The Experts below are selected from a list of 39099 Experts worldwide ranked by ideXlab platform

Camille Alain Rabbath - One of the best experts on this subject based on the ideXlab platform.

  • State-Space Modeling and Identification of Delta Wing Vortex-Coupled Roll Dynamics
    Journal of Aircraft, 2009
    Co-Authors: Brandon W. Gordon, Mehrdad Pakmehr, Camille Alain Rabbath
    Abstract:

    This paper develops a new state-space model for vortex-coupled 65-degree delta wing aircraft systems based on a modified nonlinear indicial response method combined with an internal state-space representation. Relationships between vortex breakdown location, rolling Moment Coefficient, and roll angle dynamics are determined. The state-space equations derived are subject to state delays and are also nonlinear in the vortex-coupled rolling Moment Coefficient Linear and nonlinear parameter identification methods are developed to empirically estimate the rolling Moment Coefficient as a function of the roll angle and primary vortex breakdown locations. A comparison between numerical simulations and experimental data indicates close agreement for a number of different initial conditions.

  • Robust adaptive tracking control of delta wing vortex-coupled roll dynamics using RBF neural networks
    Proceedings of 2005 IEEE Conference on Control Applications 2005. CCA 2005., 1
    Co-Authors: Mehrdad Pakmehr, Brandon W. Gordon, Camille Alain Rabbath
    Abstract:

    In this paper a robust adaptive control strategy has been proposed and applied for vortex-coupled delta wing roll dynamics with parameter uncertainty in the rolling Moment Coefficient. The robust adaptive tracking neuro-controller employs a new network of Gaussian radial basis functions (RBF) to adaptively compensate for the rolling Moment Coefficient. Rolling Moment Coefficient, as a function of left and right vortex breakdown positions, is estimated online in adaptive neuro-controller structure using a special feature of RBF networks for the delta wing case. The proposed controller is stable with good tracking performance

  • Robust adaptive tracking control of delta wing vortex-coupled roll dynamics subject to delay and SMA actuator dynamics
    IEEE International Conference Mechatronics and Automation 2005, 1
    Co-Authors: Mehrdad Pakmehr, Brandon W. Gordon, Camille Alain Rabbath
    Abstract:

    In this paper, a feedback control strategy for stabilizing vortex-coupled delta wing roll dynamics with state delay and parameter uncertainty in the rolling Moment Coefficient relying on a robust adaptive tracking neuro-controller, which employs a network of Gaussian radial basis functions (RBF) to adaptively compensate for the rolling Moment Coefficient, is proposed. The stabilizing controller is shown to render the control system globally practically stable, whereas the robust adaptive tracking neuro-controller provides satisfactory tracking performance. The rolling Moment Coefficient, as a function of left and right vortex breakdown positions, is estimated online in an adaptive neuro-controller structure using a special feature of RBF networks for the delta wing case. The numerical simulation illustrates the applicability of the developed controller.

Friedrich-karl Benra - One of the best experts on this subject based on the ideXlab platform.

  • Investigation on Thrust and Moment Coefficients of a Centrifugal Turbomachine
    International Journal of Turbomachinery Propulsion and Power, 2018
    Co-Authors: Dieter Brillert, Hans Josef Dohmen, Friedrich-karl Benra
    Abstract:

    In radial pumps and turbines, the centrifugal through-flow in both the front and the back chambers is quite common. It strongly impacts the core swirl ratio, pressure distribution, axial thrust and frictional torque. In order to investigate these relationships experimentally, a test rig was designed at the University of Duisburg-Essen and described in this paper. Based on both the experimental and numerical results, correlations are determined to predict the impacts of the centrifugal through-flow on the core swirl ratio, the thrust Coefficient and the Moment Coefficient. Two correlations respectively are determined to associate the core swirl ratio with the local through-flow Coefficient for both Batchelor type flow and Stewartson type flow. The correlations describing the thrust Coefficient and the Moment Coefficient in a rotor-stator cavity with centripetal through-flow (Hu et al., 2017) are modified for the case of centrifugal through-flow. The Daily and Nece diagram distinguishing between different flow regimes in rotor-stator cavities is extended with a through-flow coordinate into 3D. The achieved results provide a comprehensive data base which is intended to support the calculation of axial thrust and Moment Coefficients during the design process of radial pumps and turbines in a more accurate manner.

