scholarly journals Performance Improvement of Return Channel in Multistage Centrifugal Compressor Using Multi-Objective Optimization

2012 ◽  
Author(s):  
Y. Nishida ◽  
H. Kobayashi ◽  
H. Nishida ◽  
K. Sugimura
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Coefficient ◽  
Swirl Flow ◽  
Optimized Design ◽  
Original Design ◽  
Flow Angle ◽  
Second Stage ◽  
Return Channel ◽  
Multistage Centrifugal Compressor ◽  
Stage Efficiency

The effect of the design parameters of a return channel on the performance of a multistage centrifugal compressor was numerically investigated, and the shape of the return channel was optimized using a multi-objective optimization method based on a genetic algorithm to improve the performance of the centrifugal compressor. The results of sensitivity analysis using Latin hypercube sampling suggested that the inlet-to-outlet area ratio of the return vane affected the pressure loss in the return channel, and that the inlet-to-outlet radius ratio of the return vane affected the outlet flow angle from the return vane. Moreover, this analysis suggested that the number of return vanes affected both the loss and the flow angle at the outlet. As a result of optimization, the number of return vanes was increased from 14 to 22 and the area ratio was decreased from 0.71 to 0.66. The radius ratio was also decreased from 2.1 to 2.0. Performance tests on a centrifugal compressor with two return channels (the original design and optimized design) were carried out using two-stage test apparatus. The measured flow distribution exhibited a swirl flow in the center region and a reversed swirl flow near the hub and shroud sides. The exit flow of the optimized design was more uniform than that of the original design. For the optimized design, the overall two-stage efficiency and pressure coefficient were increased by 0.7% and 1.5%, respectively. Moreover, the second-stage efficiency and pressure coefficient were respectively increased by 1.0% and 3.2%, It is considered that the increase in the second-stage efficiency was caused by the increased uniformity of the flow, and the rise in the pressure coefficient was caused by a decrease in the residual swirl flow. It was thus concluded from the numerical and experimental results that the optimized return channel improved the performance of the multistage centrifugal compressor.

scholarly journals Performance Improvement of a Return Channel in a Multistage Centrifugal Compressor Using Multiobjective Optimization

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Yoshifumi Nishida ◽  
Hiromi Kobayashi ◽  
Hideo Nishida ◽  
Kazuyuki Sugimura
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Coefficient ◽  
Swirl Flow ◽  
Optimized Design ◽  
Original Design ◽  
Flow Angle ◽  
Second Stage ◽  
Return Channel ◽  
Multistage Centrifugal Compressor ◽  
Stage Efficiency

The effect of the design parameters of a return channel on the performance of a multistage centrifugal compressor was numerically investigated, and the shape of the return channel was optimized using a multiobjective optimization method based on a genetic algorithm to improve the performance of the centrifugal compressor. The results of sensitivity analysis using Latin hypercube sampling suggested that the inlet-to-outlet area ratio of the return vane affected the total pressure loss in the return channel, and that the inlet-to-outlet radius ratio of the return vane affected the outlet flow angle from the return vane. Moreover, this analysis suggested that the number of return vanes affected both the loss and the flow angle at the outlet. As a result of optimization, the number of return vane was increased from 14 to 22 and the area ratio was decreased from 0.71 to 0.66. The radius ratio was also decreased from 2.1 to 2.0. Performance tests on a centrifugal compressor with two return channels (the original design and optimized design) were carried out using two-stage test apparatus. The measured flow distribution exhibited a swirl flow in the center region and a reversed swirl flow near the hub and shroud sides. The exit flow of the optimized design was more uniform than that of the original design. For the optimized design, the overall two-stage efficiency and pressure coefficient were increased by 0.7% and 1.5%, respectively. Moreover, the second-stage efficiency and pressure coefficient were respectively increased by 1.0% and 3.2%. It is considered that the increase in the second-stage efficiency was caused by the increased uniformity of the flow, and the rise in the pressure coefficient was caused by a decrease in the residual swirl flow. It was thus concluded from the numerical and experimental results that the optimized return channel improved the performance of the multistage centrifugal compressor.

