The Experts below are selected from a list of 24 Experts worldwide ranked by ideXlab platform

Massimiliano Rovini - One of the best experts on this subject based on the ideXlab platform.

  • Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
    Journal of Engineering for Gas Turbines and Power, 2013
    Co-Authors: Giuseppe Vannini, Stefano Cioncolini, Giuseppe Del Vescovo, Massimiliano Rovini
    Abstract:

    The current centrifugal compressor design for the oil & gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational Speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “flexibility ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical Speed at infinite support stiffness according to API standard, and finally the rotordynamic stability is very much challenged. The centrifugal compressor's rotordynamic stability is strongly related to the internal seals' dynamic behavior, and for this reason, the authors' company decided several years ago to develop internally a high pressure seal test rig to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures, and the preliminary test results captured for a long labyrinth seal (smooth rotor, straight toothed stator) tested up to 200 bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as negative preswirl test, single frequency versus multifrequency test, offset versus centered seal test. The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multifrequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a pocket damper seal (PDS) with the same nominal diameter, clearance, and effective length has been tested (up to 300 bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig were mostly confirmed with the only exception for the effective damping crossover frequency which was lower than expected.

  • Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
    Volume 7B: Structures and Dynamics, 2013
    Co-Authors: Giuseppe Vannini, Stefano Cioncolini, Giuseppe Del Vescovo, Massimiliano Rovini
    Abstract:

    The current centrifugal compressor design for the Oil & Gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational Speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “Flexibility Ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical Speed at infinite support stiffness according to [1]), and finally the rotordynamic stability is very much challenged. The centrifugal compressors rotordynamic stability is strongly related to the internal seals’ dynamic behaviour, and for this reason, the authors’ company decided several years ago to develop internally a High Pressure Seal Test Rig [2] to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures and the preliminary test results captured for a long Labyrinth seal (smooth rotor, straight toothed stator) tested up to 200bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as: • Negative preswirl test • Single frequency vs. Multi-frequency test • Offset vs. Centered Seal test The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multi-frequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a Pocket Damper Seal (PDS) with the same nominal diameter, clearance and effective length has been tested (up to 300bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig [3] were mostly confirmed with the only exception for the effective damping cross-over frequency which was lower than expected.

Giuseppe Vannini - One of the best experts on this subject based on the ideXlab platform.

  • Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
    Journal of Engineering for Gas Turbines and Power, 2013
    Co-Authors: Giuseppe Vannini, Stefano Cioncolini, Giuseppe Del Vescovo, Massimiliano Rovini
    Abstract:

    The current centrifugal compressor design for the oil & gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational Speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “flexibility ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical Speed at infinite support stiffness according to API standard, and finally the rotordynamic stability is very much challenged. The centrifugal compressor's rotordynamic stability is strongly related to the internal seals' dynamic behavior, and for this reason, the authors' company decided several years ago to develop internally a high pressure seal test rig to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures, and the preliminary test results captured for a long labyrinth seal (smooth rotor, straight toothed stator) tested up to 200 bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as negative preswirl test, single frequency versus multifrequency test, offset versus centered seal test. The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multifrequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a pocket damper seal (PDS) with the same nominal diameter, clearance, and effective length has been tested (up to 300 bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig were mostly confirmed with the only exception for the effective damping crossover frequency which was lower than expected.

  • Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
    Volume 7B: Structures and Dynamics, 2013
    Co-Authors: Giuseppe Vannini, Stefano Cioncolini, Giuseppe Del Vescovo, Massimiliano Rovini
    Abstract:

    The current centrifugal compressor design for the Oil & Gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational Speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “Flexibility Ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical Speed at infinite support stiffness according to [1]), and finally the rotordynamic stability is very much challenged. The centrifugal compressors rotordynamic stability is strongly related to the internal seals’ dynamic behaviour, and for this reason, the authors’ company decided several years ago to develop internally a High Pressure Seal Test Rig [2] to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures and the preliminary test results captured for a long Labyrinth seal (smooth rotor, straight toothed stator) tested up to 200bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as: • Negative preswirl test • Single frequency vs. Multi-frequency test • Offset vs. Centered Seal test The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multi-frequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a Pocket Damper Seal (PDS) with the same nominal diameter, clearance and effective length has been tested (up to 300bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig [3] were mostly confirmed with the only exception for the effective damping cross-over frequency which was lower than expected.

