Paul Allaire | Wake Forest University (original) (raw)

Papers by Paul Allaire

Research paper thumbnail of Subsynchronous Vibration Problem And Solution In Multistage Centrifugal Compressor

Research paper thumbnail of Balancing Of Multimass Flexible Rotors

Research paper thumbnail of Design and application of squeeze film dampers for turbomachinery stabilization

Research paper thumbnail of Magnetic Bearing Design for a High Speed Rotor

The design of an example set of magnetic bearings for a small high speed compressor is presented.... more The design of an example set of magnetic bearings for a small high speed compressor is presented. The bearings were designed to replace the fluid film bearings of an existing compressor design. Reduction of parasitic power losses due to the bearings is projected to be from the current 2 kW down to approximately 200 W.

Research paper thumbnail of Closure to “Discussions of ‘Stability and Transient Characteristics of Four Multilobe Journal Bearing Configurations’” (1980, ASME J. Lubr. Technol., 102, pp. 298–299)

Journal of Lubrication Technology, 1980

Research paper thumbnail of Rotor-Bearing Dynamics Technology Design Guide. Part V. Dynamic Analysis of Incompressible Fluid Film Bearings

Research paper thumbnail of Design and implementation of a surge controller for an AMB supported compressor in the presence of piping acoustics

IEEE Conference on Decision and Control and European Control Conference, 2011

Research paper thumbnail of Vibration limiting of rotors by feedback control

Research paper thumbnail of Magnetic Actuators and Suspension for Space Vibration Control

Research paper thumbnail of Calibration of an 8-Pole Planar Radial Magnetic Actuator

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award, 1997

Force versus coil currents and air gap measurements were obtained for an 8-pole planar radial mag... more Force versus coil currents and air gap measurements were obtained for an 8-pole planar radial magnetic actuator constructed from laminated silicon iron. Static force measurements were made for journal eccentricities up to 2/3 of the nominal actuator radial clearance and various coil currents spanning the expected operating range. Three theoretical force models of varying degrees of complexity were developed using magnetic circuit theory and constant magnetic material properties. All three models were used to reduce the experimental data and an optimized expression representing the actuator force as a function of journal position and stator coil currents was found. The resulting optimized calibration model produced a proportionality constant and equivalent iron length significantly different from theoretically determined values, 29% and 130% greater respectively. A detailed error analysis was conducted to quantify the uncertainty in the bearing calibration relationship such that unce...

Research paper thumbnail of Design and Characterization of a Centrifugal Compressor Surge Test Rig

International Journal of Rotating Machinery, 2011

A detailed description of a new centrifugal compressor surge test rig is presented. The objective... more A detailed description of a new centrifugal compressor surge test rig is presented. The objective of the design and development of the rig is to study the surge phenomenon in centrifugal compression systems and to investigate a novel method of surge control by active magnetic bearing servo actuation of the impeller axial tip clearance. In this paper, we focus on the design, initial setup, and testing of the rig. The latter two include the commissioning of the rig and the experimental characterization of the compressor performance. The behavior of the compressor during surge is analyzed by driving the experimental setup into surge. Two fundamental frequencies, 21 Hz and 7 Hz, connected to the surge oscillation in the test rig are identified, and the observed instability is categorized according to the intensity of pressure fluctuations. Based on the test results, the excited pressure waves are clearly the result of surge and not stall. Also, they exhibit the characteristics of mild a...

Research paper thumbnail of An enhanced Greitzer compressor model with pipeline dynamics included

Proceedings of the 2011 American Control Conference, 2011

Research paper thumbnail of Low power magnetic bearing design for high speed rotating machinery

Magnetic suspension technology has advanced to the point of being able to offer a number of advan... more Magnetic suspension technology has advanced to the point of being able to offer a number of advantages to a variety of applications in the rotating machinery and aerospace fields. One strong advantage is the decrease in power consumption. The design and construction of a set of permanent magnet biased, actively controlled magnetic bearing for a flexible rotor are presented. Both permanent magnets and electromagnets are used in a configuration which effectively provides the necessary fluxes in the appropriate air gaps, while simultaneously keeping the undesirable destabilizing forces to a minimum. The design includes two radial bearings and a thrust bearing. The theoretical development behind the design is briefly discussed. Experimental performance results for a set of operating prototype bearings is presented. The results include measurements of load capacity, bearing stiffness and damping, and the dynamic response of the rotor. With few exceptions, the experimental results matched...

