Effects of the Circulating Jet Flow on the Suction Flow Field and Cavitation in a Canned Motor Pump

2019 ◽  
Author(s):  
Laizuo Chen ◽  
Minguan Yang ◽  
Wei Cui ◽  
Bo Gao ◽  
Ning Zhang ◽  
...  
Keyword(s):  
Flow Distribution ◽  
Leading Edge ◽  
Jet Flow ◽  
Main Stream ◽  
Cavitation Performance ◽  
Jet Nozzle ◽  
Pump Inlet ◽  
Suction Flow ◽  
Jet Structure ◽  
Canned Motor

Abstract Cavitation is a general phenomenon in centrifugal pumps. When the inlet pressure near the leading edge of the blade is lower than the saturated pressure, cavitation would develop in the impeller. As cavitation occurs, the pump head will drop rapidly and the pump efficiency will decrease. In addition, severe vibration and noise will be induced. Cavitation performance is considered as an important factor in many industrial applications, and affected by various conditions. The canned motor pump is a special type of non-seal centrifugal pump. The pump and motor are integrated. In order to cool the motor and lubricate the bearing during the operation, a portion of fluid, called the circulating flow, is withdrawn from the impeller outlet, and then flows along the cooling circle within the motor. Finally, the circulating fluid moves through the hollow shaft and merges with the main suction flow near the impeller inlet, which can be defined as the circulating jet flow. The jet flow will alter the uniform velocity distribution at the impeller inlet as its direction is opposed to the main suction flow. Consequently, it is expected that the cavitation performance of the pump will drop drastically. It is necessary to analyze the effect of the jet at the pump inlet on the cavitation performance. In this paper, in order to illustrate the jet flow on the pump performance, a numerical simulation method is applied to depict the fluid flow field and cavitation performance of a canned motor pump. For the turbulent model, the standard k-ε turbulent model is adopted. To capture the cavitation performance of the pump, the Zwart-Gerber-Belamri cavitation model was used to investigate the steady cavitation flow through the entire flow channel. It can be seen from the numerical results that the internal jet flow formed by the coolant circulation has a significant effect on cavitation performance. At the pump inlet, the velocity field is divided into three regions: the internal jet flow region, the main-stream region, and the backflow region. The internal jet presents a typical submerged jet structure and its existence results in the non-uniform inlet flow distribution. For the jet flow, it extends to the pump inlet and exhibits an asymmetric characteristic. The static pressure near the impeller inlet with the internal jet is drastically reduced compared to the case without the internal jet structure, and a local low-pressure region occurs around the outlet of the jet nozzle. The cavitation performance of the pump with the internal jet drops obviously. At the off-design condition, the cavitation performance of the pump is seriously degraded. From quantitative data, it indicates that the NPSH3 increases by more than 1.51 times compared with that of the original impeller under design condition. The cavitation inception occurs on the suction side of the leading edge of the impeller near the hub, and then cavitation also occurs near the outlet of the jet nozzle. Finally, the cavitation occurs in the transition region between the internal jet and the main-stream flow regions. So, it is believed that the deterioration of cavitation performance is caused by the combined effect of the non-uniform flow distribution and the cavitation at the internal jet region.

Numerical Simulation of Impinging Cooling on the Leading Edge of a Turbine Blade

2011 ◽  
Author(s):  
Keyong Cheng ◽  
Xiulan Huai ◽  
Jun Cai ◽  
Zhixiong Guo
Keyword(s):  
Numerical Simulation ◽  
Turbine Blade ◽  
Leading Edge ◽  
Critical Factor ◽  
Main Stream ◽  
Experimental Conditions ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lower Temperature ◽  
Simulation Parameters

In the present study, numerical simulation is carried out for impingement/effusion cooling on the leading edge of a turbine blade similar to an experimental model tested previously. The k-ε turbulence model is used, and simulation parameters are set in accordance with the experimental conditions, including temperature ratio, blowing ratio, and Reynolds number of the main stream. The accuracy and reliability of the simulation is verified by the experimental data, and the influence of various factors on fluid flow and heat transfer is analyzed in detail. The results indicate that the blowing ratio is one critical factor which affects the cooling effectiveness. The greater the blowing ratio is, the higher the cooling effectiveness is. In addition, a staggered-holes arrangement is numerically studied and compared with a line-holes arrangement. The results show that the staggered-holes arrangement has a lower temperature on the outer surface of the leading edge and has improved the cooling effectiveness.

