As an integral part of the internal air system of aero-engines,the axial throughflow of the cooling air can interact with the cavity flow between the rotating compressor disks,forming a threedimensional,unsteady,and u...As an integral part of the internal air system of aero-engines,the axial throughflow of the cooling air can interact with the cavity flow between the rotating compressor disks,forming a threedimensional,unsteady,and unstable flow field.The flow characteristics in an engine-like rotating multi-stage cavity with throughflow were investigated using particle image velocimetry,flow visualization technology and three-dimensional unsteady Reynolds-Averaged Navier-Stokes (RANS)simulations.The focus of current research was to understand the distribution of the mean swirl ratio and its variation with a wide range of non-dimensional parameters in the co-rotating cavity with high inlet pre-swirl axial throughflow.The maximum axial Reynolds number and rotational Reynolds numbers could reach 4.41×10^(4)and 1.24×10^(6),respectively.The velocity measurement results indicate that the mean swirl ratio is greater than 1 and decreases with an increase in the radial position.The flow structure is dominated by the Rossby number,and two different flow patterns (flow penetration and flow stratification) are identified and confirmed by flow visualization images.In the absence of buoyancy,the flow penetration caused by the precession of the throughflow makes it easier for the throughflow to reach a high radius region.Satisfactory consistency of results between measurements and numerical calculations is obtained.This study provides a theoretical basis and data support for toroidal vortex breakdown,which is of practical significance for the design of high-pressure compressor cavities.展开更多
The rotating disk cavity is an important part of the cooling-air system of the aero engine,and it has obviously significance to study the internal flow and heat transfer characteristics of the disc cavity,which will b...The rotating disk cavity is an important part of the cooling-air system of the aero engine,and it has obviously significance to study the internal flow and heat transfer characteristics of the disc cavity,which will be helpful to improve the efficiency of the aero engine.This paper summarizes the existing research results of domestic and overseas.The present work considers the test methods and calculation methods of the flow and heat transfer characteristics of the rotating disc cavity of the aircraft engine.It points out that,the main factors which affect the heat transfer characteristics are the disc chamber speed,the intake volume,the design of the disc cavity pre-rotation/despin structure,and the type of disc cavity system.The influence of these factors on the characteristics of flow heat transfer is summarized.Based on these factors,the disc cavity structure can be optimized and designed,which provides suggestions for reducing the weight of the turbine,improving the thrust-to-weight ratio of the aero engine,and improving the cooling efficiency.展开更多
The subject that concerns us in this work is the numerical simulation and optimal control of equilibrium of the continuous chemical lasers (CCLs). Laser Chemistry: Spectroscopy, Dynamics and Applications are a careful...The subject that concerns us in this work is the numerical simulation and optimal control of equilibrium of the continuous chemical lasers (CCLs). Laser Chemistry: Spectroscopy, Dynamics and Applications are a carefully structured introduction to the basic theory and concepts of this subject. In this paper we present the design and discuss the performances of a continuous DF chemical laser, based on the exothermic reaction: F+D2→DF(v,j)展开更多
We put forward an optimal entanglement concentration protocol（ECP） for recovering an arbitrary less-entangled multi-photon Greenberger–Horne–Zeilinger（GHZ） state into the maximally entangled GHZ state based on t...We put forward an optimal entanglement concentration protocol（ECP） for recovering an arbitrary less-entangled multi-photon Greenberger–Horne–Zeilinger（GHZ） state into the maximally entangled GHZ state based on the photonic Faraday rotation in low-quality（Q） cavity. In the ECP, only one pair of less-entangled multi-photon GHZ state and one auxiliary photon are required, and the concentration task can be realized by local operations. Moreover, our ECP can be used repeatedly to further concentrate the discarded items of conventional ECPs, which can increase its success probability largely. Under the practical imperfect detection condition, our protocol can still work with relatively high success probability. This ECP has application potential in current and future quantum communication.展开更多
The concurrence evolution of two qubits coupled with one-mode cavity separately is investigated exactly without adopting the rotating-wave approximation. The results show that for the resonant case, the concurrence ev...The concurrence evolution of two qubits coupled with one-mode cavity separately is investigated exactly without adopting the rotating-wave approximation. The results show that for the resonant case, the concurrence evolution behaviour of the system is similar to that of the Markovian case when the coupling strength is weak, while the concurrence vanishes in a finite time and might revive fractional initial entanglement before it permanently vanishes when the coupling strength is strong. And for the detuning case, the entanglement could periodically recover after complete disentanglement. These results are quite different from those of system subjected to Jaynes-Cummings model.展开更多
