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The ship gas turbine exhaust ejector is the central component parts, which can reduce or even eliminate the infrared radiation signal of ship gas turbine exhaust systems. In the design of exhaust ejector, structure forms of nozzle have a significant influence on its ejector effect. A rational nozzle, which is made to work in a narrow space and reduce the exhaust temperature effectively while minimizing...
In this paper, the cavitation characteristic of a hot water pump was numerically calculated based on mixture model. The critical net positive suction head (NPSHc) was obtained. The vapor volume fractions were obtained in different NPSH by changing the inlet pressure. Changing the temperature of the fluid, NPSHc of the pump were obtained. The results showed that when NPSH decreased, the vapor fraction...
The water hammer occurs frequently in the water conveyance system, especially in the long distance system. In order to prevent the occurrence of vaporization phenomenon in the pipelines caused by the power-off water hammer, installation of air valve is the most common water hammer protection measure. The air valve should not only discharge the air of the tube when the station start the pump, but also...
In order to further study the principle of the wave energy generating set, 3D full channel numerical calculations were carried out of the Wells turbine used for the secondary energy conversion of the wave energy generating unit. The main investigated items included the relations among turbine performance and stagger angles, as well as different blade profiles in forward and reversed flow field respectively...
In order to predict cavitation performance drop of the centrifugal pump, the RNG κ-ε turbulence model and the mass transport cavitation model are applied to simulate the cavitation flows in a centrifugal pump at different flow rates. The influence of condensation coefficient of the mass transport cavitation model on numerical simulation is analysed. According to the calculation result, the value of...
In this paper, a three-dimensional inverse design method was applied to design a hydraulic turbine and numerical simulation investigations were performed to study the effects of different blade loading on the hydraulic performances of the turbine. The paper will define blade loading as three kinds of circulation distributions named fore-loaded distribution, mid-loaded distribution and rear-loaded...
In order to study the pressure fluctuation characteristics of a pump-turbine under the abnormally low head, the geometric model of a pump-turbine is investigated using Realizable k-ε turbulence model. The unsteady numerical simulation of four operating points is conducted. The pressure signals of the points are achieved. The CFD results show good agreements with experimental ones. And then, the pressure...
The internal flow fields in a compact return diffuser have been investigated both numerically and experimentally under multi-conditions. Three-dimensional unsteady simulations are solved on high-quality structured grids with the Detached Eddy Simulation (DES) model by using the Computational Fluid Dynamics (CFD) code ANSYS-Fluent. Furthermore, a special Particle Image Velocimetry (PIV) test rig is...
In order to figure out the priority order of factors affecting centrifugal pump cavitation performance, the author carried out an orthogonal experiment on impeller geometric parameters which affects its cavitation performance, designed different impeller hydraulic models with the help of PCAD software, and used CFX software to conduct numerical stimulation calculation about its hydraulic and cavitation...
Series-parallel centrifugal pumps, which have two conditions of low pressure and high pressure, play an important role in ship engineering, thus the research of its internal flow mechanism is of great significance. In this paper, the author gave a brief introduction to the structure of a series-parallel structure centrifugal. By using speed coefficient method, main geometric parameters of the impeller...
Research on three-dimensional flow field in a postpositive tubular pumping system using numerical simulation based on the Reynolds time-averaged Navier-Stokes equations and the RNG k-ε turbulent model. By using this method, the performances of pumping system such as head, shaft power and efficiency are predicted based on the calculation of different operating conditions. The simulations were carried...
The coupled volume of fluid and level set method was applied to simulate dynamic characteristics of double bubbles; the bubble behavior was studied in five conditions. According to numerical simulation, it can be seen that: the different arrangement, distance and deformation would produce different effects on bubbles. The interactions decreased with increase in bubble distance when horizontal dispersed,...
CFD simulations on flow field of centrifugal pumps at shutoff are generally performed by means of minor-flow assumption, which are different from real operating conditions and hard to well predict pump performances at shutoff. In this paper, therefore, the zero-flow boundary condition was taken to proceed to a numerical simulation of unsteady flow for the type IS125 centrifugal pump. The pump performances...
A valveless piezoelectric micropump based on Coanda effect was presented. The effects of the angle and the length of the diffuser as well as the Reynolds number on the performance of the micropump were studied. The numerical simulation was done to obtain the flow field as well as the flow rate and the volumetric efficiency of the micropump. The range of the diffuser angle was from 15° to 60°, and...
A blade leading edge spike flow can usually be found on the condition that the discontinuous curvature curves between blade leading edge and blade surface, which is a common result of design the blade with separate curves of blade leading edge and blade surface in traditional blade design procedure. However, in recent, many researchers found that strong leading edge spike might cause significant detrimental...
Reflux hole plays an important role in the structure of the self-priming pump. Its position and area have a great influence on the self-priming capability and efficiency of the pump. In this paper, the numerical simulation of the internal flow field in the self-priming pump with different areas and positions of the reflux hole was conducted on the platform of Fluent. The simulation results show that...
Pumped-storage power plant is an essential part of a stable, safe and efficient grid to compensate the random nature of custom energy consumptions by storing extra energy during the off-peak time and delivering energy during the peak time. Reversible pump turbine is the key component of the pumped-storage power plant. As the frequent transition between different working conditions during normal operations...
The performance and stability of a high-speed centrifugal pump are closely related to its internal vortex flow. It's significant to study the vortex behaviours in a centrifugal pump, such as its coverage, distribution, physical properties, formation mechanism and energy loss, etc. To analyse these problems, the steady numerical simulations of a high-speed centrifugal pump were conducted using the...
Semispherical casing was adopted in a boiler circulating pump considering the operating safety. In order to improve the hydraulic performance and reduce the manufacture cost of the pump casing, a modification attempt on pump casing has been made by adopting a volute shape. By using both steady and unsteady numerical simulations with SST k-ω turbulence model, the hydraulic performances of pumps with...
In this paper, the author tried to find out how clearance between impeller and tongue would affect the pressure fluctuation. By changing the diameter of the impeller, six transient simulations of a centrifugal pump were conducted. Data from different monitoring points were recorded and analyzed. The result shows that pressure fluctuation decreases with the increasing of the clearance. But the high-frequency...
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