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Experimental investigation of unsteady attached cavitating flow induced pressure fluctuation

Journal of Hydrodynamics 2022年第1期34卷 31-42页

作者： Hou-sheng Zhang Guang-hao Chen Qin Wu Biao Huang School of Mechanical Engineering Beijing Institute of TechnologyBeijing100081China AVIC Jincheng Nanjing Engineering Institute of Aircraft System Nanjing211106China

This paper experimentally investigates the pressure fluctuation induced by the unsteady attached cavitating flow, with special focus on the quasi-periodic cloud cavitation. A simultaneous sampling method is adopted for the synchronous measurement of the wall pressure signals and the cavitating flow images in a convergent-divergent channel. The results show that the pressure fluctuation is composed of three parts, the flow noise, the low-frequency fluctuation, and the cavity collapse induced impulse, and the pressure evolution of the quasi-periodic cloud cavitation is well consistent with the cavitation evolution. The statistical analysis of the pressure fluctuation shows that, when σ > 1.01, the probability density function (PDF) is nearly in the normal distribution, implying the randomness of the pressure fluctuation, when 0.84 1.01, when σ pressure indicate that the fluctuation intensity increases downstream along the cavity and reaches the maximum at the cavity closure and it also increases with the decrease of the cavitation number. The spectral analysis shows that the low-frequency pressure fluctuations mainly consist of two dominant components, the cavity shedding induced fluctuation and the lock-in fluctuation. The cavity shedding induced frequency decreases with the decrease of the cavitation number but the lock-in frequency is kept nearly constant. According to the spectral analysis of the cavity area fluctuation and the modal analysis of the flow system, the lock-in is possibly caused when the fluctuation frequency of the cavity volume approaches the natural frequency of the flow system.

关键词： Cavitation pressure fluctuation statistical features lock-in phenomenon

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pressure fluctuation signal analysis of pump based on ensemble empirical mode decomposition method

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Water Science and Engineering 2014年第2期7卷 227-235页

作者： Hong PAN Min-sheng BU College of Energy and Electrical Engineering Hohai University College of Mechanical and Electrical Engineering Hohai University

pressure fluctuations, which are inevitable in the operation of pumps, have a strong non-stationary characteristic and contain a great deal of important information representing the operation conditions. With an axial-flow pump as an example, a new method for time-frequency analysis based on the ensemble empirical mode decomposition （EEMD） method is proposed for research on the characteristics of pressure fluctuations. First, the pressure fluctuation signals are preprocessed with the empirical mode decomposition （EMD） method, and intrinsic mode functions （IMFs） are extracted. Second, the EEMD method is used to extract more precise decomposition results, and the number of iterations is determined according to the number of IMFs produced by the EMD method. Third, correlation coefficients between IMFs produced by the EMD and EEMD methods and the original signal are calculated, and the most sensitive IMFs are chosen to analyze the frequency spectrum. Finally, the operation conditions of the pump are identified with the frequency features. The results show that, compared with the EMD method, the EEMD method can improve the time-frequency resolution and extract main vibration components from pressure fluctuation signals.

关键词： pressure fluctuation ensemble empirical mode decomposition intrinsic modefunction correlation coefficient

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Investigation on Reduction of pressure fluctuation for a Double-Suction Centrifugal Pump

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Chinese Journal of Mechanical Engineering 2021年第1期34卷 181-198页

作者： Qianqian Li Shiyang Li Peng Wu Bin Huang Dazhuan Wu College of Energy Engineering Zhejiang UniversityHangzhou 310058China Zhejiang Zhixin Technology Co. LtdShaoxing 312000China Ocean College Zhejiang UniversityZhoushan 310021China The State Key Laboratory of Fluid Power Tran smission and Control Hangzhou 310058China

Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap),are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6%of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps.

关键词： Double-suction centrifugal pump pressure fluctuation Flow uniformity Numerical simulation

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Impact of Impeller Stagger Angles on pressure fluctuation for a Double-Suction Centrifugal Pump

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Chinese Journal of Mechanical Engineering 2018年第1期31卷 198-211页

作者： Da-Chun Fu Fu-Jun Wang Pei-Jian Zhou Ruo-Fu Xiao Zhi-Feng Yao College of Water Resources and Civil Engineering China Agricultural University Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural University College of Mechanical Engineering Zhejiang University of Technology

pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.

