scholarly journals Some Modifications to, and Operational Experiences With, the Two-Dimensional, Finite-Difference, Boundary-Layer Code, STAN5

1981 ◽  
Author(s):  
R. E. Gaugler
Keyword(s):  
Boundary Layer ◽  
Finite Difference ◽  
Film Cooling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Transition To Turbulence ◽  
Nasa Lewis Research ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The two-dimensional, finite-difference boundary-layer code, STAN5, is the primary tool used at the NASA-Lewis Research Center for predicting turbine blade gas-side heat-transfer coefficients. A number of modifications have been made to the program to enhance its usefulness for these calculations. Experience in using STAN5 has identified some problems in the program that can be treated through program input, without modifying the program. These include the presence of a small separation bubble near the leading edge, and the effect of full-coverage film cooling on transition to turbulence. Some of the techniques used to treat these problems are described.

Interactions of Film Cooling Rows: Effects of Hole Geometry and Row Spacing on the Cooling Performance Downstream of the Second Row of Holes

2003 ◽  
Author(s):  
Christian Saumweber ◽  
Achmed Schulz
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Staggered Arrangement ◽  
Film Cooling Holes

A comprehensive set of generic experiments is conducted to investigate the interaction of film cooling rows. Five different film cooling configurations are considered on a large scale basis each consisting of two rows of film cooling holes in staggered arrangement. The hole pitch to diameter ratio within each row is kept constant at P/D = 4. The spacing between the rows is either x/D = 10, 20, or 30. Fanshaped holes or simple cylindrical holes with an inclination angle of 30 deg. and a hole length of 6 hole diameters are used. With a hot gas Mach number of Mam = 0.3, an engine like density ratio of ρc/ρm = 1.75, and a freestream turbulence intensity of Tu = 5.1% are established. Operating conditions are varied in terms of blowing ratio for the upstream and, independently, the downstream row in the range 0.5<M<2.0. The results illustrate the importance of considering ejection into an already film cooled boundary layer. Adiabatic film cooling effectiveness and heat transfer coefficients are significantly increased. The decay of effectiveness with streamwise distance is much less pronounced downstream of the second row primarily due to pre-cooling of the boundary layer by the first row of holes. Additionally, a comparison of measured effectiveness data with predictions according to the widely used superposition model of Sellers [11] is given for two rows of fanshaped holes.

scholarly journals The Superposition Approach to Local Heat Transfer Coefficients in High Density Ratio Film Cooling Flows

1999 ◽  
Author(s):  
Michael Gritsch ◽  
Stefan Baldauf ◽  
Moritz Martiny ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Cooling Flows ◽  
Heat Transfer Coefficients ◽  
High Density Ratio ◽  
The Heat Transfer Coefficient

The present paper reports on the use of the superposition approach in high density ratio film cooling flows. It arises from the linearity and homogeneity of the simplified boundary layer differential equations. However, it is widely assumed that the linearity does not hold for variable property flows. Therefore, theoretical considerations and numerical calculations will demonstrate the linearity of the heat transfer coefficient with the dimensionless coolant temperature θ as long as identical flow conditions are applied. This makes it necessary to perform at least two experiments at different θ but with the coolant to main flow temperature ratio kept unchanged. A comprehensive set of experiments is presented to demonstrate the capability of the superposition approach for determining heat transfer coefficients for different film cooling geometries. These comprise coolant injection from two dimensional tangential slots, single holes, and rows of cylindrical holes. Particularly, two dimensional local distributions of the heat transfer coefficient will be addressed.

A Transient Calorimeter Technique for Determining Regional Heat Transfer Coefficients in the Three-Temperature Flowfield at a Turbine Airfoil Leading Edge

2005 ◽  
Author(s):  
Scott R. Nowlin ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Ralf Knoche ◽  
T. Robert Kingston
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Internal Flow ◽  
Leading Edge ◽  
Internal Surface ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Novel Method ◽  
Exposed Surface Area

In this paper, the authors develop a novel method of obtaining regionally-averaged heat transfer coefficients in flowfields characterized by three temperatures using the well-known transient calorimeter technique. The technique is used to determine heat transfer in aluminum models of idealized turbine blade leading edges cooled through internal surface impingement, film cooling feed passages, and external convective film cooling. The external surface is subject to a stagnating mainstream crossflow. Importantly, the contributions to heating from the external flow and cooling from the internal flow can be separately resolved solely by heating the internal flow. Results for a basic showerhead geometry and an advanced intersecting-passage cooling configuration are presented for a range of internal and external Reynolds numbers. The intersecting-passage model shows little improvement in heat transfer coefficient over the showerhead for the flow conditions tested; however, the total cooling carried out is improved by the increase in exposed surface area. The technique’s uncertainties are fully assessed.

Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade

1997 ◽  
Vol 119 (2) ◽  
pp. 302-309 ◽  
Author(s):  
N. Abuaf ◽  
R. Bunker ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Film Cooling ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Heat Transfer Coefficients

A warm (315°C) wind tunnel test facility equipped with a linear cascade of film cooled vane airfoils was used in the simultaneous determination of the local gas side heat transfer coefficients and the adiabatic film cooling effectiveness. The test rig can be operated in either a steady-state or a transient mode. The steady-state operation provides adiabatic film cooling effectiveness values while the transient mode generates data for the determination of the local heat transfer coefficients from the temperature–time variations and of the film effectiveness from the steady wall temperatures within the same aerothermal environment. The linear cascade consists of five airfoils. The 14 percent cascade inlet free-stream turbulence intensity is generated by a perforated plate, positioned upstream of the airfoil leading edge. For the first transient tests, five cylinders having roughly the same blockage as the initial 20 percent axial chord of the airfoils were used. The cylinder stagnation point heat transfer coefficients compare well with values calculated from correlations. Static pressure distributions measured over an instrumented airfoil agree with inviscid predictions. Heat transfer coefficients and adiabatic film cooling effectiveness results were obtained with a smooth airfoil having three separate film injection locations, two along the suction side, and the third one covering the leading edge showerhead region. Near the film injection locations, the heat transfer coefficients increase with the blowing film. At the termination of the film cooled airfoil tests, the film holes were plugged and heat transfer tests were conducted with non-film cooled airfoils. These results agree with boundary layer code predictions.

