Rotating Cavitation in a Centrifugal Pump Impeller of Low Specific Speed

2002 ◽  
Vol 124 (2) ◽  
pp. 356-362 ◽  
Author(s):  
Jens Friedrichs ◽  
Gu¨nter Kosyna
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Incidence Angle ◽  
Normal Operation ◽  
Pump Impeller ◽  
Wide Range ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Cavity Closure ◽  
Operating Points

The paper describes an experimental investigation of two similar centrifugal pump impellers of low specific speed. Both impellers show rotating cavitation over a wide range of part load operating points. The occurrence of this phenomenon produces a characteristic shape of creeping head-drop compared to the more usual sudden head-drop at “normal” operation points. The onset of rotating cavitation can be assigned to a certain value of the parameter σ/2α meaning the cavity volume in relation to the incidence angle. Optical analysis by video and high-speed camera techniques illustrates the development of this instability mechanism which is mainly driven by an interaction of the cavity closure region and the following blade. Combining these observations and the results of a fourier-transformation the characteristic propagation frequencies of rotating cavitation can be presented for one impeller.

New Centrifugal Pump in Very Low Specific Speed Range

2011 ◽  
Author(s):  
Shusaku Kagawa ◽  
Junichi Kurokawa
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Rotating Disk ◽  
Capacity Curve ◽  
Speed Range ◽  
Low Specific Speed ◽  
Specific Speed

In the range of very low specific speed, such as ns < 80 [min.−1, m3/min., m], or Ns < 533 [min.−1, USGPM, ft.], stable head-capacity curve is one of the most important issues. The head-capacity curve of a conventional closed impeller tends to be unstable with a positive slope characteristic in such a very low ns range. To solve this problem, a new type of centrifugal pump “J-groove pump” is proposed and tested in this study. The J-groove pump is composed of a rotating disk mounted with many shallow radial grooves and a circular casing. The experimental results reveal that the proposed J-groove pump is quite effective in the very low specific speed range. The pump head is about 1.2 times higher than that of a conventional centrifugal pump and the head-capacity curve is almost stable, though the efficiency becomes a little lower because of a large friction power of the stationary wall. The cavitation performance is also measured and is shown to be almost same as that of a conventional centrifugal pump. This pump is applicable to high speed pump, as it has no small clearance, high strength due to simple impeller configuration, and easy to assemble. In order to determine the internal flow characteristics of the J-groove pump, CFD simulation is carried out. It is revealed that the high head of the J-groove pump is caused by a strong vortex flow existing in both clearances near the impeller tip over the whole flow range.

CFD Wind Tunnel Tests of Centrifugal Stage Return Channel Vane Cascades

2015 ◽  
Author(s):  
Y. Galerkin ◽  
L. Marenina ◽  
K. Soldatova
Keyword(s):  
Incidence Angle ◽  
Flow Behavior ◽  
Radial Component ◽  
Loss Coefficient ◽  
Centrifugal Stage ◽  
Wide Range ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Return Channel ◽  
Object Of Study

Stator part of a centrifugal compressor stage is a proper object of study by CFD calculations meaning better understanding of flow behavior, checking of field type design methods and possible improvements. Several stators with vane and vaneless diffusers for stages with different specific speed were designed by standard methodology and numerically analyzed. Results were verified. Calculation in a whole has demonstrated validity of existing recommendation. The specific velocity for stators is introduced which can be applied to match an impeller and a stator. Calculations demonstrated quick efficiency drop for stators with specific speed less than 0,215. Return channel vane cascades were studied in wide range of solidity with constant vane height and with constant radial component of velocity. Empirical formulae with non-dimensional circulation as an argument are proposed for loss coefficient, profile loss coefficient, optimal incidence angle and exit lag angle. Candidates of the low specific speed stator have demonstrated that an arbitrary channels’ wideness to diminish friction losses is not effective. Better flow organization is preferable. Modification of a crossover demonstrated positive results for high and low specific speed stators.

scholarly journals Study on the Design Method of Impeller on Low Specific Speed Centrifugal Pump

2015 ◽  
Vol 9 (1) ◽  
pp. 594-600
Author(s):  
Jianhua Liu ◽  
Xiangyang Zhao ◽  
Miaoxin Xiao
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Design Method ◽  
Simulation Method ◽  
Design Methods ◽  
Pump Impeller ◽  
External Characteristic ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Centrifugal Pump Impeller

In this work, the comparative study has been done for five kinds of design methods of the low specific speed centrifugal pump impeller adopted numerical simulation method by software of Fluent, so that the problems can be solved. Many different design methods exists for the low specific speed centrifugal pump impeller, which caused the design effect difficult to control. The numerical simulation method based on the Reynolds time averaged N-S equations (RANS) and RNG κ-ε turbulence models. Results revealed the inner flow pattern of these impeller, and these results were verified by external characteristic experiment. The research results showed that the design method, which adopted compound impeller with short blades and these short blades turned to the suction surface of long blades. Results proved that its flow distribution is even and external characteristic curve is more ideal.

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