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Now showing items 1 - 10 of 10

  • Experimental and Numerical Investigation of Sweeping Jet Film Cooling

    Hossain, Mohammad A.   Prenter, Robin   Lundgreen, Ryan K.   Ameri, Ali   Gregory, James W.   Bons, Jeffrey P.  

    A companion experimental and numerical study was conducted for the performance of a row of five sweeping jet (SJ) film cooling holes consisting of conventional curved fluidic oscillators with an aspect ratio (AR) of unity and a hole spacing of P/D =3D 8.5. Adiabatic film effectiveness (eta), thermal field (theta), convective heat transfer coefficient (h), and discharge coefficient (C-D) were measured at two different freestream turbulence levels (Tu =3D 0.4% and 10.1%) and four blowing ratios (M =3D 0.98, 1.97, 2.94, and 3.96) at a density ratio of 1.04 and hole Reynolds number of Re-D =3D 2800. Adiabatic film effectiveness and thermal field data were also acquired for a baseline 777-shaped hole. The SJ film cooling hole showed significant improvement in cooling effectiveness in the lateral direction due to the sweeping action of the fluidic oscillator. An unsteady Reynolds-averaged Navier-Stokes (URANS) simulation was performed to evaluate the flow field at the exit of the hole. Time-resolved flow fields revealed two alternating streamwise vortices at all blowing ratios. The sense of rotation of these alternating vortices is opposite to the traditional counter-rotating vortex pair (CRVP) found in a "jet in crossflow" and serves to spread the film coolant laterally.
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  • Deposition on a Cooled Nozzle Guide Vane With Nonuniform Inlet Temperatures

    Prenter, Robin   Ameri, Ali   Bons, Jeffrey P.  

    External deposition on a slot film cooled nozzle guide vane, subjected to nonuniform inlet temperatures, was investigated experimentally and computationally. Experiments were conducted using a four-vane cascade, operating at temperatures up to 1353 K and inlet Mach number of approximately 0.1. Surveys of temperature at the inlet and exit planes were acquired to characterize the form and migration of the hot streak. Film cooling was achieved on one of the vanes using a single spanwise slot. Deposition was produced by injecting sub-bituminous ash particles with a median diameter of 6.48 mu m upstream of the vane passage. Several deposition tests were conducted, including a baseline case, a hot streak-only case, and a hot streak and film cooled case. Results indicate that capture efficiency is strongly related to both the inlet temperature profiles and film cooling. Deposit distribution patterns are also affected by changes in vane surface temperatures. A computational model was developed to simulate the external and internal flow, conjugate heat transfer, and deposition. Temperature profiles measured experimentally at the inlet were applied as thermal boundary conditions to the simulation. For deposition modeling, an Eulerian-Lagrangian particle tracking model was utilized to track the ash particles through the flow. An experimentally tuned version of the critical viscosity sticking model was implemented, with predicted deposition rates matching experimental results well. Comparing overall deposition rates to results from previous studies indicates that the combined effect of nonuniform inlet temperatures and film cooling cannot be accurately simulated by simple superposition of the two independent effects; thus, inclusion of both conditions in experiments is necessary for realistic simulation of external deposition.
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  • Deposition on a Cooled Nozzle Guide Vane With Nonuniform Inlet Temperatures

    Prenter, Robin   Ameri, Ali   Bons, Jeffrey P.  

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  • Deposition With Hot Streaks in an Uncooled Turbine Vane Passage

    Casaday, Brian   Prenter, Robin   Bonilla, Carlos   Lawrence, Michael   Clum, Carey   Ameri, Ali A.   Bons, Jeffrey P.  

    The effect of hot streaks on deposition in a high pressure turbine vane passage was studied both experimentally and computationally. Modifications to Ohio State's Turbine Reaction Flow Rig allowed for the creation of simulated hot streaks in a four-vane annular cascade operating at temperatures up to 1093 degrees C. Total temperature surveys were made at the inlet plane of the vane passage, showing the variation caused by cold dilution jets. Deposition was generated by introducing sub-bituminous ash particles with a median diameter of 11.6 mu m far upstream of the vane passage. Results indicate a strong correlation between surface deposits and the hot streak trajectory. A computational model was developed in FLUENT to simulate both the flow and deposition. The flow solution was first obtained without particulates, and individual ash particles were subsequently introduced and tracked using a Lagrangian tracking model. The critical viscosity model was used to determine particle sticking upon impact with vane surfaces. Computational simulations confirm the migration of the hot streak and locations susceptible to enhanced deposition. Results show that the deposition model is overly sensitive to temperature and can severely overpredict deposition. Model constants can be tuned to better match experimental results but must be calibrated for each application.
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  • Computational Simulation of Deposition in a Cooled High-Pressure Turbine Stage With Hot Streaks

    Prenter, Robin   Ameri, Ali   Bons, Jeffrey P.  

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  • Computational Simulation of Deposition in a Cooled High-Pressure Turbine Stage With Hot Streaks

    Prenter, Robin   Ameri, Ali   Bons, Jeffrey P.  

    Ash particle deposition in a high-pressure turbine stage was numerically investigated using steady Reynolds-averaged Navier-Stokes (RANS) and unsteady Reynolds-averaged Navie-Stokes (URANS) methods. An inlet temperature profile consisting of Gaussian nonuniformities (hot streaks) was imposed on the vanes, with vane cooling simulated using a constant vane wall temperature. The steady case utilized a mixing plane at the vane-rotor interface, while a sliding mesh was used for the unsteady case. Corrected speed and mass flow were matched to an experiment involving the same geometry, so that the flow solution could be validated against measurements. Particles ranging from 1 to 65 lm were introduced into the vane domain, and tracked using an Eulerian-Lagrangian tracking model. A novel particle rebound and deposition model was employed to determine particles' stick/ bounce behavior upon impact with a surface. Predicted impact and capture distributions for different diameters were compared between the steady and unsteady methods, highlighting effects from the circumferential averaging of the mixing plane. The mixing plane simulation was found to generally under predict impact and capture efficiencies compared with the unsteady calculation, as well as under predict particle temperature upon impact with the blade surface. Quantitative impact and capture efficiency trends with the Stokes number are discussed for both the vane and blade, with companion qualitative distributions for the different Stokes regimes.
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  • [ASME ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition - Charlotte, North Carolina, USA (Monday 26 June 2017)] Volume 5C: Heat Transfer - Experimental Characterization of Reverse-Oriented Film Cooling

    Prenter, Robin   Hossain, Mohammad A.   Agricola, Lucas   Ameri, Ali   Bons, Jeffrey P.  

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  • [ASME ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition - Seoul, South Korea (Monday 13 June 2016)] Volume 2D: Turbomachinery - Computational Simulation of Deposition in a Cooled High-Pressure Turbine Stage With Hot Streaks

    Prenter, Robin   Ameri, Ali   Bons, Jeffrey P.  

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  • [ASME ASME Turbo Expo 2014: Turbine Technical Conference and Exposition - Düsseldorf, Germany (Monday 16 June 2014)] Volume 3A: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration - The Effects of Slot Film Cooling on Deposition on a Nozzle Guide Vane

    Prenter, Robin   Whitaker, Steven M.   Ameri, Ali   Bons, Jeffrey P.  

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  • [American Institute of Aeronautics and Astronautics 53rd AIAA Aerospace Sciences Meeting - Kissimmee, Florida ()] 53rd AIAA Aerospace Sciences Meeting - Measurement and Prediction of Hot Streak Profiles Generated by Axially Opposed Dilution Jets

    Prenter, Robin   Ameri, Ali   Bons, Jeffrey P.  

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