Zhong-dong Qian

Zhong-dong Qian
Wuhan University | WHU

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103
Publications
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Publications

Publications (103)
Article
Full-text available
Prediction of erosion wear in double-suction centrifugal pumps is studied numerically using an improved erosion model (EM). Experiments are also performed to verify the improved EM’s prediction ability. In the experiments, painted layers of five colors are applied to the blade surfaces using spray guns to show the erosion wear distribution, where t...
Article
Full-text available
Erosion wear is an important issue for a Francis turbine operating on rivers from the Himalayas, which directly hinders the utilization of hydropower. In this research, the severe erosion wear on the runner shroud of a Francis turbine is studied. The characteristics and physical mechanisms of the erosion wear on the runner shroud are investigated t...
Article
Full-text available
The characteristic of sediment erosion of the blade in a double-suction centrifugal pump is mainly studied because the blades of double-suction centrifugal pumps are widely observed to suffer severe erosion damage in water intake projects along the Yellow River. In order to clearly present the evolution of blade-erosion area for different sediment...
Article
Full-text available
Designing and manufacturing site-specific turbines for small hydropower is not economical. Using abundantly available Pump, from the market, as Turbine (PAT) instead of designing a completely different turbine can be much more economical for small-scale hydropower. Lot of research have been going throughout the world on this and has already proven...
Article
The runaway condition is unsteady and is of significant importance in pump turbines. In this research, the shear-stress transport (SST) k-ω turbulence model is used to simulate the unsteady flow in the vaneless region and the runner of a prototype pump turbine. The characteristics of pressure fluctuations, vortex identification based on Q criterion...
Article
Full-text available
In this paper, the open source software OpenFOAM is used to perform a numerical investigation of the cavitating flow around a modified NACA634-021 hydrofoil with bioinspired, wavy leading edge, with particular emphasis on study of the interactions between the cavitation and the streamwise vortices and the far-field radiation noise. A modified k-ω s...
Article
Full-text available
In engineering practice, the initial support system is commonly installed in the vicinity of the tunnel face after excavation, whereas the self-capacity of rock mass will fail to be utilized and the cost of the initial support system will be expensive. In this study, a methodology is proposed to determine the appropriate timing of initial support i...
Article
Full-text available
Damage of runners and other components of hydro turbine by sediment erosion and cavitation erosion is an inevitable problem associated with hydropower established in a region with mountainous topology. The paper attempts to investigate the suitability and sustainability of the reverse engineering method for the design of the eroded Francis runner....
Article
The tip leakage vortex cavitating flow generated by a straight hydrofoil is computed using Large Eddy Simulation combined with Zwart-Gerber-Belamri cavitation model. Comparisons between the numerical and experimental results show a good agreement in velocity field and complicated vortical structures, including tip leakage vortex, tip separation vor...
Article
Full-text available
Erosion wear is a major problem for hydraulic turbines operating on rivers from the Himalaya Mountains. The runner is the most important energy conversion component but it suffers heavy damage due to direct contact with the sediment-laden water. In this research, the runner's physical erosion wear mechanism is revealed using numerical simulations a...
Article
Full-text available
As a kind of water jet technology with strong impinging force and simple structure, the submerged impinging water jet can produce strong scouring action on subaqueous sediments. In order to investigate the flow field characteristics and impinging pressure of submerged impinging water jets at different impinging heights, the Wray-Agarwal (W-A) turbu...
Article
Full-text available
Mechanical energy dissipation is a major problem affecting hydraulic machinery especially under partial-load conditions. Owing to limitations of traditional methods in evaluating mechanical energy dissipation, entropy generation theory is introduced to study mechanical energy dissipation with varying discharge and tip clearance intuitively through...
Conference Paper
The flow field in the tip region of the axial-flow waterjet pump is very complex. Although it has been studied for many years, many relevant phenomena have still been a puzzle. In present paper, many detailed data on instantaneous inner structures of the tip leakage flow and evolution of the tip leakage vortex cavitation with different tip gap size...
