Suppression of Performance Curve Instability of a Mixed Flow Pump by Use of J-groove

2000 ◽  
Vol 122 (3) ◽  
pp. 592-597 ◽  
Author(s):  
Sankar L. Saha ◽  
Junichi Kurokawa ◽  
Jun Matsui ◽  
Hiroshi Imamura
Keyword(s):  
Angular Momentum ◽  
Pressure Gradient ◽  
Reverse Flow ◽  
Swirl Flow ◽  
Maximum Efficiency ◽  
Performance Curve ◽  
Positive Slope ◽  
Mixed Flow ◽  
Remarkable Effect ◽  
Flow Pump

In order to control and suppress performance curve instability characterized by the positive slope of head-capacity curve of a mixed flow pump, a very simple passive method utilizing shallow grooves mounted on a casing wall parallel to the pressure gradient (J-groove) is proposed. The optimum groove dimension and location for suppressing such an instability are determined experimentally. Results show that shallow grooves of adequate dimension and proper location can suppress such instability perfectly without decreasing the pump maximum efficiency. The remarkable effect of shallow grooves is to decrease both the swirl strength and the propagation of reverse flow at the impeller inlet region, through angular momentum absorption owing to mixing of groove reverse flow and swirl flow, yielding recovery of impeller theoretical head. [S0098-2202(00)02603-1]

Clarification of Performance Curve Instability Mechanism Using Large Eddy Simulation of Internal Flow of a Mixed-Flow Pump

2015 ◽  
Author(s):  
Isao Hagiya ◽  
Chisachi Kato ◽  
Yoshinobu Yamade ◽  
Takahide Nagahara ◽  
Masashi Fukaya
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Low Flow ◽  
Performance Curve ◽  
Instability Mechanism ◽  
Positive Slope ◽  
Mixed Flow ◽  
Flow Rates ◽  
Direction Opposite ◽  
Flow Pump

We analyzed the internal flows of a test mixed-flow pump exhibiting performance curve instability at low flow rates by using LES to clarify the performance curve instability mechanism. The LES was conducted using the open source software FrontFlow/blue [1]. In particular, we investigated in detail the flows at the flow rates, where the head curve had a positive slope under low flow rate condition. We clarified that Euler’s head drop caused by a stall near the tip of the rotor-blades is a dominant factor at the instability of the test pump. At the bottom point of the positive slope of the head curve, stall regions covered all the rotor-blade passages on the tip side. The drop of the angular momentum in the impeller caused by the stall on the leading edge side exceeds the increment caused by the decrease in the flow rate on the trailing edge at the bottom point of the positive slope. At the middle point of the positive slope of the head curve we also found regions with low-velocities in some blade passages. Such regions, namely stall cells, rotated around the impeller for one revolution while the impeller rotated almost about 20 revolutions in the direction opposite to the impeller’s rotation. The region with low-velocity first appears at the trailing edge and expands toward the leading edge. The angle of attack of the neighbouring blade in the direction opposite to the rotation of the blade increases and that blade pitch begins to stall. When that blade pitch is fully stalled, it is no longer loaded and the positive pressure gradient in that blade pitch decreases. The blade pitch is most likely to accept the excess flow. It recovers from the stalled state.

scholarly journals Dynamic Characteristics of Rotating Stall in Mixed Flow Pump

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaojun Li ◽  
Shouqi Yuan ◽  
Zhongyong Pan ◽  
Yi Li ◽  
Wei Liu
Keyword(s):  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Propagation Mechanism ◽  
Positive Slope ◽  
Mixed Flow ◽  
Outlet Flow ◽  
Research Gap ◽  
Flow Pump

Rotating stall, a phenomenon that causes flow instabilities and pressure hysteresis by propagating at some fraction of the impeller rotational speed, can occur in centrifugal impellers, mixed impellers, radial diffusers, or axial diffusers. Despite considerable efforts devoted to the study of rotating stall in pumps, the mechanics of this phenomenon are not sufficiently understood. The propagation mechanism and onset of rotating stall are not only affected by inlet flow but also by outlet flow as well as the pressure gradient in the flow passage. As such, the complexity of these concepts is not covered by the classical explanation. To bridge this research gap, the current study investigated prerotation generated at the upstream of the impeller, leakage flow at the tip clearance between the casing and the impeller, and strong reserve flow at the inlet of the diffuser. Understanding these areas will clarify the origin of the positive slope of the head-flow performance curve for a mixed flow pump. Nonuniform pressure distribution and adverse pressure gradient were also introduced to evaluate the onset and development of rotating stall within the diffuser.

scholarly journals Cause specification of performance curve instability in mixed-flow pump by LES

2016 ◽  
Vol 82 (834) ◽  
pp. 15-00533-15-00533
Author(s):  
Isao HAGIYA ◽  
Chisachi KATO ◽  
Yoshinobu YAMADE ◽  
Takahide NAGAHARA ◽  
Masashi FUKAYA
Keyword(s):  
Performance Curve ◽  
Mixed Flow ◽  
Flow Pump

scholarly journals Study of Internal Flows in a Mixed-Flow Pump Impeller at Various Tip Clearances Using 3D Viscous Flow Computations

1990 ◽  
Author(s):  
Akira Goto
Keyword(s):  
Reverse Flow ◽  
Three Dimensional ◽  
Interaction Mechanism ◽  
Secondary Flows ◽  
Wake Flow ◽  
Navier Stokes ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Pump Impeller ◽  
Flow Pump

