The Design Space Boundaries for High Flow Capacity Centrifugal Compressors

2012 ◽  
Author(s):  
Daniel Rusch ◽  
Michael Casey
Keyword(s):  
Pressure Ratio ◽  
Design Flow ◽  
Flow Coefficient ◽  
Centrifugal Compressors ◽  
Flow Capacity ◽  
Physically Based ◽  
Inlet Geometry ◽  
Eye Diameter ◽  
Swallowing Capacity ◽  
Total Pressure Ratio

A methodology has been derived allowing a fast preliminary assessment of the design of centrifugal compressors specified for high specific swallowing capacity. The method is based on one-dimensional (1D) design point values using classical turbomachinery analysis to determine the inlet geometry for the maximum mass flow function. The key results are then expressed in a series of diagrams which draw out the nature of the conflicting boundary conditions of the design. In particular it is shown how the inlet casing relative Mach number causes the design flow coefficient to decrease with the total pressure ratio and determines the inlet eye diameter. Physically-based boundaries of operation are added to the diagrams giving guidelines for the proper choice of specification values to the designer. In addition, links are given to some well-known impeller efficiency correlations, so that a preliminary estimate of the performance can be made. Comparisons are made with a range of compressor data which supports the approach. The derived methodology allows any given specifications to be checked rapidly for feasibility and development risk or can be used to define a challenging specification for the design of a new product.

The Design Space Boundaries for High Flow Capacity Centrifugal Compressors

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Daniel Rusch ◽  
Michael Casey
Keyword(s):  
Pressure Ratio ◽  
Design Flow ◽  
Flow Coefficient ◽  
Centrifugal Compressors ◽  
Flow Capacity ◽  
Physically Based ◽  
Inlet Geometry ◽  
Eye Diameter ◽  
Swallowing Capacity ◽  
Total Pressure Ratio

A methodology has been derived allowing a fast preliminary assessment of the design of centrifugal compressors specified for high specific swallowing capacity. The method is based on one-dimensional (1D) design point values using classical turbomachinery analysis to determine the inlet geometry for the maximum mass flow function. The key results are then expressed in a series of diagrams which draw out the nature of the conflicting boundary conditions of the design. In particular, it is shown how the inlet casing relative Mach number causes the design flow coefficient to decrease with the total pressure ratio and determines the inlet eye diameter. Physically based boundaries of operation are added to the diagrams giving guidelines for the proper choice of specification values to the designer. In addition, links are given to some well-known impeller efficiency correlations, so that a preliminary estimate of the performance can be made. Comparisons are made with a range of compressor data which supports the approach. The derived methodology allows any given specifications to be checked rapidly for feasibility and development risk or can be used to define a challenging specification for the design of a new product.

A New Approach to Performance Mapping of Radial Inflow Turbines

2019 ◽  
Author(s):  
Davide Biliotti ◽  
Alberto Scotti Del Greco ◽  
Francesco Cangioli ◽  
Giuseppe Iurisci
Keyword(s):  
Pressure Ratio ◽  
Flow Coefficient ◽  
Speed Ratio ◽  
Standard Equipment ◽  
Performance Variables ◽  
Flow Capacity ◽  
Start Up ◽  
Full Speed ◽  
Torque Coefficient ◽  
Traditional Performance

Abstract The performance of radial inflow turbines, and specifically of turboexpanders for oil & gas applications, has been traditionally described in terms of efficiency versus velocity speed ratio (U/C) and discharge flow coefficient (Q/N). Especially in the testing phase, this latter parameter has been often preferred to the angle setting of moveable inlet guide vanes (IGV), which are standard equipment for most turboexpanders. In practice, the expander U/C has been often considered to give the performance backbone, while the Q/N ratio has been used for secondary corrections. Moreover, although the role of pressure ratio (PR) is recognized, its impact has been experimentally unexplored in those cases where testing facilities had capacity limitations. Eventually, in case of variable nozzles, the inlet flow capacity curve has been rarely included among the output performance variables, being the attention mainly focused on efficiency. In the present paper, beside an overview and an explanation of the physical meaning of traditional performance parameters, an alternative approach based on torque mapping versus U/C is introduced and discussed in detail. As a matter of fact, numerical and experimental data show smooth and regular trends when torque coefficient is used instead of adiabatic efficiency. Moreover, performance based on torque coefficient can be more conveniently extrapolated at extreme off-design conditions such as start-up (locked rotor condition) or full speed no load. The ease of extrapolation is particularly important for machine operability, which often requires accurate modeling of transient missions at very partial loads (as for instance during start-up or shut-down). Examples will be offered to show the advantages of torque coefficient representation and how sensitive this is to IGV setting and pressure.

