The Performance Evaluation of Variations of Diffuser Geometry of the Centrifugal Compressor in a Marine Engine (70MW) Turbocharger

2008 ◽  
Author(s):  
Hong-Won Kim ◽  
Jong-Il Park ◽  
Seung-Hyup Ryu ◽  
Seong-Wook Choi ◽  
Sang-Hak Ghal
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Prediction Method ◽  
Pressure Recovery ◽  
Vaned Diffuser ◽  
High Pressure Ratio ◽  
Work Input ◽  
Interior Flow ◽  
Cfd Analyses

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on modified NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off-design behavior of three different types of diffusers, given by mean-line prediction, was investigated using CFD results and selected the NACA 65 diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.

The Performance Evaluation With Diffuser Geometry Variations of the Centrifugal Compressor in a Marine Engine (70MW) Turbocharger

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Hong-Won Kim ◽  
Jong-II Park ◽  
Seung-Hyup Ryu ◽  
Seong-Wook Choi ◽  
Sang-Hak Ghal
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Fluid Dynamic ◽  
Pressure Ratio ◽  
Prediction Method ◽  
Pressure Recovery ◽  
Vaned Diffuser ◽  
High Pressure Ratio ◽  
Work Input ◽  
Cfd Analyses

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage; for energy efficiency, it is important to recover as much of this as possible. This is the function of the diffuser, which follows the impeller. Effective pressure recovery downstream of an impeller is very important in order to realize a centrifugal compressor with a high efficiency and a high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step in order to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances change as the vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and compared with its results. The first vaned diffuser type is based on a modified NACA airfoil, the second is a channel diffuser, and the third is a conformal transformation of NACA 65-(4A10)06 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. Computational fluid dynamic (CFD) analyses and a detailed interior flow pattern study have been done. In this study, the off-design behavior of three different types of diffusers, given by the mean-line prediction, was investigated using CFD results and the NACA 65 diffuser geometry, which satisfies a wider operating range and has a higher pressure recovery than the others, was selected. The numerical results were compared with experimental data for validation and showed good agreement.

The Numerical Study on the Performance Evaluations and Flow Structures for the Diffuser of Centrifugal Compressor in a Marine Engine Turbocharger

2006 ◽  
Author(s):  
Hong-Won Kim ◽  
Seung-Hyup Ryu ◽  
Jong-Il Park ◽  
Sang-Hak Ghal ◽  
Ji-Soo Ha
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Prediction Method ◽  
Pressure Recovery ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Marine Engine ◽  
High Pressure Ratio

The centrifugal compressor of marine engine turbocharger is composed of impeller, 1st vaneless diffuser, vaned diffuser, 2nd vaneless diffuser and volute casing. An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. Mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off design behavior of three different type of diffuser, given by mean-line prediction, was investigated using CFD results and selected best diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.

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.

scholarly journals Meridional Considerations of the Centrifugal Compressor Development

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Angle Distribution ◽  
High Pressure Ratio ◽  
Structure Reliability ◽  
Compressor Performance ◽  
Meridional Profile ◽  
Compressor Efficiency ◽  
Wide Operating

Centrifugal compressor developments are interested in using optimization procedures that enable compressor high efficiency and wide operating ranges. Recently, high pressure ratio and efficiency of the centrifugal compressors require impeller design to pay attention to both the blade angle distribution and the meridional profile. The geometry of the blades and the meridional profile are very important contributions of compressor performance and structure reliability. This paper presents some recent studies of meridional impacts of the compressor. Studies indicated that the meridional profiles of the impeller impact the overall compressor efficiency and pressure ratio at the same rotational speed. Proper meridional profiles can improve the compressor efficiency and increase the overall pressure ratio at the same blade back curvature.

