Effect of the Exit System on the Performance of a Low Specific Speed Industrial Centrifugal Compressor Stage

2003 ◽  
Author(s):  
Jean-Luc Di Liberti
Keyword(s):  
Centrifugal Compressor ◽  
High Frequency ◽  
Rotating Stall ◽  
Cfd Analysis ◽  
Compressor Stage ◽  
Test Results ◽  
Centrifugal Compressor Stage ◽  
Surge Margin ◽  
Low Specific Speed ◽  
Specific Speed

A low specific speed stage was tested with two different size volutes and a return vane system. The stage was instrumented with pressure probes at various locations, including the inlet and discharge flanges, diffuser inlet, diffuser exit, and return vane inlet. Cobra probes were positioned at the diffuser inlet and the return vane inlet for the return vane configuration to measure the flow angles. High frequency transducers were installed in the diffuser. This paper presents the test results showing the effect of two different volute sizes and of the return vane system on surge margin, rotating stall onset, and overall rotor and stage performance. Rotating stall criteria are reviewed, since this stage was previously tested with a different diffuser pinch. The performance is compared with some CFD analysis.

Experimental Validation of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Timothy C. Allison ◽  
Natalie R. Smith ◽  
Robert Pelton ◽  
Jason C. Wilkes ◽  
Sewoong Jung
Keyword(s):  
Centrifugal Compressor ◽  
Operating Conditions ◽  
Successful Implementation ◽  
Compressor Stage ◽  
Test Results ◽  
Power Cycles ◽  
Casing Treatment ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Wide Range

Successful implementation of sCO2 power cycles requires high compressor efficiency at both the design-point and over a wide operating range in order to maximize cycle power output and maintain stable operation over a wide range of transient and part-load operating conditions. This requirement is particularly true for air-cooled cycles where compressor inlet density is a strong function of inlet temperature that is subject to daily and seasonal variations as well as transient events. In order to meet these requirements, a novel centrifugal compressor stage design was developed that incorporates multiple novel range extension features, including a passive recirculating casing treatment and semi-open impeller design. This design, presented and analyzed for CO2 operation in a previous paper, was fabricated via direct metal laser sintering and tested in an open-loop test rig in order to validate simulation results and the effectiveness of the casing treatment configuration. Predicted performance curves in air and CO2 conditions are compared, resulting in a reduced diffuser width requirement for the air test in order to match design velocities and demonstrate the casing treatment. Test results show that the casing treatment performance generally matched computational fluid dynamics (CFD) predictions, demonstrating an operating range of 69% and efficiency above air predictions across the entire map. The casing treatment configuration demonstrated improvements over the solid wall configuration in stage performance and flow characteristics at low flows, resulting in an effective 14% increase in operating range with a 0.5-point efficiency penalty. The test results are also compared to a traditional fully shrouded impeller with the same flow coefficient and similar head coefficient, showing a 42% range improvement over traditional designs.

Effect of Impeller Blade Loading on Compressor Stage Performance in a High Specific Speed Range

2011 ◽  
Vol 134 (4) ◽  
Author(s):  
Takanori Shibata ◽  
Manabu Yagi ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Masanori Tanaka
Keyword(s):  
Relative Velocity ◽  
Compressor Stage ◽  
Test Results ◽  
Blade Loading ◽  
Degree Of Reaction ◽  
Surge Margin ◽  
Speed Range ◽  
Specific Speed ◽  
Velocity Diffusion ◽  
Stage Efficiency

The authors previously found that compressor stage efficiency in a high specific speed range was significantly improved by employing an increased relative velocity diffusion ratio coupled with a high backsweep angle (Shibata et al., “Performance Improvement of a Centrifugal Compressor Stage by Increasing Degree of Reaction Optimizing Blade Loading of a 3D-Impeller,” ASME Paper No. GT2009-59588). In spite of such a high relative velocity diffusion ratio, the same surge margin as with a conventional design was able to be achieved by using a special front loading distribution with a lightly loaded inducer. In the present study, the blade loading distribution was further optimized in order to achieve a larger surge margin than previously. Four types of fully shrouded impellers were designed, manufactured, and tested to evaluate the effects of blade loading, backsweep angle, and relative velocity diffusion ratio on compressor performance. The design suction flow coefficient was 0.125 and the machine Mach number was 0.87. Test results showed that the developed impeller achieved 3.8% higher stage efficiency and 11% larger surge margin than the conventional design without reducing the pressure coefficient and choke margin. It was concluded that aft loading coupled with a high degree of reaction was a very effective way to improve surge margin as well as stage efficiency. Stator matching was also investigated by changing the design incidence angle, which was shown to have a little influence on surge margin in the present test results.

