Centrifugal Compressor Design for Near-Critical Point Applications

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Alireza Ameli ◽  
Ali Afzalifar ◽  
Teemu Turunen-Saaresti ◽  
Jari Backman
Keyword(s):  
Critical Point ◽  
Centrifugal Compressor ◽  
Compressibility Factor ◽  
Design Procedure ◽  
Operating Conditions ◽  
Brayton Cycle ◽  
Compressor Design ◽  
Lower Temperature ◽  
The Individual ◽  
Line Design

The supercritical CO2 (sCO2) Brayton cycle has been attracting much attention to produce the electricity power, chiefly due to its higher thermal efficiency with the relatively lower temperature at the turbine inlet compared to other common energy conversion cycles. Centrifugal compressor operating conditions in the supercritical Brayton cycle are commonly set in vicinity of the critical point, owing to smaller compressibility factor and eventually lower compressor work. This paper investigates and compares different centrifugal compressor design methodologies in close proximity to the critical point and suggests the most accurate design procedure based on the findings. An in-house mean-line design code, which is based on the individual enthalpy loss models, is compared to stage efficiency correlation design methods. Moreover, modifications are introduced to the skin friction loss calculation to establish an accurate one-dimensional design methodology. Moreover, compressor performance is compared to the experimental measurements.

Centrifugal Compressor Design for Near-Critical Point Applications

2018 ◽  
Author(s):  
Alireza Ameli ◽  
Ali Afzalifar ◽  
Teemu Turunen-Saaresti ◽  
Jari Backman
Keyword(s):  
Critical Point ◽  
Centrifugal Compressor ◽  
Compressibility Factor ◽  
Design Procedure ◽  
Operating Conditions ◽  
Brayton Cycle ◽  
Compressor Design ◽  
Lower Temperature ◽  
The Individual ◽  
Line Design

The supercritical CO2 (sCO2) Brayton cycle has been attracting much attention to produce the electricity power, chiefly due to its higher thermal efficiency with the relatively lower temperature at the turbine inlet compared to other common energy conversion cycles. Centrifugal compressor operating conditions in the supercritical Brayton cycle are commonly set in vicinity of the critical point, owing to smaller compressibility factor and eventually lower compressor work. This paper investigates and compares different centrifugal compressor design methodologies in close proximity to the critical point and suggests the most accurate design procedure based on the findings. An in-house mean-line design code, which is based on the individual enthalpy loss models, is compared to stage efficiency correlation design methods. Moreover, modifications are introduced to the skin friction loss calculation to establish an accurate 1-D design methodology. Moreover, compressor performances are compared to the experimental measurements.

Numerical Approach for Real Gas Simulations: Part II — Flow Simulation for Supercritical CO2 Centrifugal Compressor

2017 ◽  
Author(s):  
Swati Saxena ◽  
Ramakrishna Mallina ◽  
Francisco Moraga ◽  
Douglas Hofer
Keyword(s):  
Critical Point ◽  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Thermodynamic Quantities ◽  
3D Flow ◽  
Real Gas ◽  
The Real ◽  
Operating Range

This paper is presented in two parts. Part I (Tabular fluid properties for real gas analysis) describes an approach to creating a tabular representation of the equation of state that is applicable to any fluid. This approach is applied to generating an accurate and robust tabular representation of the RefProp CO2 properties. Part II (this paper) presents numerical simulations of a low flow coefficient supercritical CO2 centrifugal compressor developed for a closed loop power cycle. The real gas tables presented in part I are used in these simulations. Three operating conditions are simulated near the CO2 critical point: normal day (85 bar, 35C), hot day (105 bar, 50 C) and cold day (70 bar, 20C) conditions. The compressor is a single stage overhung design with shrouded impeller, 155 mm impeller tip diameter and a vaneless diffuser. An axial variable inlet guide vane (IGV) is used to control the incoming swirl into the impeller. An in-house three-dimensional computational fluid dynamics (CFD) solver named TACOMA is used with real gas tables for the steady flow simulations. The equilibrium thermodynamic modeling is used in this study. The real gas effects are important in the desired impeller operating range. It is observed that both the operating range (minimum and maximum volumetric flow rate) and the pressure ratio across the impeller are dependent on the inlet conditions. The compressor has nearly 25% higher operating range on a hot day as compared to the normal day conditions. A condensation region is observed near the impeller leading edge which grows as the compressor operating point moves towards choke. The impeller chokes near the mid-chord due to lower speed of sound in the liquid-vapor region resulting in a sharp drop near the choke side of the speedline. This behavior is explained by analyzing the 3D flow field within the impeller and thermodynamic quantities along the streamline. The 3D flow analysis for the flow near the critical point provides useful insight for the designers to modify the current compressor design for higher efficiency.