Aerodynamics of a Transonic Centrifugal Compressor Impeller

2002 ◽  
Author(s):  
Seiichi Ibaraki ◽  
Tetsuya Matsuo ◽  
Hiroshi Kuma ◽  
Kunio Sumida ◽  
Toru Suita
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Centrifugal Compressor ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
Flow Distortion ◽  
Flow Measurements ◽  
High Pressure Ratio ◽  
Compressor Impeller

High pressure ratio centrifugal compressors are applied to turbochargers and turboshaft engines because of their small dimensions, high efficiency and wide operating range. Such a high pressure ratio centrifugal compressor has a transonic inlet condition accompanied with a shock wave in the inducer portion. It is generally said that extra losses are generated by interaction of the shock wave and the boundary layers on the blade surface. To improve the performance of high pressure ratio centrifugal compressor it is necessary to understand the flow phenomena. Although some research works on transonic impeller flow have been published, some unknown flow physics are still remaining. The authors designed a transonic impeller, with an inlet Mach number is about 1.3, and conducted detailed flow measurements by using Laser Doppler Velocimetry (LDV). In the result the interaction between the shock wave and tip leakage vortex at the inducer and flow distortion at the downstream of inducer were observed. The interaction of the boundary layer and the shock wave was not observed. Also computational flow analysis were conducted and compared with experimental results.

Numerical Investigation of Low Solidity Vaned Diffuser Performance in a High-Pressure Centrifugal Compressor: Part I — Influence of Vane Solidity

2007 ◽  
Author(s):  
JongSik Oh ◽  
Giri L. Agrawal
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Limited Range ◽  
Design Flow ◽  
Design Parameters ◽  
Moderate Pressure ◽  
Vaned Diffuser ◽  
High Pressure Ratio ◽  
Wide Operating

The LSD (Low Solidity Diffuser) is becoming popular in most industrial centrifugal compressor designs because it is found to offer a wide operating flow range while maintaining a similar level of efficiency as in case of conventional vaned diffusers. Most related studies have been for low or moderate pressure ratio machines providing a limited range of design information for high-pressure ratio compressors. As a first step forward information of design parameters, a numerical CFD investigation was applied to a high-pressure industrial centrifugal compressor of design total-to-static pressure ratio of 4.0 with LSDs of NACA65-series profiles whose solidity varies from 0.452 to 0.968 in 5 cases with all the other design parameters fixed. Near design flow, the case of 0.839 solidity has the highest isentropic total-to-static efficiency. Other performance changes are accordingly investigated.

Study of Geometric Parameter Influence on Fishtail Pipe Diffuser Performance

2016 ◽  
Author(s):  
Ge Han ◽  
Xingen Lu ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
Chengwu Yang ◽  
...  
Keyword(s):  
High Pressure ◽  
Geometric Parameter ◽  
Centrifugal Compressor ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Critical Parameters ◽  
Complex Flow ◽  
High Pressure Ratio ◽  
Area Distribution ◽  
Parameter Influence

Centrifugal compressor stages with pipe diffusers are characterized by their high efficiency, especially under high pressure ratio conditions. Although it is believed that pipe diffuser scallop leading edge formed by the intersection of two pipes is a critical point in pipe diffuser design, there is another crucial and influential point, which is how to guide and decelerate the flow from pipe diffuser throat to the inlet of combustor chamber, with minimum loss and maximum outflow uniformity. Fishtail pipe diffuser passage is employed by Pratt&Whitney to connect impeller exit and combustor chamber inlet due to its improved performance characteristics. However, only a few comprehensive results have been published describing the complex flow patterns in the fishtail diffuser. Therefore, in the present work fishtail pipe diffusers with several different geometries were designed for a pressure ratio 8.3 centrifugal compressor stage used on a small turbo engine, aiming at providing detailed understanding of geometric parameter influence on fishtail pipe diffuser performance and flow mechanisms in complex fishtail passages. Cone length, streamwise area distribution and centerline shape are critical parameters of a fishtail pipe diffuser. Hence, parametric studies on fishtail pipe diffuser of this high pressure ratio centrifugal compressor by varying cone length, area distribution and centerline shape of the diffuser passage were performed using a state-of-the-art multi-block flow solver. These three parameters were changed respectively, while keeping other parameters unchanged. Detailed analysis was done to identify the influence on flow field in fishtail diffuser passage when these parameters were changed. It was found that increase of fishtail diffuser cone length could alleviate separation in diffuser passage, thus compressor performance is improved. And linear area distribution along passage centerline could build a more efficient fishtail pipe diffuser. A trumpet-shaped or bell-shaped passage is more likely to make flow separate. The centerline is of vital importance for a fishtail passage and it was built by two lines tangent to an ellipse in this work. It was modified by changing major and minor axes of the ellipse. Stage total pressure ratio and adiabatic efficiency maps for varying fishtail passage centerlines were obtained by numerical method, which indicate that there is an optimum range for both axes to make the fishtail pipe diffuser have a better performance. Through these works, the geometric parameter influence on fishtail diffuser performance was uncovered and physical insight into complex flows in fishtail pipe diffuser passage was obtained to give some guidelines on diffusing system design with fishtail pipe diffuser.