Article
Full-text available
The axial pump operating in the pump-as-turbine mode is a practical and cost-saving alternative suitable for low-head pico hydropower in rural and remote areas that bypasses the need for expensive turbines. Their pump characteristics, however, indicate that efficiency is low in off-design flow rates. Using the computational fluid dynamics, the adju...
Article
The ground support system has a significant impact on tunnel safety while the installation time of initial support is commonly designed by empirical method. The three dimensional numerical model, based on the engineering practice, is analyzed by FLAC3D. In this paper, an improved LDP (longitudinal displacement profile) equation is proposed, which i...
Article
Full-text available
An improved diversion-cone is designed to suppress subsurface vortices in pump intake. In experiment, the influences of size and location of the improved diversion-cone on the subsurface vortices in pump intake were studied. Experiments were conducted in a rectangle intake and 12 operating points were carried out, and the vortex frequency and vorte...
Article
Well-resolved detached eddy simulation (DES) and unsteady Reynold-averaged Navier–Stokes (URANS) simulations are conducted for a water pump-intake bay. Three cases are analysed: a high-submergence, low discharge case (Case 1), a low-submergence, low-discharge case (Case 2) and a low-submergence, high-discharge case (Case 3). The numerical model use...
Article
Full-text available
Large amounts of sediment in the Himalayan rivers causes severe silt erosion to the hydraulic machinery operating along these rivers. In this study, the effects of silt characteristics on the silt-erosion characteristics of a double-suction centrifugal pump was studied and the anti-erosion property of bionic convex domes on silt erosion under these...
Article
Pressure fluctuations in double-suction centrifugal pumps are greatly affected by the flow rate and rotational speed. An experimental investigation was carried out to determine effects of the flow rate and rotational speed for optimizing the hydraulic design and realizing stable operation. Pressure fluctuation signals were obtained at five measurem...
Article
Full-text available
The effects of varying tip clearance widths on tip flows dynamics and main flows characteristics for an axial-flow pump are studied employing computational fluid dynamics method. An analysis is presented for the distributions of turbulent kinetic energy, mean axial velocity, and mean vorticity magnitude at the specific flow rate of 0.7QBEP, focusin...
Article
The effect of the inlet guide vanes on cavitation performance of an axial pump is investigated to assess the mechanism for cavitation in pumps and improve their cavitation performance. The effect of inlet guide vane angles on cavitation performance was assessed experimentally, and computational fluid dynamics was used to analyze the inner flow fiel...
Conference Paper
The performances of an axial pump with and without inlet guide vanes (IGVs) are investigated by both experimental method and computational fluid dynamics (CFD) method. Besides the stall inception, an obvious “positive slope” phenomenon appears under off-design operating points in experiment without IGVs. The experimental data also shows that IGVs c...
Article
The present work numerically examines the effect of thermal radiation from the solid phase on the thermal and flow field inside a porous medium by investigating free convection within a saturated porous cavity. A local thermal non-equilibrium (LTNE) model is used to represent the energy transport for the solid and fluid phases. The heat flux caused...
Article
Direct matrix operation is extremely memory-consuming to solve the basic equations of the radiation-hydrodynamics (R-HD) problems, e.g., Poisson equation and radiative transfer equation (RTE), especially in the cases of large grid number and multidimensions. In this work, the fast transform spectral method (FTSM), which requires much less memory th...
Article
Full-text available
In this paper, we investigate the verification and validation (V&V) procedures for the URANS simulations of the turbulent cavitating flow around a Clark-Y hydrofoil. The main focus is on the feasibility of various Richardson extrapolation-based uncertainty estimators in the cavitating flow simulation. The unsteady cavitating flow is simulated by a...
Article
Hydraulic vibrations generally exist in large units of hydropower stations. How to predict the hydraulic vibration before a hydropower station goes into operation is a significant research subject. Establishing a fluid-solid coupling mathematical model is an important step. This work focused on interpolation methods used for fluid-solid coupling pr...
