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.

One-Dimensional and Three-Dimensional Design Strategies for Pressure Slope Optimization of High-Flow Transonic Centrifugal Compressor Impellers

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
A. Hildebrandt ◽  
T. Ceyrowsky
Keyword(s):  
Centrifugal Compressor ◽  
High Flow ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Angle Distribution ◽  
Compressor Stage ◽  
Design Point ◽  
One Dimensional ◽  
Centrifugal Compressor Stage ◽  
Transonic Centrifugal Compressor

This paper deals with the numerical and theoretical investigations of the effect of geometrical dimensions and one-dimensional (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 multipoint design process of a high flow coefficient impeller, comprising 545 computational fluid dynamics (CFD) designs is investigated in off-design and design conditions by means of Reynolds-averaged Navier–Stokes (RANS) simulation of an impeller with vaneless diffuser. For high flow coefficients of 0.16 < ϕdes < 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. This 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 toward 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 modeling 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 toward impeller stall operation.

Impact of Manufacturing Variability on the Aerodynamic Performance of a Centrifugal Compressor Stage With Curvilinear Blades

2016 ◽  
Author(s):  
A. Panizza ◽  
R. Valente ◽  
D. Rubino ◽  
L. Tapinassi
Keyword(s):  
Centrifugal Compressor ◽  
Sampling Methods ◽  
Aerodynamic Performance ◽  
High Flow ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Performance Variability ◽  
The Impact

The goal of the present study is to quantify the uncertainty in the aerodynamic performance of a centrifugal compressor stage with curvilinear impeller blades, due to impeller manufacturing variability. Impellers with curvilinear element blades allow a greater control of secondary flows with respect to impellers having ruled blades. High flow coefficient impellers for centrifugal compressors exhibit larger secondary flow than medium or low flow coefficient impellers, due to the stronger curvature of the flow path and the larger blade height for the same external diameter. Thus curvilinear blade impellers allow to improve the efficiency and range of high flow coefficient centrifugal compressor stages. As the design of these impellers is more complex than the design of ruled blade impellers, it is important to estimate the impact of the impeller manufacturing variability on the performance of the full stage. Sampling methods are often used in uncertainty propagation studies. However, sampling based approaches require a very large number of samples to have an accurate estimate of the performance uncertainty. 3D steady RANS computations are necessary to capture the impact of the geometric variability of the curvilinear blade impeller, on the stage performance. Thus, sampling methods would require an excessive computational time. In this work, the Polynomial Chaos Expansion (PCE) method with arbitrary probability distributions, implemented in DAKOTA, is used to reduce the number of runs required for the uncertainty quantification study. Manufacturing measurement data are been used to derive the histograms of the main impeller design parameters. From these histograms, numerically-generated orthogonal polynomials are computed for each parameter using a discretized Stieltjes procedure. Stochastic expansion methods such as PCE suffer from the curse of dimensionality, i.e., an exponential increase in the number of runs as the number of uncertain parameters increases. To mitigate the curse of dimensionality, sparse grids are used, which allow a drastic reduction of the number of runs. The results of the study show that the performance variability is small, thus our design with curvilinear element blades is robust with respect to impeller manufacturing variability. Using Sobol indices, we also rank the design parameters according to their impact on the performance variability.

Aerodynamic Design and Rig Test Validation of a High Flow Coefficient Process Centrifugal Compressor Stage

2021 ◽  
Author(s):  
Louis Larosiliere ◽  
Vishal Jariwala ◽  
Kapil Panchal
Keyword(s):  
Centrifugal Compressor ◽  
High Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Test Validation ◽  
Lapse Rate ◽  
Compressor Stage ◽  
Aerodynamic Design ◽  
Centrifugal Compressor Stage ◽  
Very High

Abstract Efficient and diametrically compact very high flow coefficient stages with wide operability are desirable for economic reasons in many process multistage centrifugal compressor applications. Such stages present special aerodynamic and mechanical design challenges. There is often a sizeable efficiency lapse rate as well as substantial reduction in useable operating range for traditional stages having design flow coefficients greater than 0.15 and moderate to high machine Mach numbers. This paper describes aerodynamic design and rig test validation of a very high flow coefficient (φ0 = 0.237) process centrifugal compressor stage. Some useful experience of the detailed design work required to navigate certain technical challenges and its rig test validation are reflected in the manuscript. A relatively high machine Mach number (MU ∼ 0.878) mixed-flow shrouded impeller matched with a curved radial vaneless diffuser and return channel was developed. Test results confirmed that the principal aerodynamic design intents were met or exceeded. A sensible design strategy guided by a well-anchored design method is shown to successfully extend an existing stage portfolio to very high-flow coefficients for multistage process centrifugal compressor applications.

