Deterioration of Compressor Performance Due to Tip Clearance of Centrifugal Impellers

1987 ◽  
Vol 109 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Y. Senoo ◽  
M. Ishida
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Slip Coefficient ◽  
Clearance Ratio ◽  
Flow Rates ◽  
High Pressure Ratio ◽  
Compressor Performance ◽  
Loss Efficiency ◽  
Good Agreement

The authors’ theory on the tip-clearance loss of centrifugal impellers is modified to include the variation of slip coefficient of the impeller due to the tip clearance, by deriving a rational relationship between two empirical parameters in the theory. In order to compare experimental data in the literature with prediction, examination was made regarding accuracy of available data and the way to select corresponding flow rates of a compressor with different values of tip clearance. Good agreement between data and prediction was observed. These examples demonstrate the following tendency regarding effects of various parameters on the tip clearance loss. Efficiency drop due to the tip clearance of high-pressure-ratio compressors is less than that of low-pressure-ratio compressors if the tip clearance ratio at the impeller exit is equal. The magnitude of clearance loss becomes smaller as the flow rate is reduced and also at a reduced shaft speed in cases of high-pressure-ratio compressors. The equations in the theory clearly show these tendencies.

Eliminating Static Pressure Distortion by a Large Cut Back Tongue Volute

2006 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Flow Structures ◽  
High Pressure Ratio ◽  
Compressor Performance ◽  
Stationary Frame ◽  
Good Agreement

This paper presents a physical solution by eliminating static pressure distortions of impeller exit due to a volute in a centrifugal compressor. The numerical and experimental studies on the circumferential distortion flow characteristics inside the stationary frame of a high-pressure ratio compressor with a large cut back tongue volute. The detailed flow structures and pressure distortions development inside the stationary components are discussed. The numerical results were demonstrated to be in good agreement with the experiments. The volute and diffuser interactions at design and off-design conditions were found to be much smaller for the large cut back volute in comparison with the reported from literature. The study indicated that the large cut back tongue volute design not only benefits the compressor performance but also reduces the impeller exit static pressure non-uniformity caused by discharge volute.

Impact of Main and Splitter Blade Leading Edge Contour on the Performance of High Pressure Ratio Centrifugal Compressors

2014 ◽  
Author(s):  
Rodrigo R. Erdmenger ◽  
Vittorio Michelassi
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Centrifugal Compressors ◽  
Operating Range ◽  
High Pressure Ratio ◽  
The Impact ◽  
Blade Leading Edge

The impact of leading edge sweep in an attempt to reduce shock losses and extend the stall margin on axial compressors has been extensively studied, however only a few studies have looked at understanding the impact of leading edge contouring on the performance of centrifugal compressors. The present work studies the impact of forward and aft sweep on the main and splitter blade leading edge of a generic high flow coefficient and high pressure ratio centrifugal compressor design and the impact on its overall peak efficiency, pressure ratio and operating range. The usage of aft sweep on the main blade led to an increase of the pressure ratio and efficiency, however it also led to a reduction of the stable operating range of the impeller analyzed. The forward sweep cases analyzed where the tip leading edge was displaced axially forward showed a slight increase in pressure ratio, and a significant increase on operating range. The impact of leading edge sweep on the sensitivity of the impeller performance to tip clearance was also studied. The impeller efficiency was found to be less sensitive to an increase of tip clearance for both aft and forward sweep cases studied. The forward sweep cases studied also showed a reduced sensitivity from operating range to tip clearance. The studies conducted on the splitter leading edge profile indicate that aft sweep may help to increase the operating range of the impeller analyzed by up to 16% while maintaining similar pressure ratio and efficiency characteristics of the impeller. The improvement of operating range obtained with the leading edge forward sweep and splitter aft sweep was caused by a reduction of the interaction of the tip vortex of the main blade with the splitter tip, and a reduction of the blockage caused by this interaction.

Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetric Flow Control: Part II—Non-Axisymmetric Self Recirculation Casing Treatment

2010 ◽  
Author(s):  
Xinqian Zheng ◽  
Yangjun Zhang ◽  
Mingyang Yang ◽  
Takahiro Bamba ◽  
Hideaki Tamaki
Keyword(s):  
High Pressure ◽  
Flow Control ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Asymmetric Flow ◽  
Casing Treatment ◽  
High Pressure Ratio ◽  
Compressor Performance

This is the Part II of a two-part paper involving the development of asymmetric flow control method to widen the operating range of a turbocharger centrifugal compressor with high-pressure-ratio. Non-axisymmetric Self Recirculation Casing Treatment (SRCT) as an instance of asymmetric flow control method is presented. Experimental and numerical methods were used to investigate the impact of non-axisymmetric SRCT on surge point of the centrifugal compressor. Firstly, the influence of the geometry of a symmetric SRCT on the compressor performance was studied by means of numerical simulation. The key parameter of the SRCT was found to be the distance from the main blade leading edge to the rear groove (Sr). Next, several arrangements of a non-axisymmetric SRCT were designed, based on flow analysis presented in Part I. Then, a series of experiments was carried out to analyze the influence of non-axisymmetric SRCT on the compressor performance. Results show that the non-axisymmetry SRCT has certain influence on performance and has a larger potential for stability improvement than the traditional symmetric SRCT. For the investigated SRCT, the surge flow rate of the compressor with the non-axisymmetric SRCT is about 10% lower than that of the compressor with symmetric SRCT. The largest surge margin (smallest surge flow rate) can be obtained when the phase of the largest Sr is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades.

Study of the Flow in Centrifugal Compressor

2009 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Method ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Low Flow ◽  
High Pressure Ratio ◽  
Surge Margin

An 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 centrifugal compressor is a great challenge. This paper describes a new development of high efficiency and a large surge margin flow coefficient of 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 demonstrated to be successful to extend the low solidarity diffusers to high-pressure ratio compressor. The design performance range showed the total to static efficiency of the compressor being about 85% and stability range over 35%. The experimental results showed that the test results are in good agreement with the design.

scholarly journals Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetrical Flow Control—Part II: Nonaxisymmetrical Self-Recirculation Casing Treatment

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Xinqian Zheng ◽  
Yangjun Zhang ◽  
Mingyang Yang ◽  
Takahiro Bamba ◽  
Hideaki Tamaki
Keyword(s):  
High Pressure ◽  
Flow Control ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Casing Treatment ◽  
High Pressure Ratio ◽  
Compressor Performance

This is part II of a two-part paper involving the development of an asymmetrical flow control method to widen the operating range of a turbocharger centrifugal compressor with high-pressure ratio. A nonaxisymmetrical self-recirculation casing treatment (SRCT) as an instance of asymmetrical flow control method is presented. Experimental and numerical methods were used to investigate the impact of nonaxisymmetrical SRCT on the surge point of the centrifugal compressor. First, the influence of the geometry of a symmetric SRCT on the compressor performance was studied by means of numerical simulation. The key parameter of the SRCT was found to be the distance from the main blade leading edge to the rear groove (Sr). Next, several arrangements of a nonaxisymmetrical SRCT were designed, based on flow analysis presented in part I. Then, a series of experiments were carried out to analyze the influence of nonaxisymmetrical SRCT on the compressor performance. Results show that the nonaxisymmetrical SRCT has a certain influence on the performance and has a larger potential for stability improvement than the traditional symmetric SRCT. For the investigated SRCT, the surge flow rate of the compressor with the nonaxisymmetrical SRCTs is about 10% lower than that of the compressor with symmetric SRCT. The largest surge margin (smallest surge flow rate) can be obtained when the phase of the largest Sr is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades.

The Use of the 3D-Viscous Codes in the Analysis of High Speed High Pressure Ratio Centrifugal Impellers

2000 ◽  
Author(s):  
Tarek Mekhail ◽  
Du Zhao Hui ◽  
Chen Han Ping ◽  
Willem Janson
Keyword(s):  
High Pressure ◽  
High Speed ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Internal Flow ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Field Calculation ◽  
High Pressure Ratio ◽  
Industrial Gas Turbine

Abstract The flow inside a centrifugal impeller has various complex three dimensional phenomena (flow separation, jet-wake structure, shock wave, etc.). In this study, the internal flow field calculation of Samsung, high pressure ratio, high speed, centrifugal impeller with splitter blades is obtained by commercially available CFX-Tascflow code with CFX-Turbogrid for grid generation. The results are compared to that obtained previously by Denton and Dawes codes. The impeller is used in the first stage centrifugal compressor of an industrial gas turbine. The CFX-Tascflow results showed some differences Mach number contours. Also, the calculations are performed for Krain’s backswept impeller and the results are compared to the experimental measurements. Simulation of tip clearance has been done and the results were in a good agreement with the previous experiments.