A Distinction Between Different Types of Stall in a Centrifugal Compressor Stage

1986 ◽  
Vol 108 (1) ◽  
pp. 83-92 ◽  
Author(s):  
N. Ka¨mmer ◽  
M. Rautenberg
Keyword(s):  
Energy Transfer ◽  
Centrifugal Compressor ◽  
High Frequency ◽  
Low Frequency ◽  
Rotating Stall ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Pressure Transducers ◽  
Different Types ◽  
Probe Measurements

The flow at the stall line of a centrifugal compressor with vaneless diffuser was investigated at different speeds. A distinction between three kinds of stall phenomena could be made. One type of stall with regurgitation of fluid at the impeller inlet was of a nonperiodic character, whereas two different types of periodic stall appeared at higher speeds. The rotating nature of these two types of stall was verified from a comparison of signals of peripherally spaced pressure transducers. The low-frequency rotating stall exhibited features of diffuser generated stall and a lobe number of three was measured. From a detailed investigation of the high-frequency rotating stall, which included unsteady probe measurements upstream and downstream of the impeller, it can be shown that this type of rotating stall is generated in the impeller by a periodic breakdown of energy transfer from the rotor to the flow. This conclusion is supported by the distribution of shroud static pressures.

Effect of Impeller Blade Loading on Compressor Stage Performance in a High Specific Speed Range

2010 ◽  
Author(s):  
Takanori Shibata ◽  
Manabu Yagi ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Masanori Tanaka
Keyword(s):  
Relative Velocity ◽  
Compressor Stage ◽  
Test Results ◽  
Blade Loading ◽  
Conventional Design ◽  
Surge Margin ◽  
Speed Range ◽  
Specific Speed ◽  
Velocity Diffusion ◽  
Stage Efficiency

The authors previously found that compressor stage efficiency in a high specific speed range was significantly improved by employing an increased relative velocity diffusion ratio coupled with a high backsweep angle. In spite of such a high relative velocity diffusion ratio, the same surge margin as with a conventional design could be achieved by using a special front loading distribution with a lightly loaded inducer. In the present study, the blade loading distribution was further optimized in order to achieve a larger surge margin than previously. Four types of fully shrouded impellers were designed, manufactured and tested to evaluate the effects of blade loading, backsweep angle and relative velocity diffusion ratio on compressor performance. The design suction flow coefficient was 0.125 and the machine Mach number was 0.87. Test results showed that the developed impeller achieved 3.8% higher stage efficiency and 11% larger surge margin than the conventional design without reducing the pressure coefficient and choke margin. It was concluded that aft loading coupled with a high degree of reaction was a very effective way to improve surge margin as well as stage efficiency. Stator matching was also investigated by changing the design incidence angle which was shown to have little influence on surge margin in the present test results.

scholarly journals Flow Field and Performance of a Centrifugal Compressor Rotor With Tandem Blades of Adjustable Geometry

1994 ◽  
Author(s):  
Burkhard Josuhn-Kadner
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Wake Flow ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Compressor Rotor ◽  
Surge Margin ◽  
Bladed Rotor ◽  
And Performance

A centrifugal compressor stage has been investigated mainly experimentally for aerodynamic stage optimization. The rotor consists of a separate inducer with 14 blades and an impeller with 28 blades. Both rotor components can be locked with each other at different circumferential positions thus, forming either a conventional splitter blade rotor or a tandem bladed rotor of adjustable geometry. The influence of the tandem blade geometry on the rotor and stage characteristics is studied in detail. Laser-2-Focus-System measurements were performed at nine locations all over the rotor taking three different circumferential inducer positions into account. The improvement with the tandem blade configuration on the rotor and stage characteristics is small but significant differences in the flow field of the two different impeller channels in the rear and exit part of the rotor are recognizable. The velocity differences of the jet/wake flow are reduced by using tandem blades which lead to a slight increased stage pressure ratio and surge margin.

Detailed Performance Analysis of a Centrifugal Compressor Stage With Pipe Diffuser and Immerged Tandem Deswirler

2015 ◽  
Author(s):  
Johannes Schmidt ◽  
Philipp Schwarz ◽  
Benjamin Wilkosz ◽  
Peter Jeschke ◽  
Caitlin Smythe
Keyword(s):  
Centrifugal Compressor ◽  
Pipe Flow ◽  
Major Effect ◽  
Compressor Stage ◽  
Close Coupling ◽  
Centrifugal Compressor Stage ◽  
Surge Margin ◽  
Radial Extent ◽  
Blade Row ◽  
Inlet Geometry

Commonly, the pipe diffuser and deswirler are aerodynamically decoupled from each other to ensure better mixing of the inhomogeneous pipe flow before entering the deswirler and to prevent upstream effects of the deswirler bend and blading on the pipe diffuser. Close-coupling of these two components, however, can lead to a significantly lower radial extent of the stage, resulting in a decrease of stage weight and engine frontal area. The geometry investigated includes a centrifugal compressor stage with a compact diffusion system, including a pipe diffuser and tandem deswirler whose first blade row is immerged into the pipe diffuser. Stage and component performance of this compact configuration is compared to two different stage configurations with decoupled deswirlers. Performance maps and 1-D pressure build-up data show that the compact stage is able to reach efficiency and pressure build-up of the compared stages which contain the same impeller and same diffuser inlet geometry. The performance of one of the compared stages with significantly higher radial stage extent is even exceeded. However, a loss in surge margin of about 2% has been detected which seems to be the major problem in reducing stage size by close-coupling the deswirl system to the pipe diffuser, since this can have a major effect on the diffuser inlet pressure build-up.

