Performance Improvement of a Centrifugal Compressor Stage by Increasing Degree of Reaction and Optimizing Blade Loading of a 3D Impeller

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Takanori Shibata ◽  
Manabu Yagi ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Masanori Tanaka
Keyword(s):  
Performance Improvement ◽  
Relative Velocity ◽  
High Efficiency ◽  
Pressure Coefficient ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Blade Loading ◽  
Surge Margin ◽  
Velocity Diffusion ◽  
Stage Efficiency

Performance improvement of 3D impellers in a high specific speed range was investigated using computational fluid dynamics analyses and experimental tests. In order to reduce the loss production within the stator passages, the backsweep angle of the impellers was increased. At the same time, the inlet-to-exit relative velocity diffusion ratio was also increased by increasing the impeller exit width to prevent the reduction in the pressure ratio. Moreover, the blade loading distribution at the impeller shroud side was optimized to suppress the surge margin reduction caused by the increased relative velocity diffusion ratio. Five types of unshrouded impellers were designed, manufactured, and tested to evaluate the effects of blade loading, backsweep angle, and relative velocity diffusion ratio on the compressor performance. The design suction flow coefficient was 0.125 and the machine Mach number was 0.87. Test results showed that the compressor stage efficiency was increased by 5% compared with the base design without reducing the pressure coefficient and surge margin. It was concluded that an increased relative velocity diffusion ratio coupled with large backsweep angle was a very effective way to improve the compressor stage efficiency. An appropriate blade loading distribution was also important in order to achieve a wide operating range as well as high efficiency.

Performance Improvement of a Centrifugal Compressor Stage by Increasing Degree of Reaction and Optimizing Blade Loading of a 3D-Impeller

2009 ◽  
Author(s):  
Takanori Shibata ◽  
Manabu Yagi ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Masanori Tanaka
Keyword(s):  
Performance Improvement ◽  
Relative Velocity ◽  
High Efficiency ◽  
Pressure Coefficient ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Blade Loading ◽  
Surge Margin ◽  
Velocity Diffusion ◽  
Stage Efficiency

Performance improvement of 3D impellers in a high specific speed range was investigated using computational fluid dynamics (CFD) analyses and experimental tests. In order to reduce the loss production within the stator passages, the backsweep angle of the impellers was increased. At the same time, the inlet-to-exit relative velocity diffusion ratio was also increased by increasing impeller exit width to prevent the reduction in pressure ratio. Moreover, the blade loading distribution at the impeller shroud side was optimized to suppress the surge margin reduction caused by the increased relative velocity diffusion ratio. Five types of unshrouded 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 compressor stage efficiency was increased by 5% compared to the base design without reducing the pressure coefficient and surge margin. It was concluded that an increased relative velocity diffusion ratio coupled with large backsweep angle was a very effective way to improve compressor stage efficiency. An appropriate blade loading distribution was also important in order to achieve a wide operating range as well as high efficiency.

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.

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.

Aerodynamic Performance of an Axial Compressor Stage With Variable Rotor Blades and Variable Inlet Guide Vanes

1998 ◽  
Author(s):  
Václav Cyrus
Keyword(s):  
Volume Flow Rate ◽  
Pressure Coefficient ◽  
Axial Flow ◽  
Aerodynamic Performance ◽  
Rotating Stall ◽  
Rotor Blades ◽  
Flow Coefficient ◽  
Experimental Investigations ◽  
Compressor Stage ◽  
Flow Stage

Experimental investigations of flow fields and losses in an axial flow compressor stage were carried out. The stage has hub/tip ratio of 0.7. The design values of flow coefficient and pressure coefficient are 0.6 and 0.81, respectively. Aerodynamic performance was investigated for two principal configurations: i) axial flow stage with variable rotor blades, ii) axial flow stage with variable inlet guide and stator vanes. The most efficient volume flow rate regulation of the stage was with the application of variable rotor blades. On the basis of experimental data an analysis of the origin of flow separation on the suction and pressure surfaces of rotor and stator blades was made with the use of simple design criteria. The unsteady flow of rotating stall type in the tested stage appeared after simultaneous occurence of large stall regions in both rotor and stator blade rows. The existence of large stall regions in the IGV did not affect the rotating stall onset. At high values of the IGV stagger angle change (50 deg) pressure pulsations appeared due to the occurence of stall.