Experimental and Numerical Study of Return Channel Flow Influence on Surge Margin of a Multi-Stage Centrifugal Compressor

2015 ◽  
Author(s):  
Yoshifumi Nishida ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Takahiro Nishioka
Keyword(s):  
Channel Flow ◽  
Centrifugal Compressor ◽  
Swirl Flow ◽  
Velocity Difference ◽  
Flow Angle ◽  
Blade Loading ◽  
Second Stage ◽  
Surge Margin ◽  
Multi Stage ◽  
Return Channel

Experimental and numerical studies were performed to investigate influences of the return channel flow on the surge margin of a multistage centrifugal compressor. Two return channels, which were named RCH-A and RCH-B, were designed and evaluated in a two-stage centrifugal compressor. The measured performance of the compressor suggested that the surge margin of this compressor was dominated by the operating limit of the second stage and that the surge margin of RCH-B was 5% larger than that of RCH-A. The outlet flow of RCH-A and RCH-B swirled in a counter-rotating direction near the shroud region, and the flow angle at the outlet of RCH-A was larger than that of RCH-B. CFD was conducted to investigate the internal flow in the return channel. The CFD results of both RCH-A and RCH-B showed that the flow separation occurred on the suction surface of the return vanes near the operating limit. This separation induced the velocity difference between the suction and pressure sides, and the swirl flow in the counter-rotating direction was generated by this velocity difference. The swirl flow in the counter-rotating direction increased the blade loading of the second stage impeller at the operating limit. It was considered that the blade loading of RCH-B was lower than that of RCH-A at the operating limit, because the swirl flow in the counter-rotating direction of RCH-B was weaker than that of RCH-A. Therefore, the surge margin of the second impeller with RCH-B seemed to be larger than that with RCH-A. It was conclude from the experimental and numerical results that the locally swirl flow in the counter-rotating direction at the outlet of the return channels near the shroud side influenced the surge margins of the downstream impeller and the multi-stage centrifugal compressor.

scholarly journals The Effect of Impeller Inlet Annular Turning Vanes on Multistage Centrifugal Compressor Performance

1996 ◽  
Author(s):  
Hélène Balligand ◽  
Xiubao Huang ◽  
Joost J. Brasz
Keyword(s):  
Performance Improvement ◽  
Centrifugal Compressor ◽  
Performance Measurements ◽  
Channel Bend ◽  
Improvement Potential ◽  
Through Flow ◽  
Turning Radius ◽  
Return Channel ◽  
Radial Outflow ◽  
Multistage Centrifugal Compressor

The flow path of multistage centrifugal compressors is characterized by two 180-degree turns per stage: the inlet turning bend connecting the radial inflow return channel with the radial outflow impeller and the cross-over bend connecting the radial outflow diffuser with the return channel. Due to higher flow velocity and larger width to turning radius ratio, the turning losses are substantially higher in the inlet bend than in the return channel bend. Performance measurements were taken using different annular through-flow turning vane arrangements designed to reduce the inlet turning losses and increase the overall efficiency of the multistage centrifugal compressor. The experiments have shown consistent efficiency gains with corresponding capacity increases by adding multiple annular turning vanes in the inlet bend. The performance improvement potential of the vanes depends strongly on the positioning of these vanes in the flow passage. Based on these results, an empirical turning loss model was developed with the capability to predict the performance improvement achievable with correctly positioned single or multiple turning vanes in the impeller inlet bend area.

Thickness and Blade Angle Distribution for Design of Centrifugal Compressor Stage Return Channel Vane

2015 ◽  
Author(s):  
Arindam Bera ◽  
N. K. Singh
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Thickness Distribution ◽  
Angle Distribution ◽  
Compressor Stage ◽  
Blade Angle ◽  
Flow Angle ◽  
Return Channel

Return channel de-swirl vanes form an integral part of a centrifugal compressor stage for multi-stage configuration. In this paper, a few configurations of return channel vanes (RCV) are arrived at by modifying the blade angle and thickness distribution from leading edge to the trailing edge. Influence of these two parameters on the overall performance of return channel in terms of total pressure loss co-efficient and static pressure recovery co-efficient along with stage exit flow angle are evaluated through CFD analysis. CFD results show that, proper thickness distribution after maximum thickness point to the trailing edge improves the stage exit flow angle but not the total pressure loss co-efficient and static pressure recovery co-efficient. Whereas, by suitably modifying the blade angle distribution, all the three performance parameters can be improved considerably.

Effects of Return Channel With Splitter Vanes on Performance of Multistage Centrifugal Compressor

2015 ◽  
Author(s):  
Manabu Yagi ◽  
Takahiro Nishioka ◽  
Hiromi Kobayashi ◽  
Hideo Nishida ◽  
Satoru Yamamoto
Keyword(s):  
Centrifugal Compressor ◽  
High Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Flow Coefficient ◽  
Optimum Location ◽  
Trailing Edge ◽  
Overall Efficiency ◽  
Return Channel ◽  
Multistage Centrifugal Compressor

The effects of a return channel with splitter vanes on the performance of a multistage centrifugal compressor were investigated. As a preliminary study, the optimum location of the splitter vanes was numerically examined with the aim of achieving high overall efficiency. The results indicated that the optimum location was the 30% of the normalized pitchwise distance from the suction side of the main vane, with the leading-edge located at a radius ratio to the main vane trailing-edge of 1.77. To investigate the effects of the return channel with and without the optimum splitter vanes on the overall performance, performance tests were carried out using a one-and-half-stage test rig. Three pre-swirl vanes, whose vane angles from the tangential direction at the trailing-edge were 20, 30 and 40° were used to simulate three operating conditions with low, design and high flow coefficients, respectively. The design flow coefficient of the downstream impeller was 0.073 and the peripheral Mach number was 0.87. The test results showed that the return channel with the optimum splitter vanes achieved 11.8% higher overall efficiency at the high flow coefficient with respect to the case without the splitter vanes while maintaining the same efficiency at both low and design flow coefficients. The return channel with the optimum splitter vanes was concluded to be effective for improving the efficiency of a multistage centrifugal compressor.

