Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1995 ◽  
Vol 117 (4) ◽  
pp. 585-592 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncˇl
Keyword(s):  
Development Program ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Disk Friction ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development program for centrifugal compressors are presented. Six-stage configurations with low flow coefficient were tested. The stages had channel width parameter b2/D2 = 0.01 and 0.03. For each value of the width parameter, three different impellers with inlet hub to outlet diameter ratio do/D2 = 0.3, 0.4, and 0.5 were designed. Test rig, instrumentation, and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing, and disk friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with deswirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

scholarly journals Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1994 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncl
Keyword(s):  
Rotating Stall ◽  
Development Programme ◽  
Diameter Ratio ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development programme for centrifugal compressors are presented. Six stage configurations with low flow coefficient were tested. The stages had channel width parameter bo/D2=0.01 and 0.03. For each value of the width parameter three different impellers with inlet hub to outlet diameter ratio do/D2=0.3, 0.4 and 0.5 were designed. Test rig, instrumentation and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing and disc friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with de-swirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

The Influence of Outlet Stator Part Surface Roughness on the Performance of a Very Low Flow Coefficient Centrifugal Compressor Stage

1996 ◽  
Author(s):  
Jan Paroubek ◽  
Václav Cyrus ◽  
Jiři Kynčl
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Prediction Method ◽  
Stability Limit ◽  
Aerodynamic Performance ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Return Channel ◽  
Low Flow Coefficient

An aerodynamic investigation of the influence of outlet stator part (vaneless diffuser and return channel) surface roughness on aerodynamic performance of a very low flow coefficient centrifugal stage has been carried out. The stage with design inlet flow coefficient 0.007 was tested within the range of stage Mach number Mu2=0.5–1.1. Then the surface quality of outlet stator part was improved and the tests have been repeated. Aerodynamic performance and losses in both vaneless diffuser and return channel with de-swirl vanes were investigated. The values of isentropic head coefficient increased while those of loss coefficient decreased nearly in the whole range of characteristics in the stage with improved surface quality. The detailed pressure recovery in vaneless diffuser in vicinity of design point measured and calculated by the performance prediction method is compared and discussed. The nonsteady flow phenomena were also investigated. The change of dynamic stability limit by improving of surface quality was observed.

Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part III — Influence of Diffuser Geometry on Stall Inception and Performance (2nd Impeller Tested)

2003 ◽  
Author(s):  
A. Cellai ◽  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
L. Baldassarre
Keyword(s):  
High Pressure ◽  
Rotating Stall ◽  
Point Of View ◽  
Vaneless Diffuser ◽  
Cross Sectional ◽  
Stall Inception ◽  
Last Stage ◽  
Return Channel ◽  
And Performance ◽  
Geometrical Scale

Vaneless diffuser rotating stall is a serious problem for centrifugal compressors since it limits their working range. In particular the last stage seems to be the most critical from this point of view. In the literature some good correlations can be found for predicting stall inception but they hardly cover the case of last stage configuration, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. Extensive research has been planned to define diffuser stall limits for this family of stages: three impellers characterized by different blade-outlet-width-to-impeller-radius-ratios are tested. The basic configuration comprises a 1:1 geometrical scale stage with a return channel upstream, a 2D impeller with a vaneless diffuser and a volute with a constant cross sectional area downstream. Several diffuser types with different widths, pinch shapes and diffusion ratios were tested. The results for the first impeller have already been reported in part I and II. In this part the effects of the above mentioned geometric parameter changes on stage stability and performance are presented with respect to the second impeller.

Experimental Characterization of Vaneless Diffuser Rotating Stall: Part V — Influence of Diffuser Geometry on Stall Inception and Performance (3rd Impeller Tested)

2006 ◽  
Author(s):  
G. Ferrara ◽  
L. Ferrari ◽  
L. Baldassarre
Keyword(s):  
Rotating Stall ◽  
Radius Ratio ◽  
Vaneless Diffuser ◽  
Cross Sectional ◽  
Stall Inception ◽  
Wide Range ◽  
Return Channel ◽  
And Performance ◽  
Geometrical Scale ◽  
Performance Results

Vaneless diffuser rotating stall is a serious problem for centrifugal compressors, since it limits their working range. In the literature some good correlations can be found for predicting stall inception but they have limited coverage of last stage configuration case, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. In addition, stall inception is strictly bounded to diffuser geometry (for example, diffuser width and diffusion ratio). As a part of a wide range activity on rotating stall, a stage with a blade-outlet-width-to-impeller-radius-ratio of 0.1 has been tested. The stage configuration is made up by a 1:1 geometrical scale stage with a return channel upstream, a 2D impeller with a vaneless diffuser and a volute with a constant cross sectional area downstream. Diffusers with three different widths and two diffusion ratios were tested in order to find their influence on stage stability and performance. Results obtained for impellers with lower blade-outlet-width-to-impeller-radius-ratios have been published in previous papers. The purpose of this paper is to comment the obtained results and increase the amount of experimental data available on vaneless diffuser rotating stall behaviour.

scholarly journals Low-Flow-Coefficient Centrifugal Compressor Design for Supercritical CO2

