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.

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.

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

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Robert Pelton ◽  
Sewoong Jung ◽  
Tim Allison ◽  
Natalie Smith
Keyword(s):  
Operating Conditions ◽  
Low Flow ◽  
Inlet Temperature ◽  
Compressor Stage ◽  
Stage Design ◽  
Power Cycles ◽  
Design Point ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Efficiency

Supercritical carbon dioxide (sCO2) power cycles require high compressor efficiency at both the design point and over a wide operating range. Increasing the compressor efficiency and range helps maximize the power output of the cycle and allows operation over a broader range of transient and part-load operating conditions. For sCO2 cycles operating with compressor inlets near the critical point, large variations in fluid properties are possible with small changes in temperature or pressure. This leads to particular challenges for air-cooled cycles where compressor inlet temperature and associated fluid density are subject to daily and seasonal variations as well as transient events. Design and off-design operating requirements for a wide-range compressor impeller are presented where the impeller is implemented on an integrally geared compressor–expander concept for a high temperature sCO2 recompression cycle. In order to satisfy the range and efficiency requirements of the cycle, a novel compressor stage design incorporating a semi-open impeller concept with a passive recirculating casing treatment is presented that mitigates inducer stall and extends the low flow operating range. The stage design also incorporates splitter blades and a vaneless diffuser to maximize efficiency and operating range. These advanced impeller design features are enabled through the use of direct metal laser sintering (DMLS) manufacturing. The resulting design increases the range from 45% to 73% relative to a conventional closed impeller design while maintaining high design point efficiency.

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

2017 ◽  
Author(s):  
Robert Pelton ◽  
Tim Allison ◽  
Sewoong Jung ◽  
Natalie Smith
Keyword(s):  
Operating Conditions ◽  
Low Flow ◽  
Inlet Temperature ◽  
Compressor Stage ◽  
Stage Design ◽  
Power Cycles ◽  
Design Point ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Efficiency

Supercritical carbon dioxide (sCO2) power cycles require high compressor efficiency at both the design-point and over a wide operating range. Increasing the compressor efficiency and range helps maximize the power output of the cycle and allows operation over a broader range of transient and part-load operating conditions. For sCO2 cycles operating with compressor inlets near the critical point, large variations in fluid properties are possible with small changes in temperature or pressure. This leads to particular challenges for air-cooled cycles where compressor inlet temperature and associated fluid density are subject to daily and seasonal variations as well as transient events. Design and off-design operating requirements for a wide-range compressor impeller are presented where the impeller is implemented on an integrally-geared compressor-expander (IGC) concept for a high temperature sCO2 recompression cycle. In order to satisfy the range and efficiency requirements of the cycle, a novel compressor stage design incorporating a semi-open impeller concept with a passive recirculating casing treatment is presented that mitigates inducer stall and extends the low flow operating range. The stage design also incorporates splitter blades and a vaneless diffuser to maximize efficiency and operating range. These advanced impeller design features are enabled through the use of direct metal laser sintering (DMLS) manufacturing. The resulting design increases the range from 45% to 73% relative to a conventional closed impeller design while maintaining high design point efficiency.

An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Lee Galloway ◽  
Stephen Spence ◽  
Sung In Kim ◽  
Daniel Rusch ◽  
Klemens Vogel ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Stall Inception ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Stable Operating ◽  
The Stability ◽  
Circumferential Pressure

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser (PTD). Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio (PR) compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilizing mechanism of the porous throat diffuser. The nonuniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure nonuniformity at various locations through the compressor stage and diffuser subcomponent analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser, and the stability limit is mainly governed by this element.

The performance of a centrifugal compressor with a tandem impeller in off-design conditions

2019 ◽  
Vol 234 (2) ◽  
pp. 156-172 ◽  
Author(s):  
Ziliang Li ◽  
Xingen Lu ◽  
Ge Han ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Performance Enhancement ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Complex Flow ◽  
Maximum Enhancement ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Performance ◽  
Low Efficiency

Centrifugal compressors often suffer relatively low efficiency and a terrible operating range particularly due to the complex flow structure and intense impeller/diffuser interaction. Numerous studies have focused on improving the centrifugal compressor performance using many innovative ideas, such as the tandem impeller, which has become increasingly attractive due to its ability to achieve the flow control with no additional air supply configurations and control costs in compressor. However, few studies that attempted to the investigation of tandem impeller have been published until now and the results are always contradictory. To explore the potential of the tandem impeller to enhance the compressor performance and the underlying mechanism of the flow phenomena in the tandem impellers, this paper numerically investigated a high-pressure-ratio centrifugal compressor with several tandem impellers at off-design operating speeds. The results encouragingly demonstrate that the tandem impeller can achieve a performance enhancement over a wide range of operating conditions. Approximately 1.8% maximum enhancement in isentropic efficiency and 5.0% maximum enhancement in operating range are achieved with the inducer/exducer circumferential displacement of [Formula: see text] = 25% and 50%, respectively. The observed stage performance gain of the tandem impellers decreases when the operating speed increases due to the increased inducer shock, increased wake losses, and deteriorated tandem impeller discharge flow uniformity. In addition, the tandem impeller can extend the impeller operating range particularly at low rotation speeds, which is found to be a result from the suppression of the low-momentum fluid radial movement. The results also indicate that the maximum flux capacity of the tandem impeller decreases due to the restriction of the inducer airfoil Kutta–Joukowsky condition.