Data-Driven Predesign Tool for Small-Scale Centrifugal Compressor in Refrigeration

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Mounier Violette ◽  
Picard Cyril ◽  
Schiffmann Jürg
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Procedure ◽  
Integrated System ◽  
Operating Conditions ◽  
Data Driven ◽  
Small Scale ◽  
Centrifugal Compressors ◽  
Starting Point ◽  
Isentropic Efficiency

Domestic scale heat pumps and air conditioners are mainly driven by volumetric compressors. Yet the use of reduced scale centrifugal compressors is reconsidered due to their high efficiency and power density. The design procedure of centrifugal compressors starts with predesign tools based on the Cordier line. However, the optimality of the obtained predesign, which is the starting point of a complex and iterative process, is not guaranteed, especially for small-scale compressors operating with refrigerants. This paper proposes a data-driven predesign tool tailored for small-scale centrifugal compressors used in refrigeration applications. The predesign model is generated using an experimentally validated one-dimensional (1D) code which evaluates the compressor performance as a function of its detailed geometry and operating conditions. Using a symbolic regression tool, a reduced order model that predicts the performance of a given compressor geometry has been built. The proposed predesign model offers an alternative to the existing tools by providing a higher level of detail and flexibility. Particularly, the model includes the effect of the pressure ratio, the blade height ratio, and the shroud to tip radius ratio. The analysis of the centrifugal compressor losses allows identifying the underlying phenomena that shape the new isentropic efficiency contours. Compared to the validated 1D code, the new predesign model yields deviations below 4% on the isentropic efficiency, while running 1500 times faster. The new predesign model is, therefore, of significant interest when the compressor is part of an integrated system design process.

Component Matching of Centrifugal Compressors for Turbocharger Application

2017 ◽  
Author(s):  
Hua Chen
Keyword(s):  
Centrifugal Compressor ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Flow Area ◽  
Matching Process ◽  
Compressor Design ◽  
Component Matching ◽  
Key Aspects ◽  
Stage Efficiency

Matching of various components (impeller exducer to impeller inducer, and vaneless diffuser and volute to the impeller) in a centrifugal compressor is critical for stage performance, but this is often neglected during compressor design and selection. This paper studies the importance of flow area matching for stage efficiency and how this matching process can be performed rapidly following a few simple principles. Methods for achieving optimum efficiency under different compressor operating conditions and size constraint are proposed and compared with experimental results. The purpose of this work is to draw attention to the key aspects of the matching, and provide easy-to-use design guidelines for engineers.

scholarly journals Experience With an Integrated Centrifugal Compressor Design Procedure

1984 ◽  
Author(s):  
Gregory J. Holbrook ◽  
Joost J. Brasz
Keyword(s):  
Centrifugal Compressor ◽  
Integrated Design ◽  
Design Procedure ◽  
Internal Flow ◽  
Two Dimensional ◽  
One Dimensional ◽  
Flow Models ◽  
Compressor Design ◽  
Design Case Study ◽  
The One

An integrated centrifugal compressor design procedure is described consisting of several phases, each using progressively more complex models. After initially sizing the compressor overall geometry, the detailed geometry is first determined from a one-dimensional mean streamline model. This geometry is subsequently analyzed by more complex two-dimensional hub-to-shroud and blade-to-blade internal flow models. The one-dimensional mean streamline model is a key element in this integrated design procedure, since it links the results of the preliminary sizing model with the more sophisticated two-dimensional internal flow models. It quickly determines a complete (hub and shroud contour and blade angle distributions) compressor geometry from a desired blade loading distribution and the overall performance requirements of the compressor. After a presentation of this mean streamline design model and its assumptions, an impeller design case study is given using the integrated centrifugal compressor design procedure. From a comparison between the actual flow predictions of the various models it can be concluded that the major aerodynamic trends are properly described by the mean streamline model.

