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Xinping Long - One of the best experts on this subject based on the ideXlab platform.

  • experimental study of the Cavitation noise and vibration induced by the choked Flow in a venturi reactor
    Ultrasonics Sonochemistry, 2020
    Co-Authors: Shuangjie Xu, Huaiyu Cheng, Jiong Wang, Bin Ji, Xinping Long
    Abstract:

    Abstract In this paper, the Cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating Flow in a Venturi reactor are investigated experimentally under different Cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous Cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale Cavitation Flow structure, is applied to investigate the choked cavitating Flow dynamics. The POD results show that two mechanisms, re-entrant jet Flow mechanism and shock wave mechanism, govern the shedding and collapse of Cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various Cavitation regions induced by the choked cavitating Flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant Flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of Cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked Cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for Cavitation applications such as water treatment.

  • performance of Cavitation Flow and its induced noise of different jet pump Cavitation reactors
    Ultrasonics Sonochemistry, 2019
    Co-Authors: Jiong Wang, Huaiyu Cheng, Xinping Long
    Abstract:

    Abstract Jet pump is a type of Cavitation reactor with great potential because of strong shear Flow. In the present paper, experiments were carried out to investigate the Cavitation characteristics of jet pump Cavitation reactors (JPCRs) with different throat lengths, throat types and diffuser angles. Cavitation images and sound pressure signals in water corresponding to the hydraulic parameters are introduced to judge the aggressive intensity of Cavitation in JPCRs. The Flow ratios varying from the maximum limited value to −1 were measured for all JPCRs. It suggests that throat structure plays a more important role in the Cavitation and Flow characteristics of JPCR when compared with diffuser structure. Specifically, convergent throat results in large bubble density in the diffuser while divergent throat results in choke in the throat compared to the original JPCR. And Cavitation bubble density in throat increases with increasing throat length. With the decrease of the Flow ratio (q > 0), sound pressure level (SPL) decreases from the maximum to the minimum and then increases again. As the Flow ratio decreases further (q

  • numerical investigation on the cavitating Flow in annular jet pump under different Flow rate ratio
    IOP Conference Series: Earth and Environmental Science, 2014
    Co-Authors: Longzhou Xiao, Xinping Long, Qiao Lyu, Q Q Wang
    Abstract:

    The nozzle of annular jet pump (AJP) is annular and the secondary Flow is encircled by the primary Flow which is of great differences with that of central jet pump (CJP). Since the high velocity working Flow soaring out the annular nozzle adheres to the inner wall, the Cavitation is considerably easy to be induced at the intersection of the suction chamber and the throat. This paper mainly investigated the inception and development of the Cavitation in an AJP under different Flow rate ratio q by numerical methods and the results was validated by the experimentation. The turbulent model is set as Realizable k-e model, which combined with the mixture multiphase model and the Schnerr-Sauer Cavitation model. The SIMPLEC algorithm is applied to solve the coupling of pressure and velocity. The simulated results confirms well with experimental data. As the working condition varies, specifically when the pressure of the outlet decreases to a certain value, the intersection of the suction chamber and the throat sees the inception and development of the Cavitation and the bubble generates there adheres to the inner wall. With the decreasing outlet pressure, the Cavitation region expands to the diffuser along the inner wall, and also to the axis. When the Cavitation region develops to the axis and the pressure there reaches to the critical Cavitation pressure (generally vapor pressure), the pump turns into the operation limits and the efficiency drops abruptly. Furthermore, when the Flow rate ratio q is considerably low (generally <0.2), the shearing layer and the center of the recirculation also experience the Cavitation inception. It is for this reason that the relationship between the critical Cavitation number qc and the Cavitation Flow rate ratio qc can be divided into two parts. When σc<0.31, it varies little with the increasing qc, while it increases linearly with the increasing qc when ranging from 0.31 to 1.58.

Jiong Wang - One of the best experts on this subject based on the ideXlab platform.