Analytical and Test Experiences Using a Rib Diffuser in a High Flow Centrifugal Compressor Stage

2001 ◽  
Author(s):  
James M. Sorokes ◽  
Jason A. Kopko
Keyword(s):  
Centrifugal Compressor ◽  
Quantitative Agreement ◽  
High Flow ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Centrifugal Compressor Stage ◽  
Qualitative And Quantitative

The paper addresses the use of a rib style (partial height) vaned diffuser to improve the flowfield downstream of a high flow coefficient centrifugal impeller. Empirical and analytical (3-D CFD) results are presented for both the original vaneless diffuser and the replacement rib configuration. Comparisons are made between the CFD results and the data obtained through single stage rig (SSTR) testing. Comments are offered regarding the qualitative and quantitative agreement between the empirical and analytical results.

Experimental and Numerical Investigation of the Flow in a Vaneless Diffuser of a Centrifugal Compressor Stage. Part 1: Experimental Investigation

2005 ◽  
Vol 219 (10) ◽  
pp. 1053-1059 ◽  
Author(s):  
T Sato ◽  
J M Oh ◽  
A Engeda
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Boundary Layers ◽  
Centrifugal Compressor ◽  
High Flow ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Centrifugal Compressor Stage ◽  
Very High

The flow in a radial vaneless diffuser downstream of a centrifugal compressor is highly complex, as the flow is turbulent, unsteady, viscous, and three-dimensional. Depending on the initial state of the end-wall boundary layers and the diffuser length, the flow may become fully developed or may separate from one of the walls. Therefore, to improve the diffuser performance, it is important to understand the flow field in the diffuser in detail. As the diffuser width is generally very small for most radial stages and an adverse pressure gradient exists, secondary flows are generated, making the flow fields more complicated. In addition, skewed boundary layers form on the wall surfaces. As flowrate is reduced, the flow field becomes more complicated and leads to rotating stall. This article presents detailed flow measurements in a vaneless diffuser of a centrifugal compressor stage with a very high flow coefficient radial impeller. Usually, centrifugal compressors with radial impellers are designed in the flow coefficient (ϕ) range ϕ = 0.01 - 0.16. Often, the need arises to design higher flow coefficient, ϕ, radial stages. Detailed measurements were carried out in the vaneless diffuser at seven radial positions downstream of a radial impeller designed for a very high flow coefficient of ϕ = 0.2. The experimental investigation was carried at four rotational speeds 13 000, 15 500, 18 000, and 20 500 r/min, but only the result of 20 500 r/min at near-design-point flowrate (5.11 kg/s) is reported in this article.

Experimental and Numerical Investigation of the Flow in a Vaneless Diffuser of a Centrifugal Compressor Stage. Part 2: Numerical Investigation

2005 ◽  
Vol 219 (10) ◽  
pp. 1061-1068 ◽  
Author(s):  
T Sato ◽  
J M Oh ◽  
A Engeda
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
High Flow ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Flow Measurements ◽  
Centrifugal Compressor Stage ◽  
Improved Performance ◽  
Very High

As user demands grew for improved performance and more reliable equipment and as compressor vendors sought improved analytical and design methodologies, the application of computational fluid dynamics (CFD) in the industrial world became a necessity. Fortunately, large increases in available, economic computing power together with development of improved computational methods now provide the industrial designer with much improved analytic capability. As CFD algorithms and software have continued to be developed and refined, it remains essential that validation studies be conducted in order to ensure that the results are both sufficiently accurate and can be obtained in a robust and predictable manner. Part I of this paper presented detailed flow measurements in a vaneless diffuser of a centrifugal compressor stage with a very high flow coefficient radial impeller, where measurements were carried out in the vaneless diffuser at seven radial positions downstream of the radial impeller designed for a very high flow coefficient of ϕ = 0.2. This paper, Part II, attempts to verify and validate the results numerically.

scholarly journals Influence of blade geometry on secondary flow development in a transonic centrifugal compressor

2018 ◽  
Vol 2 ◽  
pp. I1RSJ3 ◽  
Author(s):  
Moritz Mosdzien ◽  
Martin Enneking ◽  
Alexander Hehn ◽  
Daniel Grates ◽  
Peter Jeschke
Keyword(s):  
Secondary Flow ◽  
Centrifugal Compressor ◽  
Large Scale ◽  
Optimization Methods ◽  
Experimental Investigations ◽  
Compressor Stage ◽  
Impeller Blade ◽  
Flow Development ◽  
Transonic Centrifugal Compressor ◽  
Increasing Demand

Due to the increasing demand for higher efficiencies of centrifugal compressors, numerical optimization methods are becoming more and more relevant in the design process. To identify the beneficial features of a numerical optimized compressor design, this paper analyses the influence of arbitrary blade surfaces on the loss generation in a transonic centrifugal compressor. The paper therefore focuses on an analysis of the secondary flow development within the impeller blade passages. To do this, steady simulations were performed on both a baseline and an optimized blade design. Two distinct design features of the optimized compressor stage were identified, which lead to a more homogenous impeller exit flow and thus to an increase in total-to-static efficiency of 1.76% points: the positive lean in the near-tip region and the positive blade curvature in the rear part of the optimized impeller. Furthermore, through extensive experimental investigations conducted on a large scale test rig it has been possible to prove the particular impeller outflow characteristics of the baseline compressor stage.

