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| 1 | Numerical Simulation and Analysis of Solid-liquid Two-phase Flow in Centrifugal Pump显示文摘The flow with solid-liquid two-phase media inside centrifugal pumps is very complicated and the relevant method for the hydraulic design is still immature so far.There exist two main problems in the operation of the two-phase flow pumps,i.e.,low overall efficiency and severe abrasion.In this study,the three-dimensional,steady,incompressible,and turbulent solid-liquid two-phase flows in a low-specific-speed centrifugal pump are numerically simulated and analyzed by using a computational fluid dynamics(CFD) code based on the mixture model of the two-phase flow and the RNG k-two-equation turbulence model,in which the influences of rotation and curvature are fully taken into account.The coupling between impeller and volute is implemented by means of the frozen rotor method.The simulation results predicted indicate that the solid phase properties in two-phase flow,especially the concentration,the particle diameter and the density,have strong effects on the hydraulic performance of the pump.Both the pump head and the efficiency are reduced with increasing particle diameter or concentration.However,the effect of particle density on the performance is relatively minor.An obvious jet-wake flow structure is presented near the volute tongue and becomes more remarkable with increasing solid phase concentration.The suction side of the blade is subject to much more severe abrasion than the pressure side.The obtained results preliminarily reveal the characteristics of solid-liquid two-phase flow in the centrifugal pump,and are helpful for improvement and empirical correction in the hydraulic design of centrifugal pumps. | ZHANG Yuliang LI Yi CUI Baoling ZHU Zuchao DOU Huashu | 2013 | Chinese Journal of Mechanical Engineering2013，26，1： | 55 |
| 2 | Experimental Study on a Centrifugal Pump with an Open Impeller during Startup Period显示文摘Transient performance of fluid machinery during transient operating periods,such as startup and stopping,has been drawn more attentions recently due to the growing engineering needs.In this paper,the transient behavior of a prototype centrifugal pump with an open impeller during rapid startup period is studied experimentally.The variations of the rotational speed,flow rate,head,and shaft power during rapid startup period are recorded in experiments at different discharge valve openings.In addition,the non-dimensional flow rate and head are also used to analyze the transient behavior.The research result shows that the rise characteristic of the rotational speed is not basically changed by working points,while mainly depends on the startup characteristics of the driving motor.Compared with the rapid rise of the rotational speed,the flow rate rises slowly in the initial stage of startup.Moreover,the flow rate lags behind the rotational speed to rise to final stable value,and the delay becomes more severe with the increase of the discharge valve opening.The shaft power impact phenomenon generally exists in the process of startup.The non-dimensional analysis shows that the non-dimensional head is very high at the very beginning of startup,and quickly falls to the minimum,then gradually rises to final stable value,while the non-dimensional flow rate always shows the rise tendency during whole startup period.In conclusion,it is found from the non-dimensional results that the quasi-steady analysis is unable to accurately assess the transient flow during startup period. | Yuliang Zhang Zuchao Zhu Yingzi Jin Baoling Cui Yi Li Huashu Dou | 2013 | Journal of Thermal Science2013，22，1： | 5 |
| 3 | Effect of Rotational Speed on the Stability of Two Rotating Side-by-side Circular Cylinders at Low Reynolds Number显示文摘Flow around two rotating side-by-side circular cylinders of equal diameter D is numerically studied at the Reynolds number 40≤ Re ≤200 and various rotation rate θ_i. The incoming flow is assumed to be two-dimensional laminar flow. The governing equations are the incompressible Navier-Stokes equations and solved by the finite volume method(FVM). The ratio of the center-to-center spacing to the cylinder diameter is T/D=2. The objective of the present work is to investigate the effect of rotational speed and Reynolds number on the stability of the flow.The simulation results are compared with the experimental data and a good agreement is achieved. The stability of the flow is analyzed by using the energy gradient theory, which produces the energy gradient function K to identify the region where the flow is the most prone to be destabilized and the degree of the destabilization. Numerical results reveal that K is the most significant at the separated shear layers of the cylinder pair. With Re increases,the length of the wake is shorter and the vortex shedding generally exhibits a symmetrical distribution forθ_i<θ_(crit), It is also shown that the unsteady vortex shedding can be suppressed by rotating the cylinders in the counter-rotating mode. | DOU Huashu ZHANG Shuo YANG Hui SETOGUCHI Toshiaki KINOUE Yoichi | 2018 | Journal of Thermal Science2018，27，2： | 3 |