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
C. Lettieri ◽  
N. Baltadjiev ◽  
M. Casey ◽  
Z. Spakovszky
Keyword(s):  
Vortex Shedding ◽  
Supercritical Co2 ◽  
Leading Edge ◽  
Design Strategy ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Compressor Design ◽  
Low Flow Coefficient

This paper presents a design strategy for very low flow coefficient multistage compressors operating with supercritical CO2 for carbon capture and sequestration (CCS) and enhanced oil recovery (EOR). At flow coefficients less than 0.01, the stage efficiency is much reduced due to dissipation in the gas-path and more prominent leakage and windage losses. Instead of using a vaneless diffuser as is standard design practice in such applications, the current design employs a vaned diffuser to decrease the meridional velocity and to widen the gas path. The aim is to achieve a step change in performance. The impeller exit width is increased in a systematic parameter study to explore the limitations of this design strategy and to define the upper limit in efficiency gain. The design strategy is applied to a full-scale reinjection compressor currently in service. Three-dimensional, steady, supercritical CO2 computational fluid dynamics (CFD) simulations of the full stage with leakage flows are carried out with the National Institute of Standards and Technology (NIST) real gas model. The design study suggests that a nondimensional impeller exit width parameter b2* = (b2/R)ϕ of six yields a 3.5 point increase in adiabatic efficiency relative to that of a conventional compressor design with vaneless diffuser. Furthermore, it is shown that in such stages the vaned diffuser limits the overall stability and that the onset of rotating stall is likely caused by vortex shedding near the diffuser leading edge. The inverse of the nondimensional impeller exit width parameter b2* can be interpreted as the Rossby number. The investigation shows that, for very low flow coefficient designs, the Coriolis accelerations dominate the relative flow accelerations, which leads to inverted swirl angle distributions at impeller exit. Combined with the two-orders-of-magnitude higher Reynolds number for supercritical CO2, the leading edge vortex shedding occurs at lower flow coefficients than in air suggesting an improved stall margin.

Design and Analysis of Energy-Efficient Low-Flow Centrifugal Compressors

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Cheng Xu ◽  
Lei Chen ◽  
Ryoichi S. Amano
Keyword(s):  
Flow Coefficient ◽  
Low Flow ◽  
Design Strategies ◽  
Design Features ◽  
Centrifugal Compressors ◽  
Design Studies ◽  
Low Specific Speed ◽  
Specific Speed ◽  
And Performance ◽  
Low Flow Coefficient

Abstract With the increasing demands of energy-saving from industries, the low-flow coefficient and low specific speed centrifugal compressors have gained more attention. The design of this type of compressor faced many challenges, for example, high secondary flow losses, high tip leakage losses, and low exit width based on a Reynolds number. The design also lacks a reliable database for preliminary studies. The impeller design studies were limited. Most designs for low-flow coefficient and low specific speed compressor follow the traditional methods. This paper presents design studies and discusses some unique design features to improve performance of this type of compressor. The detail computational fluids dynamics (CFD) results are presented to demonstrate the success of the design strategies. A prototype compressor for fuel cell applications was built, and performance tests were performed. The test results are compared with those of the computational analysis, and the agreement is reasonably satisfactory. The compressor meets the customer's performance goals. The design features can be used for future low-flow coefficient and low specific speed centrifugal compressor design.

scholarly journals Low-Flow-Coefficient Centrifugal Compressor Design for Supercritical CO2

2013 ◽  
Author(s):  
C. Lettieri ◽  
N. Baltadjiev ◽  
M. Casey ◽  
Z. Spakovszky
Keyword(s):  
Vortex Shedding ◽  
Supercritical Co2 ◽  
Leading Edge ◽  
Design Strategy ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Compressor Design ◽  
Low Flow Coefficient

This paper presents a design strategy for very low flow coefficient multi-stage compressors operating with supercritical CO2 for Carbon Capture and Sequestration (CCS) and Enhanced Oil Recovery (EOR). At flow coefficients less than 0.01 the stage efficiency is much reduced due to dissipation in the gas-path and more prominent leakage and windage losses. Instead of using a vaneless diffuser as is standard design practice in such applications, the current design employs a vaned diffuser to decrease the meridional velocity and to widen the gas path. The aim is to achieve a step change in performance. The impeller exit width is increased in a systematic parameter study to explore the limitations of this design strategy and to define the upper limit in efficiency gain. The design strategy is applied to a full-scale re-injection compressor currently in service. Three-dimensional, steady, supercritical CO2 CFD simulations of the full stage with leakage flows are carried out with the NIST real gas model. The design study suggests that a non-dimensional impeller exit width parameter b2* = (b2/R)ϕ of 6 yields a 3.5 point increase in adiabatic efficiency relative to that of a conventional compressor design with vaneless diffuser. Furthermore, it is shown that in such stages the vaned diffuser limits the overall stability and that the onset of rotating stall is likely caused by vortex shedding near the diffuser leading edge. The inverse of the non-dimensional impeller exit width parameter b2* can be interpreted as the Rossby number. The investigation shows that, for very low flow coefficient designs, the Coriolis accelerations dominate the relative flow accelerations, which leads to inverted swirl angle distributions at impeller exit. Combined with the two-orders-of-magnitude higher Reynolds number for supercritical CO2, the leading edge vortex shedding occurs at lower flow coefficients than in air suggesting an improved stall margin.

