Investigations of the Flow Through a High Pressure Ratio Centrifugal Impeller

In an industrial research project of German and Swiss Turbo Compressor manufacturers a high pressure ratio centrifugal impeller was designed and investigated. Performance measurements and extensive laser measurements (L2F) of the flow field upstream, along the blade passage and downstream of the impeller have been carried out. In addition to that, 3D calculations have been performed, mainly for the design point. Results have been presented by Krain et al., 1995 and 1998, Eisenlohr et al., 1998 and Hah et al.,1999. During the design period of this impeller a radial blade at the inlet region was mandatory to avoid a rub at the shroud due to stress reasons. The measurements and the 3D calculations performed later, however, showed a flow separation at the hub near the leading edge due to too high incidence. Additionally a rather large exit width and a high shroud curvature near the exit caused a flow separation near the exit, which is enlarged by the radially transported wake of the already addressed hub separation. Changes to the hub blade angle distribution to reduce the hub incidence and an adaptation of the shroud blade angle distribution for the same impeller mass-flow at the design point were investigated by means of 3D calculations first with the same contours at hub and shroud; this was followed by calculations with a major change of the shroud contour including an exit width change with a minor variation of the hub contour. These calculations showed encouraging results; some of them will be presented in conjunction with the geometry data of the original impeller design.

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

Volume 2E: Turbomachinery ◽

10.1115/gt2020-14733 ◽

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%.

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Aerodynamic Analysis and Multi-Objective Optimization Design of a High Pressure Ratio Centrifugal Impeller

Volume 2D: Turbomachinery ◽

10.1115/gt2014-25496 ◽

2014 ◽

Cited By ~ 1

Author(s):

Zhendong Guo ◽

Zhiming Zhou ◽

Liming Song ◽

Jun Li ◽

Zhenping Feng

Keyword(s):

Data Mining ◽

High Pressure ◽

Pressure Ratio ◽

Differential Evolution Algorithm ◽

Aerodynamic Performance ◽

Centrifugal Impeller ◽

Tip Leakage Flow ◽

Pareto Solutions ◽

Multi Objective ◽

High Pressure Ratio

The design of high pressure ratio impellers is a challenging task. SRV2-O, a typical high pressure ratio centrifugal impeller is selected for the research. A good understanding of flow characteristics in the passage of SRV2-O is obtained by using 3D Reynolds-Averaged Navier-Stokes (RANS) solutions upon numerical validation. It confirms that tip leakage flow and shock wave boundary layer interactions produce the primary energy loss in this transonic impeller. A 3D multi-objective aerodynamic optimization and data mining method named BMOE is presented and programmed by integrating a self-adaptive multi-objective differential evolution algorithm SMODE, 3D blade parameterization method based on non-uniformed B-Spline, RANS solver technique and self-organization map (SOM) based data mining technique. Using BMOE, multi-objective aerodynamic design optimization and data mining is performed for SRV2-O. 14 Pareto solutions are obtained for maximizing isentropic efficiency and total pressure ratio of the impeller. Three typical Pareto solutions, Design A with the highest efficiency, Design B with the higher efficiency and larger pressure ratio and Design C with the maximum pressure ratio, are analyzed. Detailed analysis indicates that the aerodynamic performance of optimized designs is greatly improved. Furthermore, by SOM-based data mining on optimization results, trade-off relation between objective functions and parameter influence mechanism on impeller aerodynamic performance are visualized and explored.

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Investigation on the Optimal Design and Flow Mechanism of High Pressure Ratio Impeller with Machine Learning Method

International Journal of Aerospace Engineering ◽

10.1155/2020/8855314 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Weilin Yi ◽

Hongliang Cheng

Keyword(s):

Machine Learning ◽

High Pressure ◽

Flow Field ◽

Performance Improvement ◽

Pressure Ratio ◽

Leading Edge ◽

Design Parameters ◽

Support Vector ◽

Peak Efficiency ◽

High Pressure Ratio

The optimization of high-pressure ratio impeller with splitter blades is difficult because of large-scale design parameters, high time cost, and complex flow field. So few relative works are published. In this paper, an engineering-applied centrifugal impeller with ultrahigh pressure ratio 9 was selected as datum geometry. One kind of advanced optimization strategy including the parameterization of impeller with 41 parameters, high-quality CFD simulation, deep machine learning model based on SVR (Support Vector Machine), random forest, and multipoint genetic algorithm (MPGA) were set up based on the combination of commercial software and in-house python code. The optimization objective is to maximize the peak efficiency with the constraints of pressure-ratio at near stall point and choked mass flow. Results show that the peak efficiency increases by 1.24% and the overall performance is improved simultaneously. By comparing the details of the flow field, it is found that the weakening of the strength of shock wave, reduction of tip leakage flow rate near the leading edge, separation region near the root of leading edge, and more homogenous outlet flow distributions are the main reasons for performance improvement. It verified the reliability of the SVR-MPGA model for multiparameter optimization of high aerodynamic loading impeller and revealed the probable performance improvement pattern.

