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Y. Y. Wu - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Flows in 2-D and 3-D Simulated SDR Combustors
    Engineering Turbulence Modelling and Experiments, 2014
    Co-Authors: Tongmiin Liou, Y. Y. Wu
    Abstract:

    The mean velocity and turbulence quantities in simulated 2-D and 3-D SDR combustor flowfields were measured by using a two-component laser Doppler velocimetry system. The Reynolds number, based on the combustor height and bulk mean velocity, and momentum ratio of Axial-Inlet to side-Inlets were 4.56×104 and 0.11, respectively, for the 2-D flowfield; 5.92×104 and 0.20 for the 3-D flowfield. It is found that the well-organized dome vortices and separating bubbles in the 2-D flow are absent in the 3-D flow. To provide a reference for turbulence modelling, the 2-D flow is also characterized in terms of the turbulent structure parameter. In addition, the penetration of the Axial jet through the side-Inlet jets and the mixing of the Axial-Inlet with the side-Inlet streams are documented.

  • Self-Sustained Flow Oscillation in a Ducted Combustor with Multiple Inlets
    AIAA Journal, 1995
    Co-Authors: Tongmiin Liou, Y. Y. Wu
    Abstract:

    The impingement flowfield in a ducted combustor with one Axial Inlet and dual side Inlets was characterized qualitatively by smoke flow visualization as well as quantitatively by laser Doppler velocimetry and microphone measured velocity and wall pressure spectral characteristics, respectively. The baseline momentum ratio MR of the Axial Inlet to side Inlets was chosen to be 0.27. In this case, a resonant feedback frequency of 365 Hz, which prevailed in the entire combustor, and the second and the third harmonics, which appeared near the impingement region, were observed. The effect of MR on the flow oscillations was further studied, and the results showed that a constant Strouhal number, based on the Axial Inlet velocity and width, of 0.013 was found for MR < 0.94, and Reynolds number of 103-104 and the frequency of the oscillations varied linearly with the MR. From the investigation of the measured spectra, the feedback mechanism with appropriately proposed feedback distance and convective velocity, and of the chamber resonance curve, the onset of the oscillations was interpreted to be triggered by the coupling between the disturbance feedback frequency and the acoustic frequency of the chamber.

  • Turbulent flows in two-dimensional and three-dimensional simulated SDR combustors
    Experimental Thermal and Fluid Science, 1994
    Co-Authors: Tongmiin Liou, Y. Y. Wu
    Abstract:

    Abstract The mean velocity and turbulence quantities in simulated two-dimensional (2-D) and three-dimensional (3-D) solid-propellant ducted rocket (SDR) combustor flow fields were measured using a two-component laser-Doppler velocimetry system. The Reynolds number, based on the combustor height and bulk mean velocity and momentum ratio of the Axial Inlet to side Inlets were 4.56 × 10 4 and 0.11, respectively, for the 2-D flow field and 5.92 × 10 4 and 0.20 for the 3-D flow field. It is found that the well-organized dome vortices and separating bubbles in the 2-D flow are absent in the 3-D flow. To provide a reference for turbulence modeling, the 2-D flow is also characterized in terms of turbulent structure parameter. In addition, the penetration of the Axial jet through the side-Inlet jets and the mixing of the Axial-Inlet with the side-Inlet streams are documented.

  • spectral characteristics of velocity and wall pressure in a ducted flow with dual side and one Axial Inlets
    1992
    Co-Authors: T.-m. Liou, Y. Y. Wu
    Abstract:

    Abstract : The velocity and wall pressure spectral characteristics of the impingement of multiple Inlet jets is a ducted flow was investigated experimentally using LDV and microphone, respectively. The baseline momentum ratio of the Axial- to side-Inlet jet (MR) was chosen to be 0.27. In this case, a resonant feedback frequency of 365 Hz, which prevailed in the entire combustor, and the second and the third harmonics, which appeared near the impingement region, were observed. Also, the effect of the MR on the flow oscillations was studied and the results showed that below NR=0.94, a constant Strouhal number, based on the Axial Inlet velocity and width, of 0.013 was found; is other words, the frequency of the oscillations was triggered by the coupling between the disturbance feedback frequency and the acoustic frequency of the settling chambers of the side Inlets. (Author)

