Effects of the free‐stream density ratio on free and forced spatially developing shear layers

1995 ◽  
Vol 7 (8) ◽  
pp. 2036-2051 ◽  
Author(s):  
Marios C. Soteriou ◽  
Ahmed F. Ghoniem
Keyword(s):  
Free Stream ◽  
Density Ratio ◽  
Shear Layers ◽  
Stream Density

Hot Streaks and Phantom Cooling in a Turbine Rotor Passage: Part 1—Separate Effects

1993 ◽  
Vol 115 (4) ◽  
pp. 657-666 ◽  
Author(s):  
R. J. Roback ◽  
R. P. Dring
Keyword(s):  
Free Stream ◽  
Density Ratio ◽  
Turbine Rotor ◽  
Experimental Results ◽  
Airfoil Surface ◽  
Stream Density ◽  
Controlling Variables ◽  
Hot Streak ◽  
Cooling Air ◽  
The Impact

This paper presents experimental documentation and analytical correlations demonstrating the effects of hot streak accumulation and phantom cooling on turbine rotor airfoil surface temperature. Results are shown that quantify the impact of (1) a nonuniform temperature profile at the entrance of a turbine due to combustor-generated hot and cold streaks, and (2) cooling air discharged from the trailing edge of the upstream stator. In Part 1 of this paper, experimental results are shown for a range of controlling variables to identify where streak accumulation and phantom cooling were most likely to be strongest. These variables include streak-to-free-stream density ratio, streak injection location, and coolant-to-free-stream density and velocity ratios. In Part 2 of this paper, experimental results are shown for the combined effects of hot streak and stator coolant. An analytical model is also presented to correlate the experimental results.

Hot Streaks and Phantom Cooling in a Turbine Rotor Passage: Part 2—Combined Effects and Analytical Modeling

1993 ◽  
Vol 115 (4) ◽  
pp. 667-674 ◽  
Author(s):  
R. J. Roback ◽  
R. P. Dring
Keyword(s):  
Free Stream ◽  
Density Ratio ◽  
Turbine Rotor ◽  
Experimental Results ◽  
Combined Effects ◽  
Airfoil Surface ◽  
Stream Density ◽  
Hot Streak ◽  
Cooling Air ◽  
The Impact

This paper presents experimental documentation and analytical correlations demonstrating the effects of hot streak accumulation and phantom cooling on turbine rotor airfoil surface temperature. In particular, results are shown that quantify the impact of (1) a nonuniform temperature profile at the entrance of a turbine due to combustor-generated hot and cold streaks, and (2) cooling air discharged from the trailing edge of the upstream stator. In Part 1 of this paper, experimental results were shown for a range of controlling variables to identify where streak accumulation and phantom cooling were most likely to be strongest. These variables include streak-to-free-stream density ratio, streak injection location, and coolant-to-free-stream density and velocity ratios. In Part 2 of this paper, experimental results will be shown for the combined effects of hot streak and stator coolant on the adiabatic recovery temperature on the rotor. An analytical model is also developed to correlate the experimental results documented in Parts 1 and 2 of the paper.

scholarly journals Hot Streaks and Phantom Cooling in a Turbine Rotor Passage: Part 1 — Separate Effects

1992 ◽  
Author(s):  
Richard J. Roback ◽  
Robert P. Dring
Keyword(s):  
Free Stream ◽  
Density Ratio ◽  
Turbine Rotor ◽  
Experimental Results ◽  
Airfoil Surface ◽  
Stream Density ◽  
Controlling Variables ◽  
Hot Streak ◽  
Cooling Air ◽  
The Impact

This paper presents experimental documentation and analytical correlations demonstrating the effects of hot streak accumulation and phantom cooling on turbine rotor airfoil surface temperature. Results are shown which quantify the impact of (1) a non-uniform temperature profile at the entrance of a turbine due to combustor-generated hot and cold streaks, and (2) cooling air discharged from the trailing edge of the upstream stator. In Part 1 of this paper, experimental results are shown for a range of controlling variables to identify where streak accumulation and phantom cooling were most likely to be strongest. These variables include streak-to-free stream density ratio, streak injection location and coolant-to-free stream density and velocity ratios. In Part 2 of this paper, experimental results are shown for the combined effects of hot streak and stator coolant. An analytic model is also presented to correlate the experimental results.