关键词： Double-suction centrifugal pump Impeller stagger angle pressure fluctuation Frequency spectra analysis

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Unsteady Turbulent Simulation and pressure fluctuation Analysis for Centrifugal Pumps

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Chinese Journal of Mechanical Engineering 2009年第1期22卷 64-69页

作者： YUAN Shouqi NI Yongyan PAN Zhongyong YUAN Jianping Research Center of Fluid Machinery Engineering and Technology Jiangsu University Zhenjiang 212013 China

The pressure fluctuation in the flow passage of both impeller and casing is addressed on design condition. The initial conditions for the unsteady turbulent simulation are resulted from the steady calculations, and the three dimensional unsteady turbulent simulation concerning the rotor-stator interaction is executed by a Navier-Stoke solver embedded with k -ε turbulence model and with appropriate moving interface boundary conditions. Detecting points are distributed in the flow passage in different radial and circumferential positions to capture the static pressure fluctuation character for one cycle of the impeller. The time-domain spectrums show that the static pressure curves are periodic and have five peaks and five valleys. With the radius increasing, the pressure fluctuation peak-to-peak values in the impeller are increasing, and reach the maximum value on the interface. In the casing flow passage, those values are about 7% of local static pressure except some ones near the tongue. The values become decreasingly in the diffuser pipe. The frequency spectrums transformed by fast Fourier transform （FFT） show that the dominant frequency is approximate with the blade passing frequency, and the pressure fluctuations in impeller passage have high frequency content while those in casing ones have no such information.

关键词： centrifugal pump rotor-stator interaction unsteady turbulent flow pressure fluctuation

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APPLICATION OF LYAPUNOV EXPONENT SPECTRUM IN pressure fluctuation OF DRAFT TUBE

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Journal of Hydrodynamics 2009年第6期21卷 856-860页

作者： WANG Li-ying ZHAO Wei-guo WEI De-hua College of Water Conservancy and Hydroelectric Power Hebei University of Engineering Handan 056021 China

The Lyapunov exponent spectrum is firstly applied in the analysis of pressure fluctuation of draft tube and calculated based on the time series of vibration in experiments for different situations. Results shows that the Lyapunov exponent spectrum varies with the setting of guide vane, So the Lyapunov exponent spectrum can be used to judge the pressure fluctuation of draft tube so as to timely adjust the setting of the guide vanes to reduce the damage caused by the vibration.

关键词： Lyapunov exponent spectrum pressure fluctuation setting of guide vanes

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Numerical simulation of pressure fluctuation in Kaplan turbine

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Science China(Technological Sciences) 2008年第8期51卷 1137-1148页

作者： LIU ShuHong SHAO Jie WU ShangFeng WU YuLin Department of Thermal Engineering State Key Laboratory of Hydroscience and EngineeringTsinghua UniversityBeijing 100084China

As it is almost impossible to carry out the prototype hydro-turbine experiment be- fore the power plant is built up, rational prediction of pressure fluctuations in the prototype turbine is very important at the design stage. From this viewpoint, we at first treated the unsteady turbulent flow computation based on the modified RNG k-ε turbulence model through the whole flow passage to simulate the pressure fluctuation in a model turbine. Since fair agreement was recognized between the numerical results and the experimental data, this numerical method was applied to simulate the pressure fluctuations in the prototype turbine. From the comparison of them with the model turbine results, it is seen that their qualitative trend of pres- sure fluctuations are similar, but an appreciable difference is observed between the amplitudes of pressure fluctuation of the prototype turbine and that of the model turbine. Though the present findings may be explained by the effect of Reynolds number, further studies are expected for quantitative interpretation. We paid atten- tion to the interaction between the fluid and turbine structure. Adopting a weak fluid-solid coupling method, we studied the pressure fluctuation in the prototype turbine to clarify how the elastic behavior of runner blades influenced the charac- teristics of pressure fluctuation.