The Matching of a Vaned Diffuser With a Radial Compressor Impeller and Its Effect on the Stage Performance

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Michael Casey ◽  
Daniel Rusch
Keyword(s):  
Test Data ◽  
Pressure Ratio ◽  
Prediction Method ◽  
Design Guidelines ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Radial Compressor ◽  
High Pressure Ratio ◽  
Wide Range ◽  
Matching Equation

The matching of a vaned diffuser with a centrifugal impeller is examined with a one-dimensional (1D) analysis combined with extensive experimental data. A matching equation is derived to define the required throat area of the diffuser relative to the throat area of the impeller at different design speeds and validated by comparison with a wide range of compressor designs. The matching equation is then used to give design guidelines for the throat area of vaned diffusers operating with impellers at different tip-speed Mach numbers. An analysis of test data for a range of high pressure ratio turbocharger compressor stages is presented in which different matching between the diffuser and the impeller has been experimentally examined. The test data includes different impellers with different diffuser throat areas over a wide range of speeds. It is shown that the changes in performance with speed and diffuser throat area can be explained on the basis of the tip-speed Mach number which causes both the diffuser and impeller to choke at the same mass flow. Based on this understanding, a radial compressor map prediction method is extended to include this parameter, so that more accurate maps for matched and mismatched vaned diffusers can be predicted.

Study of the Flow in Centrifugal Compressor

2009 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Method ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Low Flow ◽  
High Pressure Ratio ◽  
Surge Margin

An unshrouded centrifugal compressor would give up clearance very large in relation to the span of the blades, because centrifugal compressors produce a sufficiently large pressure rise in fewer stages. This problem is more acute for a low flow high-pressure ratio impeller. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range for a centrifugal compressor is a great challenge. This paper describes a new development of high efficiency and a large surge margin flow coefficient of 0.145 centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in this centrifugal compressor design. The new compressor has three main parts: impeller, a low solidity diffuser and volute. The tip clearance is under a special consideration in this design to allow impeller insensitiveness to the clearance. A three-dimensional low solidity diffuser design method is proposed and applied to this design. This design demonstrated to be successful to extend the low solidarity diffusers to high-pressure ratio compressor. The design performance range showed the total to static efficiency of the compressor being about 85% and stability range over 35%. The experimental results showed that the test results are in good agreement with the design.

The Matching of a Vaned Diffuser With a Radial Compressor Impeller and its Effect on the Stage Performance

2014 ◽  
Author(s):  
Michael Casey ◽  
Daniel Rusch
Keyword(s):  
Test Data ◽  
Pressure Ratio ◽  
Prediction Method ◽  
Design Guidelines ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Radial Compressor ◽  
High Pressure Ratio ◽  
Wide Range ◽  
Matching Equation

The matching of a vaned diffuser with a centrifugal impeller is examined with a one-dimensional (1D) analysis combined with extensive experimental data. A matching equation is derived to define the required throat area of the diffuser relative to the throat area of the impeller at different design speeds and validated by comparison with a wide range of compressor designs. The matching equation is then used to give design guidelines for the throat area of vaned diffusers operating with impellers at different tip-speed Mach numbers. An analysis of test data for a range of high pressure ratio turbocharger compressor stages is presented in which different matching between the diffuser and the impeller has been experimentally examined. The test data includes different impellers with different diffuser throat areas over a wide range of speeds. It is shown that the changes in performance with speed and diffuser throat area can be explained on the basis of the tip-speed Mach number which causes both the diffuser and impeller to choke at the same mass flow. Based on this understanding, a radial compressor map prediction method is extended to include this parameter, so that more accurate maps for matched and mismatched vaned diffusers can be predicted.

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