A novel method was developed to establish a realistic three dimensional(3D) network model representing pore space in low permeability sandstone.Digital core of rock sample was established by the combination of micro-C...A novel method was developed to establish a realistic three dimensional(3D) network model representing pore space in low permeability sandstone.Digital core of rock sample was established by the combination of micro-CT scanning and image processing,then 3D pore-throat network model was extracted from the digital core through analyzing pore space topology,calculating pore-throat parameters and simplifying the shapes of pores and throats.The good agreements between predicted and measured porosity and absolute permeability verified the validity of this new network model.Gas-water flow mechanism was studied by using pore-scale simulations,and the influence of pore structure parameters,including coordination number,aspect ratio and shape factor,on gas-water flow,was investigated.The present simulation results show that with the increment of coordination number,gas flow ability in network improves and the effect of invading water on blocking gas flow weakens.The smaller the aspect ratio is,the stronger the anisotropy of the network is,resulting in the increase of seepage resistance.It is found that the shape factor mainly affects the end points in relative permeability curves,and for a highly irregular pore or throat with a small shape factor,the irreducible water saturation(Swi) and residual gas saturation(Sgr) are relatively high.展开更多
Using self-developed gas-seepage experimental installation,under the sameeffective stress conditions,coal permeability experiments on different adsorption characteristicsof gases,different temperatures and different g...Using self-developed gas-seepage experimental installation,under the sameeffective stress conditions,coal permeability experiments on different adsorption characteristicsof gases,different temperatures and different gas adsorption contents were performed,and the influence law of adsorption on coal permeability was studied.At the sametime,experimental analogy showed clearly that gas drawing plucks the permeability variationlaw.The results show that adsorption has a major impact on coal permeability.Thegreater the adsorption,the more the gas adsorption capacity and the coal permeabilitybecomes smaller.Permeability becomes smaller along with confining of pressure andtemperature,and this is in accord with local practice results.展开更多
This paper summarizes the results of the authors' 4 year experimental studies on the secondary flow losses in turbine cascades. Cascade wind tunnel experiments were carried out concerning the influence of aspect r...This paper summarizes the results of the authors' 4 year experimental studies on the secondary flow losses in turbine cascades. Cascade wind tunnel experiments were carried out concerning the influence of aspect ratios, incidence, turning angles and outer endwall divergent angles in order to unveil the evolution mechanism of secondary flow losses in turbine cascades without end clearance. Some methods for controlling the secondary flows are investigated including the blade leaning, blade cambering, endwall convergence and leading edge extension at two ends of the blade.展开更多
In this paper, an improvement of heating method for measuring wetness of the flowing wet steam is developed, the basic principle of the heating method is presented and the mathematical model has been built for analyzi...In this paper, an improvement of heating method for measuring wetness of the flowing wet steam is developed, the basic principle of the heating method is presented and the mathematical model has been built for analyzing the thermodynamics problezns during the process of heating. Moreover, an instru-ment for measuring wetness of wet steam flow was designed and made out. This instrument has been used for measuring wetness of the wet steam flow at the outlet of the nozzle rig in Thermal TUrbine Laboratory Xi’an Jiaotong University. By analyzing the relative error of the result, it was found that this instrument has fairly high accuracy it can be used as the prototype of practical instrument and has an important applicable value in engineering.展开更多
Wells turbine is a self rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. One of the principal reasons for t...Wells turbine is a self rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. One of the principal reasons for the low efficiency of the Wells turbine is its lower tangential force compared to its axial force. Guide vanes before and after the rotor suggest a means to improve the tangential force, hence its efficiency. Experimental investigations are carried out on the Wells turbine with a variable chord (VACR) blade rotor fitted with inlet and outlet guide vanes to understand the aerodynamics especiallyimprovement in efficiency and starting characteristics. Numerical simulation has been made to clarify the unsteady characteristics of the turbine with guide vanes. Studies are done at various flow coefficients covering the entire range of flow coefficients over which the turbine is operable. The efficiency,starting characteristics of the Wells turbine has improved when compared with the turbine without guide vanes.展开更多
In order to improve the performance of a Wells turbine, the effect of guide vanes with various gaps between turbine rotor and guide vane has been clarified by model testing and numerical simulation.The results have be...In order to improve the performance of a Wells turbine, the effect of guide vanes with various gaps between turbine rotor and guide vane has been clarified by model testing and numerical simulation.The results have been compared with those of the case without guide vanes. It is found that the overall characteristics are considerably improved by the inlet guide vanes. Furthermore,a suitable choice of design factor for the gap has been suggested.展开更多
This paper presents the mutual time - marching method to predict the aeroelastic stability of an oscillating blade row in 3D transonic flow. The ideal gas flow through a blade row is governed by the time dependent Eul...This paper presents the mutual time - marching method to predict the aeroelastic stability of an oscillating blade row in 3D transonic flow. The ideal gas flow through a blade row is governed by the time dependent Euler equations in conservative form which are integrated by using the explicit monotonous second order accurate Godunov-Kolgan finite volume scheme and moving hybrid H-O grid. The structure analysis uses the modal approach and 3D finite element dynamic model of blade. The blade movement is assumed as a linear combination of the first modes of blade natural oscillations with the modal coefficients depending on time. To demonstrate the capability and correctness of the method, two experimentally investigated test cases have been selected, in which the blades had performed tuned harmonic bending or torsional vibrations (The lst and 4kyhstandard configurations of the "Workshop on Aeroelasticity in Turbomacbines" by Bolcs and Fransson, 1986). The calculated results of aeroelastic behaviour of the blade row (4th standard configuration), are presented over a wide frequency range under different start regimes of interblade phase angle.展开更多
