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.

Some Studies on Low Solidity Vaned Diffusers of a Centrifugal Compressor Stage

2005 ◽  
Author(s):  
T. Ch. Siva Reddy ◽  
G. V. Ramana Murty ◽  
Prasad Mukkavilli ◽  
D. N. Reddy
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Pressure Recovery ◽  
Compressor Stage ◽  
Recovery Coefficient ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Centrifugal Compressor Stage ◽  
Pressure Recovery Coefficient

Numerical simulation of impeller and low solidity vaned diffuser (LSD) of a centrifugal compressor stage is performed individually using CFX- BladeGen and BladeGenPlus codes. The tip mach number for the chosen study was 0.35. The same configuration was used for experimental investigation for a comparative study. The LSD vane is formed using standard NACA profile with marginal modification at trailing edge. The performance parameters obtained form numerical studies at the exit of impeller and the diffuser have been compared with the corresponding experimental data. These parameters are pressure ratio, polytropic efficiency and flow angle at the impeller exit where as the parameters those have been compared at the exit of diffuser are the static pressure recovery coefficient and the exit flow angle. In addition, the numerical prediction of the blade loading in terms of blade surface pressure distribution on LSD vane has been compared with the corresponding experimental results. Static pressure recovery coefficient and flow angle at diffuser exit is seen to match closely at higher flows. The difference at lower flows could be due to the effect of interaction between impeller and diffuser combinations, as the numerical analysis was done separately for impeller and diffuser and the effect of impeller diffuser interaction was not considered.

Experimental Study of Pinch in Vaneless Diffuser of Centrifugal Compressor

2009 ◽  
Author(s):  
Teemu Turunen-Saaresti ◽  
Aki-Pekka Gro¨nman ◽  
Ahti Jaatinen
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Moderate Amount ◽  
Flow Angle ◽  
Isentropic Efficiency

A centrifugal compressor is often equipped with a vaneless diffuser because the operation range of a vaneless diffuser is wider than the operation range of vaned diffuser, and the geometry of the vaneless diffuser is simple and inexpensive. The flow field after the centrifugal compressor rotor is highly complicated and the velocity is high. A moderate amount of this velocity should be recovered to the static pressure. It is important to study the flow field in the vaneless diffuser in order to achieve guidelines for design and an optimal performance. In this article, the experimental study of the pinch in the vaneless diffuser is conducted. Five different diffuser heights were used, b/b2 = 1, b/b2 = 0.903, b/b2 = 0.854, b/b2 = 0.806 and b/b2 = 0.903 (shroud). In three of the cases, the pinch was made to both walls of the diffuser, hub and shroud, and in one case, the pinch was made to the shroud wall. The total and the static pressure, the total temperature and the flow angle were measured at the diffuser inlet and outlet by using a cobra-probe, kiel-probes and flush-mounted pressure taps. In addition, the static pressure in the diffuser was measured at three different radius ratios. The overall performance, the mass flow, the pressure ratio and the isentropic efficiency of the compressor stage were also monitored. Detailed flow field measurements were carried out at the design rotational speed and at the three different mass flows (close to the surge, design and close to the choke). The isentropic efficiency and the pressure ratio of the compressor stage was increased with the pinched diffuser. The efficiency of the rotor and the diffuser was increased, whereas the efficiency of the volute/exit cone was decreased. The pinch made to the shroud wall was the most effective. The pinch made the flow angle more radial and increased the velocity at the shroud where the secondary flow (passage wake) from the rotor is present.

Design and Numerical Investigation of Advanced Radial Inlet for a Centrifugal Compressor Stage

2004 ◽  
Author(s):  
Yunbae Kim ◽  
Jay Koch
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Compressor Stage ◽  
Flow Distortion ◽  
Centrifugal Compressor Stage ◽  
Initial Design ◽  
Wide Range

The performance of a centrifugal compressor stage can be seriously affected by inlet flow distortions due to an unsatisfactory inlet configuration and the resulting flow structure. In this study, two radial inlets were designed for a centrifugal compressor stage and investigated numerically using a commercially available 3D viscous Navier-Stokes code. The intent of the design was to minimize the total pressure loss across the inlet while distributing the flow as equally and uniformly as possible to the impeller inlet. For each inlet model, the aerodynamic performance was calculated from the simulation results and then the results from both models were evaluated and compared. The second radial inlet design outperformed the initial design in terms of total pressure loss, flow distortion and uniformity at the impeller inlet. Furthermore, the aerodynamic performance of the second radial inlet was insensitive to a wide range of mass flow rates compared to the initial design due to the distinctive geometric features implemented for the second inlet design.