In order to get a better knowledge of the heat transfer in compressor cavities of aero-engines,the simplified rotating cavity with two-plane discs,a shaft and a cylindrical rim has been investigated numerically and co...In order to get a better knowledge of the heat transfer in compressor cavities of aero-engines,the simplified rotating cavity with two-plane discs,a shaft and a cylindrical rim has been investigated numerically and compared with the available measurements.The numerical results in agreement with the available experiments show large-scale instabilities.The disk local Nusselt numbers show mainly radial rising distributions for the heated disks with radial rising temperature profiles.In the present work,at the Reynolds number of 20 000,the disk local Nusselt numbers are the correlations of the local Grashof number to the power of 1.89-2.6,and the value of the power is increased as the rotational Reynolds number goes up.At the rotational Reynolds number of 800 000,the local Nusselt numbers are the correlations of the local Grashof number to the power of 0.68-2.6,and the value of the power is decreased as Reynolds number goes up.The area-averaged disk Nusselt number is the correlation of the Reynolds number to the power of 0.479 and the rotational Grashof number to the power of 0.12.展开更多
With the aid of numerical method, both flow field and its accompanied loss mechanism within the rotating cavity are investigated in detail in the 1^(st) part of the two parts paper. For ease of comparison, rotating ca...With the aid of numerical method, both flow field and its accompanied loss mechanism within the rotating cavity are investigated in detail in the 1^(st) part of the two parts paper. For ease of comparison, rotating cavity is further classified as the rotor-stator cavity case and the rotor-rotor cavity case. Results indicate that flow within both kinds of the cavity act as the inviscid flow except that the flow near walls, neighboring the lower G region and in the vicinity of the rotating orifices. In the regions except such inviscid-flow-dominate domains, the theoretical core rotation factor can be safely used to predict the swirl ratio within the cavity. When detailed flow pattern is considered, Ekman-type flow exists near periphery of the surface's boundary layer where viscous effect is non-negligible. However, due to the complex profile of the simulated cavity case, vortices structure is varied within the cavity. By comparison, swirl ratio can be used to predict the magnitude of loss. Due to the relatively evident rotating effects of the rotor-rotor cavity, swirl ratio even increases to 1.4 in the current model, which means that flow is moving faster than the surrounding disc. Further investigation finds that this kind of highly rotating flow is accompanied with serious undesirable pressure loss. Parenthetically, unlike its counterpart, swirl ratio above 1.0 doesn't happen when fluid passes through the rotor-stator cavity. So it is suggested that rotor-rotor flow cavity with the superimposed inward throughflow should be avoided in the engine design or certain measurements should be provided when such structure design is unavoidable. Simulation done in the current paper is meaningful since these dimensional parameters are typical in the design of state-of-art. Relatively lower range of Re_φ and C_w is not considered in the current two parts paper.展开更多
文摘As an integral part of the internal air system of aero-engines,the axial throughflow of the cooling air can interact with the cavity flow between the rotating compressor disks,forming a threedimensional,unsteady,and unstable flow field.The flow characteristics in an engine-like rotating multi-stage cavity with throughflow were investigated using particle image velocimetry,flow visualization technology and three-dimensional unsteady Reynolds-Averaged Navier-Stokes (RANS)simulations.The focus of current research was to understand the distribution of the mean swirl ratio and its variation with a wide range of non-dimensional parameters in the co-rotating cavity with high inlet pre-swirl axial throughflow.The maximum axial Reynolds number and rotational Reynolds numbers could reach 4.41×10^(4)and 1.24×10^(6),respectively.The velocity measurement results indicate that the mean swirl ratio is greater than 1 and decreases with an increase in the radial position.The flow structure is dominated by the Rossby number,and two different flow patterns (flow penetration and flow stratification) are identified and confirmed by flow visualization images.In the absence of buoyancy,the flow penetration caused by the precession of the throughflow makes it easier for the throughflow to reach a high radius region.Satisfactory consistency of results between measurements and numerical calculations is obtained.This study provides a theoretical basis and data support for toroidal vortex breakdown,which is of practical significance for the design of high-pressure compressor cavities.
文摘The rotating disk cavity is an important part of the cooling-air system of the aero engine,and it has obviously significance to study the internal flow and heat transfer characteristics of the disc cavity,which will be helpful to improve the efficiency of the aero engine.This paper summarizes the existing research results of domestic and overseas.The present work considers the test methods and calculation methods of the flow and heat transfer characteristics of the rotating disc cavity of the aircraft engine.It points out that,the main factors which affect the heat transfer characteristics are the disc chamber speed,the intake volume,the design of the disc cavity pre-rotation/despin structure,and the type of disc cavity system.The influence of these factors on the characteristics of flow heat transfer is summarized.Based on these factors,the disc cavity structure can be optimized and designed,which provides suggestions for reducing the weight of the turbine,improving the thrust-to-weight ratio of the aero engine,and improving the cooling efficiency.
