James M. Sorokes

Investigation of the Circumferential Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute

The paper describes experimental and computational fluid dynamics analyses of the non-uniform static pressure distortion caused by the discharge volute in a high pressure, centrifugal compressor. The experiments described in this paper were done using a heavily instrumented gas re-injection compressor operating at over 6000 psia discharge. Instrumentation was installed to measure static, total, and dynamic pressure as well as impeller strain and mechanical vibrations. A brief description of the compressor and instrumentation are provided. Concurrent with the experimental work, CFD runs were completed to study the reasons for the pressure nonuniformity. The CFD pressure profile trends agreed well with the experimental results and provided analytical corroboration for the conclusions drawn from the test data. Conclusions are drawn regarding: a) the response of the non-uniformity to changing flow rates; b) the extent to which the non-uniformity can be detected upstream of the impeller; and c) the mechanical influences of the nonuniformity on the impellers.

On the use of five-hole probes in the testing of industrial centrifugal compressors

This paper addresses the use of 5-hole probes in the testing of industrial centrifugal compressors. The 5-hole probes utilized for this work are of the conical-tip type and were used in a non-nulling configuration (i.e., the probes do not need to be rotated or moved in any way during the tests). These 5-hole probes proved to be fairly robust, making them practical for a nonlaboratory setting such as an industrial multistage compressor test stand. A discussion of 5-hole probes and how they function is provided, including an overview of the mathematical formulations and calibrations required to translate the pressure data gathered from the 5 holes into static and total pressures, velocities and flow angles. A method to transform these variables from a probe-based coordinate system to a machine-based coordinate system is also presented and schematics of this process are provided to aid the readers understanding. The testing performed on a prototype multistage centrifugal compressor using 5-hole probes is also discussed, showing that the probes provided valuable insight into the flowfield exiting the impellers and at the return bend. The hub-to-shroud velocity profile exiting an impeller was found to be more skewed than expected and was contributing to poor performance in the downstream stationary components. The measured flowfield from one of the tests is also compared against 3-D CFD results and comments are offered regarding the agreement between the analytical and measured results. Advantages and disadvantages of 5-hole probes as compared to more conventional instrumentation are presented. Finally conclusions are drawn regarding the value of 5-hole probe data in the development and/or troubleshooting of high performance turbomachinery and in the validation/calibration of design and analysis tools.

Full-Scale Aerodynamic And Rotordynamic Testing For Large Centrifugal Compressors.

This paper describes a full-scale, flexible test vehicle designed and built by the original equipment manufacturer (OEM) to validate the aerodynamic and mechanical performance of large compressors for a variety of applications. This paper provides a description of the test vehicle as well as mechanical and aerodynamic performance data gathered during testing of the vehicle.

The Influence of Low Solidity Vaned Diffusers on the Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute

The paper is a sequel to an earlier work by Sorokes et al. 1998, “Investigation of the Circumferential Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute.” The earlier work described experimental and computational fluid dynamics analyses of the non-uniform static pressure distortion caused by the discharge volute in a high pressure, centrifugal compressor with vaneless diffusers. This paper describes additional testing and analytical work done using low solidity vaned diffusers (LSD’s) in place of select vaneless diffusers to determine the alternate diffuser’s effectiveness in eliminating or reducing the magnitude of the non-uniform pressure field. As in the earlier studies, the experiments described in this paper were done using a heavily instrumented gas re-injection compressor operating at over 6000 psia discharge pressure. Instrumentation was installed to measure static, total, and dynamic pressure as well as impeller strain and mechanical vibrations. A brief description of the compressor and instrumentation are provided.Concurrent with the experimental work, CFD runs were completed to study the effect of the alternate vaned diffusers. The CFD pressure profile trends agreed well with the experimental results and provided analytical corroboration for the conclusions drawn from the test data.Conclusions are drawn regarding: a) the effectiveness of the LSD’s on the pressure non-uniformity; b) the associated effects on the measured dynamic strains in the impellers; and c) the usefulness of computational fluid dynamics (CFD) in assessing the aerodynamic forces associated with the non-uniformity.© 2000 ASME

Recent Experiences In Full Load Full Pressure Shop Testing Of A High Pressure Gas Injection Centrifugal Compressor.