The Development, Application and Experimental Evaluation of a Design Procedure for Centrifugal Compressors

1978 ◽  
Vol 192 (1) ◽  
pp. 49-67 ◽  
Author(s):  
P. M. Came
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Design Procedure ◽  
Numerical Control ◽  
Compressor Design ◽  
Computer Based ◽  
Direct Generation ◽  
Experimental Rig ◽  
Development Application ◽  
Selection Of

A computer-based centrifugal compressor design procedure developed at the National Gas Turbine Establishment is described. The impeller design package includes a geometry modelling procedure, aerodynamic analysis, stress analysis, and the direct generation of data for manufacture by numerical control. The method of diffuser design incorporates analyses of the flow in the vaneless space and ‘semi-vaneless’ space adapted from a new performance prediction technique; published diffuser pressure recovery data are used in the selection of the diffuser channel geometry. The application of these methods to the design of a 6.5 pressure ratio centrifugal compressor stage is described. The experimental rig testing of this compressor has been used to evaluate the advantages offered by the new design procedure. By comparing the measured performance with that of an earlier compressor designed with less advanced techniques for the same aerodynamic duty, the advantages of the new design procedure are established.

The Application of a Computer-Aided Design Technique to the Conceptual Design of Turbochargers: Part A — Centrifugal Compressor Design and Turbine Matching

1996 ◽  
Author(s):  
A. Whitfield ◽  
Abu Hasan Abdullah
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Computer Aided Design ◽  
Pressure Ratio ◽  
Design Procedure ◽  
Compressor Design ◽  
Design Options ◽  
Turbine Design

In many turbomachinery applications a compressor is directly driven by a turbine; for turbocharger applications a centrifugal compressor is usually adopted which is generally driven by a radial flow turbine, although mixed flow or axial flow turbines are occasionally required. A non-dimensional design procedure is developed to provide the basic dimensions and blade angles of centrifugal compressor impellers, whilst accounting for the turbine conditions as assessed through the matching requirements. The design of the turbine is then considered further in Part B. The procedure can be applied for any desired compressor pressure ratio and target efficiency to develop an initial non-dimensional skeleton design. No other parameters are required from the initial specification and the design is developed non-dimensionally without recourse to empirical loss models and the associated uncertainties as the target efficiency must be specified. The procedure provides graphical information with respect to the impeller discharge conditions and inlet conditions from which the designer must select the most appropriate design. The screen graphics interface enables the designer to search across the design options; as this search is carried out numerical data are displayed and continuously up-dated to provide immediate information on which an infnrmed assessment can be based. In addition to the compressor design options which are provided the matching conditions for the drive turbine provides information, such as specific speed, non-dimensional mass flow rate and pressure ratio, relevant to the turbine design. Judgements with respect to the design options for the compressor can then be made with the consequences for the associated turbine design clearly in view. The non-dimensional design can be translated into an absolute design through the specification of the required mass flow rate and the inlet stagnation pressure and temperature.

scholarly journals A Contribution to the Study of the Design of an Industrial Centrifugal Compressor

1984 ◽  
Author(s):  
K. D. Papailiou ◽  
G. Bois
Keyword(s):  
Centrifugal Compressor ◽  
Design Procedure ◽  
Test Results ◽  
Interesting Point ◽  
Axial Part ◽  
Starting Point ◽  
Compressor Design ◽  
The Impact ◽  
Geometrical Dimensions ◽  
New Machine

The present work has had as a starting point an already existing high hub/tip ratio industrial centrifugal compressor design. An effort was undertaken to design a first new machine using theoretical methods, keeping, however, the overall geometrical dimensions, issued from the experience of the industry. The new design was manufactured and tested. The test results were found to be rather good, compared with the current industrial experience. Additionally, a second new design was undertaken which had as aim to diminish the axial part length, leaving untouched the hub/tip ratio. If this effort was successful, it would mean that the length of the shaft for a multistage arrangement could be diminished and, thus the need for such a high hub/tip ratio, resulting from the shaft diameter. It was found, actually, possible to reduced the axial length of the inducer by a factor of two, approximately. The second new design was manufactured and the resulting machine, when tested, was found to have the same performances as the first new design. A rather interesting point of the whole design procedure was the fact that a boundary layer calculation method was used in the blade-to-blade surface, which could take into account the influence of the Coriolis force and blade curvature on turbulence. The impact of this influence on the whole design was found to be decisive. The calculation procedure, the two designs and the overall test rests are described in the present work.