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.

Meanline Modeling of Inlet Recirculation in Automotive Turbocharger Centrifugal Compressors

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Peter Harley ◽  
Stephen Spence ◽  
Dietmar Filsinger ◽  
Michael Dietrich ◽  
Juliana Early
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Flow Coefficient ◽  
Centrifugal Compressors ◽  
Flow Paths ◽  
Operating Range ◽  
Recirculating Flow ◽  
Modeling Approach ◽  
Mass Flow Rates ◽  
Compressor Map

This study provides a novel meanline modeling approach for centrifugal compressors. All compressors analyzed are of the automotive turbocharger variety and have typical upstream geometry with no casing treatments or preswirl vanes. Past experience dictates that inducer recirculation is prevalent toward surge in designs with high inlet shroud to outlet radius ratios; such designs are found in turbocharger compressors due to the demand for operating range. The aim of the paper is to provide further understanding of impeller inducer flow paths when operating with significant inducer recirculation. Using three-dimensional (3D) computational fluid dynamics (CFD) and a single-passage model, the flow coefficient at which the recirculating flow begins to develop and the rate at which it grows are used to assess and correlate work and angular momentum delivered to the incoming flow. All numerical modeling has been fully validated using measurements taken from hot gas stand tests for all compressor stages. The new modeling approach links the inlet recirculating flow and the pressure ratio characteristic of the compressor. Typically for a fixed rotational speed, between choke and the onset of impeller inlet recirculation the pressure ratio rises gradually at a rate dominated by the aerodynamic losses. However, in modern automotive turbocharger compressors where operating range is paramount, the pressure ratio no longer changes significantly between the onset of recirculation and surge. Instead the pressure ratio remains relatively constant for reducing mass flow rates until surge occurs. Existing meanline modeling techniques predict that the pressure ratio continues to gradually rise toward surge, which when compared to test data is not accurate. A new meanline method is presented here which tackles this issue by modeling the direct effects of the recirculation. The result is a meanline model that better represents the actual fluid flow seen in the CFD results and more accurately predicts the pressure ratio and efficiency characteristics in the region of the compressor map affected by inlet recirculation.

Gas Dynamic Designs of Centrifugal Compressors for Gas Industry

2015 ◽  
Author(s):  
Y. Galerkin ◽  
A. Rekstin ◽  
K. Soldatova ◽  
A. Drozdov
Keyword(s):  
High Efficiency ◽  
Pressure Ratio ◽  
Design Procedure ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Centrifugal Compressors ◽  
Gas Industry ◽  
Design Point ◽  
Optimal Values ◽  
And Performance

Centrifugal compressors for gas industry consume huge amount of energy. As a rule, they are single-shaft, with two or more stages and with comparatively low pressure ratio. Compressors operate at low Mach numbers and high Reynolds numbers. Two design parameters influence mostly stage performances. Stage flow coefficient optimal values lie in range 0.060–0.11. Chosen number of stages establishes value of this coefficient if speed of a rotor rotation is fixed. Design loading factor optimal values are 0.42–0.52. It corresponds to high efficiency, shifts a surge limit far from a design point and makes power maximal in a design point. Some considerations about impeller and diffuser types are presented. Design procedure consists on application of the Universal modeling programs for main dimensions optimization and performance calculations. Q3D non-viscid velocity diagrams are analyzed for optimization of blade configuration. Samples of design are presented, 32 MW single-stage pipeline compressor stage with record efficiency included.

scholarly journals A Simple Calculation Method for Ratio of Relative Velocity Within Centrifugal Impeller Channel