  • experimental study of the Cavitation noise and vibration induced by the choked Flow in a venturi reactor
    Ultrasonics Sonochemistry, 2020
    Co-Authors: Shuangjie Xu, Huaiyu Cheng, Jiong Wang, Bin Ji, Xinping Long
    Abstract:

    Abstract In this paper, the Cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating Flow in a Venturi reactor are investigated experimentally under different Cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous Cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale Cavitation Flow structure, is applied to investigate the choked cavitating Flow dynamics. The POD results show that two mechanisms, re-entrant jet Flow mechanism and shock wave mechanism, govern the shedding and collapse of Cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various Cavitation regions induced by the choked cavitating Flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant Flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of Cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked Cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for Cavitation applications such as water treatment.

  • performance of Cavitation Flow and its induced noise of different jet pump Cavitation reactors
    Ultrasonics Sonochemistry, 2019
    Co-Authors: Jiong Wang, Huaiyu Cheng, Xinping Long
    Abstract:

    Abstract Jet pump is a type of Cavitation reactor with great potential because of strong shear Flow. In the present paper, experiments were carried out to investigate the Cavitation characteristics of jet pump Cavitation reactors (JPCRs) with different throat lengths, throat types and diffuser angles. Cavitation images and sound pressure signals in water corresponding to the hydraulic parameters are introduced to judge the aggressive intensity of Cavitation in JPCRs. The Flow ratios varying from the maximum limited value to −1 were measured for all JPCRs. It suggests that throat structure plays a more important role in the Cavitation and Flow characteristics of JPCR when compared with diffuser structure. Specifically, convergent throat results in large bubble density in the diffuser while divergent throat results in choke in the throat compared to the original JPCR. And Cavitation bubble density in throat increases with increasing throat length. With the decrease of the Flow ratio (q > 0), sound pressure level (SPL) decreases from the maximum to the minimum and then increases again. As the Flow ratio decreases further (q

K Sakulphan - One of the best experts on this subject based on the ideXlab platform.

  • new mode to operate centrifugal pump as impulse turbine
    Renewable Energy, 2019
    Co-Authors: K Sengpanich, Erik L J Bohez, P Thongkruer, K Sakulphan
    Abstract:

    Abstract Centrifugal pumps can be used as “Pump-as-Turbine (PaT)” by reversing the Flow and operating as a Francis turbine. The proposed concept “Impulse Pump-as-Turbine (Impulse PaT)” will use centrifugal pump impeller to be used as hydro turbine by pairing with spear valve injector from impulse hydro turbine. Spear valve injector regulate water inlet Flow rate, thus regulate power output of our new concept turbine. Additional benefit from utilized spear valve injector is low loss of turbine efficiency when operate at part-load condition, therefore this new concept turbine can be operated at wide range of Flow condition without losing good efficiency while also eliminate risk of turbine damage from Cavitation. Flow regulation through spear valve will also simplify control system for this proposed turbine compared to guide vanes. The validation methods from 1-D calculation based on Euler's turbine equation and numerical simulation by commercial CFD package shows that this new proposed concept is feasible with efficiency around 40% and wide operating range from 25% to maximum inlet Flow rate. Results from numerical calculation shows that efficiency of this new concept of turbine is limited by number of blades in commercially available pump.

François Avellan - One of the best experts on this subject based on the ideXlab platform.

  • new insight in francis turbine Cavitation vortex rope role of the runner outlet Flow swirl number
    Journal of Hydraulic Research, 2018
    Co-Authors: Arthur Tristan Favrel, Christophe Nicolet, Christian Landry, Joao Gomes Pereira, Andres Muller, François Avellan
    Abstract:

    ABSTRACTAt part load operation, Francis turbines experience the development of a Cavitation vortex rope in the draft tube, whose precession acts as a pressure excitation source. In case of resonance, the resulting pressure pulsations lead to unacceptable torque and power fluctuations on the prototype machine, putting at risk the system stability. However, the accurate prediction of resonance conditions at the prototype scale remains challenging since it requires a proper hydro-acoustic modelling of the draft tube Cavitation Flow. Furthermore, both the head and discharge values have an impact on the precession frequency of the vortex and the natural frequency of the system. The present paper demonstrates for the first time that the influence of both parameters on the frequencies of interest can be represented by a single parameter, the swirl number. Its analytical expression is derived as a function of the operating parameters of the machine. It is used to establish empirical laws enabling the determinatio...