Numerical Analysis of Overall Performance and Flow Phenomena of an Automatically Optimized Three-Dimensional Return Channel System for Multistage Centrifugal Compression Systems

2012 ◽  
Author(s):  
A. Hildebrandt
Keyword(s):  
Numerical Analysis ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Blade Design ◽  
Two Dimensional ◽  
Blade Angle ◽  
Channel System ◽  
Multi Stage ◽  
Return Channel

For multi-stage compression systems, besides the aerodynamics of the impeller and the diffuser, the U-turn and return channel blades aerodynamics play an important role for the total stage efficiency of the compression system. Due to modern CAD and CAM methodology, three-dimensional blade surfaces of an impeller but also of return channel blades are easily designed and manufactured at a similar price as old-fashioned two-dimensional blade designs. This paper presents the numerical analysis and aerodynamic optimization of a three-dimensional return channel system for multi stage single shaft centrifugal compressor machinery. In a previous paper, a two-dimensional return channel blade system had been optimized by an automatic evolutionary algorithm [1]. This previous study showed further aerodynamic potential by utilizing a three dimensional return channel blade design. The three-dimensional blade comprises of ruling surfaces. In the present paper, for a three-dimensional blade design, both the blade angle and blade thickness distributions are allowed to be varied independently for the hub and the shroud. As a result, the total pressure loss of the three dimensional return channel blade can be relatively reduced by 6% compared with a classical two-dimensional return channel blade. This reduction in total pressure loss is partly caused by the matching of the leading edge angle to the non-uniform flow angle at the U-turn outlet. Furthermore, the different blade angle distribution helps to suppress flow separation at the blade suction side near the shroud and helps to reduce flow friction on the blade surface near the hub.

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.

Numerical and Experimental Investigation of Return Channel Vane Aerodynamics With Two-Dimensional and Three-Dimensional Vanes

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
A. Hildebrandt ◽  
F. Schilling
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Static Pressure ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Field Performance ◽  
Two Dimensional ◽  
Flow Angle ◽  
Overall Performance ◽  
Return Channel

The present paper deals with the numerical and experimental investigation of the effect of return channel (RCH) dimensions of a centrifugal compressor stage on the aerodynamic performance. Three different return channel stages were investigated, two stages comprising three-dimensional (3D) return channel blades and one stage comprising two-dimensional (2D) RCH vanes. The analysis was performed regarding both the investigation of overall performance (stage efficiency, RCH total pressure loss coefficient) and detailed flow-field performance. For detailed experimental flow-field investigation at the stage exit, six circumferentially traversed three-hole probes were positioned downstream the return channel exit in order to get two-dimensional flow-field information. Additionally, static pressure wall measurements were taken at the hub and shroud pressure and suction side (SS) of the 2D and 3D return channel blades. The return channel system overall performance was calculated by measurements of the circumferentially averaged 1D flow field downstream the diffuser exit and downstream the stage exit. Dependent on the type of return channel blade, the numerical and experimental results show a significant effect on the flow field overall and detail performance. In general, satisfactory agreement between computational fluid dynamics (CFD)-prediction and test-rig measurements was achieved regarding overall and flow-field performance. In comparison with the measurements, the CFD-calculated stage performance (efficiency and pressure rise coefficient) of all the 3D-RCH stages was slightly overpredicted. Very good agreement between CFD and measurement results was found for the static pressure distribution on the RCH wall surfaces while small CFD-deviations occur in the measured flow angle at the stage exit, dependent on the turbulence model selected.

1D and 3D-Design Strategies for Pressure Slope Optimization of High-Flow Transonic Centrifugal Compressor Impellers

2018 ◽  
Author(s):  
A. Hildebrandt ◽  
T. Ceyrowsky
Keyword(s):  
Centrifugal Compressor ◽  
High Flow ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Angle Distribution ◽  
Compressor Stage ◽  
Impeller Blade ◽  
Design Point ◽  
Centrifugal Compressor Stage ◽  
Transonic Centrifugal Compressor

The present paper deals with the numerical and theoretical investigations of the effect of geometrical dimensions and 1D-design parameters on the impeller pressure slope of a transonic centrifugal compressor stage for industrial process application. A database being generated during the multi-objective and multi-point design process of a high flow coefficient impeller, comprising 545 CFD (Computational Fluid Dynamics) designs is investigated in off-design and design conditions by means of RANS (Reynolds Averaged Navier Stokes) simulation of an impeller with vaneless diffuser. For high flow coefficients of 0.16 < phi < 0.18, the CFD-setup has been validated against measurement data regarding stage and impeller performance taken from MAN test rig experimental data for a centrifugal compressor stage of similar flow coefficient. The paper aims at answering the question how classical design parameter, such as the impeller blade angle distribution, impeller suction diameter and camber line length affect the local and total relative diffusion and pressure slope towards impeller stall operation. A second order analysis of the CFD database is performed by cross-correlating the CFD data with results from impeller two-zone 1D modelling and a rapid loading calculation process by Stanitz and Prian. The statistical covariance of first order 1D-analysis parameters such as the mixing loss of the impeller secondary flow, the slip factor, impeller flow incidence is analyzed, thereby showing strong correlation with the design and off-design point efficiency and pressure slope. Finally, guide lines are derived in order to achieve either optimized design point efficiency or maximum negative pressure slope characteristics towards impeller stall operation.

