The Experts below are selected from a list of 22461 Experts worldwide ranked by ideXlab platform

Aboelyazied M. Koliub - One of the best experts on this subject based on the ideXlab platform.

  • Effect of dust on the performance of wind turbines
    Desalination, 2007
    Co-Authors: Mohammed G. Khalfallah, Aboelyazied M. Koliub
    Abstract:

    An experimental investigation on the effect of Blade Surface roughness, due to dust accumulation, on the performance of wind turbines was performed. The development of the energy generating costs of wind turbines directly depends on the wind turbine output, which depends upon the characteristics of the turbine Blades and their Surface roughness. An important operating requirement that relates to a wind turbines airfoils are its ability to perform when the smoothness of its Surface has been degraded by the dust. The effect of Surface roughness of rotor Blades due to accumulated dust on the Blade Surface of stall-regulated, horizontal axis 300 kW wind turbine was investigated. The mechanism of dust built up and accumulation on the Blade Surface of wind turbine was investigated, and the effect of operation period of wind turbine on the Blade Surface roughness intensity was investigated experimentally. Also, the quantity of dust accumulated on the Blade leading edge; and the effect of changing dust area on Blade Surface were studied. Standard roughness in Hurghada site was chosen and put in various leading edge areas. The roughness area on Blades was changed from 5 to 20% from the chord line towards the leading edge. The effect of dust on the performance of pitch-regulated 100 kW horizontal axis wind turbine was investigated. These results from pitch-regulated wind turbine were compared with 100 kW stall-regulated wind turbine.

Lansheng Xie - One of the best experts on this subject based on the ideXlab platform.

  • Hot flow behavior characterization for predicting the titanium alloy TC4 hollow Blade Surface Sinkage defects in the SPF/DB process
    International Journal of Material Forming, 2019
    Co-Authors: Ning Wang, Minghe Chen, Lansheng Xie
    Abstract:

    Titanium hollow Blade is applied in aircraft turbo-machine to gain higher thrust-to-weight ratio. The typical combined superplastic forming and diffusion bonding (SPF/DB) technology has been widely used in manufacturing complex multi-layer hollow structures such as the titanium hollow Blade. This study introduced a TC4 hollow Blade with internal reinforcing ribs fabricated with a series of hot forming operations including diffusion bonding, hot twisting, stamping and gas bulging. During the forming process, the Blade outer Surface will sink at the cavity locations due to lack of internal support. The gas pressure bulging process is necessary to repair the defect and bulge the caved Surface to the required profile. In order to predict the TC4 Blade deformation during the SPF/DB process, its hot flow behavior in the DB and SPF were separately investigated by carrying out isothermal tensile tests at corresponding temperature range and strain rate range. And taking the initial microstructure influence in consideration, samples which experienced the DB heating history were used to characterize the flow behavior in the SPF processes. A strain hardening form power law equation and a hyperbolic-sine law equation were employed to describe the constitutive relations during the DB and SPF respectively. Both models were calibrated with the hot flow curves and applied in the corresponding forming step finite element (FE) simulations. The Blade outer Surface profiles extracted from each forming step simulation showed good correlation with the experimental measurement. It proved that the hollow Blade Surface sinkage defect during the SPF/DB process can be accurately predicted by the FE simulation with the calibrated constitutive models. And the effectiveness of the gas bulging process for repairing the sinkage defect were verified in both simulation and experiment.

  • Hot flow behavior characterization for predicting the titanium alloy TC4 hollow Blade Surface Sinkage defects in the SPF/DB process
    International Journal of Material Forming, 2019
    Co-Authors: Ning Wang, Minghe Chen, Lansheng Xie
    Abstract:

    Titanium hollow Blade is applied in aircraft turbo-machine to gain higher thrust-to-weight ratio. The typical combined superplastic forming and diffusion bonding (SPF/DB) technology has been widely used in manufacturing complex multi-layer hollow structures such as the titanium hollow Blade. This study introduced a TC4 hollow Blade with internal reinforcing ribs fabricated with a series of hot forming operations including diffusion bonding, hot twisting, stamping and gas bulging. During the forming process, the Blade outer Surface will sink at the cavity locations due to lack of internal support. The gas pressure bulging process is necessary to repair the defect and bulge the caved Surface to the required profile. In order to predict the TC4 Blade deformation during the SPF/DB process, its hot flow behavior in the DB and SPF were separately investigated by carrying out isothermal tensile tests at corresponding temperature range and strain rate range. And taking the initial microstructure influence in consideration, samples which experienced the DB heating history were used to characterize the flow behavior in the SPF processes. A strain hardening form power law equation and a hyperbolic-sine law equation were employed to describe the constitutive relations during the DB and SPF respectively. Both models were calibrated with the hot flow curves and applied in the corresponding forming step finite element (FE) simulations. The Blade outer Surface profiles extracted from each forming step simulation showed good correlation with the experimental measurement. It proved that the hollow Blade Surface sinkage defect during the SPF/DB process can be accurately predicted by the FE simulation with the calibrated constitutive models. And the effectiveness of the gas bulging process for repairing the sinkage defect were verified in both simulation and experiment.

Mohammed G. Khalfallah - One of the best experts on this subject based on the ideXlab platform.

  • Effect of dust on the performance of wind turbines
    Desalination, 2007
    Co-Authors: Mohammed G. Khalfallah, Aboelyazied M. Koliub
    Abstract:

    An experimental investigation on the effect of Blade Surface roughness, due to dust accumulation, on the performance of wind turbines was performed. The development of the energy generating costs of wind turbines directly depends on the wind turbine output, which depends upon the characteristics of the turbine Blades and their Surface roughness. An important operating requirement that relates to a wind turbines airfoils are its ability to perform when the smoothness of its Surface has been degraded by the dust. The effect of Surface roughness of rotor Blades due to accumulated dust on the Blade Surface of stall-regulated, horizontal axis 300 kW wind turbine was investigated. The mechanism of dust built up and accumulation on the Blade Surface of wind turbine was investigated, and the effect of operation period of wind turbine on the Blade Surface roughness intensity was investigated experimentally. Also, the quantity of dust accumulated on the Blade leading edge; and the effect of changing dust area on Blade Surface were studied. Standard roughness in Hurghada site was chosen and put in various leading edge areas. The roughness area on Blades was changed from 5 to 20% from the chord line towards the leading edge. The effect of dust on the performance of pitch-regulated 100 kW horizontal axis wind turbine was investigated. These results from pitch-regulated wind turbine were compared with 100 kW stall-regulated wind turbine.

Zhonghe Han - One of the best experts on this subject based on the ideXlab platform.

  • Investigating the dehumidification characteristics of the low-pressure stage with Blade Surface heating
    Applied Thermal Engineering, 2020
    Co-Authors: Xu Han, Wei Zeng, Zhonghe Han
    Abstract:

    Abstract At present, the vast majority of electricity is generated by steam turbines. Nonequilibrium condensation will occur in the low-pressure stage, which will not only reduce efficiency but also corrode Blades and endanger the safety of the steam turbine. The aim of this work is to optimize the Blade Surface volume heating scheme to reduce the wetness loss. Based on thermodynamic theory, the nucleation model and droplet growth model were studied. A two-fluid model of homogeneous condensation was established from the point of view of the volume average, and the accuracy of the model was verified. The effects of stator Blade Surface volume heating, rotor Blade Surface volume heating and coupling heating on the wet steam condensation characteristics in the nucleation stage were analyzed. The research shows that stator Blade Surface volume heating can satisfactorily prevent steam condensation. When the stator Blade Surface volume heating rate is 0.375 J /(mm2·s), the average outlet wetness of the stage is 0.0158, which decreases 69.34% compared with the non-heating condition, and the entropy increase is only 0.26% higher than that of the non-heating condition. Blade Surface heating can inhibit steam condensation very well and improve the turbine efficiency to a certain extent.

