The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform

Michael Becker - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of Deep Surge in a Turbocharger Compression System
    Journal of Turbomachinery, 2016
    Co-Authors: Rick Dehner, Philip Keller, Ahmet Selamet, Michael Becker
    Abstract:

    The behavior of the Compression System in turbochargers is studied with a one-dimensional engine simulation code. The System consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a plenum, and a throttle valve exhausting to ambient. The Compression System is designed such that surge is the low mass flow rate instability mode, as opposed to stall. The compressor performance is represented through an extrapolated steady-state map. Instead of incorporating a turbine into the model, a drive torque is applied to the turbocharger shaft for simplification. Unsteady Compression System mild surge physics is then examined computationally by reducing the throttle valve diameter from a stable operating point. Such an increasing resistance decreases the mass flow rate through the Compression System and promotes surge. Mild surge is predicted as the mass flow rate is decreased below the stability limit, with oscillations of mass flow rate and pressure exhibited at the Helmholtz resonance frequency of the Compression System. The computational results are shown to be able to reproduce the experimental observations available in the literature.

  • Simulation of Mild Surge in a Turbocharger Compression System
    SAE International Journal of Engines, 2010
    Co-Authors: Rick Dehner, Philip Keller, Ahmet Selamet, Michael Becker
    Abstract:

    The behavior of the Compression System in turbochargers is studied with a one-dimensional engine simulation code. The System consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a plenum, and a throttle valve exhausting to ambient. The Compression System is designed such that surge is the low mass flow rate instability mode, as opposed to stall. The compressor performance is represented through an extrapolated steady-state map. Instead of incorporating a turbine into the model, a drive torque is applied to the turbocharger shaft for simplification. Unsteady Compression System mild surge physics is then examined computationally by reducing the throttle valve diameter from a stable operating point. Such an increasing resistance decreases the mass flow rate through the Compression System and promotes surge. Mild surge is predicted as the mass flow rate is decreased below the stability limit, with oscillations of mass flow rate and pressure exhibited at the Helmholtz resonance frequency of the Compression System. The computational results are shown to be able to reproduce the experimental observations available in the literature.

Rick Dehner - One of the best experts on this subject based on the ideXlab platform.

  • Physics of Deep Surge in an Automotive Turbocharger Centrifugal Compression System
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2019
    Co-Authors: Rick Dehner, Ahmet Selamet
    Abstract:

    Deep surge is a violent fluid instability that occurs within turbomachinery Compression Systems and limits the low-flow operating range. It is characterized by large amplitude pressure and flow rate fluctuations, where the cross-sectional averaged flow direction alternates between forward and reverse. The present study includes both measurements and predictions from a turbocharger centrifugal compressor installed on a gas stand. A three-dimensional (3D) computational fluid dynamics (CFD) model of the Compression System was constructed to carry out unsteady surge predictions. The results included here capture the transition from mild to deep surge, as the flow rate at the outlet boundary (valve) is reduced. During this transition, the amplitude of pressure and flow rate fluctuations greatly increase until they reach a repeating cyclic structure characteristic of deep surge. During the deep surge portion of the prediction, pressure fluctuations are compared with measurements at the corresponding compressor inlet and outlet transducer locations, where the amplitudes and frequencies exhibit excellent agreement. The predicted flow field throughout the Compression System is studied in detail during operation in deep surge, in order to characterize the unsteady and highly 3D structures present within the impeller, diffuser, and compressor inlet duct. Key observations include a core flow region near the axis of the inlet duct, where the flow remains in the forward direction throughout the deep surge cycle. The dominant noise generation occurs at the fundamental surge frequency, which is near the Helmholtz resonance of the Compression System, along with harmonics at integer multiples of this fundamental frequency.

  • The Physics of Deep Surge in an Automotive Turbocharger Centrifugal Compression System
    Volume 11: Acoustics Vibration and Phononics, 2018
    Co-Authors: Rick Dehner, Ahmet Selamet
    Abstract:

    Deep surge is a violent fluid instability that occurs within turbomachinery Compression Systems and limits the low-flow operating range. It is characterized by large amplitude pressure and flow rate fluctuations, where the cross-sectional averaged flow direction alternates between forward and reverse. When a compressor transitions into deep surge, the time-averaged compressor outlet pressure and temperature decrease and increase, respectively, along with a drastic rise in narrowband, low-frequency noise. The present study includes both measurements and predictions from a turbocharger centrifugal compressor installed on a gas stand. The compressor breathes air from ambient through an inlet duct with a bellmouth opening. The downstream Compression System consists of a compressor outlet duct attached to a plenum with increased cross-sectional area, and an additional duct that connects the plenum outlet to a control valve. A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of this Compression System was constructed to carry out unsteady surge predictions. The results included here capture the transition from mild to deep surge, as the flow rate at the outlet boundary (valve) is reduced. During this transition, the amplitude of pressure and flow rate fluctuations greatly increase until they reach a repeating cyclic structure characteristic of deep surge. During the deep surge portion of the prediction, pressure fluctuations are compared with measurements at the corresponding compressor inlet and outlet transducer locations, where the amplitudes and frequency exhibit excellent agreement. The predicted flow-field throughout the Compression System is studied in detail during operation in deep surge, in order to characterize the unsteady and highly 3D structures present within the impeller, diffuser, and compressor inlet duct. Key observations include a core flow region near the center of the inlet duct, where the flow remains in the forward direction throughout the deep surge cycle. The dominant noise generation occurs at the fundamental surge frequency, which is near the Helmholtz resonance of the Compression System, along with harmonics at integer multiples of this fundamental frequency.