The complex three-dimensional flow fields in a mixed-flow pump impeller are investigated by applying the incompressible version of the Dawes’ 3D Navier-Stokes code. The applicability of the code is confirmed by comparison of computations with a variety of experimentally measured jet-wake flow patterns and overall performances at four different tip clearances including the shrouded case. Based on the computations, the interaction mechanism of secondary flows and the formation of jet-wake flow are discussed. In the case of large tip clearances, the reverse flow caused by tip leakage flow is considered to be the reason for the thickening of the casing boundary layer followed by the deterioration of the whole flow field.

scholarly journals Suppression of Mixed-Flow Pump Instability and Surge by the Active Alteration of Impeller Secondary Flows

1993 ◽  
Author(s):  
Akira Goto
Keyword(s):  
Flow Characteristic ◽  
Secondary Flows ◽  
Wake Flow ◽  
Streamwise Vorticity ◽  
Jet Injection ◽  
Positive Slope ◽  
Suction Surface ◽  
Mixed Flow ◽  
Pump System ◽  
Flow Pump

An active method for enhancing pump stability, featuring water jet injection at impeller inlet, was applied to a mixed-flow pump. The stall margin, between the design point and the positive slope region of the head-flow characteristic, was most effectively enlarged by injecting the jet in the counter-rotating direction of the impeller. The counter-rotating streamwise vorticity along the casing, generated by the velocity discontinuity due to the jet injection, altered the secondary flow pattern in the impeller by opposing the passage vortex and assisting the tip leakage vortex motion. The location of the wake flow was displaced away from the casing-suction surface corner of the impeller, thus avoiding the onset of the extensive corner separation, the cause of positive slope region of the head-flow characteristic. This method was also confirmed to be effective for stabilizing a pump system already in a state of surge.

Performance of a Mixed Flow Pump with Varying Tip Clearance: Part 1

1996 ◽  
Vol 210 (4) ◽  
pp. 305-318 ◽  
Author(s):  
T K Saha ◽  
S Soundranayagam
Keyword(s):  
Angular Momentum ◽  
Flow Field ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Reversal ◽  
Tip Clearance ◽  
Mixed Flow ◽  
Three Dimensional Flow ◽  
Specific Speed ◽  
Flow Pump

Measurements of the three-dimensional flow field entering and leaving a mixed flow pump of non-dimensional specific speed k = 1.89 [ Ns = 100 r/min (metric)] are discussed as a function of flowrate. Flow reversal at inlet at reduced flows is seen to result in abnormally high total pressures in the casing region, but causes no noticeable discontinuities on the head-flow characteristics. Inlet prerotation is associated with the transport of angular momentum by the reversal eddy and begins with the initiation of flow reversal.

Design and Test for High Specific Speed Mixed Flow Pump with Volute

2011 ◽  
Vol 354-355 ◽  
pp. 669-673
Author(s):  
Xian Fang Wu ◽  
Hou Lin Liu ◽  
Ming Gao Tan ◽  
Hong Hui Li
Keyword(s):  
Cross Sections ◽  
Flow Analysis ◽  
Maximum Efficiency ◽  
Blade Angle ◽  
Mixed Flow ◽  
Commercial Code ◽  
Hydraulic Design ◽  
Velocity Circulation ◽  
Specific Speed ◽  
Flow Pump

The characteristics and research actuality on mixed flow pumps are introduced simplely. A mixed flow pump with volute as diffusion part is designed and its specific speed is 556.8. The axial velocity circulation and blade angle variety with linearity distribution are used to deisign the impeller. The fixed diffeuser between impeller and volute is deigned by arc airfoil.The cross sections of volute are all asymmetry. The commercial code FLUENT is applied to simulate the inner flow in the mixed flow pump and its energy characteristics are predicted according to the simulation results. The inner flow analysis indicates that the flow in the pump is good and the characteristic prediction shows that the pump performance can meet the design demand. The experiment test of the pump are done. When the blade angle is about 0°, the maximum efficiency of the pump is up to 85.76% and the actual efficiency at design point is about 3% higher than demand efficiency. The study fruits can instruct the hydraulic design of higher specific speed mixed flow pump with volute as diffusion part.

scholarly journals Unsteady blade-passage flows of a mixed-flow pump at performance-curve instability

2018 ◽  
Vol 84 (857) ◽  
pp. 17-00363-17-00363
Author(s):  
Isao HAGIYA ◽  
Chisachi KATO ◽  
Yoshinobu YAMADE ◽  
Masashi FUKAYA ◽  
Takahide NAGAHARA
Keyword(s):  
Performance Curve ◽  
Mixed Flow ◽  
Blade Passage ◽  
Flow Pump

Interaction between Impeller and Axial Diffuser of Mixed Flow Pump

2014 ◽  
Vol 630 ◽  
pp. 35-42 ◽  
Author(s):  
Michal Varchola ◽  
Peter Hlbočan
Keyword(s):  
Internal Flow ◽  
Performance Curve ◽  
Performance Parameters ◽  
Energy Transformation ◽  
Mixed Flow ◽  
And Performance ◽  
Design Factors ◽  
Stated Problem ◽  
Important Design ◽  
Flow Pump

Topic related to an impeller - diffuser hydraulic interaction is important especially in term of energy transformation and performance parameters. A connection of particular functional parts is one of the most important design factors which determine a shape of performance parameters and efficiency. The stated problem is possible to discuss in two possible ways. In term of internal flow pattern and in term of external pump parameters which are represented by performance curve courses. The contribution deals with the influence of the change of the impeller - axial diffuser interaction on quantitative courses of specific energy and efficiency curves.

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