Methods for and Benefits of Centrifugal Compressor Design Audits

2003 ◽  
Author(s):  
Robert J. McKee ◽  
Justin R. Hollingsworth ◽  
Anthony J. Smalley
Keyword(s):  
Torsional Vibration ◽  
High Speed ◽  
Performance Test ◽  
Equations Of State ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Design Stage ◽  
Flow Angle ◽  
Process Gas

As gas pipeline and industrial compressors become more powerful and more complex, it has become beneficial to conduct technical audits of these machines in the design stage. Detailed analysis of critical or advanced compressors by independent evaluators have identified operating limitations, resonant responses, potential vibrations, weak components, the onset of stall, and other instabilities, and have recommended ways to eliminate a variety of potential problems before the compressor is placed in operation. The suitability of a compressor and its driver for the planned service should be thoroughly evaluated, so that each component and the system not only satisfy the design conditions, but also extreme operating conditions. This paper presents a description of the tools available for design audits and gives examples of benefits that have resulted from recent audits. The rotordynamics of any large high-speed compressor should be carefully evaluated to identify potential instabilities, high vibration levels, and even destructive responses of the machine. Powerful rotordynamic analysis tools and specific knowledge exists to accurately predict bearing and seal stiffness and damping, lateral critical speeds, and damped forced responses. Some examples of significant results obtained from rotordynamic evaluations are presented, and typical problems that have been identified and eliminated are highlighted. Torsional vibration analyses for compressor trains are an essential aspect of a design audit that have identified vibration problems and weak components. Examples of torsional vibration responses and problems that can be identified and corrected are included in this paper. The aerodynamics of a compressor is a design audit topic to which attention should be paid. Thermophysical properties of the process gas, as it is compressed, are important quantities which can be accurately determined by modern equations of state. The internal velocity distribution and pressure rise per impeller and diffuser can be evaluated to identify areas of excess loss, poor work transfer, or restrictions within a compressor. Flow angles such as at the impeller and diffuser entrances can be predicted and evaluated. The diffuser inlet flow angle is a critical indicator of the onset of rotating stall. This type of aerodynamic analysis also provides important input for performance test planning and evaluation. This paper concludes with a summary of benefits of design audits for pipeline and industrial compressors.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

An Impact of Self-Recirculation Casing Treatment (SRCT) Configurations on Impeller Stall Margin and the Flow Field

2012 ◽  
Author(s):  
Yan Ma ◽  
Guang Xi ◽  
Guangkuan Wu
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Angle ◽  
Stall Margin ◽  
Casing Treatment ◽  
Swirl Velocity ◽  
Inlet Swirl ◽  
Unsteady Simulation

The present paper describes an investigation of stall margin enhancement and a detailed analysis of the impeller flow field due to self-recirculation casing treatment (SRCT) configuration of a high-speed small-size centrifugal impeller. The influence of different SRCT configurations on the impeller flow field at near-stall condition has been analyzed, highlighting the improvement in stall flow ability. This paper also discusses the influence of the SRCT configurations on the inlet flow angle, inlet swirl velocity and loss distribution in the impeller passage to understand the mechanism of the SRCT configurations in enhancing the stall margin of the impeller. The variation of the bleed flow rate at different operating conditions is also presented in this paper. Finally, the time-averaged unsteady simulation results at near-stall point are presented and compared with steady-state solutions.

High Pressure CO2 Compressor Testing for Tupi 1, Tupi 2, and Tupi 3

2012 ◽  
Author(s):  
Gary M. Colby ◽  
Timothy R. Griffin ◽  
Manoj K. Gupta ◽  
Harry F. Miller ◽  
Steven E. Nove ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Test ◽  
Mechanical Test ◽  
Magnetic Bearing ◽  
Operating Conditions ◽  
Actual Process ◽  
Process Gas ◽  
High Pressure Co2 ◽  
Hydrocarbon Gas ◽  
Design And Manufacture

This paper describes the mechanical and aerodynamic testing of the high-pressure CO2 compressors for the Tupi I, Tupi II, and Tupi III projects. This includes the results of the API 617 mechanical test and a special magnetic bearing exciter test to demonstrate rotordynamic stability at design operating conditions, as well as the results of the ASME PTC-10 Type 2 inert gas performance test and the ASME PTC-10 Type 1 full load–full pressure test on a CO2–hydrocarbon gas mixture equivalent to the actual process gas. A brief description of the compressor design and manufacture is also presented.