文摘The subject that concerns us in this work is the numerical simulation and optimal control of equilibrium of the continuous chemical lasers (CCLs). Laser Chemistry: Spectroscopy, Dynamics and Applications are a carefully structured introduction to the basic theory and concepts of this subject. In this paper we present the design and discuss the performances of a continuous DF chemical laser, based on the exothermic reaction: F+D2→DF(v,j)
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474168 and 61401222)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20151502)+1 种基金the Qing Lan Project of Jiangsu Province,Chinaa Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘We put forward an optimal entanglement concentration protocol（ECP） for recovering an arbitrary less-entangled multi-photon Greenberger–Horne–Zeilinger（GHZ） state into the maximally entangled GHZ state based on the photonic Faraday rotation in low-quality（Q） cavity. In the ECP, only one pair of less-entangled multi-photon GHZ state and one auxiliary photon are required, and the concentration task can be realized by local operations. Moreover, our ECP can be used repeatedly to further concentrate the discarded items of conventional ECPs, which can increase its success probability largely. Under the practical imperfect detection condition, our protocol can still work with relatively high success probability. This ECP has application potential in current and future quantum communication.
基金supported by the State Key Program for Basic Research of China(Grant No.2007CB307002)the Natural Science Foundation of Guangdong Province of China(Grant No.8151063201000051)
文摘The concurrence evolution of two qubits coupled with one-mode cavity separately is investigated exactly without adopting the rotating-wave approximation. The results show that for the resonant case, the concurrence evolution behaviour of the system is similar to that of the Markovian case when the coupling strength is weak, while the concurrence vanishes in a finite time and might revive fractional initial entanglement before it permanently vanishes when the coupling strength is strong. And for the detuning case, the entanglement could periodically recover after complete disentanglement. These results are quite different from those of system subjected to Jaynes-Cummings model.
文摘In order to get a better knowledge of the heat transfer in compressor cavities of aero-engines,the simplified rotating cavity with two-plane discs,a shaft and a cylindrical rim has been investigated numerically and compared with the available measurements.The numerical results in agreement with the available experiments show large-scale instabilities.The disk local Nusselt numbers show mainly radial rising distributions for the heated disks with radial rising temperature profiles.In the present work,at the Reynolds number of 20 000,the disk local Nusselt numbers are the correlations of the local Grashof number to the power of 1.89-2.6,and the value of the power is increased as the rotational Reynolds number goes up.At the rotational Reynolds number of 800 000,the local Nusselt numbers are the correlations of the local Grashof number to the power of 0.68-2.6,and the value of the power is decreased as Reynolds number goes up.The area-averaged disk Nusselt number is the correlation of the Reynolds number to the power of 0.479 and the rotational Grashof number to the power of 0.12.
基金the National Natural Science Foundation of China for sponsoring the research described in the current paper(No.51406204)
文摘With the aid of numerical method, both flow field and its accompanied loss mechanism within the rotating cavity are investigated in detail in the 1^(st) part of the two parts paper. For ease of comparison, rotating cavity is further classified as the rotor-stator cavity case and the rotor-rotor cavity case. Results indicate that flow within both kinds of the cavity act as the inviscid flow except that the flow near walls, neighboring the lower G region and in the vicinity of the rotating orifices. In the regions except such inviscid-flow-dominate domains, the theoretical core rotation factor can be safely used to predict the swirl ratio within the cavity. When detailed flow pattern is considered, Ekman-type flow exists near periphery of the surface's boundary layer where viscous effect is non-negligible. However, due to the complex profile of the simulated cavity case, vortices structure is varied within the cavity. By comparison, swirl ratio can be used to predict the magnitude of loss. Due to the relatively evident rotating effects of the rotor-rotor cavity, swirl ratio even increases to 1.4 in the current model, which means that flow is moving faster than the surrounding disc. Further investigation finds that this kind of highly rotating flow is accompanied with serious undesirable pressure loss. Parenthetically, unlike its counterpart, swirl ratio above 1.0 doesn't happen when fluid passes through the rotor-stator cavity. So it is suggested that rotor-rotor flow cavity with the superimposed inward throughflow should be avoided in the engine design or certain measurements should be provided when such structure design is unavoidable. Simulation done in the current paper is meaningful since these dimensional parameters are typical in the design of state-of-art. Relatively lower range of Re_φ and C_w is not considered in the current two parts paper.
