Unsteady static pressure was measured and time-accurate numerical simulations were conducted in order to analyze unsteady behaviour of the centrifugal compressor diffuser. The unsteady static pressure was measured at ...Unsteady static pressure was measured and time-accurate numerical simulations were conducted in order to analyze unsteady behaviour of the centrifugal compressor diffuser. The unsteady static pressure was measured at the diffuser inlet and outlet at three different circumferential positions. Operation points near the surge, the design operation point and operation point near the choke were used in measurements. The time-accurate simulations were conducted at the design operation point and operation point near the choke. The whole compressor was modelled and the low Reynolds number k-εturbulence model was utilized in numerical simulations. The gathered numerical and experimental unsteady pressures were compared with each other.展开更多
Aerodynamic noise due to interaction between incoming turbulence and rotating blades is an important component in the wind turbine noise. The rod-airfoil configuration is used to investigate the interactive phenomenon...Aerodynamic noise due to interaction between incoming turbulence and rotating blades is an important component in the wind turbine noise. The rod-airfoil configuration is used to investigate the interactive phenomenon experimentally and nu- merically. Distribution of unsteady pressure on the airfoil surface is measured for different rod positions and airfoil attack angles. Two National Advisory Committee for Aeronatics （NACA） airfoils, NACA0012 and NACA0018, and two wind turbine airfoils, S809 and S825 are investigated. In addition, for low angles of attack, the flow field around the airfoil＇s leading edge is investigated with the particle image velocimetry （PIV）. The experimental results indicate that unsteady pressure disturbances on the airfoil surface are related to the rod vortex shedding. Meanwhile, the interaction flow field of the rod and NACA0012 airfoil is simulated with the unsteady Reynolds averaged Navier-Stokes method （URANS）, and the obtained pressure spectra are compared with the experimental results.展开更多
The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible non-Newto- nian Casson fluid bounded by two parallel non-conducting porous plates has been studied with heat transfer consider...The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible non-Newto- nian Casson fluid bounded by two parallel non-conducting porous plates has been studied with heat transfer considering the Hall effect. The fluid is acted upon by a uniform and exponential decaying pressure gradient. An external uniform magnetic field is applied perpendicular to the plates and the fluid motion is subjected to a uniform suction and injection. The lower plate is stationary and the upper plate is suddenly set into mo- tion and simultaneously suddenly isothermally heated to a temperature other than the lower plate temperature. Numerical solutions are obtained for the governing momentum and energy equations taking the Joule and viscous dissipations into consideration. The effect of unsteady pressure gradient, the Hall term, the parameter describing the non-Newtonian behavior on both the velocities and temperature distributions have been stud- ied.展开更多
The inherent unsteady pressure fluctuations on the rotating blade suction surface of an axial compressor were experimentally measured by directly mounting five high response miniature pressure transducers into the rot...The inherent unsteady pressure fluctuations on the rotating blade suction surface of an axial compressor were experimentally measured by directly mounting five high response miniature pressure transducers into the rotor blade along a streamline at 50% span respectively. The results show that the unsteady pressure fluctuations of rotor blade surface could be measured successfully by this means. The relations about the period, altitude of unsteady pressure with rotating speed, the discipline of pressure fluctuation along the streamwise direction were obtained.展开更多
An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport tur...An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves.展开更多
文摘Unsteady static pressure was measured and time-accurate numerical simulations were conducted in order to analyze unsteady behaviour of the centrifugal compressor diffuser. The unsteady static pressure was measured at the diffuser inlet and outlet at three different circumferential positions. Operation points near the surge, the design operation point and operation point near the choke were used in measurements. The time-accurate simulations were conducted at the design operation point and operation point near the choke. The whole compressor was modelled and the low Reynolds number k-εturbulence model was utilized in numerical simulations. The gathered numerical and experimental unsteady pressures were compared with each other.
基金Project supported by the National Basic Research Program of China (973 Program) (No. 2007CB714604)
文摘Aerodynamic noise due to interaction between incoming turbulence and rotating blades is an important component in the wind turbine noise. The rod-airfoil configuration is used to investigate the interactive phenomenon experimentally and nu- merically. Distribution of unsteady pressure on the airfoil surface is measured for different rod positions and airfoil attack angles. Two National Advisory Committee for Aeronatics （NACA） airfoils, NACA0012 and NACA0018, and two wind turbine airfoils, S809 and S825 are investigated. In addition, for low angles of attack, the flow field around the airfoil＇s leading edge is investigated with the particle image velocimetry （PIV）. The experimental results indicate that unsteady pressure disturbances on the airfoil surface are related to the rod vortex shedding. Meanwhile, the interaction flow field of the rod and NACA0012 airfoil is simulated with the unsteady Reynolds averaged Navier-Stokes method （URANS）, and the obtained pressure spectra are compared with the experimental results.
文摘The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible non-Newto- nian Casson fluid bounded by two parallel non-conducting porous plates has been studied with heat transfer considering the Hall effect. The fluid is acted upon by a uniform and exponential decaying pressure gradient. An external uniform magnetic field is applied perpendicular to the plates and the fluid motion is subjected to a uniform suction and injection. The lower plate is stationary and the upper plate is suddenly set into mo- tion and simultaneously suddenly isothermally heated to a temperature other than the lower plate temperature. Numerical solutions are obtained for the governing momentum and energy equations taking the Joule and viscous dissipations into consideration. The effect of unsteady pressure gradient, the Hall term, the parameter describing the non-Newtonian behavior on both the velocities and temperature distributions have been stud- ied.
文摘The inherent unsteady pressure fluctuations on the rotating blade suction surface of an axial compressor were experimentally measured by directly mounting five high response miniature pressure transducers into the rotor blade along a streamline at 50% span respectively. The results show that the unsteady pressure fluctuations of rotor blade surface could be measured successfully by this means. The relations about the period, altitude of unsteady pressure with rotating speed, the discipline of pressure fluctuation along the streamwise direction were obtained.
文摘An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves.