  • ldv measurements of the flowfield in a simulated combustor with Axial and side Inlets
    Experimental Thermal and Fluid Science, 1992
    Co-Authors: Tongmiin Liou, Y. Y. Wu
    Abstract:

    Abstract The Axial and transverse mean velocity and turbulence intensity components as well as Reynolds stresses and turbulent kinetic energy were measured by using a four-beam two-color laser-Doppler velocimetry (LDV) system for the isothermal flowfield of a simulated combustor that consisted of a plexiglass rectangular duct with two opposing 90° side Inlets and one Axial Inlet. The Reynolds number, based on the air density, combustor height, and bulk mean velocity, was 4.56 × 10 4 . The ratio of the Axial-Inlet to side-Inlet jet momentum was 1.28. Various flow regions are characterized by the measured mean flow pattern. The LDV-measured mean reattachment length of the separating bubble compares fairly well with the corresponding flow visualization photograph. Moreover, the lengths needed to reach both unidirectional flow and fully developed mean flow are determined. Regions where turbulence is anisotropic and where turbulent kinetic energy and shear stresses dominate are also identified. The information presented will be useful in testing and developing combustor models in this area.

Bruno Le Naour - One of the best experts on this subject based on the ideXlab platform.

  • Design and Experimental Assessment of Bladeless Turbines for Axial Inlet Supersonic Flows
    Journal of Engineering for Gas Turbines and Power, 2020
    Co-Authors: James Braun, Guillermo Paniagua, Francois Falempin, Bruno Le Naour
    Abstract:

    Abstract Supersonic Inlet flow is usually considered to be detrimental to the performance of turbine systems. A new class of bladeless turbines was developed, which allows for power extraction from supersonic Axial inflows without swirl with minimal maintenance cost. This is achieved through a wavy hub surface that promotes shocks and expansion fans and hence generates torque. In a first step, a baseline bladeless turbine is designed and the power extraction is analyzed. The bladeless turbine surface is parametrized in matlab and subsequently imported into Hexpress (Numeca) to mesh an unstructured grid. The first layer thickness is kept below one for all the simulations. The unstructured mesh is loaded into cfd++ (Metacomp) to solve the three dimensional steady Reynolds-averaged Navier–Stokes (RANS) equations. Second, the work extraction principle is broken down from a three-dimensional unsteady problem into a two-dimensional steady phenomenon. An experimental campaign is outlined and test details are discussed. Finally, after the experimental characterization, the operational envelope and scaling of the bladeless turbine are described for several reduced mass flows, reduced speeds, and geometrical features of the turbine (amplitude of the wavy surface, helix angle, hub radius, and length of the Axial turbine).

  • Design and Experimental Assessment of Bladeless Turbines for Axial Inlet Supersonic Flows
    Volume 3: Coal Biomass Hydrogen and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Sys, 2019
    Co-Authors: James Braun, Guillermo Paniagua, Francois Falempin, Bruno Le Naour
    Abstract:

    Abstract Supersonic Inlet flow is usually considered to be detrimental to the performance of turbine systems. This paper demonstrates an effective manner to harness power from supersonic Axial inflow without swirl. The bladeless Axial turbine allows for power extraction from harsh environments with minimal maintenance costs. In a first step, a baseline bladeless turbine is designed and the power extraction is analyzed. The bladeless turbine surface is parametrized in Matlab and subsequently imported into Hexpress (Numeca) to mesh an unstructured grid. The first layer thickness is kept below one for all the simulations. The unstructured mesh is loaded into CFD++ (Metacomp) to solve the three dimensional steady Reynolds Averaged Navier Stokes equations. Second, the work extraction principle is broken down from a three-dimensional unsteady problem into a two-dimensional steady phenomenon. An experimental campaign is outlined and test details are discussed. Finally, after the experimental characterization, the operational envelope and scaling of the bladeless turbine is described for several reduced mass flows, reduced speeds and geometrical features of the turbine (amplitude of the wavy surface, helix angle, hub radius and length of the Axial turbine).

