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Effects of Acoustic Resonance and Volute Geometry on Phase Resonance in a Centrifugal Fan
Tsujimoto, Yoshinobu,Tanaka, Hiroshi,Doerfler, Peter,Yonezawa, Koichi,Suzuki, Takayuki,Makikawa, Keisuke Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.2
The effects of acoustic resonance and volute geometry on phase resonance are studied theoretically and experimentally using a centrifugal fan. One dimensional theoretical model is developed taking account of the reflection from the discharge pipe end. It was found that the phase resonance occurs, even with the effects of acoustic resonance, when the rotational speed of rotor-stator interaction pattern agrees with the sound velocity. This was confirmed by experiments with and without a silencer at the discharge pipe exit. The pressure wave measurements showed that there are certain effects of the cross-sectional area change of the volute which is neglected in the one dimensional model. To clarify the effects of area change, experiments were carried out by using a ring volute with a constant area. It was demonstrated that the phase resonance occurs for both interaction modes travelling towards/away from the volute. The amplitude of travelling wave grows towards the volute exit for the modes rotating towards the volute exit, in the same direction as the impeller. However, a standing wave is developed in the volute for the modes rotating away from the volute exit in the opposite direction as the impeller, as a result of the interaction of a growing wave while travelling towards the tongue and a reflected wave away from the tongue.
Effects of Acoustic Resonance and Volute Geometry on Phase Resonance in a Centrifugal Fan
Yoshinobu Tsujimoto,Koichi Yonezawa,Hiroshi Tanaka,Peter Doerfler,Takayuki Suzuki,Keisuke Makikawa 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.2
The effects of acoustic resonance and volute geometry on phase resonance are studied theoretically and experimentally using a centrifugal fan. One dimensional theoretical model is developed taking account of the reflection from the discharge pipe end. It was found that the phase resonance occurs, even with the effects of acoustic resonance, when the rotational speed of rotor-stator interaction pattern agrees with the sound velocity. This was confirmed by experiments with and without a silencer at the discharge pipe exit. The pressure wave measurements showed that there are certain effects of the cross-sectional area change of the volute which is neglected in the one dimensional model. To clarify the effects of area change, experiments were carried out by using a ring volute with a constant area. It was demonstrated that the phase resonance occurs for both interaction modes travelling towards/away from the volute. The amplitude of travelling wave grows towards the volute exit for the modes rotating towards the volute exit, in the same direction as the impeller. However, a standing wave is developed in the volute for the modes rotating away from the volute exit in the opposite direction as the impeller, as a result of the interaction of a growing wave while travelling towards the tongue and a reflected wave away from the tongue.
Yonezawa, Koichi,Toyahara, Shingo,Motoki, Shingo,Tanaka, Hiroshi,Doerfler, Peter,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.2
Phase resonance in Francis type hydraulic turbine is studied. The phase resonance is a phenomenon that the pressure fluctuation in the penstock of hydraulic turbine installation can become very large when the pressure waves from each guide vane caused by the interaction with the runner vane reach the penstock with the same phase. Experimental and numerical studies have been carried out using a centrifugal fan. In the present study, comparisons between the pump mode and the turbine mode operations are made. The experimental and numerical results show that the rotational direction of the rotor does not affect characteristics of the pressure fluctuation but the propagation direction of the rotorstator interaction mode plays an important role. Flow rate fluctuations through the stator are examined numerically. It has been found that the blade passing flow rate fluctuation component can be evaluated by the difference of the fluctuating pressure at the inlet and the outlet of the stator. The amplitude of the blade passage component of the pressure fluctuation is greater at the stator inlet than the one at the stator outlet. The rotor-stator interaction mode component is almost identical at the inlet and the outlet of the stator. It was demonstrated that the pressure fluctuation in the volute and connecting pipe normalized by the flow rate fluctuation becomes the same for pump and turbine mode operations, and depends on the rotational direction on the interaction mode.
Koichi Yonezawa,Shingo Toyahara,Shingo Motoki,Hiroshi Tanaka,Peter Doerfler,Yoshinobu Tsujimoto 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.2
Phase resonance in Francis type hydraulic turbine is studied. The phase resonance is a phenomenon that the pressure fluctuation in the penstock of hydraulic turbine installation can become very large when the pressure waves from each guide vane caused by the interaction with the runner vane reach the penstock with the same phase. Experimental and numerical studies have been carried out using a centrifugal fan. In the present study, comparisons between the pump mode and the turbine mode operations are made. The experimental and numerical results show that the rotational direction of the rotor does not affect characteristics of the pressure fluctuation but the propagation direction of the rotor-stator interaction mode plays an important role. Flow rate fluctuations through the stator are examined numerically. It has been found that the blade passing flow rate fluctuation component can be evaluated by the difference of the fluctuating pressure at the inlet and the outlet of the stator. The amplitude of the blade passage component of the pressure fluctuation is greater at the stator inlet than the one at the stator outlet. The rotor-stator interaction mode component is almost identical at the inlet and the outlet of the stator. It was demonstrated that the pressure fluctuation in the volute and connecting pipe normalized by the flow rate fluctuation becomes the same for pump and turbine mode operations, and depends on the rotational direction on the interaction mode.
Cavitation Surge in a Small Model Test Facility Simulating a Hydraulic Power Plant
Koichi Yonezawa,Daisuke Konishi,Kazuyoshi Miyagawa,François Avellan,Peter Doerfler,Yoshinobu Tsujimoto 한국유체기계학회 2012 International journal of fluid machinery and syste Vol.5 No.4
Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rates higher and lower than the swirl free flow rate, both with and without a surge tank placed just upstream of the inlet volute. The surge frequency at smaller flow rate was much smaller than the swirl mode frequency caused by the whirl of vortex rope. An unsteady CFD was carried out with two boundary conditions: (1) the flow rate is fixed to be constant at the volute inlet, (2) the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.
Phase Resonance in a Centrifugal Compressor
Nishiyama, Yumeto,Suzuki, Takayuki,Yonezawa, Koichi,Tanaka, Hiroshi,Doerfler, Peter,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.3
Phase resonance in a centrifugal compressor was experimentally observed and simulated with a commercial CFD code. It was found that pressure fluctuation at the volute outlet becomes the maximum when the rotational speed of the modes caused by the rotor-stator interaction agrees with the sound velocity. A simple one-dimensional theory is presented to explain the phase resonance in turbomachinery.
Cavitation Surge in a Small Model Test Facility simulating a Hydraulic Power Plant
Yonezawa, Koichi,Konishi, Daisuke,Miyagawa, Kazuyoshi,Avellan, Francois,Doerfler, Peter,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2012 International journal of fluid machinery and syste Vol.5 No.4
Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rate, both with and without a surge tank placed just upstream of the inlet volute. The surge frequency at smaller flow rate was much smaller than the swirl mode frequency caused by the whirl of vortex rope. An unsteady CFD was carried out with two boundary conditions: (1) the flow rate is fixed to be constant at the volute inlet, (2) the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.