Tip Leakage Flow Instability in a Centrifugal Compressor

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Teng Cao ◽  
Tadashi Kanzaka ◽  
Liping Xu ◽  
Tobias Brandvik
Keyword(s):  
Shear Layer ◽  
Centrifugal Compressor ◽  
Large Scale ◽  
Flow Instability ◽  
Leading Edge ◽  
Main Stream ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Unstable Flow ◽  
Tip Leakage

Abstract In this paper, an unsteady tip leakage flow phenomenon is identified and investigated in a centrifugal compressor with a vaneless diffuser at near-stall conditions. This phenomenon is associated with the inception of a rotating instability in the compressor. The study is based on numerical simulations that are supported by experimental measurements. The study confirms that the unstable flow is governed by a Kelvin–Helmholtz type instability of the shear layer formed between the main-stream flow and the tip leakage flow. The shear layer instability induces large-scale vortex roll-up and forms vortex tubes, which propagate circumferentially, resulting in measured pressure fluctuations with short wavelength and high amplitude which rotate at about half of the blade speed. The 3D vortex tube is also found to interact with the main blade leading edge, causing the reduction of the blade loading identified in the experiment. The paper also reveals that the downstream volute imposes a once-per-rev circumferential nonuniform back pressure at the impeller exit, inducing circumferential loading variation at the impeller inducer, and causing circumferential variation in the unsteady tip leakage flow.

Flow Analysis of Spray Jet and Direct Jet Nozzle for Fire Water Monitor

2010 ◽  
Vol 139-141 ◽  
pp. 913-916 ◽  
Author(s):  
Guo Liang Hu ◽  
Wei Gang Chen ◽  
Zhi Gang Gao
Keyword(s):  
Flow Analysis ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
Jet Flow ◽  
Extended Length ◽  
Jet Nozzle ◽  
Simulation Results ◽  
Steady Velocity ◽  
Nozzle Structure

In order to investigate the influence rules between the jet nozzle of fire water monitor and the jet performances, two typical jet nozzle, the spray jet and direct jet nozzle was designed to analysis the jet flow characteristics. Flow simulation of the jet nozzle was completed using fluent kits. The outlet velocity of the spray jet nozzle and direct jet nozzle were investigated in detail, and the influence rules of the nozzle structure on the outlet velocity was also discussed. The simulation results show that the steady velocity of the jet nozzle is about 34m/s that coinciding the contour magnitude, and the better extended length of the direct jet nozzle is about 50mm length that can improve the jet performances. The results can verify the reasonableness of the designed nozzle, it also can optimize the nozzle structure and increase the jet performance of the fire water monitor.

scholarly journals Experimental Study of the Jet Engine Exhaust Flow Field of Aircraft and Blast Fences

2015 ◽  
Vol 27 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Haifu Wang ◽  
Liangcai Cai ◽  
Xiaolei Chong ◽  
Hao Geng
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Wind Velocity ◽  
Maximum Rate ◽  
Dynamic Pressure ◽  
Jet Flow ◽  
Engine Exhaust ◽  
Jet Engine ◽  
Jet Nozzle

A combined blast fence is introduced in this paper to improve the solid blast fences and louvered ones. Experiments of the jet engine exhaust flow (hereinafter jet flow for short) field and tests of three kinds of blast fences in two positions were carried out. The results show that the pressure and temperature at the centre of the jet flow decrease gradually as the flow moves farther away from the nozzle. The pressure falls fast with the maximum rate of 41.7%. The dynamic pressure 150 m away from the nozzle could reach 58.8 Pa, with a corresponding wind velocity of 10 m/s. The temperature affected range of 40°C is 113.5×20 m. The combined blast fence not only reduces the pressure of the flow in front of it but also solves the problems that the turbulence is too strong behind the solid blast fences and the pressure is too high behind the louvered blast fences. And the pressure behind combined blast fence is less than 10 Pa. The height of the fence is related to the distance from the jet nozzle. The nearer the fence is to the nozzle, the higher it is. When it is farther from the nozzle, its height can be lowered.

