The Experts below are selected from a list of 4443 Experts worldwide ranked by ideXlab platform

S D Morris - One of the best experts on this subject based on the ideXlab platform.

Toyotaka Sonoda - One of the best experts on this subject based on the ideXlab platform.

  • A New Concept of a Two-Dimensional Supersonic Relative Inlet Mach Number Compressor Cascade
    Volume 7: Turbomachinery Parts A and B, 2009
    Co-Authors: Toyotaka Sonoda, Markus Olhofer, Toshiyuki Arima, Bernhard Sendhoff
    Abstract:

    In this study, a numerical shape optimization method based on evolutionary algorithms coupled with a verified CFD solver has been applied to the ambitious target of a shock free 2-D supersonic Inlet Mach Number compressor cascade. The study is based on the DLR-PAV-1.5 supersonic compressor cascade designed by the pre-compression blading concept. The DLR cascade airfoil has been optimized using a verified CFD code. A superior performance of the optimized supersonic cascade with about 24% reduction of the total pressure loss coefficient compared to the original cascade has been realized. The flow mechanisms observable around the blade with improved performance and the resulting design concept are discussed in this paper.Copyright © 2009 by ASME

  • Aerodynamic Characteristics of Supercritical Outlet Guide Vanes at Low Reynolds Number Conditions
    Journal of Turbomachinery, 2006
    Co-Authors: Toyotaka Sonoda, Heinzadolf Schreiber
    Abstract:

    As a part of an innovative aerodynamic design concept for a single stage low pressure turbine, a high turning outlet guide vane is required to remove the swirl from the hot gas. The airfoil of the vane is a highly loaded compressor airfoil that has to operate at very low Reynolds Numbers (Re∼ 120,000). Recently published numerical design studies and experimental analysis on alternatively designed airfoils showed that blade profiles with an extreme front loaded pressure distribution are advantageous for low Reynolds Number conditions. The advantage even holds true for an increased Inlet Mach Number at which the peak Mach Number on the airfoils reaches and exceeds the critical conditions (M ss >1.0). This paper discusses the effect of the Inlet Mach Number and Reynolds Number on the cascade performance for both a controlled diffusion airfoil (CDA) (called baseline) and a numerically optimized front loaded airfoil. The results show that it is advantageous to design the profile with a fairly steep pressure gradient immediately at the front part in order to promote early transition or to prevent too large laminar-even shock induced-separations with the risk of a bubble burst. Profile Mach Number distributions and wake traverse data are presented for design and off-design conditions. The discussion of Mach Number distributions and boundary layer behavior is supported by numerical results obtained from the blade-to-blade flow solver MISES.

  • Aerodynamic Characteristics of Supercritical Outlet Guide Vanes at Low Reynolds Number Conditions
    Volume 6: Turbomachinery Parts A and B, 2006
    Co-Authors: Toyotaka Sonoda, Heinzadolf Schreiber
    Abstract:

    As a part of an innovative aerodynamic design concept for a single stage low pressure turbine, a high turning outlet guide vane is required to remove the swirl from the hot gas. The airfoil of the vane is a highly loaded compressor airfoil that has to operate at very low Reynolds Numbers (Re ∼ 120,000). Recently published numerical design studies and experimental analysis on alternatively designed airfoils showed that blade profiles with an extreme front loaded pressure distribution are advantageous for low Reynolds Number conditions. The advantage even holds true for an increased Inlet Mach Number at which the peak Mach Number on the airfoils reaches and exceeds the critical conditions (Mss > 1.0). This paper discusses the effect of the Inlet Mach Number and Reynolds Number on the cascade performance for both a controlled diffusion airfoil (CDA) (called baseline) and a numerically optimized front loaded airfoil. The results show that it is advantageous to design the profile with a fairly steep pressure gradient immediately at the front part in order to promote early transition or to prevent too large laminar — even shock induced — separations with the risk of a bubble burst. Profile Mach Number distributions and wake traverse data are presented for design and off-design conditions. The discussion of Mach Number distributions and boundary layer behavior is supported by numerical results obtained from the blade-to-blade flow solver MISES.Copyright © 2006 by ASME

Kevin T. Lowe - One of the best experts on this subject based on the ideXlab platform.

  • The Experimental Studies of Improving the Aerodynamic Performance of a Turbine Exhaust System
    Journal of Engineering for Gas Turbines and Power, 2014
    Co-Authors: Stephen A. Guillot, Hans D. Hamm, Ulrich E. Stang, Kevin T. Lowe
    Abstract:

    Analysis and testing were conducted to optimize an axial diffuser–collector gas turbine exhaust. Two subsonic wind tunnel facilities were designed and built to support this program. A 1/12th scale test rig enabled rapid and efficient evaluation of multiple geometries. This test facility was designed to run continuously at an Inlet Mach Number of 0.41 and an Inlet hydraulic diameter-based Reynolds Number of 3.4 × 105. A 1/4th geometric scale test rig was designed and built to validate the data in the 1/12th scale rig. This blow-down rig facilitated testing at a nominally equivalent Inlet Mach Number, while the Reynolds Number was matched to realistic engine conditions via back pressure. Multihole pneumatic pressure probes, particle image velocimetry (PIV), and surface oil flow visualization were deployed in conjunction with computational tools to explore physics-based alterations to the exhaust geometry. The design modifications resulted in a substantial increase in the overall pressure recovery coefficient of +0.07 (experimental result) above the baseline geometry. The optimized performance, first measured at 1/12th scale and obtained using computational fluid dynamics (CFD) was validated at the full scale Reynolds Number.