Rotating Instability in an Annular Cascade: Detailed Analysis of the Instationary Flow Phenomena

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Benjamin Pardowitz ◽  
Ulf Tapken ◽  
Robert Sorge ◽  
Paul Uwe Thamsen ◽  
Lars Enghardt
Keyword(s):  
Unsteady Flow ◽  
High Speed ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Pressure Waves ◽  
Flow Profile ◽  
Rotating Instability ◽  
Annular Cascade

Rotating instability (RI) occurs at off-design conditions in compressors, predominantly in configurations with large tip or hub clearance ratios of s* ≥3%. RI is the source of the blade tip vortex noise and a potential indicator for critical operating conditions like rotating stall and surge. The objective of this paper is to give more physical insight into the RI phenomenon using the analysis results of combined near-field measurements with high-speed particle image velocimetry (PIV) and unsteady pressure sensors. The investigation was pursued on an annular cascade with hub clearance. Both the unsteady flow field next to the leading edge as well as the associated rotating pressure waves were captured. A special analysis method illustrates the characteristic pressure wave amplitude distribution, denoted as “modal events” of the RI. Moreover, the slightly adapted method reveals the unsteady flow structures corresponding to the RI. Correlations between the flow profile, the dominant vortex structures, and the rotating pressure waves were found. Results provide evidence to a new hypothesis, implying that shear layer instabilities constitute the basic mechanism of the RI.

An Investigation of Rotating Stall and Surge of a 10-Stage Subsonic Compressor

1985 ◽  
Author(s):  
Xie Jinan ◽  
Bai Xiaoxu
Keyword(s):  
Transient Process ◽  
Phase Plane ◽  
Performance Test ◽  
Pressure Rise ◽  
Calculation Model ◽  
Rotating Stall ◽  
Stationary Condition ◽  
Process Pattern ◽  
Flow Pressure ◽  
Rise Phase

This article covers the analysis and study of the surge characteristic in a full-scale 10-stage subsonic compressor under the condition of performance test. The transient responses which arised after the compressor enters in non-stationary condition range are estimated through an improved nonlinear calculation model. There are two different kinds of response (or transient processe) model: stall pattern and surge pattern. The calculated results coincide with the test very well. When relative turning speed ñ ≤ 0.5, the system transient process is shown in stall pattern; when ñ ≥ 0.6, it is surge pattern. The obtainted calculation result has been drawn as a system transient process locus in the nondimensional flow-pressure rise phase plane. The nondimensional parameters affecting system transient process pattern were analysed and compared with the results made by E.M. Greitzer.

scholarly journals Stall Inception in a High-Speed Low Aspect Ratio Fan Including the Effects of Casing Treatments

1994 ◽  
Author(s):  
S. E. Gorrell ◽  
P. M. Russler
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Stall Inception ◽  
Casing Treatment ◽  
Low Aspect Ratio ◽  
Casing Treatments