scholarly journals Anti-Cavitation Design of the Symmetric Leading-Edge Shape of Mixed-Flow Pump Impeller Blades

Symmetry ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 46 ◽  
Author(s):  
Di Zhu ◽  
Ran Tao ◽  
Ruofu Xiao
Keyword(s):  
Fluid Dynamics ◽  
Genetic Algorithm ◽  
Design Method ◽  
Leading Edge ◽  
Mixed Flow ◽  
Pump Impeller ◽  
Cavitation Performance ◽  
Optimal Sample ◽  
Dynamics Method ◽  
Flow Pump

Mixed-flow pumps compromise large flow rate and high head in fluid transferring. Long-axis mixed-flow pumps with radial–axial “spacing” guide vanes are usually installed deeply under water and suffer strong cavitation due to strong environmental pressure drops. In this case, a strategy combining the Diffusion-Angle Integral Design method, the Genetic Algorithm, and the Computational Fluid Dynamics method was used for optimizing the mixed-flow pump impeller. The Diffusion-Angle Integral Design method was used to parameterize the leading-edge geometry. The Genetic Algorithm was used to search for the optimal sample. The Computational Fluid Dynamics method was used for predicting the cavitation performance and head–efficiency performance of all the samples. The optimization designs quickly converged and got an optimal sample. This had an increased value for the minimum pressure coefficient, especially under off-design conditions. The sudden pressure drop around the leading-edge was weakened. The cavitation performance within the 0.5–1.2 Qd flow rate range, especially within the 0.62–0.78 Qd and 1.08–1.20 Qd ranges, was improved. The head and hydraulic efficiency was numerically checked without obvious change. This provided a good reference for optimizing the cavitation or other performances of bladed pumps.

Effect of Periodic Wake Passing on Film Effectiveness of Inclined Discrete Cooling Holes Around the Leading Edge of a Blunt Body

1996 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Eitaro Koyabu ◽  
Shigemichi Yamawaki
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Turbine Blades ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Surface ◽  
Main Stream ◽  
Test Model ◽  
Free Stream Turbulence ◽  
Secondary Air

Detailed studies are conducted on film effectiveness of inclined discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of a typical turbine blade and are angled at 30 and 90 degree to the surface in the spanwise and streamwise directions, respectively. A spoked-wheel type wake generator is used in this study to simulate periodically incoming wakes to turbine blades. In addition, two types of turbulence grids are used to elevate a free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. Most of the dominant flow conditions are reproduced in this study except for the air density ratio of the secondary air and the main stream. For each of the blowing ratios, wall temperature around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals to obtain traces of the injected secondary air on the test surface, which consequently helps us interpret the data of the thermocouples.

Effects of Flow Injection From Outer Casing Upon Turbine Nozzle Vane Flow Field

2002 ◽  
Author(s):  
K. Funazaki ◽  
C. F. F. Favaretto ◽  
T. Tanuma
Keyword(s):  
Flow Field ◽  
Flow Injection ◽  
Three Dimensional ◽  
Leading Edge ◽  
Main Stream ◽  
Flow Angle ◽  
Aerodynamic Loss ◽  
Nozzle Vane ◽  
Design Variables ◽  
The Impact

In the present paper steady three-dimensional numerical calculations were performed in order to investigate the effects of flow injection from the outer casing upon turbine nozzle vane flow field. Several test cases were analyzed by applying different nozzle vane configurations such as the blade lean, injection slot width and distance from the leading edge. Numerical simulations were conducted considering the no injection case, 5% and 10% main stream flow injection from the outer casing. The impact of the flow injection design variables and the blade lean angle on the aerodynamic loss in terms of the energy loss coefficient and the outlet flow angle were analyzed through a parametric study.