This paper presents recent full load, full pressure field gas (ASME PTC-10 Class 1) test experiences and resolution of problems encountered on a high pressure barrel compressor. It is broken into three major sections. The first section includes a description of how the compressor is being applied as part of a high pressure gas injection train at Prudhoe Bay, Alaska. The second section describes the methods used to determine the full load, full pressure test configuration, test gas medium, and operating conditions. The final section discusses the actual test chronology and traces the methods used to identify the sources of the two vibration anomalies. Finally, comments are included regarding benefits of a cooperative atmosphere between the vendor and the end user when resolving problems.

High Inlet Relative Mach Number Centrifugal Compressor Impeller Design

This document presents an overview of impeller inlet relative Mach number, how the parameter is calculated, and its importance as an indicator of impeller performance. Comments are also offered regarding the comparison of inlet relative Mach numbers obtained from different compressor vendors. A sample impeller is used to illustrate the various methods used to calculate the inlet relative Mach number. Test data for that impeller is also offered to indicate the performance map achievable with high Mach number designs. Please note that this document is not intended to be an all-inclusive treatment of the subject; rather, it summarizes the OEM’s methodologies and perspective.Copyright

The Influence of Shroud Curvature and Other Related Factors on Impeller Performance Characteristics

The paper discusses a computational fluid dynamics (CFD) study done to assess the influence of cover or shroud curvature on impeller performance. The paper describes the various designs and the CFD and finite element analyses (FEA) methods used. Aerodynamic and mechanical analysis results are presented for four impellers of varying cover curvature and axial length. Comments are offered regarding the mechanical issues that must be considered when increasing the length of impellers.Copyright

CENTRIFUGAL STAGE PERFORMANCE PREDICTION AND VALIDATION FOR HIGH MACH NUMBER APPLICATIONS

Steve Kowalski is an Aero-Thermo Engineer in the Research and Development Department of DresserRand. His responsibilities include the design, development and analysis of aerodynamic components of centrifugal compressors. He has been employed at Dresser-Rand since 2007. He holds a B.S. degree from Michigan State University (Mechanical Engineering, 2002) and an M.S. degree from Michigan State University (Mechanical Engineering, 2005). Prior to joining Dresser-Rand, he worked as a teaching/research assistant at Michigan State University.

Modeling And Prediction Of Sidestream Inlet Pressure For Multistage Centrifugal Compressors

It is common for some compressors in certain applications to have one or more incoming sidestreams that introduce flow other than at the main inlet to mix with the core flow. In most cases, the pressure levels at these sidestreams must be accurately predicted to meet contractual performance guarantees. The focus of this paper is the prediction of sidestream flange pressure when the return channel outlet conditions are provided. A model to predict the impact of local curvature in the mixing section is presented and compared with both Computational Fluid Dynamics work and measured test data.

Centrifugal Compressor Evolution

Engineer with 34 years of experience at Dresser-Rand Company, in Olean, New York. He is involved in centrifugal compressor research and development testing. He previously spent 28 years in the Aerodynamics Group, becoming the Supervisor of Aerodynamics in 1984 and promoted to Manager of Aero/Thermo Design Engineering in 2001. During Mr. Sorokes’ time in the Aerodynamics Group, his primary responsibilities included the development, design, and analysis of all aerodynamic components of centrifugal compressors. His professional interests include: aerodynamic design, aeromechanical phenomenon (i.e., rotating stall), and other aspects of large centrifugal compressors. Mr. Sorokes graduated from St. Bonaventure University (1976). He is a member of AIAA, ASME, and the ASME Turbomachinery Committee. He has authored or coauthored more than 35 technical papers and has instructed seminars and tutorials at Texas A&M and Dresser-Rand. He currently holds two U.S. Patents and has two other patents pending.