The stall inception process in high-speed compressor components is important to understand in order to increase stage loading while maintaining stall margin. This paper presents the results of an in depth experimental investigation on the stall inception of a two stage, high-speed, low aspect ratio fan that is representative of current operational commercial and military fan technology. High-response static pressure measurements are presented which detail the stall inception process of the fan under various operating conditions. These conditions include: varied corrected speeds, a smooth case, a circumferential groove casing treatment, and a recirculating cavity casing treatment. Stage pressure characteristics and radial pressure ratio profiles are presented for the different operating conditions. The stage performance data, together with the static pressure data, are analyzed to provide a clear and thorough understanding of the stall inception process and how the process may vary under different conditions. Experimental results show that a stage may stall on the positive, neutral, or negative sloped part of the pressure characteristic. The three casing treatments had a significant effect on the rotor tip flow and these variations changed the stall inception path of the fan. Stall inception was characterized by the formation of a stall inception cell which grew to fully developed rotating stall. Properties affected by the changing tip flow include the stall inception duration, stall inception cell frequency, existence of modal waves, duration of modal waves, and modal wave frequency. In some instances modal waves appear to play a role in stall inception, in others they do not.

Simulation Method of Torsional Vibration Waveform of Reciprocating Engine Crankshaft Systems by Transition Matrix Method

1999 ◽  
Author(s):  
Katsuhiko Wakabayashi ◽  
Yasuhiro Honda ◽  
Tomoaki Kodama ◽  
Hiroshi Okamura
Keyword(s):  
Diesel Engines ◽  
Torsional Vibration ◽  
Matrix Method ◽  
Transition Matrix ◽  
High Speed ◽  
Decay Constant ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Design Stage ◽  
High Speed Diesel

Abstract The torsional vibration of the crankshaft system of high speed diesel engines has become more excessive with the increase of engine power and with the decrease of engine rigidity. So it is necessary in the design stage to improve accuracy in the calculation of maximum torsional vibration amplitude at resonant engine speed. At first, this paper refers to a method for obtaining experimentally engine damping that is necessary for the calculation of torsional vibration. If the value of the damping cannot be accurately estimated, the accuracy of the calculated result is still not satisfactory. In this experiment, the decay constant is obtained from the record of the damped, free torsional vibration waveforms which can be got by stopping abruptly combustion in steady operating. It is also shown that the damping ratio, which is approximately 0.03 to 0.04 in high-speed, small diesel engines, can be got from the already-obtained decay constant. Secondly, authors try to calculate directly resultant amplitude by using a step by step transition matrix method. The simulated waveforms of torsional vibration of a high speed diesel engine are compared with the experimental results and it is shown that the calculated results by the transition matrix method are accurate. At the same time, this paper refers to a method for the estimation of engine damping coefficient that is necessary for the calculation of torsional vibration. In this method, the damping coefficient can be got from the previously obtained damping ratio.

An Experimental Study of Stall Suppression and Associated Changes to the Flow Structures in the Tip Region of an Axial Low Speed Fan Rotor by Axial Casing Grooves

2017 ◽  
Author(s):  
Huang Chen ◽  
Yuanchao Li ◽  
Subhra Shankha Koley ◽  
Nick Doeller ◽  
Joseph Katz
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Pressure Rise ◽  
Leading Edge ◽  
Suction Side ◽  
Rotating Stall ◽  
Flow Structures ◽  
Flow Angle ◽  
Low Speed ◽  
Flow Characterization

The effects of axial casing grooves on the performance and flow structures in the tip region of an axial low speed fan rotor have been studied experimentally in the JHU refractive index-matched liquid facility. The four-per-passage semicircular grooves are skewed by 45° in the positive circumferential direction, and have a diameter of 65% of the rotor blade axial chord length. A third of the groove overlaps with the blade front, and the rest extends upstream. These grooves have a dramatic effect on the machine performance, reducing the stall flow rate by 40% compared to the same machine with a smooth endwall. However, they reduce the pressure rise at high flow rates. The flow characterization consists of qualitative visualizations of vortical structures using cavitation, as well as stereo-PIV (SPIV) measurements in several meridional and (z,θ) planes covering the tip region and interior of the casing grooves. The experiments are performed at a flow rate corresponding to pre-stall conditions for the untreated machine. They show that the flow into the downstream sides of the grooves and the outflow from their upstream sides vary periodically. The inflow peaks when the downstream end is aligned with the pressure side (PS) of the blade, and decreases, but does not vanish, when this end is located near the suction side (SS). These periodic variations have three primary effects: First, substantial fractions of the leakage flow and the tip leakage vortex (TLV) are entrained periodically into the groove. Consequently, in contrast to the untreated flow, The TLV remnants remain confined to the vicinity of the entrance to the groove, and the TLV strength diminishes starting from the mid-chord. Second, the grooves prevent the formation of large scale backflow vortices (BFVs), which are associated with the TLV, propagate from one blade passage to the next, and play a key role in the onset of rotating stall in the untreated fan. Third, the flow exiting from the grooves causes periodic variations of about 10° in the relative flow angle around the blade leading edge, presumably affecting the blade loading. The distributions of turbulent kinetic energy provide statistical evidence that in contrast to the untreated casing, very little turbulence originating from a previous TLV, including the BFVs, propagates from the PS to the SS of the blade. Hence, the TLV-related turbulence remain confined to the entrance to groove. Elevated, but lower turbulence is also generated as the outflow from the groove jets into the passage.