On Improving the Surge Margin of a Tip-Critical Axial Compressor Rotor

2017 ◽  
Author(s):  
Marcus Lejon ◽  
Tomas Grönstedt ◽  
Niklas Andersson ◽  
Lars Ellbrant ◽  
Hans Mårtensson
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Incoming Flow ◽  
Objective Functions ◽  
Blade Loading ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Surge Margin ◽  
Clearance Flow

Delaying breakdown of the flow in the tip region of a tip-critical compressor rotor as long as possible, i.e. improving the surge margin, is of great interest to the turbomachinery community and is the focus of this study. The surge margin of ten compressor rotors is evaluated numerically, each with different blade loading and geometry at the tip. Previous work in the field has shown the dependence of an interface in the tip region of a compressor rotor between the incoming flow and the tip clearance flow with the passage flow coefficient ϕ. Previous work in the field has also shown that a higher incoming meridional momentum in the tip region can be beneficial to the surge margin of a tip-critical rotor. The present study generalizes these findings by taking into account the local blade loading of the rotor tip section and the level of loss in the tip region. The surge margin is found to improve if the blade loading of the rotor tip section is increased, which acts to increase the incoming mass flow rate and improve the surge margin provided that an increase in loss, mainly related to the strength and direction of the tip clearance flow, does not negate the effect as the compressor is throttled. Two quantities are proposed as objective functions to be used for optimization to achieve a compressor rotor with high surge margin based on the flow field at the design point. Finally, an optimization and analysis of the results is made to demonstrate the proposed objective functions in practise.

Development of a Low Flow Coefficient Single Stage Centrifugal Compressor

2005 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Method ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Low Flow ◽  
High Pressure Ratio ◽  
Surge Margin ◽  
Low Flow Coefficient

A low flow coefficient unshrouded centrifugal compressor would give up clearance very large in relation to the span of the blades, because centrifugal compressors produce a sufficiently large pressure rise in fewer stages. This problem is more acute for a low flow high-pressure ratio impeller. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range for a low flow coefficient centrifugal compressor is a great challenge. This paper describes a new development of high efficiency and large surge margin low flow coefficient (0.145) centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in this centrifugal compressor design. The new compressor has three main parts: impeller, a low solidity diffuser and volute. The tip clearance is under a special consideration in this design to allow impeller insensitiveness to the clearance. A three-dimensional low solidity diffuser design method is proposed and applied to this design. This design is successful to extend the low solidarity diffusers to high-pressure ratio compressor. It is demonstrated that the design is in a great success. The design performance range of the total to static efficiency of the compressor is about 85% and stability range is over 35%. The experimental results showed that the test results are in good agreement with the design.

Optimizing a Suction Channel to Improve Performance of a Centrifugal Compressor Stage

2010 ◽  
Author(s):  
Manabu Yagi ◽  
Takanori Shibata ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Masanori Tanaka ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Compressor Stage ◽  
Flow Distortion ◽  
Dominant Design ◽  
Improvement Effect ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Flow ◽  
Stage Efficiency

Design parameters for a suction channel of process centrifugal compressors were investigated, and an optimizing method to improve efficiency by using the new design parameters was proposed. Both pressure loss and circumferential flow distortion in the suction channel were evaluated by using computational fluid dynamics (CFD). The main dimensions, which had a large influence on pressure loss and circumferential flow distortion, were identified by using design of experiments (DOE). Next, the passage sectional area ratios Ac/Ae, Ae/As, and Ac/As were found to be the dominant design parameters for the pressure loss and circumferential flow distortion, where Ac, Ae and As are passage sectional areas for the casing upstream side, casing entrance and impeller eye, respectively. Then the shape of the suction channel was optimized using Ac/Ae, Ae/As, and Ac/As. Finally, to evaluate the improvement effect of optimizing the values of Ac/Ae, Ae/As, and Ac/As on compressor stage performance, a base suction channel and an optimized type of suction channel were manufactured and tested. The design suction flow coefficient was 0.1 and the peripheral Mach number was 0.78. Test results showed that the optimized suction channel achieved 3.8% higher stage efficiency than the base one while maintaining the overall operating range from surge to choke. The method for optimizing suction channels by using the three described design parameters was concluded to be very effective for improving the stage efficiency.

