Performances of Centrifugal Compressor Impellers in Steady and Unsteady Flow Regimes Under Inlet Flow Distortions

2001 ◽  
Author(s):  
V. Michelassi ◽  
S. Pazzi ◽  
S. Echtner ◽  
P. Giangiacomo ◽  
F. Martelli ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Characteristic Curve ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Load Factor ◽  
Inlet Distortion ◽  
Inlet Conditions ◽  
Operational Range

The performance of a centrifugal impeller is predicted under steady ideal axial inlet conditions. The operational range is given in terms of load and flow coefficient and polytropic efficiency. The flow field at the exit of the impeller is analyzed to show how it deteriorates while moving close to the stall limit of the characteristic curve. The effect of a strong inlet distortion obtained by intentionally altering the geometry of an inlet volute on the impeller is analyzed. The investigation is carried out for two different distortions, without and with pre swirl, and for two pressure ratios, close to the design point and close to the stall limit of the operational range. The effect of the distortion is analyzed by both a quasi-steady and unsteady approaches. The first method, while faster, is found to give results in partial disagreement with the fully unsteady analysis and is therefore abandoned. The impeller under unsteady distorted inlet is found to have degraded performances in terms of efficiency and load factor, but the overall operational range seems not be significantly affected by the fluctuations of inlet total pressure and angles.

Effects of Inlet Pressure Distortion on the Performance and Flow Field of a Centrifugal Compressor at Off-Design Conditions

2012 ◽  
Author(s):  
N. Sitaram ◽  
M. Govardhan ◽  
K. V. Murali
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Static Pressure ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Performance Measurements ◽  
Perforated Sheet ◽  
Sector Angle

The present paper presents experimental results on the effects of inlet total pressure distortion on the performance and flow field of a centrifugal compressor. The total pressure at inlet is artificially distorted by means of a perforated sheet, which is supported by a support mesh. A total of eleven configurations, including clean inlet configuration, are tested. Performance measurements and impeller inlet and exit flow studies at three flow coefficients, one near design flow coefficient, one below design flow coefficient and one above design flow coefficient, are carried out. The present paper presents and discusses results at off-design flow coefficients and the effects of stage loading on the distortion effects are presented. A new parameter, Distortion Index (DI) is introduced. As DI increases, the mass averaged total pressure at exit stations decreases. Distortion sector angle of 60° having the lowest total pressure is found to be the critical sector for circumferential distortion configurations. As the Distortion Correlation parameter, DC(60) increases, the mass averaged total pressure for circumferential distortion configuration decreases, except in the case of low flow coefficient where DC(60) is nearly constant. DC(60) also increases with sector angle. The static pressure normalized with static pressure for clean inlet decreases as the distortion sector angle is increased. Distortion attenuates the static pressure as the flow passes through the vaneless diffuser. The attenuation increases with the distortion sector angle.

Effects of Inlet Distortion on the Flow Field in a Transonic Compressor Rotor

1996 ◽  
Author(s):  
Chunill Hah ◽  
Douglas C. Rabe ◽  
Thomas J. Sullivan ◽  
Aspi R. Wadia
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Viscous Flow ◽  
Total Pressure ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aerodynamic Loss ◽  
Transonic Compressor ◽  
Inlet Distortion ◽  
Compressor Rotor

The effects of circumferential distortions in inlet total pressure on the flow field in a low-aspect-ratio, high-speed, high-pressure-ratio, transonic compressor rotor are investigated in this paper. The flow field was studied experimentally and numerically with and without inlet total pressure distortion. Total pressure distortion was created by screens mounted upstream from the rotor inlet. Circumferential distortions of 8 periods per revolution were investigated at two different rotor speeds. The unsteady blade surface pressures were measured with miniature pressure transducers mounted in the blade. The flow fields with and without inlet total pressure distortion were analyzed numerically by solving steady and unsteady forms of the Reynolds-averaged Navier-Stokes equations. Steady three-dimensional viscous flow calculations were performed for the flow without inlet distortion while unsteady three-dimensional viscous flow calculations were used for the flow with inlet distortion. For the time-accurate calculation, circumferential and radial variations of the inlet total pressure were used as a time-dependent inflow boundary condition. A second-order implicit scheme was used for the time integration. The experimental measurements and the numerical analysis are highly complementary for this study because of the extreme complexity of the flow field. The current investigation shows that inlet flow distortions travel through the rotor blade passage and are convected into the following stator. At a high rotor speed where the flow is transonic, the passage shock was found to oscillate by as much as 20% of the blade chord, and very strong interactions between the unsteady passage shock and the blade boundary layer were observed. This interaction increases the effective blockage of the passage, resulting in an increased aerodynamic loss and a reduced stall margin. The strong interaction between the passage shock and the blade boundary layer increases the peak aerodynamic loss by about one percent.