  • Calibrating a Large Compressor's Rotordynamic Model: Method and Application
    2006
    Co-Authors: Giuseppe Vannini, Anthony J. Smalley, Tim Hattenbach, Hans P. Weyermann, Justin R. Hollingsworth
    Abstract:

    This paper defines and demonstrates an effective, sequential process of rotor bearing model calibration, for a large centrifugal compressor. The calibration process involves a series of measurements and corresponding predictions, including free-free mode shapes and frequencies, casing shaker test data, amplitude and phase variation with Speed, and change of vibration with known changes in unbalance. The process first uses the measured free-free data and comparison with matching predictions to calibrate the mass elastic model for the rotor alone; it then applies measured casing response to shaker excitation, measured variation of frequency and phase, and dual peak characteristics at the first critical Speed, to identify the correct support characteristics. The paper demonstrates application of the calibrated model and established uncertainty in its predictions to assure integrity not readily demonstrated by testing alone. Specifically the margin between Maximum Continuous Speed and the second critical Speed is shown to be acceptable, and the amplitude of vibration at Maximum Continuous Speed is shown to stay well below the seal clearances at all seal locations.

Alexandre Scalabrin - One of the best experts on this subject based on the ideXlab platform.

  • Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors
    Journal of Engineering for Gas Turbines and Power, 2004
    Co-Authors: Ilmar Santos, Rodrigo Nicoletti, Alexandre Scalabrin
    Abstract:

    In this paper the complete set of modified Reynolds' equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a Maximum Speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high Maximum Continuous Speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e., using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.

  • Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors
    Volume 4: Turbo Expo 2003, 2003
    Co-Authors: Ilmar Santos, Rodrigo Nicoletti, Alexandre Scalabrin
    Abstract:

    In this paper the complete set of modified Reynolds’ equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a Maximum Speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high Maximum Continuous Speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e. using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.Copyright © 2003 by ASME

Ilmar Santos - One of the best experts on this subject based on the ideXlab platform.

  • Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors
    Journal of Engineering for Gas Turbines and Power, 2004
    Co-Authors: Ilmar Santos, Rodrigo Nicoletti, Alexandre Scalabrin
    Abstract:

    In this paper the complete set of modified Reynolds' equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a Maximum Speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high Maximum Continuous Speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e., using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.

  • Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors
    Volume 4: Turbo Expo 2003, 2003
    Co-Authors: Ilmar Santos, Rodrigo Nicoletti, Alexandre Scalabrin
    Abstract:

    In this paper the complete set of modified Reynolds’ equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a Maximum Speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high Maximum Continuous Speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e. using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.Copyright © 2003 by ASME

Giuseppe Del Vescovo - One of the best experts on this subject based on the ideXlab platform.

  • Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
    Journal of Engineering for Gas Turbines and Power, 2013
    Co-Authors: Giuseppe Vannini, Stefano Cioncolini, Giuseppe Del Vescovo, Massimiliano Rovini
    Abstract:

    The current centrifugal compressor design for the oil & gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational Speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “flexibility ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical Speed at infinite support stiffness according to API standard, and finally the rotordynamic stability is very much challenged. The centrifugal compressor's rotordynamic stability is strongly related to the internal seals' dynamic behavior, and for this reason, the authors' company decided several years ago to develop internally a high pressure seal test rig to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures, and the preliminary test results captured for a long labyrinth seal (smooth rotor, straight toothed stator) tested up to 200 bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as negative preswirl test, single frequency versus multifrequency test, offset versus centered seal test. The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multifrequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a pocket damper seal (PDS) with the same nominal diameter, clearance, and effective length has been tested (up to 300 bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig were mostly confirmed with the only exception for the effective damping crossover frequency which was lower than expected.

  • Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
    Volume 7B: Structures and Dynamics, 2013
    Co-Authors: Giuseppe Vannini, Stefano Cioncolini, Giuseppe Del Vescovo, Massimiliano Rovini
    Abstract:

    The current centrifugal compressor design for the Oil & Gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational Speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “Flexibility Ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical Speed at infinite support stiffness according to [1]), and finally the rotordynamic stability is very much challenged. The centrifugal compressors rotordynamic stability is strongly related to the internal seals’ dynamic behaviour, and for this reason, the authors’ company decided several years ago to develop internally a High Pressure Seal Test Rig [2] to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures and the preliminary test results captured for a long Labyrinth seal (smooth rotor, straight toothed stator) tested up to 200bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as: • Negative preswirl test • Single frequency vs. Multi-frequency test • Offset vs. Centered Seal test The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multi-frequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a Pocket Damper Seal (PDS) with the same nominal diameter, clearance and effective length has been tested (up to 300bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig [3] were mostly confirmed with the only exception for the effective damping cross-over frequency which was lower than expected.