the associated advantage.展开更多
When a wave shaper is embedded in a liner,Mach wave will emerge above the liner,which affects the head shape of an explosively formed projectile.Mach wave parameters,including radius and pressure need to be determined...When a wave shaper is embedded in a liner,Mach wave will emerge above the liner,which affects the head shape of an explosively formed projectile.Mach wave parameters,including radius and pressure need to be determined to effectively match Mach wave with the liner,so that a good head shape can be obtained.An analytical calculation model for Mach wave parameter is presented based on three-shock theory,and the theoretical values agree well with the experimental ones.The analysis shows that when the radius of the wave shaper is constant,the radius of the Mach wave increases,whereas the pressure decreases while increasing the distance between the liner and the wave shaper.When the distance between the liner and the wave shaper is constant,the radius of the Mach wave increases,whereas the pressure decreases when decreasing the radius of the wave shaper.展开更多
In this paper, by taking into account the thickness of the incident shock as well as the influence of the boundary layer, we point out that even in a regular reflection there should be present a contact discontinuity....In this paper, by taking into account the thickness of the incident shock as well as the influence of the boundary layer, we point out that even in a regular reflection there should be present a contact discontinuity. By using the smallest energy criterion, the inclined angle of this contact discontinuity can be determined for differen incident angle. Then, with this inclined contact discontinuity, together with the law of conservation of mass, the mechanism for the transition from a regular reflection to a Mach reflection or a von Neumann reflection becomes clear. The important roles played by the leftest point in the reflected shock polar are identified.展开更多
In this paper, a realistic interpretation(REIN) of the wave function in quantum mechanics is briefly presented. We demonstrate that in the REIN, the wave function of a microscopic object is its real existence rather t...In this paper, a realistic interpretation(REIN) of the wave function in quantum mechanics is briefly presented. We demonstrate that in the REIN, the wave function of a microscopic object is its real existence rather than a mere mathematical description.Specifically, the quantum object can exist in disjointed regions of space just as the wave function is distributed, travels at a finite speed, and collapses instantly upon a measurement. Furthermore, we analyze the single-photon interference in a Mach-Zehnder interferometer(MZI) using the REIN. Based on this, we propose and experimentally implement a generalized delayed-choice experiment, called the encounter-delayed-choice experiment, where the second beam splitter is decided whether or not to insert at the encounter of two sub-waves along the arms of the MZI. In such an experiment, the parts of the sub-waves, which do not travel through the beam splitter, show a particle nature, whereas the remaining parts interfere and thus show a wave nature. The predicted phenomenon is clearly demonstrated in the experiment, thus supporting the REIN idea.展开更多
Based on Hong's theory, previous random models, and a generalized expression suitable for FFT calculation, the interaction between irregular waves and vertical walls is numerically simulated. The results of simu...Based on Hong's theory, previous random models, and a generalized expression suitable for FFT calculation, the interaction between irregular waves and vertical walls is numerically simulated. The results of simulation demonstrate that the wave energy changes with the incidence angle and the distance from the wall. Particularly, the Mach effect and the combined wave spectrum characteristics are analyzed in detail, which are significant in both theory and practice.展开更多
In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their lo...In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their load carrying capacity and stability, a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible air flow governing equations. The realizable κ-ε model was used as a turbulent closure illustrate that the interaction exists between shock waves The supersonic flow field near air inlets was analyzed. The flow structures and boundary layer, and the flow separation is formed at the lower comer and the lower wall around the point of a maximum velocity. The numerical results show that the conversion from supersonic flow to subsonic flow in spherical air bearing occurs through a shock region （pseudo-shock）, and the viscous boundary layer results in the flow separation and reverse flow near the shock. The calculation results basically agree with the corresponding experimental data.展开更多
鉴于爆震燃烧具有自增压、传播速度快等优点,提出了将燃气轮机中等压燃烧替换为爆震燃烧的理念,并建立了基于爆震燃烧的燃气轮机理想热力循环模型,对比研究了DCGT(detonation cycle of gas turbine)、Brayton和Humphrey 3种循环燃气轮...鉴于爆震燃烧具有自增压、传播速度快等优点,提出了将燃气轮机中等压燃烧替换为爆震燃烧的理念,并建立了基于爆震燃烧的燃气轮机理想热力循环模型,对比研究了DCGT(detonation cycle of gas turbine)、Brayton和Humphrey 3种循环燃气轮机的综合性能。在压气机压比、吸热量和透平背压相同的条件下,数据分析结果表明DCGT循环燃气轮机较其他2种循环更具优势,在压比为16时其循环热效率较Brayton循环提高15.4%,燃料消耗率降低13.5%;DCGT循环燃气轮机在压比为6.6时的总体性能与压比为16时的Brayton循环相当。展开更多
基金supported by the the National Science and Technology Major Project of China(No.2017-III-0003-0027)the Science Fund for Creative Research Groups of the NSFC(No.51621062)Tsinghua University-Zhang Jiagang Joint Institute for Hydrogen Energy and Lithium-Ion Battery Technology。
文摘Shock waves can significantly affect the film cooling for supersonic flow and shock waves may have different influence when impinging in different regions.The present study numerically compared the results of shock wave impinging in three different regions and analyzed the effect of impinging region.The shock wave generators were located at x/s=5,25,45 with 4°,7°and 10°shock wave incidence.The mainstream Mach number was 3.2 and the coolant Mach number was 1.2 or 1.5.The numerical results illustrated that the shock wave impinged in the further upstream region led to a larger high-pressure region and a larger vortex in the boundary layer.Moreover,placing the shock wave generator upstream resulted in the lower mass fraction of coolant in the downstream region.The velocity in the upstream part of the cooling layer was lower than the midstream and downstream part,which resulted in the less ability to resist the shock wave impingement.Therefore,the upstream impingement deteriorated the cooling performance to a greater extent.The study also manifested that the stronger shock wave had a larger effect on supersonic film cooling.Increasing the coolant inlet Mach number can increase the blowing ratio and reduce the mixing,which was of benefit to improve cooling effect.