1986 ◽  
Author(s):  
Shimpei Mizuki ◽  
Ichiro Watanabe
Keyword(s):  
Total Pressure ◽  
Relative Velocity ◽  
Pressure Ratio ◽  
Empirical Relationship ◽  
Simple Calculation ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Simple Method ◽  
Flow Angle ◽  
Total Pressure Ratio

A simple but accurate method of calculating ratio of relative velocities within centrifugal impeller channels is proposed using a one-dimensional flow model, whose major parameters are specific speed, non-dimensional root-mean square radius of the inducer inlet, slip factor, flow coefficient and flow angle at impeller exit. After the non dimensional relative velocity at inducer inlet and that at impeller exit are derived, the ratio of relative velocity at impeller exit to that at inducer inlet is obtained. In addition to this, the ratio is divided into two parts: one ratio for the inducer portion and another ratio for the radial portion of the impeller channel. The computations are conducted both for adiabatic inviscid flow and for two conditions assumed for viscous flow, in which one used an empirical relationship between the total pressure ratio and the peripheral speed of impeller and the other used experimental values for the total pressure ratio as a funtion of the flow rate. By the present simple method, the non-dimensional relative velocities as well as the ratios of the relative velocities for the inlets and the exits of an inducer and an impeller channel are calculated accurately.

Meanline Modelling of Inlet Recirculation in Automotive Turbocharger Centrifugal Compressors

2014 ◽  
Author(s):  
Peter Harley ◽  
Stephen Spence ◽  
Dietmar Filsinger ◽  
Michael Dietrich ◽  
Juliana Early
Keyword(s):  
Pressure Ratio ◽  
Flow Coefficient ◽  
Centrifugal Compressors ◽  
Flow Paths ◽  
Operating Range ◽  
Recirculating Flow ◽  
Mass Flow Rates ◽  
Modelling Techniques ◽  
Compressor Map ◽  
Modelling Approach

This study provides a novel meanline modelling approach for centrifugal compressors. All compressors analysed are of the automotive turbocharger variety and have typical upstream geometry with no casing treatments or pre-swirl vanes. Past experience dictates that inducer recirculation is prevalent toward surge in designs with high inlet shroud to outlet radius ratios; such designs are found in turbocharger compressors due to the demand for operating range. The aim of the paper is to provide further understanding of impeller inducer flow paths when operating with significant inducer recirculation. Using 3D Computational Fluid Dynamics (CFD) and a single-passage model, the flow coefficient at which the recirculating flow begins to develop and the rate at which it grows are used to assess and correlate work and angular momentum delivered to the incoming flow. All numerical modelling has been fully validated using measurements taken from hot gas stand tests for all compressor stages. The new modelling approach links the inlet recirculating flow and the pressure ratio characteristic of the compressor. Typically for a fixed rotational speed, between choke and the onset of impeller inlet recirculation the pressure ratio rises gradually at a rate dominated by the aerodynamic losses. However, in modern automotive turbocharger compressors where operating range is paramount, the pressure ratio no longer changes significantly between the onset of recirculation and surge. Instead the pressure ratio remains relatively constant for reducing mass flow rates until surge occurs. Existing meanline modelling techniques predict that the pressure ratio continues to gradually rise toward surge, which when compared to test data is not accurate. A new meanline method is presented here which tackles this issue by modelling the direct effects of the recirculation. The result is a meanline model that better represents the actual fluid flow seen in the CFD results and more accurately predicts the pressure ratio and efficiency characteristics in the region of the compressor map affected by inlet recirculation.

Experimental Aerodynamic Analysis Relative to Three High Pressure Ratio Centrifugal Compressors

1987 ◽  
Author(s):  
Y. Ribaud
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Flow Coefficient ◽  
Careful Study ◽  
Test Results ◽  
Centrifugal Compressors ◽  
Inlet Flow ◽  
High Pressure Ratio ◽  
Experimental Parameters ◽  
Surge Line

The test results of three high pressure ratio centrifugal compressors are analyzed. Two of them show one or two discontinuities in the surge line. A careful study of the different experimental parameters indicates the existence of three different operating zones for the rotor. For the low inlet flow coefficients, two recirculations take place in the rotor: one at the inlet and the other at the outlet. For moderate flow coefficients, the outlet recirculation disappears. In these regions, the occurrence of these recirculations is explained and a simple model is given. The inlet recirculation can stabilize the flow if a 2D blade stall occurs but it is not possible in the third zone where the inlet flow coefficient is higher than the critical value.