A Study of a Single Stage Centrifugal Compressor

2006 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Method ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Low Flow ◽  
High Pressure Ratio ◽  
Surge Margin ◽  
Low Flow Coefficient

A low flow coefficient unshrouded centrifugal compressor would give up clearance very large in relation to the span of the blades, because centrifugal compressors produce a sufficiently large pressure rise in fewer stages. This problem is more acute for a low flow high-pressure ratio impeller. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range for a low flow coefficient centrifugal compressor is a great challenge. This paper describes a new development of high efficiency and large surge margin low flow coefficient (0.145) centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in this centrifugal compressor design. The new compressor has three main parts: impeller, a low solidity diffuser and volute. The tip clearance is under a special consideration in this design to allow impeller insensitiveness to the clearance. A three-dimensional low solidity diffuser design method is proposed and applied to this design. This design is successful to extend the low solidarity diffusers to high-pressure ratio compressor. It is demonstrated that the design is in a great success. The design performance range of the total to static efficiency of the compressor is about 85% and stability range is over 35%. The experimental results showed that the test results are in good agreement with the design.

Performance Studies on a Compressor Stage With Uncambered Constant Thickness Low Solidity Diffuser Vanes

Volume 3 ◽  
2004 ◽  
Author(s):  
G. V. Ramana Murty ◽  
T. Ch. Siva Reddy ◽  
M. V. S. S. S. M. Prasad ◽  
G. Rama Raju
Keyword(s):  
Performance Studies ◽  
Static Pressure ◽  
Experimental Studies ◽  
Design Flow ◽  
Flow Coefficient ◽  
Constant Thickness ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Blade Loading ◽  
Stage Performance

The results of experimental studies on a centrifugal compressor stage using uncambered constant thickness low solidity diffuser vanes (LSD) are reported in this paper. In the present work, efforts are concentrated for study of stage performance with LSD vanes for a typical compressor stage at a tip mach number of 0.35. The effect of solidity and setting angle on overall stage performance is evaluated in terms of flow coefficient, head coefficient and efficiency. The results were normalised with the data available at design flow using vaneless diffuser. Improvement in performance as well as static pressure recovery was observed with LSD vanes of the chosen configuration as compared to vaneless diffuser configuration. Variation of blade loading is studied from the measurements of static pressure on pressure and suction surfaces of LSD vane.

CFD Simulation of Fouling on Axial Compressor Stages

2009 ◽  
Author(s):  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Mauro Venturini
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Pressure Coefficient ◽  
Axial Compressor ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Choked Flow ◽  
Performance Reduction

Three-dimensional numerical simulations of the effect of fouling on an axial compressor stage were carried out. As a case study, the NASA Stage 37 was considered for the numerical investigation, which was performed by means of a commercial computational fluid dynamic code. The numerical model was validated against the experimental data available from literature. Computed performance maps and main flow field features showed a good agreement with the experimental data. The model was considered representative of a realistic compressor stage. The model was then used to simulate the occurrence of fouling by imposing different combinations of added thickness and surface roughness levels. The effect of fouling on compressor performances was studied. Reductions of the flow coefficient and of the pressure coefficient were found to be of the same order of magnitude of the experimental results found in literature. The model developed seems to overcome some of the limitations of other models found in literature that tend to significantly underestimate the actual values of performance reduction. The numerical results were also used to analyze and debug the stage performance scaling procedure used in stage stacking models in order to represent fouling in multistage compressors. The analysis highlighted that scaling can adequately represent the behavior of the fouled stage in the choked flow region, but it does not capture the reduction of the maximum of the pressure coefficient which is instead revealed by the numerical simulations. Finally, blockage due to fouling was investigated both qualitatively and quantitatively.

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