  • Simulation of Deep Surge in a Turbocharger Compression System
    Journal of Turbomachinery, 2016
    Co-Authors: Rick Dehner, Philip Keller, Ahmet Selamet, Michael Becker
    Abstract:

    The behavior of the Compression System in turbochargers is studied with a one-dimensional engine simulation code. The System consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a plenum, and a throttle valve exhausting to ambient. The Compression System is designed such that surge is the low mass flow rate instability mode, as opposed to stall. The compressor performance is represented through an extrapolated steady-state map. Instead of incorporating a turbine into the model, a drive torque is applied to the turbocharger shaft for simplification. Unsteady Compression System mild surge physics is then examined computationally by reducing the throttle valve diameter from a stable operating point. Such an increasing resistance decreases the mass flow rate through the Compression System and promotes surge. Mild surge is predicted as the mass flow rate is decreased below the stability limit, with oscillations of mass flow rate and pressure exhibited at the Helmholtz resonance frequency of the Compression System. The computational results are shown to be able to reproduce the experimental observations available in the literature.

  • Simulation of Mild Surge in a Turbocharger Compression System
    SAE International Journal of Engines, 2010
    Co-Authors: Rick Dehner, Philip Keller, Ahmet Selamet, Michael Becker
    Abstract:

    The behavior of the Compression System in turbochargers is studied with a one-dimensional engine simulation code. The System consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a plenum, and a throttle valve exhausting to ambient. The Compression System is designed such that surge is the low mass flow rate instability mode, as opposed to stall. The compressor performance is represented through an extrapolated steady-state map. Instead of incorporating a turbine into the model, a drive torque is applied to the turbocharger shaft for simplification. Unsteady Compression System mild surge physics is then examined computationally by reducing the throttle valve diameter from a stable operating point. Such an increasing resistance decreases the mass flow rate through the Compression System and promotes surge. Mild surge is predicted as the mass flow rate is decreased below the stability limit, with oscillations of mass flow rate and pressure exhibited at the Helmholtz resonance frequency of the Compression System. The computational results are shown to be able to reproduce the experimental observations available in the literature.

Ahmet Selamet - One of the best experts on this subject based on the ideXlab platform.

  • Physics of Deep Surge in an Automotive Turbocharger Centrifugal Compression System
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2019
    Co-Authors: Rick Dehner, Ahmet Selamet
    Abstract:

    Deep surge is a violent fluid instability that occurs within turbomachinery Compression Systems and limits the low-flow operating range. It is characterized by large amplitude pressure and flow rate fluctuations, where the cross-sectional averaged flow direction alternates between forward and reverse. The present study includes both measurements and predictions from a turbocharger centrifugal compressor installed on a gas stand. A three-dimensional (3D) computational fluid dynamics (CFD) model of the Compression System was constructed to carry out unsteady surge predictions. The results included here capture the transition from mild to deep surge, as the flow rate at the outlet boundary (valve) is reduced. During this transition, the amplitude of pressure and flow rate fluctuations greatly increase until they reach a repeating cyclic structure characteristic of deep surge. During the deep surge portion of the prediction, pressure fluctuations are compared with measurements at the corresponding compressor inlet and outlet transducer locations, where the amplitudes and frequencies exhibit excellent agreement. The predicted flow field throughout the Compression System is studied in detail during operation in deep surge, in order to characterize the unsteady and highly 3D structures present within the impeller, diffuser, and compressor inlet duct. Key observations include a core flow region near the axis of the inlet duct, where the flow remains in the forward direction throughout the deep surge cycle. The dominant noise generation occurs at the fundamental surge frequency, which is near the Helmholtz resonance of the Compression System, along with harmonics at integer multiples of this fundamental frequency.

  • The Physics of Deep Surge in an Automotive Turbocharger Centrifugal Compression System
    Volume 11: Acoustics Vibration and Phononics, 2018
    Co-Authors: Rick Dehner, Ahmet Selamet
    Abstract:

    Deep surge is a violent fluid instability that occurs within turbomachinery Compression Systems and limits the low-flow operating range. It is characterized by large amplitude pressure and flow rate fluctuations, where the cross-sectional averaged flow direction alternates between forward and reverse. When a compressor transitions into deep surge, the time-averaged compressor outlet pressure and temperature decrease and increase, respectively, along with a drastic rise in narrowband, low-frequency noise. The present study includes both measurements and predictions from a turbocharger centrifugal compressor installed on a gas stand. The compressor breathes air from ambient through an inlet duct with a bellmouth opening. The downstream Compression System consists of a compressor outlet duct attached to a plenum with increased cross-sectional area, and an additional duct that connects the plenum outlet to a control valve. A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of this Compression System was constructed to carry out unsteady surge predictions. The results included here capture the transition from mild to deep surge, as the flow rate at the outlet boundary (valve) is reduced. During this transition, the amplitude of pressure and flow rate fluctuations greatly increase until they reach a repeating cyclic structure characteristic of deep surge. During the deep surge portion of the prediction, pressure fluctuations are compared with measurements at the corresponding compressor inlet and outlet transducer locations, where the amplitudes and frequency exhibit excellent agreement. The predicted flow-field throughout the Compression System is studied in detail during operation in deep surge, in order to characterize the unsteady and highly 3D structures present within the impeller, diffuser, and compressor inlet duct. Key observations include a core flow region near the center of the inlet duct, where the flow remains in the forward direction throughout the deep surge cycle. The dominant noise generation occurs at the fundamental surge frequency, which is near the Helmholtz resonance of the Compression System, along with harmonics at integer multiples of this fundamental frequency.

  • Simulation of Deep Surge in a Turbocharger Compression System
    Journal of Turbomachinery, 2016
    Co-Authors: Rick Dehner, Philip Keller, Ahmet Selamet, Michael Becker
    Abstract:

    The behavior of the Compression System in turbochargers is studied with a one-dimensional engine simulation code. The System consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a plenum, and a throttle valve exhausting to ambient. The Compression System is designed such that surge is the low mass flow rate instability mode, as opposed to stall. The compressor performance is represented through an extrapolated steady-state map. Instead of incorporating a turbine into the model, a drive torque is applied to the turbocharger shaft for simplification. Unsteady Compression System mild surge physics is then examined computationally by reducing the throttle valve diameter from a stable operating point. Such an increasing resistance decreases the mass flow rate through the Compression System and promotes surge. Mild surge is predicted as the mass flow rate is decreased below the stability limit, with oscillations of mass flow rate and pressure exhibited at the Helmholtz resonance frequency of the Compression System. The computational results are shown to be able to reproduce the experimental observations available in the literature.

  • Simulation of Mild Surge in a Turbocharger Compression System
    SAE International Journal of Engines, 2010
    Co-Authors: Rick Dehner, Philip Keller, Ahmet Selamet, Michael Becker
    Abstract:

    The behavior of the Compression System in turbochargers is studied with a one-dimensional engine simulation code. The System consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a plenum, and a throttle valve exhausting to ambient. The Compression System is designed such that surge is the low mass flow rate instability mode, as opposed to stall. The compressor performance is represented through an extrapolated steady-state map. Instead of incorporating a turbine into the model, a drive torque is applied to the turbocharger shaft for simplification. Unsteady Compression System mild surge physics is then examined computationally by reducing the throttle valve diameter from a stable operating point. Such an increasing resistance decreases the mass flow rate through the Compression System and promotes surge. Mild surge is predicted as the mass flow rate is decreased below the stability limit, with oscillations of mass flow rate and pressure exhibited at the Helmholtz resonance frequency of the Compression System. The computational results are shown to be able to reproduce the experimental observations available in the literature.

Ma Guoyuan - One of the best experts on this subject based on the ideXlab platform.

  • working performance of r 32 two stage Compression System in domestic air conditioner
    Energy and Buildings, 2015
    Co-Authors: Xu Shuxue, Ma Guoyuan
    Abstract:

    Abstract A numerical simulation model of a two-stage Compression refrigeration System with vapor injection using R-32 as refrigeration is newly presented in this paper. The middle chamber state of the twin rotary compressor with vapor injection was simulated. Based on that, the whole System model was set up and it was validated by comparing the predictions with measured data. The results show that, compared with No-injection cycle, R-32 vapor injection System provides very significant performance improvements for cooling performance. The most suitable volume ratio of the high-pressure cylinder to low-pressure is between 0.65 and 0.78; Compared with the single-stage Compression System, the cooling capacity and COP of the two-stage Compression System can improve 5–15% and 10–12%, respectively; The optimum vapor injection pressure corresponding to the comprehensive cooling performance was 1.3–1.8 MPa.

J. Smeulers - One of the best experts on this subject based on the ideXlab platform.

  • Stability parameter identification for a centrifugal Compression System
    2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
    Co-Authors: J. Van Helvoirt, BARBARA JAGER, Maarten Steinbuch, J. Smeulers
    Abstract:

    This paper presents the application of a lumped parameter model to describe the dynamic behavior of a centrifugal Compression System including surge. The response of the model is compared with experimental surge measurements from an industrial single stage compressor test rig. A parametric analysis of the model reveals the large influence of the stability parameter on the transient response. However, a good value for this parameter is not easily obtained from surge data. Therefore, an identification method is proposed to uniquely determine the stability parameter that is based on an approximate realization algorithm, making use of the fact that the step response of the System has the characteristics of a first order System. Simulation results show that this method can provide an estimate for the stability parameter of a centrifugal Compression System.