Numerical Investigation of the Unsteady Flow Inside a Centrifugal Compressor Stage With Pipe Diffuser

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Daniel R. Grates ◽  
Peter Jeschke ◽  
Reinhard Niehuis
Keyword(s):  
Experimental Data ◽  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Measurement Techniques ◽  
Navier Stokes ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Transonic Centrifugal Compressor ◽  
Computational Fluid Dynamics Cfd ◽  
The Subject

The subject of this paper is the investigation of unsteady flow inside a transonic centrifugal compressor stage with a pipe-diffuser by utilizing unsteady 3D Reynolds-averaged Navier–Stokes simulations (unsteady 3D URANS). The computational fluid dynamics (CFD) results obtained are compared with detailed experimental data gathered using various steady and unsteady measurement techniques. The basic phenomena and mechanisms of the complex and highly unsteady flow inside the compressor with a pipe-diffuser are presented and analyzed in detail.

Surge Inception in a Transonic Centrifugal Compressor Stage

2011 ◽  
Author(s):  
Isabelle Tre´binjac ◽  
Nicolas Bulot ◽  
Xavier Ottavy ◽  
Nicolas Buffaz
Keyword(s):  
Centrifugal Compressor ◽  
Short Wavelength ◽  
Stokes Equations ◽  
Pressure Sensors ◽  
Experimental Investigations ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Choked Flow ◽  
Centrifugal Compressor Stage ◽  
Transonic Centrifugal Compressor

Numerical and experimental investigations were conducted in a transonic centrifugal compressor stage composed of a backswept splittered unshrouded impeller and a vaned diffuser. Unsteady 3D simulations were performed with the code elsA that solves the turbulent averaged Navier-Stokes equations, at three operating points: choked flow, peak efficiency and near surge. Unsteady pressure measurements up to 150 kHz were carried out in the entry zone of the vaned diffuser (in the vaneless space and in the semi-vaneless space) when the compressor came into surge. These static pressure sensors were mounted on the shroud enwall. The paper focuses on the vaneless and semi-vaneless space where the surge originates. A detailed analysis of the flow pattern coming from the unsteady computations from choked flow towards surge led to identify the physical mechanisms involved in the surge inception. It is shown that, when approaching surge, the flow is destabilized by a severe modification of the shock system in the vaned diffuser inlet. The first perturbation is acquired from the transducer located just upstream of the shock foot (i.e. on the vane suction side surface), indicating a movement of the shock towards the vaneless space. This perturbation travels upstream and leads to the strongest short-wavelength perturbation acquired from the transducer located just upstream of the vane leading edge. This strongest short-wavelength perturbation which level may reach almost four times the mean exit pressure value triggers the full scale instability.

Flow Studies on a Centrifugal Compressor Stage With Low Solidity Diffuser Vanes

2002 ◽  
Author(s):  
Prasad Mukkavilli ◽  
G. Rama Raju ◽  
A. Dasgupta ◽  
G. V. Ramana Murty ◽  
K. V. Jagadeshwar Chary
Keyword(s):  
Centrifugal Compressor ◽  
Design Flow ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Centrifugal Compressor Stage ◽  
Setting Angle ◽  
Set Up ◽  
Flow Improvement ◽  
Stagger Angle

Diffusers are found to play a significant role in the performance of centrifugal compressors. Extensive studies have been in progress in various research laboratories for improvement of performance with various types of diffusers. One such effort for study of performance of a centrifugal compressor stage with Low Solidity Diffuser (LSD) vanes is presented in this paper. The study was conducted at a tip mach number of 0.35. An exclusive test rig was set up for carrying out these flow studies. The LSD vane is formed using standard NACA profile with marginal modification at the trailing edge region. The study encompasses the variation of setting angle of the LSD vane and the vane solidity. The effect of solidity and the setting angle on overall stage performance is evaluated in terms of flow coefficient, head coefficient and efficiency normalised with respect to these parameters for the case of vaneless diffuser at design flow. Improvement in performance as well as static pressure recovery was observed with LSD as compared to vaneless diffuser configuration. It is concluded from these studies that there is an optimum solidity and stagger angle for the given stage with LSD vanes for the chosen configuration.

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