scholarly journals Analysis of Secondary Flows in Centrifugal Impellers

2005 ◽  
Vol 2005 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Klaus Brun ◽  
Rainer Kurz
Keyword(s):  
Meridional Flow ◽  
Secondary Flows ◽  
Centrifugal Impeller ◽  
Flow Profile ◽  
Streamwise Vorticity ◽  
Rotating System ◽  
Head Losses ◽  
Compressor Performance ◽  
Flow Head ◽  
Small Shear

Secondary flows are undesirable in centrifugal compressors as they are a direct cause for flow (head) losses, create nonuniform meridional flow profiles, potentially induce flow separation/stall, and contribute to impeller flow slip; that is, secondary flows negatively affect the compressor performance. A model based on the vorticity equation for a rotating system was developed to determine the streamwise vorticity from the normal and binormal vorticity components (which are known from the meridional flow profile). Using the streamwise vorticity results and the small shear-large disturbance flow method, the onset, direction, and magnitude of circulatory secondary flows in a shrouded centrifugal impeller can be predicted. This model is also used to estimate head losses due to secondary flows in a centrifugal flow impeller. The described method can be employed early in the design process to develop impeller flow shapes that intrinsically reduce secondary flows rather than using disruptive elements such as splitter vanes to accomplish this task.

On the Generation of the Streamwise Component of Vorticity for Flows in Rotating Passages

1957 ◽  
Vol 8 (4) ◽  
pp. 369-383 ◽  
Author(s):  
Austin G. Smith
Keyword(s):  
Approximate Calculation ◽  
Fluid Velocity ◽  
Tangential Velocity ◽  
Axial Flow ◽  
Secondary Flows ◽  
Centrifugal Impeller ◽  
Streamwise Vorticity ◽  
Total Head ◽  
Qualitative Consideration

SummaryA method is presented for the calculation of the streamwise component of vorticity, for flows in rotating passages. The method may be regarded as an extension of the methods applied in recent years to the calculation of secondary flows in stationary passages.Attention is concentrated on the quantityI=p+½ρV2−½ρU2,whereVis the fluid velocity relative to the rotor andUis the rotor tangential velocity.Iremains constant along a streamline in the rotor, and is found to enter into the equation for the generation of vorticity in much the same way as the total head enters for flow in stationary passages.An approximate calculation of the streamwise vorticity generated in a simple axial-flow rotor is made, and qualitative consideration is given to the flow in a centrifugal impeller. Just as for the calculation of secondary flows in stationary passages, an approximate shape of the streamline must be assumed before the secondary flows can be calculated.

Measured and Predicted Secondary Flows in a Centrifugal Impeller

1971 ◽  
Vol 93 (1) ◽  
pp. 126-131 ◽  
Author(s):  
J. H. G. Howard ◽  
E. Lennemann
Keyword(s):  
Secondary Flows ◽  
Centrifugal Impeller ◽  
Streamwise Vorticity ◽  
Complex Flow ◽  
Primary Flow ◽  
Slip Rings ◽  
Rotating Impeller ◽  
Vorticity Generation ◽  
Hot Film ◽  
Simple Combination

The complete velocity distribution, including both primary and secondary velocities, has been measured in passages of centrifugal impellers of simple shape. Comparison is made with theoretically predicted secondary vorticities based on a simple combination of an inviscid primary flow and a streamwise vorticity generation analysis. The measured velocities were obtained in a water-flow impeller rig using a miniature, cylindrical, hot-film probe positioned on the rotating impeller and traversed and controlled remotely through slip rings. The understanding of the complex flow patterns was assisted by a photographic study employing a hydrogen bubble, flow visualization technique.

Assessment of Viscous Flows in High-Speed Micro Rotating Machinery for Energy Conversion Applications

2001 ◽  
Author(s):  
Luc G. Fréchette
Keyword(s):  
Shear Flow ◽  
Energy Conversion ◽  
Viscous Flow ◽  
High Speed ◽  
Applied Pressure ◽  
Secondary Flows ◽  
System Level ◽  
Flow Profile ◽  
System Level Design ◽  
Level Design

