scholarly journals Discussion: “Measured and Predicted Secondary Flows in a Centrifugal Impeller” (Howard, J. H. G., and Lennemann, E., 1971, ASME J. Eng. Power, 93, pp. 126–131)

1971 ◽  
Vol 93 (1) ◽  
pp. 132-132
Author(s):  
T. Katsanis
Keyword(s):  
Secondary Flows ◽  
Centrifugal Impeller

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 Experimental Investigation of the Steady and Unsteady Relative Flow in a Model Centrifugal Impeller Passage

1993 ◽  
Author(s):  
M. Abramian ◽  
J. H. G. Howard
Keyword(s):  
Laser Doppler Anemometry ◽  
Quantitative Description ◽  
Rotating Stall ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Relative Flow

The behaviour of the relative flow in centrifugal turbomachines is extremely complex due to the existence of various fluid dynamic phenomena and their interaction. At design and off-design operating conditions, the relative flow is subject to stationary unsteadiness which includes flow separation and wakes associated with passage pressure gradients, secondary flows, and boundary layer stability. It may also be subject to periodic unsteadiness such as is the rotating stall and cyclic flow phenomena induced by the casing. This paper describes detailed measurements of the relative velocity field in a very low specific speed centrifugal pump impeller (Ns=515). Measurements were conducted by means of a recently developed rotating laser-Doppler anemometry system. Detailed quantitative description of the mean and fluctuating components of the primary and secondary velocity fields are presented for an impeller without volute at design, 50% design and shut-off conditions. The flow pattern in this low specific speed impeller with high blade loading is dominated by the relative eddy (a phenomenon also present in potential flow) which has suppressed suction side separation. When the impeller was fitted with a volute, the cyclic variation of the impeller exit flow, induced by the volute at low flow rates, is also presented.

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.

scholarly journals A Rotating Laser-Doppler Anemometry System for Unsteady Relative Flow Measurements in Model Centrifugal Impellers

1993 ◽  
Author(s):  
M. Abramian ◽  
J. H. G. Howard
Keyword(s):  
Laser Doppler Anemometry ◽  
Fluid Dynamic ◽  
Rotating Stall ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Laser Doppler ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Flow Measurements ◽  
Relative Flow

The behaviour of the relative flow in centrifugal turbomachines is extremely complex due to the existence of various fluid dynamic phenomena and their interaction. At design and off-design operating conditions, the relative flow is subject to stationary unsteadiness which includes the flow separation and wakes associated with passage pressure gradients, secondary flows, and boundary layer stability. It is also subject to periodic unsteadiness from the rotating stall and the cyclic flow phenomena induced by the casing. This paper describes the mechanical and optical design of a rotating laser-Doppler anemometry system which allows direct measurement of the relative flow by means of an optical de-rotator. By isolating the impeller rotational frequency from the sampling frequency, it allows direct time-average measurements of the stationary behaviour of the relative flow along with the ensemble (phase)-average measurements of its periodic behaviour. Its success is demonstrated with measurements conducted in a low specific speed centrifugal impeller fitted with a single volute. Sample results of the time-averaged blade-to-blade variation of total relative velocities along with their associated turbulence intensities are reported. The (periodic) cyclic variations of the impeller exit flow, induced by the volute at low flow rates, are also presented for the suction and pressure sides.

A Rotating Laser-Doppler Anemometry System for Unsteady Relative Flow Measurements in Model Centrifugal Impellers

1994 ◽  
Vol 116 (2) ◽  
pp. 260-268 ◽  
Author(s):  
M. Abramian ◽  
J. H. G. Howard
Keyword(s):  
Laser Doppler Anemometry ◽  
Fluid Dynamic ◽  
Rotating Stall ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Laser Doppler ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Flow Measurements ◽  
Relative Flow

The behavior of the relative flow in centrifugal turbomachines is extremely complex due to the existence of various fluid dynamic phenomena and their interaction. At design and off-design operating conditions, the relative flow is subject to stationary unsteadiness, which includes the flow separation and wakes associated with passage pressure gradients, secondary flows, and boundary layer stability. It is also subject to periodic unsteadiness from the rotating stall and the cyclic flow phenomena induced by the casing. This paper describes the mechanical and optical design of a rotating laser-Doppler anemometry system, which allows direct measurement of the relative flow by means of an optical derotator. By isolating the impeller rotational frequency from the sampling frequency, it allows direct time-averaged measurements of the stationary behavior of the relative flow along with the ensemble (phase)-averaged measurements of its periodic behavior. Its success is demonstrated with measurements conducted in a low specific speed centrifugal impeller fitted with a single volute. Sample results of the time-averaged blade-to-blade variation of total relative velocities along with their associated turbulence intensities are reported. The (periodic) cyclic variations of the impeller exit flow, induced by the volute at low flow rates, are also presented for the suction and pressure sides.

The Development of Wake Flow in a Centrifugal Impeller

1980 ◽  
Vol 102 (2) ◽  
pp. 382-389 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Three Dimensional ◽  
Suction Side ◽  
Secondary Flows ◽  
Wake Flow ◽  
Centrifugal Impeller ◽  
Three Dimensional Flow ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Compressor Impeller ◽  
Rotating Impeller

Three-dimensional flow, leading to the formation and the growth of a wake in a centrifugal impeller, has been studied. Results of flow measurements in a 1 m dia, shrouded, centrifugal compressor impeller running at 500 rpm are presented. Relative velocities and rotary stagnation pressures (p* = p + 1/2ρW2 − 1/2ρω2r2) were measured, on five cross-sectional planes between the inlet and outlet of the impeller, using pressure probes which were traversed within the rotating impeller passage. Particular attention was given to the convection of low p* fluid by secondary flows and to the formation of the wake in the shroud/suction-side corner region of the passage.

Suppression of secondary flows in a centrifugal impeller by optimisation design

2020 ◽  
Vol 37 (9) ◽  
pp. 3023-3044
Author(s):  
Xing Xie ◽  
Zhenlin Li ◽  
Baoshan Zhu ◽  
Hong Wang
Keyword(s):  
Control Parameter ◽  
Aerodynamic Performance ◽  
Secondary Flows ◽  
Inverse Design ◽  
Design System ◽  
Centrifugal Impeller ◽  
Cfd Analysis ◽  
Blade Loading ◽  
Content Type ◽  
Multi Objective

Purpose The purpose of this study is to suppress secondary flows and improve aerodynamic performance of a centrifugal impeller. Design/methodology/approach A multi-objective optimisation design system was described. The optimization design system was composed of a three-dimensional (3D) inverse design, multi-objective optimisation and computational fluid dynamics (CFD) analysis. First, the control parameter ΔCp for the secondary flows was derived and selected as the optimisation objective. Then, aimed at minimising ΔCp, a 3D inverse design for impellers with different blade loading distributions and blade lean angles was completed and multi-objective optimisation was conducted. Lastly, the improvement in the distribution of secondary flows and aerodynamic performance of the optimal impeller was demonstrated by CFD analysis. Findings The study derived the control parameter ΔCp for the secondary flows. ΔCp can indicate the distribution of secondary flows both near the blade pressure and suction surfaces. As ΔCp decreased, secondary flows decreased. The blade loading distribution with fore maximum blade loading at the shroud and aft maximum blade loading at the hub, coupled with a small negative blade lean angle, could help suppress secondary flows and improve aerodynamic efficiency. Originality/value A direct control method on internal flow field characteristic-secondary flows by optimisation design was proposed for a centrifugal impeller. The impeller optimisation design process saves time by avoiding substantial CFD sample calculations.

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