Research paper thumbnail of Review: Rotor Balancing

Shock and Vibration, 1998

This article reviews the literature concerning the balancing of rotors including the origins of v... more This article reviews the literature concerning the balancing of rotors including the origins of various balancing techniques including ones that use influence coefficient, modal, unified, no phase, and no amplitude methods to balance. This survey covers the computational algorithms as well as the physical concepts involved in balancing rotating equipment.

Research paper thumbnail of Flow-Rate Observers in the Suppression of Compressor Surge Using Active Magnetic Bearings

Journal of Turbomachinery, 2013

Surge is a dynamic flow instability that can cause extensive damage to compressors and other comp... more Surge is a dynamic flow instability that can cause extensive damage to compressors and other components. One common challenge that many surge control methods in the literature face when implemented in industrial applications is the unavailability of the high performance actuators and accurate flow rate measurements that are required to suppress surge. In this paper we present the experimental results of employing active magnetic bearings in order to suppress the surge instability in a centrifugal compressor. In addition, we compare how the selection of the flow estimation method affects the effectiveness of the implemented surge suppression controller. The experimental data demonstrates that the best combination of controller and flow estimator tested in this work allows the compressor to operate deep into the former surge region when the controller is activated, moving the minimum flow rate at the surge initiation point by 21%. This allows the compression system to operate at the h...

Research paper thumbnail of Experimentally Determined Rotor Power Losses in Homopolar and Heteropolar Magnetic Bearings

Journal of Engineering for Gas Turbines and Power, 1999

The identification of parameters that dictate the magnitude of rotor power losses in radial magne... more The identification of parameters that dictate the magnitude of rotor power losses in radial magnetic bearings is very important for many applications. Low loss performance of magnetic bearings in aerospace equipment such as jet engines and flywheel energy storage systems is especially critical. Two basic magnetic bearing designs are employed in industrial practice today: the homopolar design, where the flux paths are of a mixed radial/axial orientation, and the heteropolar design, where the flux paths are primarily radial in nature. The stator geometry and flux path of a specific bearing can have a significant effect on the rotor losses. This paper describes the detailed measurement of rotor losses for experimentally comparable homopolar and heteropolar designs. The two test bearing configurations are identical except for geometric features that determine the direction of the flux path. Both test bearing designs have the same air gap length, tip clearance ratio, surface area under t...

Research paper thumbnail of Rotor Power Losses in Planar Radial Magnetic Bearings—Effects of Number of Stator Poles, Air Gap Thickness, and Magnetic Flux Density

Journal of Engineering for Gas Turbines and Power, 1999

Rotor Power losses in magnetic bearings cannot be accurately calculated at this time because of t... more Rotor Power losses in magnetic bearings cannot be accurately calculated at this time because of the complexity of the magnetic field distribution and several other effects. The losses are due to eddy currents, hysteresis, and windage. This paper presents measured results in radial magnetic bearing configurations with eight pole and 16 pole stators and two laminated rotors. Two different air gaps were tested. The rotor power losses were determined by measuring the rundown speed of the rotor after the rotor was spun up to speeds of approximately 30,000 rpm, DN = 2,670,000 mm-rpm, in atmospheric air. The kinetic energy of the rotor is converted to heat by magnetic and air drag power loss mechanisms during the run down. Given past publications and the opinions of researchers in the field, the results were quite unexpected. The measured power losses were found to be nearly independent of the number of poles in the bearing. Also, the overall measured rotor power loss increased significant...

Research paper thumbnail of Constrained Control Design for Magnetic Bearing Systems

Journal of Dynamic Systems, Measurement, and Control, 2005

We study control problems in magnetic bearing systems that are subject to both input and state co... more We study control problems in magnetic bearing systems that are subject to both input and state constraints. Apart from the usual restrictions on voltages and currents in the circuit systems, most magnetic bearing systems are subject to a severe state constraint: the motion of the rotor (the suspended object) is only allowed in an extremely small airgap, otherwise the collision of the rotor and the stator would cause severe damages. Traditional methods for avoiding a collision include increasing the airgap and increasing the currents, which would usually result in unnecessarily large capacity of power supply and power loss. In this paper we present a systematic approach for dealing with all the input and state constraints by using some recently developed tools for constrained control design. Issues on the stability region, robustness, disturbance rejections, and transient response are addressed. We hope that by dealing with the constraints properly, safety operation can be ensured wi...