  • numerical and experimental evidence of the inter blade Cavitation vortex development at deep part load operation of a francis turbine
    IOP Conference Series: Earth and Environmental Science, 2016
    Co-Authors: K Yamamoto, Arthur Tristan Favrel, Christian Landry, Andreas Muller, François Avellan
    Abstract:

    Francis turbines are subject to various types of the Cavitation Flow depending on the operating condition s. In order to compensate for the stochastic nature of renewable energy sources, it is more and more required to extend the operating range of the generating units, from deep part load to full load conditions. In the deep part load condition, the formation of Cavitation vortices in the turbine blade-to-blade channel s called inter -blade Cavitation vortex is often observed. The understanding of the dynamic characteristics of these inter -blade vortices and their formation mechanisms is of key importance in an effort of developing reliable Flow simulation tools. This paper reports the numerical and experimental investigations carried out in order to establish the vortex characteristics, especially the inception and the development of the vortex structure. The unsteady RANS simulation for the multiphase Flow is performed with the SST - SA S turbulence model by using the commercial Flow solver ANSYS CFX. The simulation results in terms of the vortex structure and the Cavitation volume are evaluated by comparing them to the Flow visualization s of the blade channel acquired through a specially instrumented guide vane as well as from the downstream of the runner across the draft tube cone. The inter-blade Cavitation vortex is successfully captured by the simulation and both numerical and experimental results evidence that the inter -blade vortices are attached to the runner hub.

  • francis turbine draft tube modelling for prediction of pressure fluctuations on prototype
    Journal of Physics: Conference Series, 2015
    Co-Authors: Sébastien Alligné, Arthur Tristan Favrel, Christophe Nicolet, Christian Landry, François Avellan
    Abstract:

    The prediction of pressure fluctuations amplitudes on Francis turbine prototype is a challenge for hydro-equipment industry since it is subjected to guarantees to ensure smooth and reliable operation of the hydro units. The European FP7 research project Hyperbole aims to setup a methodology to transpose the pressure fluctuations measured on the reduced scale model to the prototype generating units. This paper presents this methodology which relies on an advanced modelling of the draft tube Cavitation Flow, and focuses on the transposition to the prototype of the draft tube model parameters identified on the reduced scale model. Different modelling assumptions of the draft tube are considered and their influence on the eigenmodes and the forced response of the system are presented.

Huaiyu Cheng - One of the best experts on this subject based on the ideXlab platform.

  • experimental study of the Cavitation noise and vibration induced by the choked Flow in a venturi reactor
    Ultrasonics Sonochemistry, 2020
    Co-Authors: Shuangjie Xu, Huaiyu Cheng, Jiong Wang, Bin Ji, Xinping Long
    Abstract:

    Abstract In this paper, the Cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating Flow in a Venturi reactor are investigated experimentally under different Cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous Cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale Cavitation Flow structure, is applied to investigate the choked cavitating Flow dynamics. The POD results show that two mechanisms, re-entrant jet Flow mechanism and shock wave mechanism, govern the shedding and collapse of Cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various Cavitation regions induced by the choked cavitating Flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant Flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of Cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked Cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for Cavitation applications such as water treatment.

  • performance of Cavitation Flow and its induced noise of different jet pump Cavitation reactors
    Ultrasonics Sonochemistry, 2019
    Co-Authors: Jiong Wang, Huaiyu Cheng, Xinping Long
    Abstract:

    Abstract Jet pump is a type of Cavitation reactor with great potential because of strong shear Flow. In the present paper, experiments were carried out to investigate the Cavitation characteristics of jet pump Cavitation reactors (JPCRs) with different throat lengths, throat types and diffuser angles. Cavitation images and sound pressure signals in water corresponding to the hydraulic parameters are introduced to judge the aggressive intensity of Cavitation in JPCRs. The Flow ratios varying from the maximum limited value to −1 were measured for all JPCRs. It suggests that throat structure plays a more important role in the Cavitation and Flow characteristics of JPCR when compared with diffuser structure. Specifically, convergent throat results in large bubble density in the diffuser while divergent throat results in choke in the throat compared to the original JPCR. And Cavitation bubble density in throat increases with increasing throat length. With the decrease of the Flow ratio (q > 0), sound pressure level (SPL) decreases from the maximum to the minimum and then increases again. As the Flow ratio decreases further (q