  • Investigation on thrust and Moment Coefficients of a centrifugal turbomachine
    2017
    Co-Authors: Dieter Brillert, Hans Josef Dohmen, Friedrich-karl Benra
    Abstract:

    In radial pumps and turbines, the centrifugal through-flow is quite common, which has strong impacts on the core swirl ratio, pressure distribution, axial thrust and frictional torque. The impact of centrifugal through-flow on above parameters are still not sufficiently investigated with different circumferential Reynolds numbers and dimensionless axial gap widths. A test rig is designed at the University of Duisburg-Essen and descirbed in this paper. Based on the experimental results, correlations are determined to predict the impact of the centrifugal through-flow on the core swirl ratio, the thrust Coefficient and the Moment Coefficient with good accuracy. Part of the 3D Daily&Nece diagram from a former study of the authors is extended with centrifugal through-flow. The results will provide a data base for calculation of axial thrust and Moment Coefficient in order to design radial pumps and turbines with smooth impellers.

  • Investigation on the Influence of Surface Roughness on the Moment Coefficient in a Rotor-Stator Cavity With Centripetal Through-Flow
    Volume 1A Symposia: Keynotes; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Fluid Machinery; Industrial and Environmental Appli, 2017
    Co-Authors: Dieter Brillert, Hans Josef Dohmen, Friedrich-karl Benra
    Abstract:

    In radial pumps and turbines, the leakage flow (centripetal through-flow) is quite common from the outer radius of the impeller to the impeller eye, which has major impact on frictional torque. There is still an uncertainty on the impact of surface roughness on the Moment Coefficient. Part of the 2D Daily&Nece diagram where the flow is categorized into four regimes is extended into 3D with the third axis of through-flow Coefficient by distinguishing the profiles of tangential velocity. After classifying the flow regimes with respect to the centripetal through-flow, two correlations are developed to predict the impact of the axial gap, the global Reynolds number, the through-flow Coefficient and the surface roughness on the Moment Coefficient according to the experimental results for both regime III and regime IV. Using the proposed equations for the Moment Coefficient, the influence of the centripetal through-flow and surface roughness can be better considered when designing radial pumps and turbines.

Abdulnaser I. Sayma - One of the best experts on this subject based on the ideXlab platform.

  • a numerical investigation of Moment Coefficient and flow structure in a rotor stator cavity with rotor mounted bolts
    Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2013
    Co-Authors: Elham Roshani Moghaddam, Christopher A. Long, Abdulnaser I. Sayma
    Abstract:

    The torque associated with overcoming the losses on a rotating disc is of particular importance to the designers of gas turbine engines. Not only does this represent a reduction in useful work, but it also gives rise to unwanted heating of metal surfaces and the adjacent fluid. This article presents a numerical study on the effect of rotor-mounted bolts on the Moment Coefficient and velocity distributions within a rotor–stator cavity under conditions representative of modern gas turbine engine design. Steady-state, two-dimensional and three-dimensional, computational fluid dynamics simulations are obtained using the FLUENT commercial code with a standard k–ɛ turbulence model. The model is validated against experimental data and then used to investigate the effects of varying the number of bolts and also a continuous ring. Two test cases are investigated: one corresponds to where the flow structure is dominated by the superimposed flow (λT = 0.35); and the other, where rotation is expected to govern the fl...

  • A numerical investigation of Moment Coefficient and flow structure in a rotor–stator cavity with rotor-mounted bolts
    Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2013
    Co-Authors: Elham Roshani Moghaddam, Christopher A. Long, Abdulnaser I. Sayma
    Abstract:

    The torque associated with overcoming the losses on a rotating disc is of particular importance to the designers of gas turbine engines. Not only does this represent a reduction in useful work, but it also gives rise to unwanted heating of metal surfaces and the adjacent fluid. This article presents a numerical study on the effect of rotor-mounted bolts on the Moment Coefficient and velocity distributions within a rotor–stator cavity under conditions representative of modern gas turbine engine design. Steady-state, two-dimensional and three-dimensional, computational fluid dynamics simulations are obtained using the FLUENT commercial code with a standard k–ɛ turbulence model. The model is validated against experimental data and then used to investigate the effects of varying the number of bolts and also a continuous ring. Two test cases are investigated: one corresponds to where the flow structure is dominated by the superimposed flow (λT = 0.35); and the other, where rotation is expected to govern the fl...