关键词： RNG k-ε turbulence model Kaplan turbine pressure fluctuation unsteady flow simulation

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STUDIES ON STATISTICAL CHARACTERISTICS OF THE pressure fluctuation AMPLITUDE IN OUTLET WORKS

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Journal of Hydrodynamics 1997年第2期9卷 46-50页

作者： Ding, Zhuoyi Liu, Caiyun Yangtze River Scientific Research Inst Wuhan China

The pressure fluctuation amplitude is very important for the load design of structures and to research flow cavitation, using 182 sample records of fluctuation pressure obtained from model tests and prototype observations for many kinds of outlet works,this paper studies statistical characteristics of fluctuating pressure amplitude in outlet works. The results indicate that the probability of fluctuating pressure amplitude in outlet works obeys Gaussian normal distribution,and the verification of prototype observation data from Gezhouba project further proves that the conclusion is true.

关键词： structures load design,flow cavitation pressure fluctuation

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A Unique Modelling Strategy to Dynamically Simulate the Performance of a Lobe Pump for Industrial Applications

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Advances in Chemical Engineering and Science 2024年第2期14卷 57-73页

作者： Deepak Kumar Kanungo Rabiranjan Murmu Harekrushna Sutar Bharat Heavy Electricals Limited Corporate R & D Hyderabad Telangana India Chemical Engineering Department Indira Gandhi Institute of Technology Sarang Odisha India

The performance of a newly designed tri-lobe industrial lobe pump of high capacity is simulated by using commercial CFD solver Ansys Fluent. A combination of user-defined-functions and meshing strategies is employed to capture the rotation of the lobes. The numerical model is validated by comparing the simulated results with the literature values. The processes of suction, displacement, compression and exhaust are accurately captured in the transient simulation. The fluid pressure value remains in the range of inlet pressure value till the processes of suction and displacement are over. The instantaneous process of compression is accurately captured in the simulation. The movement of a particular working chamber is traced along the gradual degree of lobe’s rotation. At five different degrees of lobe’s rotation, pressure contour plots are reported which clearly shows the pressure values inside the working chamber. Each pressure value inside the working chamber conforms to the particular process in which the working chamber is operating. Finally, the power requirement at the shaft of rotation is estimated from the simulated values. The estimated value of power requirement is 3.61 BHP FHP whereas the same calculated theoretically is 3 BHP FHP. The discrepancy is attributed to the assumption of symmetry of blower along the thickness.

关键词： CFD Lobe Pump Moving Dynamic Mesh pressure fluctuation Transient Simulation

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pressure fluctuation in a Gas-Solid Fluidized Bed with Coarse Granules

Pressure Fluctuation in a Gas-Solid Fluidized Bed with Coars...

引用

The Sixth International Conference on Measurement and Control of Granular Materials

作者： Xiaoguang Li Delong Xu Haihong Fan Guoxian Xiao Institute of material science and engineering,Xi’an University of Architecture and Technology,Xi’an 710055 Chang’an University,Xi’an 710061

pressure fluctuation in a gas-solid fluidized bed with coarse granules was investigated by using a cold model bed.The variance of pressure fluctuation tends to increase with increasing average gas velocity.Bubbles were mainly occurred at the central part of bed under low gas velocity condition while under high gas velocity condition bubbles distributed over the bed cross section.At the minimum velocity of fluidization, the maximum fluctuation in the Power spectral density of the pressure fluctuation was detected to 3.5×10 Pa·s at the frequency of 2.51 Hz of the dominant frequency.As the bed became turbulent the maximum was 12.3×10 Pa·s observed at 3.13Ha of the dominant frequency. The investigation on three dimension reconstructed phase space,correlation dimension and Lyapunav exponent showed that the systems of gas-solid fluidized bed with coarse granules have characteristics of chaos.Its correlation dimension gets to 7.87 and the minimum variable number describing state space is 20 and Lyapunav exponent is positive value and neighbor orbit is fit to rule of exponent dissipation and average dissipation rate is 1.34.

关键词： Coarse Granules Fluidized bed pressure fluctuation Standard deviation dominant frequency, Chaos

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