Article
Full-text available
The pressure fluctuations and runner loads on a pump-turbine runner during runaway process are very violent and the corresponding flow evolution is complicated. To study these phenomena and their correlations in depth, the runaway processes of a model pump-turbine at four guide vane openings (GVOs) were simulated by three-dimensional computational...
Article
Full-text available
In this paper, the turbulent attached cavitating flow around a Clark-Y hydrofoil is investigated by the large eddy simulation (LES) method coupled with a homogeneous cavitation model. The predicted lift coefficient and the cavity volume show a distinctly quasi-periodic process with cavitation shedding and the results agree fairly well with the avai...
Article
With the large flow rate and high pump head, double-suction centrifugal pumps are widely used in irrigation pumping stations along the Yellow River. However, the performance of these pumps is affected by the characteristics of silt particles in water flow, which has been seldom studied. Therefore, this paper aims to investigate the effects of the s...
Article
Micro-hydropower applications can provide cost-effective solutions for the energy generation in rural, remote, and hilly areas where cost is prohibitive to connecting to the major power grid. To reduce the initial capital cost and the payback period, the pump as turbine (PAT) is often chosen to replace the conventional turbine. However, PATs usuall...
Article
The dynamics of air entrainment and suppression schemes in a pump sump are investigated. Four different turbulence models (standard k-ε model, realizable k-ε model, renormalization group (RNG) k-ε model and shear-stress transport (SST) k-ε model) and the volume of fluid (VOF) multiphase model are employed to simulate the three-dimensional unsteady...
Article
Full-text available
Understanding the formation mechanism of the S-shaped characteristics (SSCs) and the relationship between flow structures and the runaway instability (RI) is the prerequisite for optimizing runner design to promote operational reliability and flexibility. In this study, a new turbine equation is derived to reveal the prime cause of the SSCs, and th...
Article
The reinforced concrete bifurcation in hydropower station is consistently under high internal water pressure, and its diameter is usually larger than common duct junctions. To diminish or to decrease the heavy plastic zone and stress concentration, structure rounding is commonly used on bifurcation. This will bring some changes to the flow characte...
Conference Paper
Full-text available
A bionic blade with convex domes was applied in a double suction centrifugal pump to improve erosion resistance of the blade surfaces in this study. The hydraulic performance of the pump was simulated and the numerical results were in good agreement with the experiment data. The erosion rates of the smooth blade and bionic blades with convex domes...
Article
Full-text available
The cavitation performance of an axial flow pump with inlet guide vanes for different flow rates is studied in this article. The effects of inlet guide vanes on pump hydraulic performance and cavitation are investigated, where the total vapor fraction of impeller zone (Ftv) is calculated to predict the critical net positive suction head, which is c...
Article
Full-text available
The water flow and movement of silt in a prototype double-suction centrifugal pump was simulated using an Euler-Lagrange multiphase flow model. J-Grooves were adopted to protect the impeller ring from silt abrasion. The influence of J-grooves on the silt concentration and pump efficiency was analyzed. The results show that the radial component of t...
Article
Full-text available
During transients, hydroturbines may demonstrate some dynamic characteristics that differ from the corresponding static characteristics in steady operating conditions. To study the dynamic characteristics of a pump-turbine, we simulated the runaway transients in a model pumped-storage plant by coupling one-dimensional (1D) water conveyance system a...
Article
Full-text available
Based on the thermo-physical properties of plasma air, the temperature and flow fields of an insulator–arrester with a multi-chamber system are investigated using three-dimensional computational fluid dynamics. The plasma flow is assumed to be steady incompressible laminar flow and in local thermodynamic equilibrium. The results obtained show that...
Article
Purpose – The purpose of this paper is to examine the initial mixing of wastewater discharged from submerged outfall diffusers and the influence of port configurations on wastewater distribution based on computational results. Design/methodology/approach – Marine wastewater discharges from multiport diffusers are investigated by numerically solvin...
