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RISS 인기검색어
- 검색키워드
- 저자 : Zu-chao Zhu (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Weixiang Ye,Zu-chao Zhu,Zhong-Dong Qian,Xianwu Luo 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7
In this study, a modified partially averaged Navier–Stokes model (MSST PANS) is proposed by treating a modified shear stress transport (SST) k–ω model as the parent turbulence model. The unstable turbulent flow in a centrifugal pump that considers the curvature and rotation effect is investigated as the test case to evaluate the performance of the MSST PANS model and analyze the flow instability in a centrifugal pump. The SST k–ω and the standard k–ε PANS models are also evaluated for comparison. Results show that the MSST PANS model exhibits excellent performance and delivers the most satisfactory prediction results of the positive slope of the characteristic curve, time-averaged internal flows, and velocity profiles. The energy loss based on the energy balance equations is adopted to provide an explanation of the internal flow evolutions in pumps. The findings also indicate energy loss distribution is associated with the positive slope phenomenon. The high-velocity gradient flows at the entrance of the blade-toblade passage and the reverse flows at the impeller exit are the main reasons for the high turbulent kinetic energy in the impeller. The MSST PANS model demonstrates promising applications in the field of hydraulic machinery, where unstable turbulent flows are prevalent.
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Investigation on characteristics of pressure fluctuation in a centrifugal pump with clearance flow
Lulu Zheng,Xiaoping Chen,Wei Zhang,Zu-chao Zhu,Jinglei Qu,Mengmeng Wang,Xiaojie Ma,Xueli Cheng 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9
Clearance flow has great impact on pressure fluctuation of centrifugal pumps. Numerical calculations are performed to study the pressure fluctuation characteristics of centrifugal pump with wear ring clearance, especially in the regions of interaction between main flow and clearance flow (IMC) and clearance. The accuracy of numerical calculations is illustrated by comparing the experiments of performance and pressure fluctuation. Results show that, in clearance region the pressure fluctuation is still governed by blade passing frequency (f BPF ). Its amplitude of dominate frequency of pressure fluctuation becomes larger as the probe approaches the impeller exit. In IMC region, the pressure fluctuation at impeller outlet is dominated by f BPF . However, the dominate frequency at the entrance of impeller is less than f BPF . In addition, as the flow rate increased, the amplitude of dominate frequency of pressure fluctuation increases at impeller entrance, whereas an inverse trend is observed at wear ring clearance region.
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Xiaoping Chen,Wenjin Zhang,Shaolong Wang,Zu-chao Zhu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12
On the basis of the weakly compressible assumption, large-eddy simulation of a high-speed centrifugal pump is performed at a rotational speed of 9685 r/min and flow rate of approximately quarter load (0.23 Qd). Three cryogenic media, namely, liquid methane (MM), liquid nitrogen (MN), and liquid oxygen (MO), are used. Results show that many of the internal flow characteristics derived and validated for normal-temperature water still hold for cryogenic media. Pump efficiency, maximum density deviation, and total entropy generation rate increase with the increase in the reference density. The dominant frequencies of the pressure spectrum are 12 and 6 times the rotation frequency and insensitive to the cryogenic media. The average amplitude of the first-order dominant frequency between MN and MO deviates from that of MM by approximately 10 %. The maximum deviations of the average amplitudes of second-order dominant and axial frequencies are 34.9 % and 32.3 %, respectively. The variation in standard deviation exceeds 40 % for all cryogenic media.
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Weak compressibility effects on the pressure fluctuation at RSI in a high-speed centrifugal pump
Shaolong Wang,Xiaoping Chen,Xiaojun Li,BaoLing Cui,Zu-chao Zhu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.10
This study presents large eddy simulation of high-speed centrifugal pump at approximate quarter load (0.23 Q d ) and design load (Q d ) conditions. Two liquid models, including weak compressible and incompressible assumptions, are considered to investigate the weak compressibility effects (WCE) on the pressure fluctuation at rotor-stator interaction (RSI). Researches show that the performance is slightly increased by the WCE at both the flow rates, which deviate from the experimental data within 5 %. There is a phase deviation between the pressure fluctuation of the two assumptions. The amplitudes of pressure fluctuation and pressure spectra are affected by the WCE, especially in the guide vane channel far away from the tongue. The first and second frequencies of pressure spectra are 12 and 6 times the rotation frequency, respectively, which are insensitive to the WCE. The influence of WCE on the pressure fluctuation and pressure spectra is significant at 0.23 Q d and gradually weakened at Q d .
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Metrological performance investigation of swirl flowmeter affected by vortex inflow
Qi Liu,Jia-hui Ye,Guang Zhang,Zhe Lin,Hong-guang Xu,Zu-chao Zhu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6
In fluid transportation industries, long straight transition pipelines upstream of flowmeters are required to eliminate the influence of disturbed inflow on flow metering accuracy. To ensure an accurate flow measurement, the straight transition pipeline, which is often lengthy, can be shortened, particularly when the installation space is limited. However, the characteristics of disturbed flow (mainly characterized by vortex inflow) evolving along the straight transition pipeline to affect the metrological performance must be investigated for optimizing the pipeline length. The objective of this study was to investigate the metrological performance of a swirl flowmeter affected by the vortex inflow caused by flow regulation with a sleeve valve. The effect of a straight transition pipeline length upstream of a swirl flowmeter on the evolving characteristics of the vortex inflow was investigated experimentally and by conducting a numerical simulation under flow regulation parameters, including valve openings and flow velocities. The flow coefficients for different straight transition pipeline lengths were investigated to verify the flow simulation. The periodic pressure variation in the swirl flowmeter was monitored and its corresponding characteristic frequency was analyzed. It was found that the metrological characteristics of the swirl flowmeter were extremely affected by a smaller valve opening, which can be improved by lengthening the straight transition pipeline. By analyzing the velocity vector and vorticity in the internal flow field, the vortex inflow was found to be vulnerable to dissipation within a longer straight transition pipeline. The average vorticity at the cross-section of the entrance to the swirl flowmeter was adopted to evaluate the inflow vortex intensity. Additionally, a power curve model was established to assess the critical characteristic frequency determined by the maximum unaffected inflow vorticity for different straight transition pipeline lengths. This study can provide helpful insights to the metrological performance and pipeline arrangement in the field of fluid transportation engineering.
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