文摘The Euler equations for two dimensional, steady, isentropic, and inviscid flow are considered. All the elementary waves are classified into incoming and outgoing waves under the assumption that there is a singular point in the configuration of the solution.The interactions of at most two incoming waves are dealt with in this paper, and all six kinds of configurations for the solutions are obtained. They are the Mach reflection (one kind), the shock wave S transmits contact discontinuity J (two kinds), the overtaking of two incoming shock waves (two kinds), and the collision of two incoming shock waves (one kind).
基金co-supported by the National Key R&D Program of China (No. 2018YFB1900500)the National S&T Major Project of China (No. J2019-Ⅲ-0019-0063)
文摘The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film cooling.The results indicate that without shock-wave impingement and with helium as the coolant,segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection,especially at larger coolant Mach numbers.However,with nitrogen as the coolant,the cooling effect of the segmented-injection system is very close to that of the single-injection system.Mixing at the impinging region is enhanced significantly when there is an incident shock wave.When the shock wave impinges between the two coolant inlets,segmented cooling-stream injection improves film cooling effectiveness in the midstream and downstream regions more than single injection because only part of the cooling stream undergoes the enhanced mixing effect of the shock wave.The advantage of segmented injection is reduced when the impinging region is behind the second coolant inlet.The further downstream the impinging region,the smaller the associated advantage.
文摘When a wave shaper is embedded in a liner,Mach wave will emerge above the liner,which affects the head shape of an explosively formed projectile.Mach wave parameters,including radius and pressure need to be determined to effectively match Mach wave with the liner,so that a good head shape can be obtained.An analytical calculation model for Mach wave parameter is presented based on three-shock theory,and the theoretical values agree well with the experimental ones.The analysis shows that when the radius of the wave shaper is constant,the radius of the Mach wave increases,whereas the pressure decreases while increasing the distance between the liner and the wave shaper.When the distance between the liner and the wave shaper is constant,the radius of the Mach wave increases,whereas the pressure decreases when decreasing the radius of the wave shaper.
基金supported by the NNSF of China(11271323,91330105)the Zhejiang Provincial Natural Science Foundation of China(LZ13A010002)supported by a GRF grant(City U 11303015)from the Research Grants Council of Hong Kong SAR,China
文摘In this paper, by taking into account the thickness of the incident shock as well as the influence of the boundary layer, we point out that even in a regular reflection there should be present a contact discontinuity. By using the smallest energy criterion, the inclined angle of this contact discontinuity can be determined for differen incident angle. Then, with this inclined contact discontinuity, together with the law of conservation of mass, the mechanism for the transition from a regular reflection to a Mach reflection or a von Neumann reflection becomes clear. The important roles played by the leftest point in the reflected shock polar are identified.
基金supported by the National Natural Science Foundation of China(Grants No.11474181)the National Basic Research Program of China(Grant No.2011CB9216002)the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics,Tsinghua University
文摘In this paper, a realistic interpretation(REIN) of the wave function in quantum mechanics is briefly presented. We demonstrate that in the REIN, the wave function of a microscopic object is its real existence rather than a mere mathematical description.Specifically, the quantum object can exist in disjointed regions of space just as the wave function is distributed, travels at a finite speed, and collapses instantly upon a measurement. Furthermore, we analyze the single-photon interference in a Mach-Zehnder interferometer(MZI) using the REIN. Based on this, we propose and experimentally implement a generalized delayed-choice experiment, called the encounter-delayed-choice experiment, where the second beam splitter is decided whether or not to insert at the encounter of two sub-waves along the arms of the MZI. In such an experiment, the parts of the sub-waves, which do not travel through the beam splitter, show a particle nature, whereas the remaining parts interfere and thus show a wave nature. The predicted phenomenon is clearly demonstrated in the experiment, thus supporting the REIN idea.
文摘Based on Hong's theory, previous random models, and a generalized expression suitable for FFT calculation, the interaction between irregular waves and vertical walls is numerically simulated. The results of simulation demonstrate that the wave energy changes with the incidence angle and the distance from the wall. Particularly, the Mach effect and the combined wave spectrum characteristics are analyzed in detail, which are significant in both theory and practice.
基金Project(2002AA742049) supported by the National High Technology Research and Development Program of China
文摘In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their load carrying capacity and stability, a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible air flow governing equations. The realizable κ-ε model was used as a turbulent closure illustrate that the interaction exists between shock waves The supersonic flow field near air inlets was analyzed. The flow structures and boundary layer, and the flow separation is formed at the lower comer and the lower wall around the point of a maximum velocity. The numerical results show that the conversion from supersonic flow to subsonic flow in spherical air bearing occurs through a shock region （pseudo-shock）, and the viscous boundary layer results in the flow separation and reverse flow near the shock. The calculation results basically agree with the corresponding experimental data.
文摘鉴于爆震燃烧具有自增压、传播速度快等优点,提出了将燃气轮机中等压燃烧替换为爆震燃烧的理念,并建立了基于爆震燃烧的燃气轮机理想热力循环模型,对比研究了DCGT(detonation cycle of gas turbine)、Brayton和Humphrey 3种循环燃气轮机的综合性能。在压气机压比、吸热量和透平背压相同的条件下,数据分析结果表明DCGT循环燃气轮机较其他2种循环更具优势,在压比为16时其循环热效率较Brayton循环提高15.4%,燃料消耗率降低13.5%;DCGT循环燃气轮机在压比为6.6时的总体性能与压比为16时的Brayton循环相当。