  • Effect of Blade Surface roughness on condensation process in a stator cascade
    International Journal of Numerical Methods for Heat & Fluid Flow, 2019
    Co-Authors: Xu Han, Xiangyu Liu, Yunyun Yuan, Zhonghe Han
    Abstract:

    The flow state of wet steam will affect the thermodynamic and aerodynamic characteristics of steam turbine. The purpose of this study is to effectively control the wetness losses caused by wet steam condensation, and hence a cascade of 600 MW steam turbine was taken as the research object.,The influence of Blade Surface roughness on the condensation characteristics was analyzed, and the dehumidification mechanism and wetness control effect were obtained.,With the increase of Blade Surface roughness, the peak nucleation rate decreases gradually. According to the Mach number distribution on the Blade Surface, there is a sensitive region for the influence of roughness on the aerodynamic performance of cascade. The sensitive region of nucleation rate roughness should be between 50 and 150 µm.,The increase of Blade Surface roughness will increase the dynamic loss in cascade, but it can reduce the thermodynamic loss caused by condensation to a certain extent.

  • Effect of Blade Surface roughness on condensation process in a stator cascade
    International Journal of Numerical Methods for Heat & Fluid Flow, 2019
    Co-Authors: Xu Han, Xiangyu Liu, Yunyun Yuan, Zhonghe Han
    Abstract:

    Purpose The flow state of wet steam will affect the thermodynamic and aerodynamic characteristics of steam turbine. The purpose of this study is to effectively control the wetness losses caused by wet steam condensation, and hence a cascade of 600 MW steam turbine was taken as the research object. Design/methodology/approach The influence of Blade Surface roughness on the condensation characteristics was analyzed, and the dehumidification mechanism and wetness control effect were obtained. Findings With the increase of Blade Surface roughness, the peak nucleation rate decreases gradually. According to the Mach number distribution on the Blade Surface, there is a sensitive region for the influence of roughness on the aerodynamic performance of cascade. The sensitive region of nucleation rate roughness should be between 50 and 150 µm. Originality/value The increase of Blade Surface roughness will increase the dynamic loss in cascade, but it can reduce the thermodynamic loss caused by condensation to a certain extent.

Dale B. Taulbee - One of the best experts on this subject based on the ideXlab platform.

  • Prediction of Unsteady Rotor-Surface Pressure and Heat Transfer From Wake Passings
    Journal of Turbomachinery-transactions of The Asme, 1992
    Co-Authors: Le T. Tran, Dale B. Taulbee
    Abstract:

    The research described in this paper is a numerical investigation of the effects of unsteady flow of gas turbine heat transfer, particularly of a rotor Blade Surface. The unsteady flow in a rotor Blade passage and the unsteady heat transfer of the Blade Surface as a result of wake/Blade interaction are modeled by the inviscid flow/boundary layer approach. The Euler equations that govern the inviscid flow are solved using a time-accurate marching scheme

  • Prediction of Unsteady Rotor-Surface Pressure and Heat Transfer From Wake Passings
    Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration, 1991
    Co-Authors: Le T. Tran, Dale B. Taulbee
    Abstract:

    The research described in this paper is a numerical inves- tigation of the effects of unsteady flow on gas turbine heat transfer, particularly on a rotor Blade Surface. The un- steady flow in a rotor Blade passage and the unsteady heat transfer on the Blade Surface as a result of wake/Blade in- teraction are modeled by the inviscid flow/boundary laver approach. The Euler equations which govern the inviscid flow are solved using a time accurate marching scheme. The unsteady flow in the Blade passage is induced by pe- riodically moving a wake model across the passage inlet. Unsteady flow solutions in the passage provide pressure gradients and boundary conditions for the boundary-layer equations which govern the viscous flow adjacent to the Blade Surface. Numerical solutions of the unsteady turbu- lent boundary layer yield Surface heat flux values which can then be compared to experimental data. Comparisons with experimental data show that unsteady heat flux on the Blade suction Surface is well predicted, but the predic- tions of unsteady heat flux on