Numerical Investigation of Low Solidity Vaned Diffuser Performance in a High-Pressure Centrifugal Compressor: Part II—Influence of Vane Stagger

2008 ◽  
Author(s):  
JongSik Oh ◽  
Charles W. Buckley ◽  
Giri L. Agrawal
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Poor Performance ◽  
Design Flow ◽  
Design Parameters ◽  
Vaned Diffuser ◽  
High Pressure Ratio ◽  
Compressor Performance

As the second part, following the authors’ previous study, the influence of the LSD (Low Solidity Diffuser) vane stagger on high-pressure ratio centrifugal compressor performance is numerically investigated with all the other design parameters fixed, while vane solidities are in the range from 0.70 to 0.85. Vane stagger is varied for 6 cases from 8.55 deg to 22.37 deg with the NACA65-(4A10)06 airfoil profile, and the Stage interface scheme is applied for an interaction treatment. As the vane stagger increases, changing from 10.55 deg to 19.58 deg, the compressor overall performance is generally improved, but two extreme cases of vane stagger of 8.55 deg and 22.37 deg provide poor performance. Vane stagger of 19.58 deg shows the highest efficiency and pressure rise near design flow, while vane stagger of 13.76 deg has the largest operating range with acceptable performance of efficiency and pressure ratio.

Influence of Splitter Blades on the Performance of a Single-Stage Centrifugal Compressor With Pressure Ratio 12.0

2020 ◽  
Author(s):  
Wenchao Zhang ◽  
Zhenzhong Sun ◽  
Baotong Wang ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Flow Separation ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
High Pressure Ratio ◽  
Clearance Flow ◽  
Aerodynamic Configuration

Abstract High performance centrifugal compressors with high pressure ratio are highly applied in turboshaft engines in order to obtain higher power-to-weight ratio and lower fuel consumption. The optimization of the aerodynamic configuration design of splitter blades is one of the effective ways to achieve higher efficiency. An in-house designed single-stage centrifugal compressor with a pressure ratio up to 12.0 is studied in this paper. By using a three-dimensional CFD (computational fluid dynamic) method, this paper investigates influences of the number of splitter blades and their leading edge position on the flow field characteristics and aerodynamic performance of the centrifugal compressor with ultra-high pressure ratio. Results show that three critical flow characteristics lead to severe losses in centrifugal compressor impeller when only full blades are applied. Those flow characteristics include the strong shock wave, the severe tip clearance flow at the inlet region and the severe flow separation at the rear region. Therefore, the inlet blade number should be reduced to decrease the loss caused by strong shock waves and tip clearance flow, while the outlet blade number should be sufficient enough to suppress flow separation. By optimizing the number and the leading edge position of splitters, the performance can be improved under the reduction of combined losses caused by shock waves, tip clearance flow and flow separation. When an aerodynamic configuration with single-splitters is used, numerical results indicate that the leading edge position of splitter blades should be located at 60% of the main blade chord length, and the centrifugal impeller isentropic efficiency with ultra-high pressure ratio can be increased from 82.4% (the aerodynamic configuration with only full blades) to 89.5%; when an aerodynamic configuration with double-splitters is used, the leading edge positions of middle and short splitter blades should be respectively located at 40% and 60% of the main blade chord length, and the impeller isentropic efficiency can be further improved to 90.9%.

scholarly journals Investigation Into the Effect of Tip Clearance on Centrifugal Compressor Performance

1988 ◽  
Author(s):  
Joost J. Brasz
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Clearance Ratio ◽  
Impeller Blade ◽  
Linear Effect ◽  
Work Input ◽  
Parallel Wall ◽  
Compressor Performance ◽  
Improved Performance

The axial clearance between the tip of the blades of an unshrouded impeller and its stationary shroud has been varied to study its effect on overall compressor performance. The compressor under investigation consisted of an inlet nozzle, a 3D open impeller with full inducer, a parallel-wall vaneless diffuser and a collector. High-accuracy overall performance data were obtained for this compressor. The experiments were carried out in a closed-loop centrifugal compressor test rig with the impeller running at a rotational Mach number u2/a0 = 1.39. The impeller tip diameter was 0.516 m, its tip width 0.021 m and the impeller blade exit angle was 30 degrees from radial. Assuming a linear relationship, the experimental data indicates a pressure ratio decrease of 0.77 percent, an efficiency loss of 0.31 points, an input head reduction of about 0.25 percent and an output head reduction of about 0.65 percent for each percent increase in clearance ratio. However, the data seems to indicate a non-linear effect showing stronger performance sensitivity at smaller clearances. The test data are compared against a clearance loss model. Improved performance prediction is obtained by including the effect of clearance on impeller work input.

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