| 4 | Numerical and Experimental Investigation on Aerodynamic Performance of Small Axial Flow Fan with Hollow Blade Root显示文摘To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance,a modification of conventional axial fan blades with numerical and experimental investigation is presented.Hollow blade root is manufactured near the hub.The numerical and experimental results show that hollow blade root has some effect on the static performance.Static pressure of the modified fan is generally the same with that of the datum fan,while,the efficiency curve of the modified fan has a different trend with that of the datum fan.The highest efficiency of the modified fan is 10% greater than that of the datum fan.The orthogonal experimental results of fan noise show that hollow blade root is a feasible method of reducing fan noise,and the maximum value of noise reduction is about 2 dB.The factors affecting the noise reduction of hollow blade root are in the order of importance as follows: hollow blade margin,hollow blade height and hollow blade width.The much smoother pressure distribution of the modified fan than that of the datum fan is the main mechanism of noise reduction of hollow blade root.The research results will provide the proof of the parameter optimization and the structure design for high performance and low noise small axial fans. | Zhang Li Jin Yingzi1 Dou Huashu Jin Yuzhen | 2013 | Journal of Thermal Science2013，22，5： | 3 |
| 5 | Effects of Tangential Velocity Distribution on Flow Stability in a Draft Tube显示文摘Numerical simulations of the flow in the draft tube of a Francis turbine are carried out in order to elucidate the effects of tangential velocity on flow stability.Influence of the location of the maximum tangential velocity is explored considering the equality of the total energy at the inlet of the draft tube.It is found that the amplitude of the pressure fluctuation decreases when the location of the maximum of the tangential velocity moves from the centre to the wall on the cross section.Thus,the stability of the flow in the draft tube increases with the moving of the location of the maximum tangential velocity.However,the relative hydraulic loss increases and the recovery coefficient of the draft tube decreases slightly. | DOU Huashu NIU Lin CAO Shuliang | 2014 | Journal of Thermal Science2014，23，5： | 2 |
| 6 | Physics of Flow Instability and Tarbu- lent Transition in Shear Flows 显示文摘 | DOU Huashu | 2011 | International Journal of Physical Science2011，6，6： | 1 |
| 7 | Mechanism of Flow Instability and Tran- sition to Turbulence 显示文摘 | DOU Huashu | 2006 | International Journal of Non- Linear Mech- anics2006，41，51： | 1 |
| 8 | Physics of Flow Instability and Turbu- lent Transition in Shear Flows 显示文摘 | DOU Huashu | 2011 | International Journal of Physical Science2011，6，14： | 1 |
| 9 | Mechanism of flow instability and transition to turbulence显示文摘 | Dou Huashu | 2006 | International Journal of Non-Linear Mechanics2006，41，5： | 1 |
| 10 | Physics of flow instability and turbulent transition in shear flows显示文摘 | Dou Huashu | 2011 | International Journal of Physical Science2011，6，6： | 1 |
| 11 | Instability of Taylor-Couctte flow between concentric rotating cylinders 显示文摘 | Dou Huashu Khoo B C Yeo K S | 2008 | International Journal of Thermal Sciences2008，47，11： | 1 |
| 12 | Criteria of turbulent transition in parallel flows显示文摘 | Dou Huashu Khoo B C | 2010 | Modern Physics Letters B2010，24，13： | 1 |
| 13 | A Unified Instability Region for the Extended Taylor-Goldstein Problem of Hydrodynamic Stability显示文摘We consider inviscid,incompressible shear flows with variable density and variable cross section.For this problem,we derived a new estimate for the growth rate of an unstable mode and a parabolic instability region which intersects semiellipse instability region under some condition. | S.Sridevi Huashu Dou V.Ganesh | 2017 | Advances in Applied Mathematics and Mechanics2017，9，6： | 0 |
| 14 | An Improved Prediction Model of Vortex Shedding Noise from Blades of Fans显示文摘The main source of the noise of an axial flow fan is the fluctuating pressure field on blade surfaces caused by the shedding of vortices at the trailing edge of blades.An analytical model to predict the vortex shedding noise generated at the trailing edge of blades of axial flow fans was proposed by Lee in 1993.In this model,for mathematical convenience,an idealized vortex street is considered.However,the agreement between the analytical results and the experimental data needs to be improved because of the simplification about the Karman vortex street in the wake of blade.In the present study,a modified model is proposed based on the prediction model by Lee.The boundary layer theory is used to analyze and calculate the boundary layer development on both the pressure and the suction sides of blades.Considering the effect of boundary layer separation on the location of noise source,the predicted overall sound pressure level compares favorably with the experimental data of an axial fan.In the calculation of A-weighted sound pressure level(La),considering the effect of static pressure on radiate energy,the predicted broadband noise with the modified model compares favorably with the experimental data of a multiblade centrifugal fan. | DOU Huashu LI Zhehong LIN Peifeng WEI Yikun CHEN Yongning CAO Wenbin HE Haijiang | 2016 | Journal of Thermal Science2016，25，6： | 0 |
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