scholarly journals Numerical and Experimental Investigations on Optimized 3D Compressor Airfoils

2018 ◽  
Author(s):  
Jan Mihalyovics ◽  
Christian Brück ◽  
Dieter Peitsch ◽  
Ilias Vasilopoulos ◽  
Marcus Meyer
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Experimental Studies ◽  
Total Pressure Loss ◽  
Design Parameters ◽  
Flow Conditions ◽  
Flow Angle ◽  
Flow Phenomena ◽  
The Impact ◽  
Stator Design

The objective of the presented work is to perform numerical and experimental studies on compressor stators. This paper presents the modification of a baseline stator design using numerical optimization resulting in a new 3D stator. The Rolls Royce in-house compressible flow solver HYDRA was employed to predict the 3D flow, solving the steady RANS equations with the Spalart-Allmaras turbulence model, and its corresponding discrete adjoint solver. The performance gradients with respect to the input design parameters were used to optimize the stator blade with respect to the total pressure loss over a prescribed incidence range, while additionally minimizing the flow deviation from the axial direction at the stator exit. Non-uniform profile boundary conditions, being derived from the experimental measurements, have been defined at the inlet of the CFD domain. The presented results show a remarkable decrease in the axial exit flow angle deviation and a minor decrease in the total pressure loss. Experiments were conducted on two compressor blade sets investigating the three-dimensional flow in an annular compressor stator cascade. Comparing the baseline flow of the 42° turning stator shows that the optimized stator design minimizes the secondary flow phenomena. The experimental investigation discusses the impact of steady flow conditions on each stator design while focusing on the comparison of the 3D optimized design to the baseline case. The flow conditions were investigated using five-hole probe pressure measurements in the wake of the blades. Furthermore, oil-flow visualization was applied to characterize flow phenomena. These experimental results are compared with the CFD calculations.

A Numerical Study of Volute Design in Centrifugal Compressor

2001 ◽  
Author(s):  
Weili Yang ◽  
Peter Grant ◽  
James Hitt
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Loss ◽  
Total Pressure ◽  
Numerical Study ◽  
Flow Behavior ◽  
Numerical Results ◽  
Total Pressure Loss ◽  
Pressure Loss Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Operating Points

Abstract Our principle goal of this study is to develop a CFD based analysis procedure that could be used to analyze the geometric tradeoffs in scroll geometry when space is limited. In the study, a full centrifugal compressor stage at four different operating points from near surge to near choke is analyzed using Computational Fluid Dynamics (CFD) and laboratory measurement. The study concentrates on scroll performance and its interaction with a vaneless diffuser and impeller. The numerical results show good agreement with test data in scroll circumferential pressure distribution at different ΛAR, total pressure loss coefficient, and pressure distortion at the tongue. The CFD analysis also predicts a reasonable choke point of the stage. The numerical results provide overall flow field in the scroll and diffuser at different operating points. From examining the flow fields, one can have a much better understanding of rather complicated flow behavior such as jet-wake mixing, and choke. One can examine total pressure loss in detail to provide crucial direction for scroll design improvement in areas such as volute tongue, volute cross-section geometry and exit conical diffuser.

Performance Characteristics of Two- and Three-Dimensional Impellers in Centrifugal Compressors

1988 ◽  
Vol 110 (1) ◽  
pp. 110-114 ◽  
Author(s):  
H. Harada
Keyword(s):  
Centrifugal Compressor ◽  
Closed Loop ◽  
Three Dimensional ◽  
Test Stand ◽  
Performance Characteristics ◽  
Working Fluid ◽  
Angle Distribution ◽  
Blade Angle ◽  
Operating Range ◽  
Overall Performance

The overall performance of two- and three-dimensional impellers of a centrifugal compressor were tested and compared. A closed-loop test stand with Freon gas as the working fluid was employed for the experiments. The inlet and outlet velocity distributions of all impellers were measured using three-hole cobra probes. As a result, it has been revealed that three-dimensional impeller in terms of efficiency, head coefficient, and operating range. Further, it has also been clarified that the impeller slip factor is affected by blade angle distribution.

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