The Effect of Inlet Distortion on the Performance Characteristics of a Centrifugal Compressor

1983 ◽  
Vol 105 (2) ◽  
pp. 223-230 ◽  
Author(s):  
I. Ariga ◽  
N. Kasai ◽  
S. Masuda ◽  
Y. Watanabe ◽  
I. Watanabe
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Performance Characteristics ◽  
Performance Tests ◽  
Velocity Measurements ◽  
Test Rig ◽  
Low Speed ◽  
Inlet Distortion ◽  
Surge Margin ◽  
The Given

The present paper concerns itself with the effects of total pressure (and thus velocity) distortion on performance characteristics and surge margin of centrifugal compressors. Both radial and circumferential distortions were investigated. The performance tests as well as the velocity measurements within the impeller passages were carried out with a low-speed compressor test rig with the inlet honeycomb as the distortion generators and compared with the case of “no distortion” as a datum. The results indicated that the inlet distortion exerted unfavorable influences on the efficiency and the surge margin of the given compressor, though the influence of the radial distortion was much stronger than that of the circumferential one. Various distortion indices were further examined in order to correlate the performance to the inlet distortion.

Investigation on Effect of Curvilinear Element Blades on Centrifugal Impeller Performance

2017 ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Hiromi Kobayashi ◽  
Takahiro Nishioka
Keyword(s):  
Centrifugal Compressor ◽  
Performance Test ◽  
Design Guidelines ◽  
Secondary Flows ◽  
Flow Coefficient ◽  
Numerical Calculations ◽  
Centrifugal Impeller ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Compressor Impeller

This study experimentally and numerically investigates the effect of application of curvilinear element blades to fully-shrouded centrifugal compressor impeller on the performance of centrifugal compressor stage. Design suction flow coefficient of compressor stage investigated in this study is 0.125. The design guidelines for the curvilinear element blades which had been previously developed was applied to line element blades of a reference conventional impeller and a new centrifugal compressor impeller with curvilinear element blades was designed. Numerical calculations and performance tests of two centrifugal compressor stages with the conventional impeller and the new one were conducted to investigate the effectiveness of application of the curvilinear element blades and compare the inner flowfield in details. Despite 0.5% deterioration of the impeller efficiency, it was confirmed from the performance test results that the compressor stage with the new impeller achieved 1.7% higher stage efficiency at the design point than that with the conventional one. Moreover, it was confirmed that the compressor stage with the new impeller achieved almost the same off-design performance as that of the conventional stage. From results of the numerical calculations and the experiments, it is considered that this efficiency improvement of the new stage was achieved by suppression of the secondary flows in the impeller due to application of negative tangential lean. The suppression of the secondary flows in the impeller achieved uniformalized flow distribution at the impeller outlet and increased the static pressure recovery coefficient in the vaneless diffuser. As a result, it is thought that the total pressure loss was reduced downstream of the vaneless diffuser outlet in the new stage.

Numerical Investigation of Effect of Inlet Distortion on Compressor Flow Field and Stability

2017 ◽  
Author(s):  
HaoGuang Zhang ◽  
Kang An ◽  
Feng Tan ◽  
YanHui Wu ◽  
WuLi Chu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Total Pressure ◽  
Tip Clearance ◽  
Numerical Work ◽  
Stall Margin ◽  
Numerical Investigations ◽  
Inlet Distortion ◽  
Compressor Rotor ◽  
The Stability