Ml Munjal - One of the best experts on this subject based on the ideXlab platform.

  • Theory and Design of the Double-Tuned CoAxial and Flow-Reversal Mufflers: A New Perspective
    Journal of The Institution of Engineers (India): Series C, 2020
    Co-Authors: Ml Munjal
    Abstract:

    Double-tuning an expansion chamber consists in extending the Inlet–outlet pipes into the chamber by certain specific lengths so that the TL peaks due to the quarter-wave resonances of the annular cavities cancel or tune out the TL troughs due to the Axial standing waves in the simple expansion chamber. The transfer matrix method is combined with the direct electroacoustic analogies in this paper to derive simple analytical expressions for the TL spectra of the double-tuned coAxial chamber (DTCAC) muffler or the Axial-Inlet, Axial-outlet muffler, the double-tuned flow-reversal chamber (DTFRC) muffler or the Inlet–outlet same-end muffler and the semi-tuned coAxial chamber (STCAC) or Axial-Inlet, Axial-outlet muffler. It has been shown that barring the rather inconsequential sharp narrow peaks, the underlying overarching wide-band TL curve corresponds to a hypothetical simple expansion chamber, the effective lengths and diameter of which for the DTCAC muffler, DTFRC muffler and STCAC muffler have been tabulated at the end of this paper. This novel approach would simplify analysis and facilitate synthesis of mufflers with more than one semi-tuned as well as double-tuned chambers. Finally, some guidelines for design of these tuned mufflers for the HVAC systems have been given where it has been emphasized that physical lengths of the extended pipes would be different from the acoustic lengths to the extent of the end corrections.

  • plane wave analysis of rectangular Axial Inlet Axial outlet and transverse Inlet transverse outlet air cleaners
    Noise Control Engineering Journal, 2011
    Co-Authors: Ml Munjal, N K Mukherjee
    Abstract:

    In this work, one-dimensional flow-acoustic analysis of two basic configurations of air cleaners, (i) Rectangular Axial-Inlet, Axial-Outlet (RAIAO) and (ii) Rectangular Transverse-Inlet, Transverse-Outlet (RTITO), has been presented. This 1-D analytical approach has been verified with the help of 3-D FEM based software. Through subtraction of the acoustic performance of the bare plenum (without filter element) from that of the complete air cleaner box, the solitary performance of the filter element has been evaluated. Part of the present analysis illustrates that the analytical formulation remains effective even with offset positioning of the air pipes from the centre of the cross section of the air cleaner. The 1-D analytical tool computes much faster than its 3-D simulation counterpart. The present analysis not only predicts the acoustical impact of mean flow, but it also depicts the scenario with increased resistance of the filter element. Thus, the proposed 1-D analysis would help in the design of acoustically efficient air cleaners for automotive applications. (C) 2011 Institute of Noise Control Engineering.

  • 1 d acoustical analysis of Axial Inlet transverse outlet air cleaners of rectangular and circular cross section
    International Journal of Acoustics and Vibration, 2010
    Co-Authors: Ml Munjal, N K Mukherjee
    Abstract:

    This paper deals with the prediction of the acoustical performance of two basic types of air cleaners: 1) rectangular Axial-Inlet transverse-outlet (RAITO) and 2) circular Axial-Inlet transverse-outlet (CAITO), through 1-D acoustical analysis. Predictions of the acoustical performance of the air cleaners have been validated with 3-D FEM results. The acoustical performance of the cleaner box has been compared with the bare plenum performance (without any filter element) in order to estimate the acoustical performance of the filter element. It has been shown that even if Inlet and outlet pipes do not lie exactly on the centre of the corresponding cross section, the 1-D formulation still can predict the transmission loos (TL) with reasonable accuracy in the low- and mid-frequency zones. The 1-D model presented here is not only more convenient and much faster than the 3-D model, and it has the additional advantage of being able to incorporate the effect of mean flow, particularly the dissipative effect of mean flow at the Inlet/outlet of the air cleaner. This 1-D model would facilitate a rational design of an air cleaner for control of the intake noise of internal-combustion engines.