Examination of Rotating Stall Inception in a Small High Speed Axial Compressor

2009 ◽  
Author(s):  
L. G. N. Bennett ◽  
W. D. E. Allan
Keyword(s):  
High Speed ◽  
Gasoline Engine ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Pressure Measurements ◽  
Operating Life ◽  
Fourier Decomposition ◽  
Stall Inception ◽  
Prediction And Prevention

Rotating stall is an internal aerodynamic disturbance that limits the performance and operating life of a compressor. It has been studied with the aim of developing techniques for its prediction and prevention. To further the understanding of rotating stall inception, a test rig was constructed with the axial stages of a Rolls Royce Model 250-C20B small, high speed axial compressor as the test article. A gasoline engine was used to power the compressor and airflow was throttled through a pneumatically controlled valve. Simultaneous static pressure measurements were taken with seven high speed transducers arranged in two configurations: distributed both axially and circumferentially around the compressor casing. The compressor characteristic was mapped and detailed pressure measurements were taken between normal and surge operating conditions. Previous studies of high speed multi-stage compressors have shown both modal and spike type stall inception at different compressor stages. Other examinations of the Model 250 compressor have shown stall inception occurring at the first stage of the compressor. Similar results were observed in this study and an analysis was conducted using a variety of signal processing techniques including pressure trace inspection and discrete spatial Fourier decomposition.

Experimental Study on Different Tip Clearance of Low-Speed Axial Fan

2021 ◽  
Author(s):  
Ming Zhang ◽  
Jia Li ◽  
Xu Dong ◽  
Dakun Sun ◽  
Xiaofeng Sun
Keyword(s):  
Experimental Studies ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Signal Spectrum ◽  
Tip Clearance Flow ◽  
Low Speed ◽  
Clearance Flow ◽  
Casing Pressure

Abstract Tip clearance flow is not only the source of undesirable noise but also a potential indicator for critical operating conditions with rotating stall or surge. It can induce blade vibration, which would cause premature blade failure when the vibration is strong enough. The paper presents experimental studies on the effects of tip clearance on the stall inception process in a low-speed high-load single stage fan with different tip clearance. From the point of view of flow range, it has been proved by computations that there is an optimal gap value, and an explanation is given according to different stall mechanisms of large and small tip clearance. However, the experiment of no tip clearance is not easy to achieve. In this experiment, a wearable soft wall casing was used to achieve “zero clearance”, and an explicit conclusion was obtained. The pressure rise and efficiency are improved at small tip clearance. Instantaneous Casing Pressure Field Measurement was carried out: instantaneous casing pressure fields were measured by 9 high response pressure transducers mounted on the casing wall. At the near stall point with large tip clearance, a narrow band increase of the amplitudes in the frequency spectrum at roughly half of the blade passing frequency can be observed according to the spectrum of static pressure at points on the endwall near the leading-edge and above the rotor. This phenomenon was explained from two aspects: tip clearance flow structure and pressure signal spectrum.

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