scholarly journals Hot Streaks and Phantom Cooling in a Turbine Rotor Passage: Part 2 — Combined Effects and Analytical Modelling

1992 ◽  
Author(s):  
Richard J. Rdback ◽  
Robert P. Dring
Keyword(s):  
Free Stream ◽  
Density Ratio ◽  
Turbine Rotor ◽  
Experimental Results ◽  
Combined Effects ◽  
Airfoil Surface ◽  
Stream Density ◽  
Hot Streak ◽  
Cooling Air ◽  
The Impact

This paper presents experimental documentation and analytical correlations demonstrating the effects of hot streak accumulation and phantom cooling on turbine rotor airfoil surface temperature. In particular, results are shown which quantify the impact of (1) a non-uniform temperature profile at the entrance of a turbine due to combustor-generated hot and cold streaks, and (2) cooling air discharged from the trailing edge of the upstream stator. In Part 1 of this paper, experimental results are shown for a range of controlling variables to identify where streak accumulation and phantom cooling were most likely to be strongest. These variables include streak-to-free stream density ratio, streak injection location and coolant-to-free stream density and velocity ratios. In Part 2 of this paper, experimental results are shown for the combined effects of hot streak and stator coolant on the adiabatic recovery temperature on the rotor. An analytical model is also developed to correlate the experimental results documented in Parts 1 and 2 of the paper.

Effect of Periodic Wake Passing on Film Effectiveness of Discrete Cooling Holes Around the Leading Edge of a Blunt Body

1997 ◽  
Vol 119 (2) ◽  
pp. 292-301 ◽  
Author(s):  
K. Funazaki ◽  
M. Yokota ◽  
S. Yamawaki
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Turbine Blades ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Model ◽  
Free Stream Turbulence ◽  
Aero Engine ◽  
Secondary Air ◽  
Wake Passing

Detailed studies are conducted on film effectiveness of discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of typical turbine blades except for the spanwise inclination angle. Secondary air is heated so that the temperature difference between the mainstream and secondary air is about 20 K. In this case, the air density ratio of the mainstream and secondary air becomes less than unity, therefore the flow condition encountered in an actual aero-engine cannot be simulated in terms of the density ratio. A spoke-wheel type wake generator is used in this study. In addition, three types of turbulence grids are used to elevate the free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. For each of the blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals in order to obtain qualitative information of film effectiveness distribution.

The Effect of Periodic Wake Passing on Film Effectiveness of Discrete Cooling Holes Around the Leading Edge of a Blunt Body

1995 ◽  
Author(s):  
K. Funazaki ◽  
M. Yokota ◽  
S. Yamawaki
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Turbine Blades ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Model ◽  
Free Stream Turbulence ◽  
Aero Engine ◽  
Secondary Air ◽  
Wake Passing

Detailed studies are conducted on film effectiveness of discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of typical turbine blades except for the spanwise inclination angle. Secondary air is heated so that the temperature difference between the mainstream and secondary air is about 20K. In this case, air density ratio of the mainstream and secondary air becomes less than unity, therefore the flow condition encountered in an actual aero-engine can not be simulated in terms of the density ratio. A spoke-wheel type wake generator is used in this study. In addition, three types of turbulence grids are used to elevate the free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. For each of the blowing ratios, wall temperature around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals in order to obtain qualitative information of film effectiveness distribution.