The compressor aerodynamic design is conducted under the condition of clean inlet in general, but a compressor often operates under the condition of inlet distortion in the practical application. It has been proven by a lot of experimental and numerical investigations that inlet distortion can decrease the performance and stability of compressors. The circumferential or radial distorted inlet in mostly numerical investigations is made by changing the total pressure and total temperature in the inlet ring surface of the compressors. In most of inlet distortion experiments, distorted inlets are usually created by using wire net, flashboards, barriers or the generator of rotating distortion. The fashion of generating distorted inlet for experiment is different from that for numerical simulation. Consequently, the flow mechanism of affecting the flow field and stability of a compressor with distorted inlet for experiment is partly different than that for numerical simulation. In the numerical work reported here, the inlet distortion is generated by setting some barriers in the inlet ring surface of an axial subsonic compressor rotor. Two kinds of distorted inlet are investigated to exploring the effect of distorted range on the flow field and stability of the compressor with ten-passage unsteady numerical method. The numerical results show that the inlet distortions not only degrade the total pressure and efficiency of the compressor rotor, but also decrease the stability of the rotor. The larger the range of distorted inlet is, the stronger the adverse effect is. The comprehensive stall margin for the inlet distortion of 24 degrees and 48 degrees of ten-passages is reduced about 3.35% and 5.88% respectively. The detailed analysis of the flow field in the compressor indicates that the blockage resulted from tip clearance leakage vortex (TLV) and the flow separation near the suction surfaces of some blades tip for distorted inlet is more serious than that resulted from TLV for clean inlet. Moreover, the larger the range of distorted inlet is, the larger the range of the blockage is. The analysis of unsteady flow shows that during this process, which is that one rotor blade passes through the region affected by the distorted inlet, the range of the blockage in the rotor passage increases first, then reduces, and increases last.

Improving a Vaned Diffuser for a Given Centrifugal Impeller by 3D Inverse Design

2002 ◽  
Author(s):  
Mehrdad Zangeneh ◽  
Damian Vogt ◽  
Christian Roduner
Keyword(s):  
Flow Field ◽  
Viscous Flow ◽  
Centrifugal Compressor ◽  
Inverse Method ◽  
Flow Distribution ◽  
Inverse Design ◽  
Centrifugal Impeller ◽  
Design Code ◽  
Vaned Diffuser ◽  
Blade Loading

In this paper the application of 3D inverse design code TURBOdesign−1 to the design of the vane geometry of a centrifugal compressor vaned diffuser is presented. For this study the new diffuser is designed to match the flow leaving the conventional impeller, which is highly non-uniform. The inverse method designs the blade geometry for a given specification of thickness and blade loading distribution. The paper describes the choice of loading distribution used in the design as well as the influence of the diffuser inlet flow distribution on the vane geometry and flow field. The flow field in the new diffuser is analysed by a 3D viscous flow code and the result is compared to that of the conventional diffuser. Finally the results of testing the stage performance of the new diffuser is compared with that of the conventional stage.

Design and Off-Design Flow Fields of a Transonic Centrifugal Compressor Impeller

2009 ◽  
Author(s):  
Seiichi Ibaraki ◽  
Kunio Sumida ◽  
Toru Suita
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Flow Structure ◽  
Centrifugal Compressor ◽  
Flow Fields ◽  
Design Flow ◽  
Centrifugal Impeller ◽  
Tip Leakage ◽  
Operating Range ◽  
Transonic Centrifugal Compressor

For reasons of their small dimensions, relatively higher efficiency and wider operating range transonic centrifugal compressors are usually applied to turbochargers and turboshaft engines. The flow field of a transonic centrifugal impeller is completely three dimensional and accompanied by shock waves, tip leakage vortices, secondary flows and interactions of them. Especially the operating range of a transonic centrifugal compressor decreases rapidly with increased pressure ratio. The expansion of the compressor operating range is one of the important issues. Also the higher off-design performance is strongly required for the applications like as turbochargers which have to operate from near surge limit to choke limit. The authors carried out the detailed flow measurement of a transonic centrifugal impeller with an inlet Mach number of 1.3 at design and off-design conditions by using Laser Doppler Velocimeter (LDV) and high frequency pressure transducers. The flow fields of design and off-design conditions were compared and discussed in this paper. As a result authors found out the difference and the similarity of the flow structure between design and off-design conditions. The location of the shock wave differs with the flow rate and influences the flow field of the inducer. The interaction of the shock wave and tip leakage vortex shows the same manner. Also detailed Navier-Stokes computations were conducted to elucidate the complicated vortical flow structure with the experimental results.

scholarly journals The Effect of Inlet Distortion on the Performance Characteristics of a Centrifugal Compressor