  • The Experimental Studies of Improving the Aerodynamic Performance of a Turbine Exhaust System
    Volume 1B: Marine; Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2014
    Co-Authors: Stephen A. Guillot, Hans D. Hamm, Ulrich E. Stang, Kevin T. Lowe
    Abstract:

    Analysis and testing was conducted to optimize an axial diffuser-collector gas turbine exhaust. Two subsonic wind tunnel facilities were designed and built to support this program. A 1/12th scale test rig enabled rapid and efficient evaluation of multiple geometries. This test facility was designed to run continuously at an Inlet Mach Number of 0.41 and an Inlet hydraulic diameter-based Reynolds Number of 3.4 × 105. A 1/4th geometric scale test rig was designed and built to validate the data in the 1/12th scale rig. This blow-down rig facilitated testing at a nominally equivalent Inlet Mach Number, while the Reynolds Number was matched to realistic engine conditions via back pressure. Multi-hole pneumatic pressure probes, particle image velocimetry and surface oil flow visualization was deployed in conjunction with computational tools to explore physics-based alterations to the exhaust geometry. The design modifications resulted in a substantial increase in the overall pressure recovery coefficient of +0.07 (experimental result) above the baseline geometry. The optimized performance, first measured at 1/12th scale and obtained using CFD was validated at the full scale Reynolds Number.Copyright © 2014 by Solar Turbines Incorporated

Vishnu Hariharan - One of the best experts on this subject based on the ideXlab platform.

  • Numerical characterization of 3D nonreacting supersonic cavity combustor with Inlet Mach Number variation
    International Journal of Hydrogen Energy, 2020
    Co-Authors: Yared Girma Mengistu, Debi Prasad Mishra, Vishnu Hariharan
    Abstract:

    Abstract A numerical investigation of a cavity-based supersonic combustor with non-reacting upstream hydrogen fuel injection is conducted to study the effects of Inlet Mach Number (Ma) on flow structure and fuel-air mixing. Three different freestream Mach Number cases (1.5, 2.5 and 3.5) are investigated at a constant fuel flow rate, injected at the sonic condition by considering governing equations for compressible, turbulent flow using Shear Stress Transport (SST) k-ω model. The complex flow structure is investigated by identifying various flow features namely, upstream three-dimensional bow shock, compression waves, Mach reflection, vortex in the separated boundary layer and horseshoe vortices at the downstream of the injection port. Besides this, the flow physics involved in these complex flow features are unravelled. Moreover, the performance of the combustor is characterized quantitatively in terms of mixing efficiency, total pressure loss and coefficient of pressure. However, the mixing efficiency and total pressure loss for the operating condition of Ma = 1.5, exhibits better performance than that of the other Mach Number cases (2.5, 3.5) due to decrease in inclination angle of reattachment shock from 47.6° to 29.9°. The present numerical investigation also demonstrates that the three-dimensional simulation is essential in the characterization of fuel-air mixing in supersonic cavity-based combustors.

  • Investigation on supersonic combustion of hydrogen with variation of combustor Inlet conditions
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Vishnu Hariharan, Ratna Kishore Velamati, Chockalingam Prathap
    Abstract:

    Abstract The present work numerically investigated the effect of variation in the Inlet Mach Number and stagnation temperature on the mixing of fuel with the oxidizer and the subsequent stabilization of a flame in a combustor at supersonic conditions. Dimensions of the studied combustor were taken from literature. It had a 10° wedge located at the top wall of the combustor. The combustor was modeled and analyzed using ANSYS FLUENT software. Three-dimensional, compressible, reacting flow calculations with a detailed chemistry model were performed. Turbulence was modeled using SST k-ω model. Necessary grid refinement was done to capture the incident oblique shock formed at the 10° wedge. Hydrogen was injected through the fuel Inlet port. The computations were performed for Mach Numbers of 2.0, 2.5 and 3.0 at the combustor Inlet for a combustion Inlet stagnation temperature of 1500 K. Later, the combustor Inlet Mach Number was kept constant at 2.5 and the combustor Inlet stagnation temperature was varied as follows: 1500 K, 1700 K, and 1900 K. The results indicated that as the combustor Inlet Mach Number increased, the location of incidence of the oblique shock shifted to the downstream of the fuel Inlet and it resulted in the better mixing of the fuel with cross flow stream of air and led to better degree of combustion of hydrogen. The contours of mole fraction of OH radical and hydrogen also corroborated the improvement in the mixing of fuel with the cross flow air and the subsequent flame stabilization at higher Mach Numbers. The flow pattern, mixing of fuel with air and flame stabilization was not affected significantly till 1700 K whereas for 1900 K, combustion of hydrogen was more uniform.

Jaromír Horáček - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Comparison of Unsteady Channel Compressible Flow with Low Inlet Mach Numbers
    Numerical Mathematics and Advanced Applications 2011, 2012
    Co-Authors: Petra Pořízková, Karel Kozel, Jaromír Horáček
    Abstract:

    This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low Inlet airflow velocity. The unsteadiness is caused by a prescribed periodic motion of the channel wall. Instudy three different governing systems of equations are considered – Full system, Adiabatic system, Iso-energetic system. Unsteady flow fields for Inlet Mach Number \(M_{\infty } = 0.012\) and frequency 100Hz are presented.

  • Mathematical Modeling of Flow in Human Vocal Tract
    Springer Proceedings in Physics, 2011
    Co-Authors: Petra Pořízková, Karel Kozel, Jaromír Horáček
    Abstract:

    This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low Inlet airflow velocity. The unsteadiness is caused by a prescribed periodic motion of the channel wall. Unsteady flow fields for Inlet Mach Number M ∞ = 0. 012 and frequency 100 Hz are presented.