Mark J. Kuzdzal

Rotordynamic Stability Measurement During Full-Load, Full-Pressure Testing Of A 6000 Psi Reinjection Centrifugal Compressor.

Full-load, full-pressure rotordynamic stability measurements were conducted on a seven-stage, back-to-back centrifugal compressor. To validate rotordynamic predictions, the rotor was excited while operating at full load and full pressure during factory testing. This was accomplished through means of a magnetic bearing, which was attached to the free end of the rotor. This device injected an asynchronous force into the rotor system to excite the first forward whirling mode. This technique measures the rotor’s logarithmic decrement (log dec), which indicates the level of stability, or damping, in the rotor. The device is designed to be nonintrusive to the original dynamics of the rotor and may be easily installed/removed on the test stand. This paper discusses the techniques used to measure the rotordynamic stability from a fullload, full-pressure test of a 6000 psi reinjection compressor. The results demonstrate the effectiveness of swirl brakes and damper seals in producing a compressor that becomes more stable as discharge pressure increases. This approach to compressor design is in stark contrast to traditional designs in which the stability degrades with increasing pressure, ultimately leading to rotordynamic instability. This technology ensures trouble-free startup and operation of these compressors in the field, minimizing risk for the end-user.

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.

Noise Control of an 11,000 Horsepower Single Stage Pipeline Centrifugal Compressor

Centrifugal compressors installed for natural gas transmission produce significant noise. Many of these compressors have a single impeller with high power input. Large diameter pipes are typically connected to the inlet and discharge of the compressors. As a result, a single stage pipeline compressor not only has a strong noise source but also has a large structure to radiate noise to the ambient. As pipeline compressors are installed close to residential areas, community noise complaints become a concern to pipeline companies and compressor manufacturers. To make compressors more environmentally friendly, duct resonator acoustic arrays have been developed to lower the acoustic energy emanating to the environment. This paper focuses on acoustic technology applied to a single stage pipeline direct-inlet compressor with a 28-inch diameter impeller. The effectiveness of the duct resonator acoustic array is described in this paper with field noise data from three different tests — one test before the compressor was retrofitted with the resonator arrays and two tests afterwards. A baseline noise test was first conducted in January 2002 to obtain the compressor noise signature and to establish the baseline noise data. Using the baseline noise data, duct resonator arrays were designed, manufactured, and retrofitted into the compressor to reduce noise. A second test was performed in October 2002, just after the upgrade, to check the effectiveness of the resonator arrays. The compressor was tested under six different operating points (two speed lines at three points per speed line) from overload to surge during both the first and the second tests. In February 2004, fifteen months after the second test, a third noise test of the same unit was performed to assess the effectiveness of the resonator array over time. The purpose of this third test was to identify if there was any degradation of noise attenuation due to fouling. A comparison of the data taken on the third noise survey with those measured on the second noise survey indicated there was no change in noise levels. After the third test, the unit was disassembled for an aerodynamic retrofit. At this point, the array was inspected and found to be clean. This indicates that the duct resonator array has been performing well since its installation. Fouling has not been detected and the array performance did not degrade over time. This paper provides acoustic data for all three field tests conducted with a focus on the technology applied to reduce the acoustic energy of this centrifugal compressor.© 2007 ASME

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.

Minimizing Pressure Pulsations in a Centrifugal Compressor

As a centrifugal impeller rotates, it converts shaft mechanical power into fluid power - static and dynamic pressure. As a result of this aerodynamic process, the flow in the compressor has steady and unsteady components. The latter is undesirable as it can manifest itself as pressure pulsations that consequently cause machine vibration, noise and alternating stress in the impeller. Typically a centrifugal compressor has strong pressure pulsation amplitude at the blade passing frequency and /or its harmonics. The installation of diffuser vanes to enhance the compressor peak efficiency further increases the magnitude of these pressure pulsations. Dominant pulsations typically occur at the impeller exit and diffuser entrance region, and are a major excitation source to a centrifugal compressor and its associated piping. This internal aeroacoustic energy source propagates pressure waves through various paths in the compressor system and eventually couples to the structure and impeller and causes structural vibration and sound radiation. This paper focuses on a technique to control pressure pulsations in a centrifugal compressor. Two examples along with test data will be discussed.Copyright

Discussion Group T07: Advanced Topics in Centrifugal Compressor Design

Suggested Topics: • Meeting current rotordynamics stability standards • High flow coefficient/Mach number impellers • Complicated high pressure gas properties. E.g., CO2, acid gas, H2S • Validity of CFD modeling • Modern manufacturing/forming methodologies • Simulation and dynamic process modeling • Handling of Chlorides in sour/acid gas applications, including piping; end-user strategies • Materials for compressors in extreme acid/sour gas applications with and without chlorides • Hermetically-sealed compression

Diagnosis and Solution of High Noise and Vibration Issues After a Propylene Refrigeration Compressor Re-Rate

High noise and vibration levels were experienced in a propylene refrigeration centrifugal compressor piping system. The noise and vibration problems began after an ethylene plant re-rate that accomplished its aero-thermal performance expectations. The high noise and vibration was measured as a discrete source with the peak noise and vibration frequency occurring near 480 Hz. Fatigue failures of small bore piping appurtenances had also occurred. Comprehensive site measurements were performed to diagnose the root cause of the noise and vibration. In-pipe pressure pulsations, piping vibration, pipe wall strain levels, external sound pressure, and pipe surface sound intensity were measured to identify the excitation source. Analysis of the measured data indicated that the 480 Hz acoustic source originated within the compressor, upstream of the side stream discharge nozzle. Typically centrifugal compressors tend to produce dominant noise at the blade passing frequency and its harmonics. The blade passing frequency (1544 Hz) was well above the 480 Hz measured dominant frequency. Further analysis of the data lead to the belief that an acoustic standing wave inside the compressor flow path was responsible for the noise and vibration. This paper will discuss the source of the issue, how the issue was diagnosed, and what solution was implemented to address the issue. A considerable amount of data gathering and analysis will be described in the paper to support the diagnosis of the root cause of the noise and vibration. After the excitation source was correctly identified, a duct resonator array was designed and installed upstream of the discharge pipe to minimize the acoustic energy entering the pipe. The noise and vibration solution was validated with actual field data measured before and after the installation of the duct resonator array.Copyright