Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hi...Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning (cooling) system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.展开更多
A detailed investigation of a thermodynamic process in a structured packing distillation column is of great impor- tance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stage mod...A detailed investigation of a thermodynamic process in a structured packing distillation column is of great impor- tance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stage model and the accu- racy of a non-equilibrium stage model, a hybrid model is developed to predict the structured packing column in cryogenic air separation. A general solution process for the equilibrium stage model is developed to solve the set of equations of the hybrid model, in which a separation efficiency function is introduced to obtain the resulting tri-diagonal matrix and its solution by the Thomas algorithm. As an example, the algorithm is applied to analyze an upper column of a cryogenic air separation plant with the capacity of 17000 m3·h-1. Rigorous simulations are conducted using Aspen RATEFRAC module to validate the approach. The temperature and composition distributions are in a good agreement with the two methods. The effects of inlet/outlet position and flow rate on the temperature and composition distributions in the column are analyzed. The results demonstrate that the hybrid model and the solution algorithms are effective in analvzin~ the distillation process for a a cryogenic structured packing column.展开更多
To investigate the influence of design parameters on the performance of separation device,the structure and air-operated test of a low-shock separation device are introduced and analyzed in this paper.According to the...To investigate the influence of design parameters on the performance of separation device,the structure and air-operated test of a low-shock separation device are introduced and analyzed in this paper.According to the law of energy conservation and aerodynamics,a mathematical model is built.Because the preload used to ensure the connection reliability has the discreteness,which will influence the separation process,the influence of preload discreteness on the air-operated separation process is simulated and tested.Simulation results are consistent with the experimental results.It is shown that the change of preload has an obvious influence on the separation process.The study is useful for the design and optimization of separation device.展开更多
In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a w...In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code.In the case of rear surface separation,the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle.The aerodynamic noise level then becomes small according to the vortex scale in the blade chord.When the flow is separated at the leading edge,a separated vortex of low pressure is formed at the vicinity of the trailing edge.The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake.It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.展开更多
文摘Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning (cooling) system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.
基金Supported by the Major State Basic Research Development Program of China(2011CB706501)the National Natural Science Foundation of China(51276157)
文摘A detailed investigation of a thermodynamic process in a structured packing distillation column is of great impor- tance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stage model and the accu- racy of a non-equilibrium stage model, a hybrid model is developed to predict the structured packing column in cryogenic air separation. A general solution process for the equilibrium stage model is developed to solve the set of equations of the hybrid model, in which a separation efficiency function is introduced to obtain the resulting tri-diagonal matrix and its solution by the Thomas algorithm. As an example, the algorithm is applied to analyze an upper column of a cryogenic air separation plant with the capacity of 17000 m3·h-1. Rigorous simulations are conducted using Aspen RATEFRAC module to validate the approach. The temperature and composition distributions are in a good agreement with the two methods. The effects of inlet/outlet position and flow rate on the temperature and composition distributions in the column are analyzed. The results demonstrate that the hybrid model and the solution algorithms are effective in analvzin~ the distillation process for a a cryogenic structured packing column.
文摘To investigate the influence of design parameters on the performance of separation device,the structure and air-operated test of a low-shock separation device are introduced and analyzed in this paper.According to the law of energy conservation and aerodynamics,a mathematical model is built.Because the preload used to ensure the connection reliability has the discreteness,which will influence the separation process,the influence of preload discreteness on the air-operated separation process is simulated and tested.Simulation results are consistent with the experimental results.It is shown that the change of preload has an obvious influence on the separation process.The study is useful for the design and optimization of separation device.
文摘In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code.In the case of rear surface separation,the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle.The aerodynamic noise level then becomes small according to the vortex scale in the blade chord.When the flow is separated at the leading edge,a separated vortex of low pressure is formed at the vicinity of the trailing edge.The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake.It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.