1982 ◽  
Author(s):  
I. Ariga ◽  
N. Kasai ◽  
S. Masuda ◽  
Y. Watanabe ◽  
I. Watanabe
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Performance Characteristics ◽  
Performance Tests ◽  
Velocity Measurements ◽  
Test Rig ◽  
Low Speed ◽  
Inlet Distortion ◽  
Surge Margin ◽  
The Given

The present paper concerns itself with the effects of total pressure (and thus velocity) distortion on performance characteristics and surge margin of centrifugal compressors. Both radial and circumferential distortions were investigated. The performance tests as well as the velocity measurements within the impeller passages were carried out with a low speed compressor test rig with the inlet honeycomb as the distortion generators and compared with the case of “no distortion” as a datum. The results indicated that the inlet distortion exerted unfavorable influences on the efficiency and the surge margin of the given compressor, though the influence of the radial distortion was much stronger than that of the circumferential one. Various distortion indices were further examined in order to correlate the performance to the inlet distortion.

Flow Field Analysis of Inlet Distortion in a Transonic Fan With Straight and Bowed Stator Blade

2007 ◽  
Author(s):  
Peng Sun ◽  
Jingjun Zhong ◽  
Guotai Feng
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Three Dimensional ◽  
Field Analysis ◽  
Navier Stokes ◽  
Fan Performance ◽  
Inlet Distortion ◽  
Flow Loss ◽  
Stator Blade ◽  
Transonic Fan

The performance and stability of a fan in clean and distorted inlet flow can be improved through the use of bowed stator blades. Measurements between the blade rows in transonic and supersonic flow are too complex to provide any useful insights, so 3D flow simulations are required. In this paper, a time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan is carried out using “Fluent-parallel” in a parallel supercomputer. Two sets of simulations are performed. The first simulation focuses on a better understanding of inlet total pressure distortion effects on a transonic fan. The second set of numerical simulation aims at studying the improvements of fan performance made by bowed stator blades. Three aspects are contained in this paper. The first is about the distortion effects on characteristics of the fan stage with straight stator. The effects of bowed stator on fan performance with inlet distortion are demonstrated secondly. One hand bowed stator increases the loss in rotor. On the other hand, it reduces the flow loss in stator. Finally, the patterns of flow loss caused by total pressure distortion with straight/bowed stator are compared. The scale of vortex in stator induced by inlet total pressure distortion is weakened by bowed blades, which decreases the stator loss.

Investigation of Stall Process in a Centrifugal Compressor With a Volute Under Transonic Conditions

2019 ◽  
Author(s):  
Ce Yang ◽  
Wenli Wang ◽  
Hanzhi Zhang ◽  
Yanzhao Li ◽  
Ding Tong ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Cell Formation ◽  
Internal Flow ◽  
Growth Zone ◽  
Asymmetric Structure ◽  
Stall Inception ◽  
Stall Cells ◽  
Inlet Conditions

Abstract In a centrifugal compressor with a volute, the internal flow field is circumferentially nonuniform owing to the asymmetric structure of the volute. Currently, the mechanisms by which the volute influences the stall inception circumferential position and the stall process in a transonic centrifugal compressor are not clear. In this study, the stall process in the centrifugal compressor with a volute is investigated under transonic inlet conditions. Obtained by experimental and simulation results, the static pressure distributions around the casing wall are compared with each other. Thereafter, an unsteady simulation is conducted on the stall process under transonic inlet conditions. By analyzing the stall cell evolution pattern at the impeller inlet, the stall process can be divided into three stages: stall onset, stall development, and stall maturation. The spike-type stall inceptions occur twice at the tip in the circumferential 135° position of the impeller inlet. This circumferential position is also the affected position of the high static pressure region induced by the volute tongue. Because of the circumferentially nonuniform flow field, there is a stall cell decay zone and a stall cell formation/growth zone at the impeller inlet. For the compressor under study, the approximate circumferential range of 135° to 270° is the decay zone, and the circumferential range of 270° to 360° is the formation/growth zone. The stall inception cannot occur in the decay zone. However, the stall cells can pass through the decay zone when the stall cell size is large enough. The first stall inception cannot propagate circumferentially, while the second one can. The propagation speed of stall cells in the circumferential direction is at approximately 70% of the rotational speed of impeller.

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