On Effects of Impeller-Diffuser Interaction in the “Radiver” Centrifugal Compressor

2007 ◽  
Author(s):  
Paolo Boncinelli ◽  
Mirco Ermini ◽  
Samuele Bartolacci ◽  
Andrea Arnone
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Operating Conditions ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Flow Unsteadiness ◽  
Physical Mechanisms ◽  
Stage Performance ◽  
Radial Gap

In the present work, effects of impeller-diffuser interaction were investigated in the “Radiver” centrifugal compressor stage exploiting CFD techniques. Two diffuser geometries, differing in the radial gap between impeller exit and diffuser inlet, were analyzed by means of both steady and unsteady computations at two different operating conditions. Physical mechanisms by which interaction affects the flow field were identified and discussed. Flow unsteadiness was found to marginally affect the stage performance, but to have a relevant impact on the flow field.

Numerical Investigation of Different Casing Treatments on Performance of a High Speed Centrifugal Compressor Stage

2011 ◽  
Author(s):  
Yan Ma ◽  
Guang Xi ◽  
Guangkuan Wu
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
High Speed ◽  
The Other ◽  
Compressor Stage ◽  
Stall Margin ◽  
Casing Treatment ◽  
Centrifugal Compressor Stage ◽  
And Performance ◽  
Casing Treatments

In this paper, two different casing treatment devices—one adopting inlet recirculation at the shroud side of the impeller inlet and the other adopting circumferential casing grooves at the shroud side of the vaneless space, are designed for a high speed centrifugal compressor stage. The effects of different casing treatments to the flow range and performance of the centrifugal compressor stage are studied numerically. The results indicate that traditional inlet recirculation at impeller inlet does not extend the stall margin of the stage and the performance deteriorates due to the adding of the extra device. The study also shows that, when the location of the bleed slot moves downstream, the performance of the stage deteriorates due to the longer flow path. Moreover, the 2mm depth circumferential casing grooves extend the stall margin by about 12.05%. By contrast, the 6mm depth and 10mm depth grooves extend the stall margin by 3% and 2.4% respectively.

Investigation of an Inversely Designed Centrifugal Compressor Stage: Part 2 — Experimental Investigations

2003 ◽  
Author(s):  
M. Schleer ◽  
S. S. Hong ◽  
M. Zangeneh ◽  
C. Roduner ◽  
B. Ribi ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Centrifugal Compressor ◽  
Design Method ◽  
Inverse Design ◽  
Compressor Stage ◽  
Time Resolved ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Federal Institute ◽  
Inverse Design Method

This paper presents an experimental investigation of two centrifugal compressor stage configurations. The baseline configuration has been designed using conventional design engineering tools. The second configuration was designed using advanced inverse design rules as described in part 1 (Zangeneh et al. 2003). It is designed to match the choke flow as well as the best point of the conventionally designed stage. The experimental investigation is conducted in the industry-scale centrifugal compressor facility at the Turbomachinery Laboratory of the Swiss Federal Institute of Technology. Performance maps for both configurations at several speed-lines are presented. These plots show the overall behavior of the stages designed using the different design approaches and their operating range. Time resolved measurements show details of the unsteady flow field within the diffuser close to the impeller exit. The time resolved data has been analyzed to assist the explanation of changes in the characteristics and associated efficiency penalties and gains. The processed data shows the benefits of the new inverse design method with respect to an improvement of the compressor efficiency and the operating range. It is seen that the application of an inverse design method results in a more uniform flow into the diffuser.

Design and Numerical Investigation of Advanced Radial Inlet for a Centrifugal Compressor Stage

2004 ◽  
Author(s):  
Yunbae Kim ◽  
Jay Koch
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Compressor Stage ◽  
Flow Distortion ◽  
Centrifugal Compressor Stage ◽  
Initial Design ◽  
Wide Range

The performance of a centrifugal compressor stage can be seriously affected by inlet flow distortions due to an unsatisfactory inlet configuration and the resulting flow structure. In this study, two radial inlets were designed for a centrifugal compressor stage and investigated numerically using a commercially available 3D viscous Navier-Stokes code. The intent of the design was to minimize the total pressure loss across the inlet while distributing the flow as equally and uniformly as possible to the impeller inlet. For each inlet model, the aerodynamic performance was calculated from the simulation results and then the results from both models were evaluated and compared. The second radial inlet design outperformed the initial design in terms of total pressure loss, flow distortion and uniformity at the impeller inlet. Furthermore, the aerodynamic performance of the second radial inlet was insensitive to a wide range of mass flow rates compared to the initial design due to the distinctive geometric features implemented for the second inlet design.

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