scholarly journals Experimental Validation of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles

2018 ◽  
Author(s):  
Timothy C. Allison ◽  
Natalie R. Smith ◽  
Robert Pelton ◽  
Sewoong Jung ◽  
Jason C. Wilkes
Keyword(s):  
Centrifugal Compressor ◽  
Operating Conditions ◽  
Successful Implementation ◽  
Compressor Stage ◽  
Test Results ◽  
Power Cycles ◽  
Casing Treatment ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Wide Range

Successful implementation of sCO2 power cycles requires high compressor efficiency at both the design-point and over a wide operating range in order to maximize cycle power output and maintain stable operation over a wide range of transient and part-load operating conditions. This requirement is particularly true for air-cooled cycles where compressor inlet density is a strong function of inlet temperature that is subject to daily and seasonal variations as well as transient events. In order to meet these requirements, a novel centrifugal compressor stage design was developed that incorporates multiple novel range extension features, including a passive recirculating casing treatment and semi-open impeller design. This design, presented and analyzed for CO2 operation in a previous paper, was fabricated via direct metal laser sintering and tested in an open-loop test rig in order to validate simulation results and the effectiveness of the casing treatment configuration. Predicted performance curves in air and CO2 conditions are compared, resulting in a reduced diffuser width requirement for the air test in order to match design velocities and demonstrate the casing treatment. Test results show that the casing treatment performance generally matched CFD predictions, demonstrating an operating range of 69% and efficiency above air predictions across the entire map. The casing treatment configuration demonstrated improvements over the solid wall configuration in stage performance and flow characteristics at low flows, resulting in an effective 14% increase in operating range with a 0.5-point efficiency penalty. The test results are also compared to a traditional fully shrouded impeller with the same flow coefficient and similar head coefficient, showing a 42% range improvement over traditional designs.

The Influence of a Diffuser Width on the Unsteady Performance of a Centrifugal Compressor Stage

2002 ◽  
Author(s):  
Abraham Engeda
Keyword(s):  
Centrifugal Compressor ◽  
Time Domain ◽  
Rotating Stall ◽  
Compressor Stage ◽  
Relative Speed ◽  
Vaneless Diffuser ◽  
Flow Rates ◽  
Centrifugal Compressor Stage ◽  
Different Types ◽  
Unsteady Performance

An experimental investigation was conducted to determine the effect of the vaneless diffuser width on the unsteady flow performance of a centrifugal compressor stage. Two compressor configurations with different vaneless diffuser width were investigated at four different impeller speeds and compared in the frequency and time domain. Only one diffuser rotating stall but different types of impeller rotating stalls were detected. The experiments show that the diffuser has a strong influence on the flow in the impeller including in areas way upstream. Analysis of the results indicated: • With increasing diffuser width the onset of impeller rotating stall was shifted to lower flow rates. • With increasing diffuser width the frequencies of the rotating stalls decreased. • There is a common tendency in most of the experiments to lower numbers of rotating cells with increasing relative speed. The impeller rotating stalls can be subdivided in a slow pattern with a relative speed to the impeller of 0.21 to 0.29 and a fast pattern with a relative speed of 0.50 to 0.56. This occurrence of two rotating pressure patterns confirms analytical results presented in previous investigations.

Investigation of Efficient CFD Methods for Rotating Stall Prediction in a Centrifugal Compressor Stage

2014 ◽  
Author(s):  
Daniel DeMore ◽  
Elham Maghsoudi ◽  
Jorge Pacheco ◽  
James Sorokes ◽  
Brad Hutchinson ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Computational Study ◽  
Transformation Method ◽  
Rotating Stall ◽  
Computational Domain ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Ansys Cfx ◽  
Minimum Number ◽  
Stall Cells

The Time Transformation Method in ANSYS CFX is investigated as an efficient substitution to Transient Rotor Stator (TRS) analysis for rotating stall prediction in a centrifugal compressor stage. The computational study was performed by varying the number of blade sectors to determine how the circumferential extent of the computational domain affects the accuracy of the stall prediction. The results obtained using a minimum number of blades, approximately one-quarter the full blade count, and approximately one-half the full blade count were compared to both TRS and steady simulations on the same mesh to characterize the predictive capability of each approach. It is shown that both steady and unsteady methods are able to predict the formation of stall cells, but significant qualitative and quantitative differences exist in the flowfield results. The largest mass flow rate at which rotating stall was captured and the number of stall cells were in good agreement with the experimental data.

A CFD Study on a Base and a Flow-Trimmed Low Specific Speed Centrifugal Compressor

2010 ◽  
Author(s):  
Donghui Zhang ◽  
Jean-Luc Di Liberti ◽  
Michael Cave
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Test Results ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Compressor Efficiency

A numerical study on a baseline and a 25% trimmed compressor is presented in this paper. The CFD results are compared with the test results and good agreements are reached. Both CFD and test results show that flow trimming reduces the compressor efficiency and flow range. For compressors with specific speed lower than 0.038, flow trimming is not recommended.

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