  • A Numerical Investigation of Moment Coefficient and Flow Structure in a Rotor-Stator Cavity With Rotor Mounted Bolts
    Volume 7: Turbomachinery Parts A B and C, 2011
    Co-Authors: Elham Roshani Moghaddam, Daniel Coren, Christopher A. Long, Abdulnaser I. Sayma
    Abstract:

    The torque associated with overcoming the losses on a rotating disc is of particular importance to the designers of gas turbine engines. Not only does this represent a reduction in useful work, but it also gives rise to unwanted heating of metal surfaces and the adjacent fluid. This paper presents a numerical study on the effect of rotor-mounted bolts on the Moment Coefficient and velocity distributions within a rotor-stator cavity under conditions representative of modern gas turbine engine design. Steady-state, 2D and 3D, CFD simulations are obtained using the FLUENT commercial code with a standard k- turbulence model. The model is validated against experimental data and then used to investigate the effects of varying the number of bolts and also a continuous ring. Two test cases are investigated: one corresponds to where the flow structure is dominated by the superimposed flow (T = 0.35); the other, where rotation is expected to govern the flow structure (T = 0.35). It is possible to separate out the contributions due to skin friction and pressure related (form drag and pumping loss) in the CFD results. This shows that the contribution of skin friction to the overall Moment Coefficient reduces as the number of bolts increases and the pressure related losses increase. There also appears to be a point where increasing the number of bolts does not bring about an increase in the overall Moment Coefficient. It is also interesting to report that the Moment Coefficient associated with a continuous ring is similar to that for a plain disc.

Dieter Brillert - One of the best experts on this subject based on the ideXlab platform.

  • Investigation on Thrust and Moment Coefficients of a Centrifugal Turbomachine
    International Journal of Turbomachinery Propulsion and Power, 2018
    Co-Authors: Dieter Brillert, Hans Josef Dohmen, Friedrich-karl Benra
    Abstract:

    In radial pumps and turbines, the centrifugal through-flow in both the front and the back chambers is quite common. It strongly impacts the core swirl ratio, pressure distribution, axial thrust and frictional torque. In order to investigate these relationships experimentally, a test rig was designed at the University of Duisburg-Essen and described in this paper. Based on both the experimental and numerical results, correlations are determined to predict the impacts of the centrifugal through-flow on the core swirl ratio, the thrust Coefficient and the Moment Coefficient. Two correlations respectively are determined to associate the core swirl ratio with the local through-flow Coefficient for both Batchelor type flow and Stewartson type flow. The correlations describing the thrust Coefficient and the Moment Coefficient in a rotor-stator cavity with centripetal through-flow (Hu et al., 2017) are modified for the case of centrifugal through-flow. The Daily and Nece diagram distinguishing between different flow regimes in rotor-stator cavities is extended with a through-flow coordinate into 3D. The achieved results provide a comprehensive data base which is intended to support the calculation of axial thrust and Moment Coefficients during the design process of radial pumps and turbines in a more accurate manner.

  • Investigation on thrust and Moment Coefficients of a centrifugal turbomachine
    2017
    Co-Authors: Dieter Brillert, Hans Josef Dohmen, Friedrich-karl Benra
    Abstract:

    In radial pumps and turbines, the centrifugal through-flow is quite common, which has strong impacts on the core swirl ratio, pressure distribution, axial thrust and frictional torque. The impact of centrifugal through-flow on above parameters are still not sufficiently investigated with different circumferential Reynolds numbers and dimensionless axial gap widths. A test rig is designed at the University of Duisburg-Essen and descirbed in this paper. Based on the experimental results, correlations are determined to predict the impact of the centrifugal through-flow on the core swirl ratio, the thrust Coefficient and the Moment Coefficient with good accuracy. Part of the 3D Daily&Nece diagram from a former study of the authors is extended with centrifugal through-flow. The results will provide a data base for calculation of axial thrust and Moment Coefficient in order to design radial pumps and turbines with smooth impellers.