基金Project(2013CB228005) supported by the National Program on Key Fundamental Research Project of ChinaProject(14ZB0047) supported by the Department of Education of Sichuan Province,China
文摘A novel method was developed to establish a realistic three dimensional(3D) network model representing pore space in low permeability sandstone.Digital core of rock sample was established by the combination of micro-CT scanning and image processing,then 3D pore-throat network model was extracted from the digital core through analyzing pore space topology,calculating pore-throat parameters and simplifying the shapes of pores and throats.The good agreements between predicted and measured porosity and absolute permeability verified the validity of this new network model.Gas-water flow mechanism was studied by using pore-scale simulations,and the influence of pore structure parameters,including coordination number,aspect ratio and shape factor,on gas-water flow,was investigated.The present simulation results show that with the increment of coordination number,gas flow ability in network improves and the effect of invading water on blocking gas flow weakens.The smaller the aspect ratio is,the stronger the anisotropy of the network is,resulting in the increase of seepage resistance.It is found that the shape factor mainly affects the end points in relative permeability curves,and for a highly irregular pore or throat with a small shape factor,the irreducible water saturation(Swi) and residual gas saturation(Sgr) are relatively high.
文摘Using self-developed gas-seepage experimental installation,under the sameeffective stress conditions,coal permeability experiments on different adsorption characteristicsof gases,different temperatures and different gas adsorption contents were performed,and the influence law of adsorption on coal permeability was studied.At the sametime,experimental analogy showed clearly that gas drawing plucks the permeability variationlaw.The results show that adsorption has a major impact on coal permeability.Thegreater the adsorption,the more the gas adsorption capacity and the coal permeabilitybecomes smaller.Permeability becomes smaller along with confining of pressure andtemperature,and this is in accord with local practice results.
文摘This paper summarizes the results of the authors' 4 year experimental studies on the secondary flow losses in turbine cascades. Cascade wind tunnel experiments were carried out concerning the influence of aspect ratios, incidence, turning angles and outer endwall divergent angles in order to unveil the evolution mechanism of secondary flow losses in turbine cascades without end clearance. Some methods for controlling the secondary flows are investigated including the blade leaning, blade cambering, endwall convergence and leading edge extension at two ends of the blade.
文摘In this paper, an improvement of heating method for measuring wetness of the flowing wet steam is developed, the basic principle of the heating method is presented and the mathematical model has been built for analyzing the thermodynamics problezns during the process of heating. Moreover, an instru-ment for measuring wetness of wet steam flow was designed and made out. This instrument has been used for measuring wetness of the wet steam flow at the outlet of the nozzle rig in Thermal TUrbine Laboratory Xi’an Jiaotong University. By analyzing the relative error of the result, it was found that this instrument has fairly high accuracy it can be used as the prototype of practical instrument and has an important applicable value in engineering.
文摘Wells turbine is a self rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. One of the principal reasons for the low efficiency of the Wells turbine is its lower tangential force compared to its axial force. Guide vanes before and after the rotor suggest a means to improve the tangential force, hence its efficiency. Experimental investigations are carried out on the Wells turbine with a variable chord (VACR) blade rotor fitted with inlet and outlet guide vanes to understand the aerodynamics especiallyimprovement in efficiency and starting characteristics. Numerical simulation has been made to clarify the unsteady characteristics of the turbine with guide vanes. Studies are done at various flow coefficients covering the entire range of flow coefficients over which the turbine is operable. The efficiency,starting characteristics of the Wells turbine has improved when compared with the turbine without guide vanes.
文摘In order to improve the performance of a Wells turbine, the effect of guide vanes with various gaps between turbine rotor and guide vane has been clarified by model testing and numerical simulation.The results have been compared with those of the case without guide vanes. It is found that the overall characteristics are considerably improved by the inlet guide vanes. Furthermore,a suitable choice of design factor for the gap has been suggested.
文摘This paper presents the mutual time - marching method to predict the aeroelastic stability of an oscillating blade row in 3D transonic flow. The ideal gas flow through a blade row is governed by the time dependent Euler equations in conservative form which are integrated by using the explicit monotonous second order accurate Godunov-Kolgan finite volume scheme and moving hybrid H-O grid. The structure analysis uses the modal approach and 3D finite element dynamic model of blade. The blade movement is assumed as a linear combination of the first modes of blade natural oscillations with the modal coefficients depending on time. To demonstrate the capability and correctness of the method, two experimentally investigated test cases have been selected, in which the blades had performed tuned harmonic bending or torsional vibrations (The lst and 4kyhstandard configurations of the "Workshop on Aeroelasticity in Turbomacbines" by Bolcs and Fransson, 1986). The calculated results of aeroelastic behaviour of the blade row (4th standard configuration), are presented over a wide frequency range under different start regimes of interblade phase angle.