N K Mukherjee - One of the best experts on this subject based on the ideXlab platform.

  • plane wave analysis of rectangular Axial Inlet Axial outlet and transverse Inlet transverse outlet air cleaners
    Noise Control Engineering Journal, 2011
    Co-Authors: Ml Munjal, N K Mukherjee
    Abstract:

    In this work, one-dimensional flow-acoustic analysis of two basic configurations of air cleaners, (i) Rectangular Axial-Inlet, Axial-Outlet (RAIAO) and (ii) Rectangular Transverse-Inlet, Transverse-Outlet (RTITO), has been presented. This 1-D analytical approach has been verified with the help of 3-D FEM based software. Through subtraction of the acoustic performance of the bare plenum (without filter element) from that of the complete air cleaner box, the solitary performance of the filter element has been evaluated. Part of the present analysis illustrates that the analytical formulation remains effective even with offset positioning of the air pipes from the centre of the cross section of the air cleaner. The 1-D analytical tool computes much faster than its 3-D simulation counterpart. The present analysis not only predicts the acoustical impact of mean flow, but it also depicts the scenario with increased resistance of the filter element. Thus, the proposed 1-D analysis would help in the design of acoustically efficient air cleaners for automotive applications. (C) 2011 Institute of Noise Control Engineering.

  • 1 d acoustical analysis of Axial Inlet transverse outlet air cleaners of rectangular and circular cross section
    International Journal of Acoustics and Vibration, 2010
    Co-Authors: Ml Munjal, N K Mukherjee
    Abstract:

    This paper deals with the prediction of the acoustical performance of two basic types of air cleaners: 1) rectangular Axial-Inlet transverse-outlet (RAITO) and 2) circular Axial-Inlet transverse-outlet (CAITO), through 1-D acoustical analysis. Predictions of the acoustical performance of the air cleaners have been validated with 3-D FEM results. The acoustical performance of the cleaner box has been compared with the bare plenum performance (without any filter element) in order to estimate the acoustical performance of the filter element. It has been shown that even if Inlet and outlet pipes do not lie exactly on the centre of the corresponding cross section, the 1-D formulation still can predict the transmission loos (TL) with reasonable accuracy in the low- and mid-frequency zones. The 1-D model presented here is not only more convenient and much faster than the 3-D model, and it has the additional advantage of being able to incorporate the effect of mean flow, particularly the dissipative effect of mean flow at the Inlet/outlet of the air cleaner. This 1-D model would facilitate a rational design of an air cleaner for control of the intake noise of internal-combustion engines.

L Jones - One of the best experts on this subject based on the ideXlab platform.

  • design improvements and r d achievements for vacuum vessel and in vessel components towards iter construction
    Nuclear Fusion, 2003
    Co-Authors: Kimihiro Ioki, F Elio, V Arabash, Mikio Enoeda, W Daenne, P Arabaschi, S Chiocchio, A Gervash, C Ibbo, L Jones
    Abstract:

    During the preparation of the procurement specifications of ITER for long lead-time items, several detailed vacuum vessel (VV) design improvements are being pursued, such as elimination of the inboard triangular support, adding a separate interspace between inner and outer shells for independent leak detection of field joints, and revising the VV support system to gain more structural performance margin. Improvements to the blanket design are also under investigation, an inter-modular key instead of two prismatic keys and a co-Axial Inlet?outlet cooling connection instead of two parallel pipes. One of the most important achievements in the VV R&D has been demonstration of the necessary assembly tolerances. Further development of cutting, welding and non-destructive tests for the VV has been continued, and thermal and hydraulic tests have been performed to simulate the VV cooling conditions. In FW/blanket and divertor, full-scale prototypical mock-ups of the FW panel, the blanket shield block, and the divertor components, have been successfully fabricated. These results make us confident in the validity of our design and give us possibilities of alternate fabrication methods.