Article
Full-text available
Water flow and silt movement in a double-suction centrifugal pump were simulated using an Euler-Lagrange multiphase flow model. Blade erosion rates were predicted using a particle erosion model and the influence of inlet and outlet shapes on silt abrasion was analyzed. The results show: the inlet relative velocity is larger on the suction side than...
Article
Purpose – A radial offset jet has the flow characteristics of a radial jet and an offset jet, which are encountered in many engineering applications. The purpose of this paper is to study the dynamics and mass transfer characteristics of the radial offset jet with an offset ratio 6, 8 and 12. Design/methodology/approach – Three turbulence models,...
Article
The water flow and movement of silt in a prototype double suction centrifugal pump was simulated using an Euler–Lagrange multiphase flow model. Back-blade and J-groove configurations were adopted to protect the impeller ring from silt abrasion. Four back-blades and four J-grooves were considered. The results show that the relative velocity of water...
Article
The scouring funnel in front of a bottom orifice under the condition of fixed water levels is simulated by using an Eulerian two-phase model, with onsideration of the flow-particle and particle-particle interactions. The predictions of the scouring funnel shape agree well with laboratory measurements. The flow-field characteristics of the two phase...
Chapter
Condition monitoring is the process of monitoring a condition parameter in machinery, so that a significant change is indicative of a developing failure. The use of conditional monitoring allows maintenance to be scheduled, or other actions taken to avoid the consequences of failure before it actually occurs.
Chapter
Generally, hydraulic excitations that induce vibrations in hydraulic machinery can be categorized as follows:
Chapter
This chapter mainly focuses on the instability of hydraulic turbine system. The stability of pumping system and the nonlinear models of hydraulic turbine system transient in hydro power plants are also introduced.
Chapter
The study of structural dynamics focuses on a structure’s behaviour when it is subjected to dynamic loading. Dynamic analysis can be used to research dynamic displacements, time-history, and modal analysis. A static load is one that does not vary, whereas a dynamic load changes with time. If it changes slowly, the structure’s response may be determ...
Chapter
Rotordynamics is a branch of system dynamics dealing with mechanical devices in which at least one part, usually referred to as rotor, rotates with the angular momentum.
Chapter
Flows in pumps or hydraulic turbines are unsteady due to the system rotation, flow instabilities and mutual interactions between rotating and stationary parts. Flow instabilities are mostly viscous phenomena such as boundary layer transition and vortex shedding that produce small amplitude pressure fluctuations at relatively low frequencies. The un...
Chapter
The purpose of this chapter is to provide a theoretical background of vibration in mechanical systems. The theories and mathematical structures presented in this chapter are classical and based on the book by Krodkiewski (2008). In fact, vibration study is rooted in Newton’s Law of Motion. The last four hundred years saw an increased interest in th...
Chapter
A numerical model describes a scientific system in language of numbers. There are two kinds of models in mathematics: the lumped parameter model and the distributed parameter model. If the model is homogeneous, or represents a consistent state throughout the entire system, the parameters are distributed, and the model may be referred to as a contin...
Chapter
Mechanical analysis of hydraulic machinery includes two fields, structural dynamics and rotor dynamics. Structural dynamics is a subset that covers areas of structural behavior subjected to dynamic loading. Rotordynamics is a specialized branch of applied mechanics concerned with the behavior and diagnosis of rotating structures.
Chapter
The shaft stability of generating and pumping units plays a crucial role on the units’ operation: It directly affects the safe operation and also influences the life of units.
Article
Slurry jets in a static uniform environment were simulated with a two-phase mixture model in which flow-particle interactions were considered. A standard k-ε turbulence model was chosen to close the governing equations. The computational results were in agreement with previous laboratory measurements. The characteristics of the two-phase flow field...
Article
When there is a turbulent circular wall jet discharge from a nozzle into a stagnant ambient area with initial momentum, the velocity field changes greatly, especially near the wall or the interface between the jet and surrounding fluid. This accounts for the great velocity gradi