Research paper thumbnail of Computational Design and Experimental Testing of a Novel Axial Flow LVAD

Research paper thumbnail of Design and Transient Computational Fluid Dynamics Study of a Continuous Axial Flow Ventricular Assist Device

Research paper thumbnail of Subsynchronous Vibration Problem And Solution In Multistage Centrifugal Compressor

Research paper thumbnail of Balancing Of Multimass Flexible Rotors

Research paper thumbnail of Design and application of squeeze film dampers for turbomachinery stabilization

Research paper thumbnail of Magnetic Bearing Design for a High Speed Rotor

The design of an example set of magnetic bearings for a small high speed compressor is presented.... more The design of an example set of magnetic bearings for a small high speed compressor is presented. The bearings were designed to replace the fluid film bearings of an existing compressor design. Reduction of parasitic power losses due to the bearings is projected to be from the current 2 kW down to approximately 200 W.

Research paper thumbnail of Closure to “Discussions of ‘Stability and Transient Characteristics of Four Multilobe Journal Bearing Configurations’” (1980, ASME J. Lubr. Technol., 102, pp. 298–299)

Journal of Lubrication Technology, 1980

Research paper thumbnail of Rotor-Bearing Dynamics Technology Design Guide. Part V. Dynamic Analysis of Incompressible Fluid Film Bearings

Research paper thumbnail of Design and implementation of a surge controller for an AMB supported compressor in the presence of piping acoustics

IEEE Conference on Decision and Control and European Control Conference, 2011

Research paper thumbnail of Vibration limiting of rotors by feedback control

Research paper thumbnail of Magnetic Actuators and Suspension for Space Vibration Control

Research paper thumbnail of Calibration of an 8-Pole Planar Radial Magnetic Actuator

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award, 1997

Force versus coil currents and air gap measurements were obtained for an 8-pole planar radial mag... more Force versus coil currents and air gap measurements were obtained for an 8-pole planar radial magnetic actuator constructed from laminated silicon iron. Static force measurements were made for journal eccentricities up to 2/3 of the nominal actuator radial clearance and various coil currents spanning the expected operating range. Three theoretical force models of varying degrees of complexity were developed using magnetic circuit theory and constant magnetic material properties. All three models were used to reduce the experimental data and an optimized expression representing the actuator force as a function of journal position and stator coil currents was found. The resulting optimized calibration model produced a proportionality constant and equivalent iron length significantly different from theoretically determined values, 29% and 130% greater respectively. A detailed error analysis was conducted to quantify the uncertainty in the bearing calibration relationship such that unce...

Research paper thumbnail of Design and Characterization of a Centrifugal Compressor Surge Test Rig

International Journal of Rotating Machinery, 2011

A detailed description of a new centrifugal compressor surge test rig is presented. The objective... more A detailed description of a new centrifugal compressor surge test rig is presented. The objective of the design and development of the rig is to study the surge phenomenon in centrifugal compression systems and to investigate a novel method of surge control by active magnetic bearing servo actuation of the impeller axial tip clearance. In this paper, we focus on the design, initial setup, and testing of the rig. The latter two include the commissioning of the rig and the experimental characterization of the compressor performance. The behavior of the compressor during surge is analyzed by driving the experimental setup into surge. Two fundamental frequencies, 21 Hz and 7 Hz, connected to the surge oscillation in the test rig are identified, and the observed instability is categorized according to the intensity of pressure fluctuations. Based on the test results, the excited pressure waves are clearly the result of surge and not stall. Also, they exhibit the characteristics of mild a...

Research paper thumbnail of An enhanced Greitzer compressor model with pipeline dynamics included

Proceedings of the 2011 American Control Conference, 2011

Research paper thumbnail of Low power magnetic bearing design for high speed rotating machinery

Magnetic suspension technology has advanced to the point of being able to offer a number of advan... more Magnetic suspension technology has advanced to the point of being able to offer a number of advantages to a variety of applications in the rotating machinery and aerospace fields. One strong advantage is the decrease in power consumption. The design and construction of a set of permanent magnet biased, actively controlled magnetic bearing for a flexible rotor are presented. Both permanent magnets and electromagnets are used in a configuration which effectively provides the necessary fluxes in the appropriate air gaps, while simultaneously keeping the undesirable destabilizing forces to a minimum. The design includes two radial bearings and a thrust bearing. The theoretical development behind the design is briefly discussed. Experimental performance results for a set of operating prototype bearings is presented. The results include measurements of load capacity, bearing stiffness and damping, and the dynamic response of the rotor. With few exceptions, the experimental results matched...