  • Investigation on the Influence of Surface Roughness on the Moment Coefficient in a Rotor-Stator Cavity With Centripetal Through-Flow
    Volume 1A Symposia: Keynotes; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Fluid Machinery; Industrial and Environmental Appli, 2017
    Co-Authors: Dieter Brillert, Hans Josef Dohmen, Friedrich-karl Benra
    Abstract:

    In radial pumps and turbines, the leakage flow (centripetal through-flow) is quite common from the outer radius of the impeller to the impeller eye, which has major impact on frictional torque. There is still an uncertainty on the impact of surface roughness on the Moment Coefficient. Part of the 2D Daily&Nece diagram where the flow is categorized into four regimes is extended into 3D with the third axis of through-flow Coefficient by distinguishing the profiles of tangential velocity. After classifying the flow regimes with respect to the centripetal through-flow, two correlations are developed to predict the impact of the axial gap, the global Reynolds number, the through-flow Coefficient and the surface roughness on the Moment Coefficient according to the experimental results for both regime III and regime IV. Using the proposed equations for the Moment Coefficient, the influence of the centripetal through-flow and surface roughness can be better considered when designing radial pumps and turbines.

Mehrdad Pakmehr - One of the best experts on this subject based on the ideXlab platform.

  • State-Space Modeling and Identification of Delta Wing Vortex-Coupled Roll Dynamics
    Journal of Aircraft, 2009
    Co-Authors: Brandon W. Gordon, Mehrdad Pakmehr, Camille Alain Rabbath
    Abstract:

    This paper develops a new state-space model for vortex-coupled 65-degree delta wing aircraft systems based on a modified nonlinear indicial response method combined with an internal state-space representation. Relationships between vortex breakdown location, rolling Moment Coefficient, and roll angle dynamics are determined. The state-space equations derived are subject to state delays and are also nonlinear in the vortex-coupled rolling Moment Coefficient Linear and nonlinear parameter identification methods are developed to empirically estimate the rolling Moment Coefficient as a function of the roll angle and primary vortex breakdown locations. A comparison between numerical simulations and experimental data indicates close agreement for a number of different initial conditions.

  • Robust adaptive tracking control of delta wing vortex-coupled roll dynamics using RBF neural networks
    Proceedings of 2005 IEEE Conference on Control Applications 2005. CCA 2005., 1
    Co-Authors: Mehrdad Pakmehr, Brandon W. Gordon, Camille Alain Rabbath
    Abstract:

    In this paper a robust adaptive control strategy has been proposed and applied for vortex-coupled delta wing roll dynamics with parameter uncertainty in the rolling Moment Coefficient. The robust adaptive tracking neuro-controller employs a new network of Gaussian radial basis functions (RBF) to adaptively compensate for the rolling Moment Coefficient. Rolling Moment Coefficient, as a function of left and right vortex breakdown positions, is estimated online in adaptive neuro-controller structure using a special feature of RBF networks for the delta wing case. The proposed controller is stable with good tracking performance

  • Robust adaptive tracking control of delta wing vortex-coupled roll dynamics subject to delay and SMA actuator dynamics
    IEEE International Conference Mechatronics and Automation 2005, 1
    Co-Authors: Mehrdad Pakmehr, Brandon W. Gordon, Camille Alain Rabbath
    Abstract:

    In this paper, a feedback control strategy for stabilizing vortex-coupled delta wing roll dynamics with state delay and parameter uncertainty in the rolling Moment Coefficient relying on a robust adaptive tracking neuro-controller, which employs a network of Gaussian radial basis functions (RBF) to adaptively compensate for the rolling Moment Coefficient, is proposed. The stabilizing controller is shown to render the control system globally practically stable, whereas the robust adaptive tracking neuro-controller provides satisfactory tracking performance. The rolling Moment Coefficient, as a function of left and right vortex breakdown positions, is estimated online in an adaptive neuro-controller structure using a special feature of RBF networks for the delta wing case. The numerical simulation illustrates the applicability of the developed controller.