Supersonic Flow Past Wing-Body Combinations

1953 ◽  
Vol 4 (3) ◽  
pp. 287-314 ◽  
Author(s):  
W. Chester
Keyword(s):  
Supersonic Flow ◽  
Aspect Ratio ◽  
Leading Edge ◽  
The Body ◽  
Infinite Cylinder ◽  
Main Stream ◽  
Exact Equation ◽  
Body Of Revolution ◽  
Flow Past ◽  
General Conditions

SummaryThe supersonic flow past a combination of a thin wing and a slender body of revolution is discussed by means of the linearised equation of motion. The exact equation is first established so that the linearised solution can be fed back and the order of the error terms calculated. The theory holds under quite general conditions which should be realised in practice.The wing-body combination considered consists of a wing symmetrically situated on a pointed body of revolution and satisfying the following fairly general conditions. The wing leading edge is supersonic at the root, and the body is approximately cylindrical downstream of the leading edge. The body radius is of an order larger than the wing thickness, but is small compared with the chord or span of the wing.It is found that if the wing and body are at the same incidence, and the aspect ratio of the wing is greater than 2 (M2-1)-½, where M is the main stream Mach number, the lift is equivalent to that of the complete wing when isolated. If the wing only is at incidence then the lift is equivalent to that of the part of the wing lying outside the body.The presence of the body has a more significant effect on the drag. If, for example, the body is an infinite cylinder of radius a, and the wing is rectangular with aspect ratio greater than 2(M2-1)-½, then the drag of the wing is decreased by a factor (1-2a/b), where 2b is the span of the wing.When these conditions do not hold the results are not quite so simple but are by no means complicated.

An IHX Design for Pool Type LMFBR System Application

1980 ◽  
Vol 102 (3) ◽  
pp. 563-567
Author(s):  
D. D. DeFur
Keyword(s):  
Pressure Drop ◽  
Tube Bundle ◽  
Flow Distribution ◽  
Significant Feature ◽  
Transient Conditions ◽  
Mechanical Feature ◽  
Cold Pools ◽  
Side Pressure ◽  
Pump Inlet ◽  
Pool Type

This paper presents the design of a 500 MWt Intermediate Heat Exchanger (IHX) for application in a multi-zone pool-type Liquid Metal Fast Breeder Reactor System. The primary feature around which this design was developed is the ability to function under all steady-state and transient conditions without the need for a distinct mechanical feature to accommodate differential thermal expansion between the tube bundle and shell. This is accomplished by using thermal baffles and judiciously adjusting the ratio of shell length in contact with the hot and cold pools of the multi-zone reactor. Thus, the component shell is maintained at a higher temperature than the tube bundle and the tubes are basically tension members. Under certain transient conditions the tubes heat up and become compression members but are not loaded to the point of buckling. A secondary, but not less significant, feature is the low primary side pressure drop and good flow distribution offered by this design. (Multi-zone reactor systems have no hard piping between the IHX outlet and primary pump inlet; therefore, the relatively small differential head of sodium between the two pools is the only driving element which causes flow through the primary side of the IHX. For this reason, a low primary side pressure drop is essential). To accomplish this, the primary sodium flows through the tube side of the component where the flow channel is simple and unimpeded by tube supports or other restrictions. Secondary flow distribution, through the shell side of the unit, can be adjusted as required since a higher pressure drop can be tolerated.

Intermittent Phenomena in the Flow Over a Rib Roughened Surface

1991 ◽  
Vol 113 (2) ◽  
pp. 206-209 ◽  
Author(s):  
T. Mullin ◽  
S. R. Martin
Keyword(s):  
Strouhal Number ◽  
Nuclear Reactor ◽  
Laser Doppler Anemometry ◽  
Leading Edge ◽  
Main Stream ◽  
Recirculation Bubble ◽  
Nuclear Reactor Fuel ◽  
Roughened Surface ◽  
Turbulent Water ◽  
Rib Roughened

Laser Doppler anemometry has been used to make measurements of a small recirculation bubble in a turbulent water flow over a rib roughened surface. The bubble occurs near the leading edge of a transverse rib which is a model of the ribbed surface used to enhance cooling on nuclear reactor fuel pins. The bubble is transient, and spectral and correlation measurements were made to investigate any periodicity. It was found that the bubble itself did not show any periodicity but there was evidence for fluctuations in the main stream with a Strouhal number of 0.1.

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