scholarly journals Direction for High-Performance Supercritical CO2 Centrifugal Compressor Design for Dry Cooled Supercritical CO2 Brayton Cycle

2019 ◽  
Vol 9 (19) ◽  
pp. 4057 ◽  
Author(s):  
Cho ◽  
Bae ◽  
Jeong ◽  
Lee ◽  
Lee
Keyword(s):  
Mach Number ◽  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Performance Test ◽  
Structural Integrity ◽  
Pressure Ratio ◽  
Compressibility Factor ◽  
Total Efficiency ◽  
Brayton Cycle ◽  
Compressor Performance

To overcome the degradation of the cycle efficiency of a supercritical carbon dioxide (S-CO2) Brayton cycle with dry cooling, this study proposes an improved design of an S-CO2 centrifugal compressor. The conventional air centrifugal compressor can achieve higher efficiency as backsweep angle increases. However, the structural issue restricts the maximum allowable angle (−50~−56°). In this study, an S-CO2 centrifugal compressor performance was examined while changing the backward sweep angle at impeller exit to study if the previous optimum backsweep angle for an air centrifugal compressor is still valid when the fluid has changed. It is shown through an analysis that an S-CO2 centrifugal compressor can achieve the highest efficiency at −70° backsweep angle, which is greater than the typical design value. The S-CO2 centrifugal compressor is less restricted from a structural integrity issue because it has low relative Mach number regardless of the low sound speed near critical point (Tc = 304.11 K, Pc = 7377 kPa). It is also shown in the paper that the variation of compressibility factor does not impact on its total to total efficiency since its Mach number is still lower than unity. Finally, it is also shown that a backward sweep impeller can achieve higher pressure ratio and operate stably in wider range as the mass flow rate is decreased. As further works, the suggested concept will be validated by the structural analysis and the compressor performance test.

Sensitivity Study of S-CO2 Compressor Design for Different Real Gas Approximations

2016 ◽  
Author(s):  
Jekyoung Lee ◽  
Seong Kuk Cho ◽  
Jae Eun Cha ◽  
Jeong Ik Lee
Keyword(s):  
Thermodynamic Property ◽  
Critical Point ◽  
Technology Development ◽  
Static Condition ◽  
Sensitivity Study ◽  
Ideal Gas ◽  
Brayton Cycle ◽  
Real Gas ◽  
Compressor Design ◽  
Turbomachinery Design

With the efforts of many researchers and engineers on the Supercritical CO2 (S-CO2) Brayton cycle technology development, the S-CO2 Brayton cycle is now considered as one of the key power technologies for the future. Since S-CO2 Brayton cycle has advantages in economics due to high efficiency and compactness of system, various industries have been trying to develop technologies on the design and analysis of S-CO2 Brayton cycle components. Among various technical issues on the S-CO2 Brayton cycle technology development, treatment of thermodynamic property near the critical point of S-CO2 is very important since the property shows non-linear variation which causes large error on design and analysis results for ideal gas based methodologies. Due to the special behavior of thermodynamic property of CO2 near the critical point, KAIST research team has been trying to develop a S-CO2 compressor design and analysis tool to reflect real gas effect accurately for better design and performance prediction results. The main motivation for developing an in-house code is to establish turbomachinery design methodology based on general equations to improve accuracy of design and analysis results for various working fluids including S-CO2. One of the key improvements of KAIST_TMD which is an in-house tool for S-CO2 turbomachinery design and analysis is the conversion process between stagnation condition and static condition. Since fluid is moving with high flow velocity in a compressor, the conversion process between stagnation and static condition is important and it can have an impact on the design and analysis results significantly. A common process for the conversion is based on the specific heat ratio which is typically a constant from ideal gas assumption. However, specific heat ratio cannot be assumed as a constant for the case of S-CO2 compressor design and analysis because it varies dramatically near the critical point. Thus, in this paper, sensitivity study results on the state condition conversion between stagnation and static conditions with different approaches will be presented and further analysis on impact of the selected approaches on the final impeller design results will be discussed.

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