Loss Mechanisms in Shear-Force Pump With Multiple Corotating Disks

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Baotong Wang ◽  
Koji Okamoto ◽  
Kazuo Yamaguchi ◽  
Susumu Teramoto
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Shear Force ◽  
High Efficiency ◽  
Internal Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Test Rig ◽  
Pump System ◽  
Low Flow Coefficient

In a shear-force pump with multiple corotating disks, the pressure gain is obtained by utilizing the shear force produced on the surfaces of the rotating disks. Thus, it is expected to have advantages as a microfluid device compared to a conventional bladed compressor or pump, which suffers greatly from viscous loss. However, in previous studies, a shear-force pump could not achieve high efficiency in experiments, even though very good efficiencies were predicted in numerical and analytical studies on the flow field between corotating disks. Therefore, the objective of the present work was to investigate the internal flow dynamics and clarify the loss mechanisms in a complete shear-force pump device consisting of both rotor and stationary components. In order to achieve this goal, a numerical simulation using an independent rotor analysis was first performed on the internal flow field between two corotating disks to evaluate the isentropic efficiency and pressure coefficient that could be achieved. Then, an experimental test rig for a shear-force pump was designed and built, and an experiment was carried out to determine the performance of a complete pump device with the same corotating disk design as the independent rotor analysis. In addition, a numerical simulation was executed for the flow field of a pump system consisting of both rotor and stationary components based on the present test rig to investigate the flow field and loss factors of this device. The results of this independent rotor analysis showed that the corotating disks can achieve a fairly high efficiency at a low flow coefficient with a high dynamic pressure, and the flow direction is extremely close to the tangential direction at the disk outlet, which caused difficulties in the design of the diffuser and scroll. In the experimental test, the high total pressure loss in the parallel diffuser and scroll parts was observed. This was found to be the result of the significant friction loss caused by the long flow path due to strong recirculation in the diffuser and scroll volute, which was found in the simulation results for the internal flow in the whole pump system. In addition, a reverse flow appeared in the rotor part at a low flow coefficient, which significantly deteriorated the rotor performance. These conclusions provided some clues for improving the performance of a shear-force pump device in future work.

Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part II — Influence of Diffuser Geometry on Stage Performance

2002 ◽  
Author(s):  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
M. De Lucia ◽  
L. Baldassarre
Keyword(s):  
Experimental Tests ◽  
Rotating Stall ◽  
Geometric Parameters ◽  
Flow Coefficient ◽  
Low Flow ◽  
Main Task ◽  
Stage Performance ◽  
The Impact ◽  
Prediction Criteria

Extensive research on centrifugal compressors has been planned. The main task of the research is to improve present prediction criteria coming from the literature with particular attention to low flow coefficient impellers (low width to radius ratios) where they are no more valid. Very little data has been published for this kind of stages, especially for the last stage configuration (with discharge volute). Many experimental tests have been planned to investigate different configurations. A simulated stage with a backward channel upstream, a 2D impeller with a vaneless diffuser and a constant cross section volute downstream constitute the basic configuration. Several diffuser types with different widths, pinch shapes and diffusion ratios were tested. The effect of geometric parameters on stage stability has been discussed inside part I of the present work; the purpose of this part of the work is to illustrate the effect of the same geometric parameters on stage performance and to quantify the impact of stability improvements on stage losses.

Experimental Characterization of Vaneless Diffuser Rotating Stall: Part VI — Reduction of Three Impeller Results

2006 ◽  
Author(s):  
E. A. Carnevale ◽  
G. Ferrara ◽  
L. Ferrari ◽  
L. Baldassarre
Keyword(s):  
Rotating Stall ◽  
Radius Ratio ◽  
Vaneless Diffuser ◽  
Cross Sectional ◽  
Stall Inception ◽  
Return Channel ◽  
Geometrical Scale ◽  
And Diffusion ◽  
Basic Configuration

Vaneless diffuser rotating stall is a major problem for centrifugal compressors since it is a limit to their working range. In the literature some good correlations for predicting stall inception can be found but they do not adequately cover the case of the last stage configuration, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. Extensive research has been performed to define diffuser stall limits for this family of stages: three impellers characterized by different blade-outlet-width-to-impeller-radius-ratios have been tested with different diffuser configurations (different pinch shapes, diffuser widths and diffusion ratios). The basic configuration comprises a 1:1 geometrical scale stage with a return channel upstream, a 2D impeller with a vaneless diffuser and a volute with a constant cross sectional area downstream. Several diffuser types with different widths and diffusion ratios were tested. Detailed experimental results have been reported in previous works [1, 2, 3 and 4]. In this paper experimental data are reviewed in order to analyze impeller influence on diffuser stability and to develop some summarizing consideration on stall behavior of vaneless diffuser for impeller with low blade-outlet-width-to-impeller-radius-ratio.

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