Abstract This paper investigates the characteristics of viscous flow in the micron-scale clearances surrounding high-speed micro-rotors currently being developed for miniature energy conversion applications. Analysis and experimental results from 4 mm diameter microfabricated rotors operated above 1 million rpm are used to describe the viscous flow characteristics, and provide guidelines for system-level design. To first order, the flow is characterized as fully developed shear flow (Couette flow) across the small gaps, induced by the rotor motion. However, secondary flows are induced perpendicular to the direction of rotor motion when externally applied pressure gradients exist along the small gaps. The developing flow in the entrance region of the small gaps in this secondary flow direction impacts the shear flow profile, hence affecting the drag on the disk. The effect of other inertial forces, such as Coriolis and centrifugal forces, are investigated analytically and numerically and found to affect the shear flow profile on the fluid in the motor gap at high rotational speeds. Since viscous losses are prevelant in microsystems, appropriate modeling is necessary for system-level design.

Investigation on Effect of Curvilinear Element Blades on Centrifugal Impeller Performance

2017 ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Hiromi Kobayashi ◽  
Takahiro Nishioka
Keyword(s):  
Centrifugal Compressor ◽  
Performance Test ◽  
Design Guidelines ◽  
Secondary Flows ◽  
Flow Coefficient ◽  
Numerical Calculations ◽  
Centrifugal Impeller ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Compressor Impeller

This study experimentally and numerically investigates the effect of application of curvilinear element blades to fully-shrouded centrifugal compressor impeller on the performance of centrifugal compressor stage. Design suction flow coefficient of compressor stage investigated in this study is 0.125. The design guidelines for the curvilinear element blades which had been previously developed was applied to line element blades of a reference conventional impeller and a new centrifugal compressor impeller with curvilinear element blades was designed. Numerical calculations and performance tests of two centrifugal compressor stages with the conventional impeller and the new one were conducted to investigate the effectiveness of application of the curvilinear element blades and compare the inner flowfield in details. Despite 0.5% deterioration of the impeller efficiency, it was confirmed from the performance test results that the compressor stage with the new impeller achieved 1.7% higher stage efficiency at the design point than that with the conventional one. Moreover, it was confirmed that the compressor stage with the new impeller achieved almost the same off-design performance as that of the conventional stage. From results of the numerical calculations and the experiments, it is considered that this efficiency improvement of the new stage was achieved by suppression of the secondary flows in the impeller due to application of negative tangential lean. The suppression of the secondary flows in the impeller achieved uniformalized flow distribution at the impeller outlet and increased the static pressure recovery coefficient in the vaneless diffuser. As a result, it is thought that the total pressure loss was reduced downstream of the vaneless diffuser outlet in the new stage.

Hydrodynamic Design System for Pumps Based on 3-D CAD, CFD, and Inverse Design Method

2002 ◽  
Vol 124 (2) ◽  
pp. 329-335 ◽  
Author(s):  
Akira Goto ◽  
Motohiko Nohmi ◽  
Takaki Sakurai ◽  
Yoshiyasu Sogawa
Keyword(s):  
Computer Aided Design ◽  
High Performance ◽  
Design Method ◽  
High Reliability ◽  
Secondary Flows ◽  
System Structure ◽  
Inverse Design ◽  
Design System ◽  
Centrifugal Impeller ◽  
Inverse Design Method

A computer-aided design system has been developed for hydraulic parts of pumps including impellers, bowl diffusers, volutes, and vaned return channels. The key technologies include three-dimensional (3-D) CAD modeling, automatic grid generation, CFD analysis, and a 3-D inverse design method. The design system is directly connected to a rapid prototyping production system and a flexible manufacturing system composed of a group of DNC machines. The use of this novel design system leads to a drastic reduction of the development time of pumps having high performance, high reliability, and innovative design concepts. The system structure and the design process of “Blade Design System” and “Channel Design System” are presented. Then the design examples are presented briefly based on the previous publications, which included a centrifugal impeller with suppressed secondary flows, a bowl diffuser with suppressed corner separation, a vaned return channel of a multistage pump, and a volute casing. The results of experimental validation, including flow fields measurements, were also presented and discussed briefly.

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.

scholarly journals Compressor performance influenced by distribution of tip clearance of centrifugal impeller.

1987 ◽  
Vol 53 (486) ◽  
pp. 496-499
Author(s):  
Yasutoshi SENOO ◽  
Hiroshi HAYAMI ◽  
Masahiro ISHIDA ◽  
Kohji NAKASHIMA ◽  
LI Fuzhong
Keyword(s):  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Compressor Performance
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