Design Consideration of a Centrifugal Compressor Impeller With High Mach Number and High Swirl Angle at Exit

2010 ◽  
Author(s):  
Kangsoo Im
Keyword(s):  
Mach Number ◽  
Centrifugal Compressor ◽  
Swirl Flow ◽  
Stable Operation ◽  
Compression Process ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Compressor Impeller ◽  
High Mach ◽  
Exit Mach Number

A centrifugal compressor impeller with high exit Mach number (M = 0.8–1.1) & high outlet flow angle (ALPHA 2 = 78–85 degrees) was designed. The objective of this work is to create a real condition for the better understanding of the behavior of the fluid flow in transonic and high swirl flow vaned diffusers. Particular attention was given to the flows located at the rotor–stator interface. The unsteady interaction between impeller and diffuser plays an important role in the compression process, especially in high loaded impellers. Actually, the vaned diffuser has to tolerate the distorted upstream flow due to the jet-wake structure coming from the impeller. Following the impeller design, numerical investigations were conducted for the transonic centrifugal compressor impeller composed of backswept unshrouded blades. The characteristic plots of the impeller resulting from the simulations show a good stable operation.

Experimental Study of the Effect of the Tip Clearance to the Diffuser Flow Field and Stage Performance of a Centrifugal Compressor

2012 ◽  
Author(s):  
Ahti Jaatinen ◽  
Teemu Turunen-Saaresti ◽  
Aki Grönman ◽  
Pekka Röyttä ◽  
Jari Backman
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
High Speed ◽  
Flow Region ◽  
Flow Fields ◽  
Tip Clearance ◽  
Flow Angle ◽  
Lower Stage ◽  
Diffuser Flow ◽  
Stage Efficiency

The effect of tip clearance to the centrifugal compressor diffuser flow fields and stage overall performance are studied experimentally. The relative tip clearance (tip clearance divided by the impeller exit blade height) is increased by shimming the shroud side casing of a high-speed variable speed driven industrial centrifugal compressor. Four different relative tip clearances are studied: 0.027, 0.053, 0.082, and 0.106. The stage efficiency and pressure ratios are measured, as well as the diffuser flow fields. The diffuser flow fields are measured both at the diffuser inlet and outlet. The total pressure and flow angle are measured with a cobra probe, and the total pressure and temperature with three Kiel probes. Static pressures are measured adjacent to the probe measurements. As expected, increasing the tip clearance leads to lower stage efficiency and pressure ratios. The decrement in the efficiency due to the increasing of the tip clearance is higher with higher mass flows, and at lower rotational speeds. Increasing tip clearance increases the size of the secondary flow region present at the impeller outlet near the shroud.

Effect of Tip Clearance in a Low Speed Centrifugal Compressor

2005 ◽  
Author(s):  
P. Usha ◽  
N. Sitaram
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Static Pressure ◽  
Pressure Coefficient ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Velocity Variation ◽  
Fine Grid ◽  
Flow Angle ◽  
Low Speed

Effect of tip clearance on flow field of a low speed centrifugal compressor is presented. Computational study of centrifugal compressor is carried out using structured multi block grid with fine grid in the tip clearance region. Results are obtained with finite volume method upwind scheme using TASCflow software. Centrifugal compressor impeller with four values of clearances i.e., τ = 0%, 1%, 2% and 5% of blade height at trailing edge are examined at five flow coefficients 0.28, 0.34, 0.42 (design value), 0.48 and 0.52. The effect of tip clearance on total pressure coefficient and static pressure coefficient from inlet to outlet of the compressor is analysed at flow coefficient of 0.52. The drop in static pressure coefficient and total pressure coefficient with increase in tip clearance is found to be high at the tip of the blade due to high pressure fluid leakage at the tip of the blade. The static pressure coefficient, total pressure coefficient and tangential velocity variation at outlet are presented at flow coefficient of 0.52. Mass averaged performance graph show the reduction of performance with tip clearance. Total pressure coefficient contours are analysed in five meridional locations at φ = 0.42. Relative velocity vectors are plotted at five meridional locations for τ = 5% at φ = 0.48. Relative flow angle contours are presented at five meridional locations for all clearances at φ = 0.28.

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