Research paper thumbnail of Review: Rotor Balancing

Shock and Vibration, 1998

This article reviews the literature concerning the balancing of rotors including the origins of v... more This article reviews the literature concerning the balancing of rotors including the origins of various balancing techniques including ones that use influence coefficient, modal, unified, no phase, and no amplitude methods to balance. This survey covers the computational algorithms as well as the physical concepts involved in balancing rotating equipment.

Research paper thumbnail of Flow-Rate Observers in the Suppression of Compressor Surge Using Active Magnetic Bearings

Journal of Turbomachinery, 2013

Surge is a dynamic flow instability that can cause extensive damage to compressors and other comp... more Surge is a dynamic flow instability that can cause extensive damage to compressors and other components. One common challenge that many surge control methods in the literature face when implemented in industrial applications is the unavailability of the high performance actuators and accurate flow rate measurements that are required to suppress surge. In this paper we present the experimental results of employing active magnetic bearings in order to suppress the surge instability in a centrifugal compressor. In addition, we compare how the selection of the flow estimation method affects the effectiveness of the implemented surge suppression controller. The experimental data demonstrates that the best combination of controller and flow estimator tested in this work allows the compressor to operate deep into the former surge region when the controller is activated, moving the minimum flow rate at the surge initiation point by 21%. This allows the compression system to operate at the h...

Research paper thumbnail of Experimentally Determined Rotor Power Losses in Homopolar and Heteropolar Magnetic Bearings

Journal of Engineering for Gas Turbines and Power, 1999

The identification of parameters that dictate the magnitude of rotor power losses in radial magne... more The identification of parameters that dictate the magnitude of rotor power losses in radial magnetic bearings is very important for many applications. Low loss performance of magnetic bearings in aerospace equipment such as jet engines and flywheel energy storage systems is especially critical. Two basic magnetic bearing designs are employed in industrial practice today: the homopolar design, where the flux paths are of a mixed radial/axial orientation, and the heteropolar design, where the flux paths are primarily radial in nature. The stator geometry and flux path of a specific bearing can have a significant effect on the rotor losses. This paper describes the detailed measurement of rotor losses for experimentally comparable homopolar and heteropolar designs. The two test bearing configurations are identical except for geometric features that determine the direction of the flux path. Both test bearing designs have the same air gap length, tip clearance ratio, surface area under t...

Research paper thumbnail of Rotor Power Losses in Planar Radial Magnetic Bearings—Effects of Number of Stator Poles, Air Gap Thickness, and Magnetic Flux Density

Journal of Engineering for Gas Turbines and Power, 1999

Rotor Power losses in magnetic bearings cannot be accurately calculated at this time because of t... more Rotor Power losses in magnetic bearings cannot be accurately calculated at this time because of the complexity of the magnetic field distribution and several other effects. The losses are due to eddy currents, hysteresis, and windage. This paper presents measured results in radial magnetic bearing configurations with eight pole and 16 pole stators and two laminated rotors. Two different air gaps were tested. The rotor power losses were determined by measuring the rundown speed of the rotor after the rotor was spun up to speeds of approximately 30,000 rpm, DN = 2,670,000 mm-rpm, in atmospheric air. The kinetic energy of the rotor is converted to heat by magnetic and air drag power loss mechanisms during the run down. Given past publications and the opinions of researchers in the field, the results were quite unexpected. The measured power losses were found to be nearly independent of the number of poles in the bearing. Also, the overall measured rotor power loss increased significant...

Research paper thumbnail of Constrained Control Design for Magnetic Bearing Systems

Journal of Dynamic Systems, Measurement, and Control, 2005

We study control problems in magnetic bearing systems that are subject to both input and state co... more We study control problems in magnetic bearing systems that are subject to both input and state constraints. Apart from the usual restrictions on voltages and currents in the circuit systems, most magnetic bearing systems are subject to a severe state constraint: the motion of the rotor (the suspended object) is only allowed in an extremely small airgap, otherwise the collision of the rotor and the stator would cause severe damages. Traditional methods for avoiding a collision include increasing the airgap and increasing the currents, which would usually result in unnecessarily large capacity of power supply and power loss. In this paper we present a systematic approach for dealing with all the input and state constraints by using some recently developed tools for constrained control design. Issues on the stability region, robustness, disturbance rejections, and transient response are addressed. We hope that by dealing with the constraints properly, safety operation can be ensured wi...

Research paper thumbnail of Computational Design and Experimental Testing of a Novel Axial Flow LVAD

Research paper thumbnail of Design and Transient Computational Fluid Dynamics Study of a Continuous Axial Flow Ventricular Assist Device