Modal Analysis of Inclined Jet Film Cooling Flows With Density Variation

2013 ◽  
Author(s):  
Prasad Kalghatgi ◽  
Sumanta Acharya
Keyword(s):  
Modal Analysis ◽  
Wall Temperature ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Intermediate Frequency ◽  
Hydrodynamic Flow ◽  
Dynamic Mode Decomposition ◽  
Flow Structures ◽  
Dynamic Mode

Thermal and hydrodynamic flow field over a flat surface cooled with a single round inclined film cooling jet and fed by a plenum chamber is numerically investigated using Large Eddy Simulation (LES) and validated with published measurements. The calculations are done for a free stream Reynolds number Re = 16000, density ratio of coolant to free stream fluid ρj/ρ∞ = 2.0 and blowing ratio BR = ρjV/ρ∞V = 1.0. A short delivery tube with aspect ratio l/D = 1.75 and 35° inclination is considered. The evolution of the Kelvin-Helmholtz (K-H), hairpin and Counter-Rotating Vortex Pair (CVP) vortical structures are discussed to identify their origins. Modal analysis of the complete 3D flow and temperature field is carried out using a Dynamic Mode Decomposition (DMD) technique. The modal frequencies are identified, and the specific modal contribution towards the cooling wall temperature fluctuation is estimated on the film cooling wall. The low and intermediate frequency modes associated with streamwise and hairpin flow structures are found to have largest contribution (in-excess of 28%) towards wall temperature (or cooling effectiveness) fluctuations. The high frequency Kelvin-Helmholtz mode contributes towards initial mixing in the region of film cooling hole away from the wall. The individual modal temperature fluctuations on the wall and their corresponding hydrodynamic flow structures are presented and discussed.

Effect of Periodic Wake Passing on Film Effectiveness of Inclined Discrete Cooling Holes Around the Leading Edge of a Blunt Body

1996 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Eitaro Koyabu ◽  
Shigemichi Yamawaki
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Turbine Blades ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Surface ◽  
Main Stream ◽  
Test Model ◽  
Free Stream Turbulence ◽  
Secondary Air

Detailed studies are conducted on film effectiveness of inclined discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of a typical turbine blade and are angled at 30 and 90 degree to the surface in the spanwise and streamwise directions, respectively. A spoked-wheel type wake generator is used in this study to simulate periodically incoming wakes to turbine blades. In addition, two types of turbulence grids are used to elevate a free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. Most of the dominant flow conditions are reproduced in this study except for the air density ratio of the secondary air and the main stream. For each of the blowing ratios, wall temperature around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals to obtain traces of the injected secondary air on the test surface, which consequently helps us interpret the data of the thermocouples.

scholarly journals Turbulent shear-layer mixing: growth-rate compressibility scaling

2000 ◽  
Vol 414 ◽  
pp. 35-45 ◽  
Author(s):  
M. D. SLESSOR ◽  
M. ZHUANG ◽  
P. E. DIMOTAKIS
Keyword(s):  
Growth Rate ◽  
Shear Layer ◽  
Free Stream ◽  
Layer Growth ◽  
Turbulent Shear ◽  
Turbulent Shear Layer ◽  
Thermal Energy Conversion ◽  
Layer Growth Rate ◽  
Stream Density ◽  
Convective Mach Number

A new shear-layer growth-rate compressibility-scaling parameter is proposed as an alternative to the total convective Mach number, Mc. This parameter derives from considerations of compressibility as a means of kinetic-to-thermal-energy conversion and can be significantly different from Mc for flows with far-from-unity free-stream-density and speed-of-sound ratios. Experimentally observed growth rates are well-represented by the new scaling.

Experimental Validation of Quasisteady Assumption in Modeling of Unsteady Film-Cooling

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Stefan Bernsdorf ◽  
Martin G. Rose ◽  
Reza S. Abhari
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Three Dimensional ◽  
Flow Region ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Jet Trajectory ◽  
Air Streams

This paper reports on the validation of the assumption of quasisteady behavior of pulsating cooling injection in the near hole flow region. The respective experimental data are taken in a flat plate wind tunnel at ETH Zürich. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative nondimensionals are achieved, providing a faithful model at a larger scale. Heating the free stream air and strongly cooling the coolant gives the required density ratio between coolant and free-stream. The coolant is injected with different frequency and amplitude. The three-dimensional velocities are recorded using nonintrusive PIV, and seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The general flow field, the jet trajectory, and the streamwise circulation are utilized in the validation of the quasisteady assumption.

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