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

Volume 2D: Turbomachinery ◽

10.1115/gt2014-27062 ◽

2014 ◽

Cited By ~ 2

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.

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

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2010-22582 ◽

2010 ◽

Cited By ~ 7

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.

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

Journal of Turbomachinery ◽

10.1115/1.4006637 ◽

2012 ◽

Vol 135 (2) ◽

Cited By ~ 26

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.

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Experimental and Computational Investigation of the Time-Averaged and Time-Resolved Pressure Loading on a Vaneless Counter-Rotating Turbine

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/2000-gt-0445 ◽

2000 ◽

Cited By ~ 15

Author(s):

C. W. Haldeman ◽

M. G. Dunn ◽

R. S. Abhari ◽

P. D. Johnson ◽

X. A. Montesdeoca

Keyword(s):

Experimental Data ◽

High Pressure ◽

Pressure Ratio ◽

Three Dimensional ◽

Low Pressure ◽

Navier Stokes ◽

Experimental Program ◽

Time Resolved ◽

Design Point ◽

High Pressure Ratio

The experimental program reported here was executed using full-scale vaneless counter-rotating engine hardware operating at nondimensionally scaled aerodynamic design point conditions. Measurements were obtained for three different pressure ratio values: design point, low pressure ratio, and high pressure ratio. For brevity, only the design point data will be presented in this paper. Time-averaged and time-resolved surface pressures on the high pressure turbine (HPT) vane, HPT blade, and low pressure turbine (LPT) blades are presented. Additionally, three-dimensional (3D) Navier-Stokes computational fluid dynamics (CFD) predictions are presented for comparison with experimental data. The results presented show that the predictions qualitatively capture the flowfield physics, but require some additional calibration to fully match experimental data quantitatively.

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Numerical assessment of a very high pressure ratio centrifugal impeller

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/916/1/012035 ◽

2020 ◽

Vol 916 ◽

pp. 012035

Author(s):

O Dumitrescu ◽

V Drăgan ◽

I Porumbel ◽

B Gherman

Keyword(s):

High Pressure ◽

Pressure Ratio ◽

Centrifugal Impeller ◽

High Pressure Ratio ◽

Numerical Assessment ◽

Very High

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Free-Form Versus Ruled Inducer Design in a Transonic Centrifugal Impeller

Volume 2C: Turbomachinery ◽

10.1115/gt2017-63538 ◽

2017 ◽

Cited By ~ 1

Author(s):

Hamid Hazby ◽

Chris Robinson ◽

Michael Casey ◽

Daniel Rusch ◽

Rene Hunziker

Keyword(s):

Pressure Ratio ◽

Leading Edge ◽

Free Form ◽

Centrifugal Impeller ◽

Vaned Diffuser ◽

Design Concepts ◽

High Pressure Ratio ◽

Mechanical Constraints ◽

Compressor Impeller ◽

Form Design

The detailed design of the inducer of a high pressure ratio transonic radial compressor impeller with a design inlet tip relative Mach number of 1.4 is considered. Numerical analysis has been used to compare a datum impeller with ruled inducer design with a number of different free-form design concepts, generated following the same aerodynamic design philosophy. The datum stage and one with a free-form inducer, referred to as ‘barrelled forward swept’, with forward swept leading edge near the tip and increased chord at mid-span, have been manufactured and tested. The tests were performed with the same stationary components, including the casing, vaned diffuser and the volute. The design with a barrelled forward sweep of the inducer allows the designer more control of the strength and position of the passage shock at the inlet while meeting mechanical constraints. Interestingly, the performance is also enhanced at off-design points at lower tip-speeds. The measurements show that the stage tested with the swept impeller achieves higher efficiency of between 0.5% and 1.6% compared to the datum design, depending on the operating speed. The CFD simulations are used to further study the flow at part speeds, in order to explain the causes of the observed performance differences at off design conditions.

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