Design of High Specific Speed Mixed Flow Micro-Compressor for Co-Flow Jet Actuators

2019 ◽  
Author(s):  
Kewei Xu ◽  
Gecheng Zha
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Flow Coefficient ◽  
High Mass ◽  
Aerodynamic Design ◽  
Mixed Flow ◽  
Work Distribution ◽  
Specific Speed ◽  
Total Pressure Ratio

Abstract This paper conducts aerodynamic design of a high specific speed mixed flow micro-compressor used as an actuator for Co-flow Jet (CFJ) Active Flow Control (AFC) airfoil. The aerodynamic design poses several challenges, including: 1) Small size with very low Reynolds number; 2) High specific speed for mixed-flow compressor due to high mass flow rate and low total pressure ratio; 3) Static pressure ratio lower than 1 to match the low pressure of CFJ airfoil leading edge (LE) suction peak. The numerical design approach is validated with a mixed flow micro-compressor with very good agreement between the predicted performance and the measured data. Front loaded rotor blade work distribution is adopted to decrease boundary layer loss at the blade surface. Free vortex work distribution is applied for the rotor span to reduce spanwise mixing loss. The rotor efficiency achieved by the numerical prediction is 91.7%. Significant loss is observed downstream of the rotor when the flow reaches the stator and the outlet guide vane (OGV). For the stator, it is found that an inlet and outlet flow path area ratio of 1.05 achieves a very high total pressure recovery of 99.29%. A very good stage isentropic efficiency of 84.3% is achieved. The final design of micro-compressor achieves a flow coefficient of 0.3 at the design point with a total pressure ratio of 1.117 and a static pressure ratio of 0.987. A structure FEM analysis indicates that the rotor blades satisfy the structure strength and modal frequency requirement.

A new method for performance map prediction of automotive turbocharger compressors with both vaneless and vaned diffusers

2020 ◽  
pp. 095440702097125
Author(s):  
Xiaojian Li ◽  
Yijia Zhao ◽  
Zhengxian Liu ◽  
Huadong Yao ◽  
Hua Chen
Keyword(s):  
Experimental Data ◽  
Elliptic Equation ◽  
Pressure Ratio ◽  
Polynomial Equation ◽  
Flow Coefficient ◽  
Impeller Outlet ◽  
Performance Map ◽  
Physically Based ◽  
Outlet Flow ◽  
Empirical Coefficients

A new approach to predict the performance maps of automotive turbocharger compressors is presented. Firstly, a polynomial equation is applied to fit the experimental data of flow coefficient ratios for the centrifugal compressors with both vaneless and vaned diffusers. Based on this equation, the choke and surge flow coefficients under different machine Mach numbers can be quickly predicted. Secondly, a physically based piecewise elliptic equation is used to define compressors’ characteristic curves in terms of efficiency ratio. By introducing the flow coefficient ratio into the efficiency correlation, the empirical coefficients in the piecewise elliptic equation are uniquely calibrated by the experimental data, forming a unified algebraic equation to match the efficiency maps of the compressors with both vaneless and vaned diffusers. Then, a new universal equation, which connects the work coefficient, the impeller outlet flow coefficient and the non-dimensional equivalent impeller outlet width, is derived by using classical aerothermodynamic method. The off-design pressure ratio is predicted based on the equivalent impeller outlet width with less knowledge of the compressor geometry and no empirical coefficients. Finally, three state-of-the-art turbocharger compressors (one with vaneless diffuser, two with vaned diffusers) are chosen to validate the proposed method, and the results show a satisfactory accuracy for the performance map prediction. This method can be used for the preliminary design of turbocharger compressors with both vaneless and vaned diffusers, or to assess the design feasibility and challenges of the given design specifications.

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