The Influence of the Boundary Layer State and Reynolds Number on Film Cooling and Heat Transfer on a Cooled Nozzle Guide Vane

2000 ◽  
Author(s):  
Hans Reiss ◽  
Albin Bölcs
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Guide Vane ◽  
Suction Side ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Film cooling and heat transfer measurements were carried out on a cooled nozzle guide vane in a linear cascade, using a transient liquid crystal technique. Three flow conditions were realized: the nominal operating condition of the vane with an exit Reynolds number of 1.47e6, as well as two lower flow conditions: Re2L = 1.0e6 and 7.5e5. The vane model was equipped with a single row of inclined round film cooling holes with compound angle orientation on the suction side. Blowing ratios ranging form 0.3 to 1.5 were covered, all using foreign gas injection (CO2) yielding an engine-representative density ratio of 1.6. Two distinct states of the incoming boundary layer onto the injection station were compared, an undisturbed laminar boundary layer as it forms naturally on the suction side, and a fully turbulent boundary layer which was triggered with a trip wire upstream of injection. The aerodynamic flow field is characterized in terms of profile Mach number distribution, and the associated heat transfer coefficients around the uncooled airfoil are presented. Both detailed and spanwise averaged results of film cooling effectiveness and heat transfer coefficients are shown on the suction side, which indicate considerable influence of the state of the incoming boundary layer on the performance of a film cooling row. The influence of the mainstream flow condition on the film cooling behavior at constant blowing ratio is discussed for three chosen injection regimes.

Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade

1995 ◽  
Author(s):  
N. Abuaf ◽  
R. Bunker ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Film Cooling ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Heat Transfer Coefficients

A warm (315 C) wind tunnel test facility equipped with a linear cascade of film cooled vane airfoils was used in the simultaneous determination of the local gas side heat transfer coefficients and the adiabatic film cooling effectiveness. The test rig can be operated in either a steady-state or a transient mode. The steady-state operation provides adiabatic film cooling effectiveness values while the transient mode generates data for the determination of the local heat transfer coefficients from the temperature-time variations and of the film effectiveness from the steady wall temperatures within the same aero-thermal environment. The linear cascade consists of five airfoils. The 14% cascade inlet free stream turbulence intensity is generated by a perforated plate, positioned upstream of the airfoil leading edge. For the first transient tests, five cylinders having roughly the same blockage as the initial 20% axial chord of the airfoils were used. The cylinder stagnation point heat transfer coefficients compare well with values calculated from correlations. Static pressure distributions measured over an instrumented airfoil agree with inviscid predictions. Heat transfer coefficients and adiabatic film cooling effectiveness results were obtained with a smooth airfoil having three separate film injection locations, two along the suction side, and the third one covering the leading edge showerhead region. Near the film injection locations, the heat transfer coefficients increase with the blowing film. At the termination of the film cooled airfoil tests, the film holes were plugged and heat transfer tests were conducted with non-film cooled airfoils. These results agree with boundary layer code predictions.

Prediction of Heat Transfer Characteristics for Discrete Hole Film Cooling for Turbine Blade Applications

1990 ◽  
Vol 112 (3) ◽  
pp. 504-511 ◽  
Author(s):  
D. K. Tafti ◽  
S. Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Three Dimensional ◽  
Hole Injection ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Injection Process ◽  
Prediction Scheme

A two-dimensional injection model is used with a two-dimensional low Reynolds number k-ε model boundary layer code. The three-dimensional effects of the discrete hole injection process are introduced in the two-dimensional prediction scheme through an “entrainment fraction” (Υ). An established correlation between Υ and the injection parameters obtained in a previous paper is used to predict the film cooling effectiveness (η) and heat transfer coefficients for multirow injection, injection into a laminar boundary layer, and finally injection on convex curved surfaces. Predictions of η are in good agreement with experimental data for most of the cases tested. Predictions of Stanton numbers defined by St(0) and St(l) are good for low injection ratios (M) but as M increases the values are underpredicted. In spite of some shortcomings, in the authors’ opinion the present two-dimensional prediction scheme is one of the most comprehensive developed so far. It is seen that the entrainment fraction Υ is quite universal in its application to two-dimensional predictions of the discrete hole film cooling process.

An Experimental Investigation of Film Cooling Heat Transfer Coefficients Using the Mass/Heat Analogy

1995 ◽  
Vol 117 (4) ◽  
pp. 851-858 ◽  
Author(s):  
Y. Sun ◽  
I. S. Gartshore ◽  
M. E. Salcudean
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Experimental Investigation ◽  
Mass Flow ◽  
Film Cooling ◽  
Wall Function ◽  
Transfer Coefficients ◽  
Correction Formula ◽  
Heat Transfer Coefficients

An experimental investigation has been carried out to determine the heat/mass transfer coefficient downstream of a two-dimensional, normal, film cooling injection slot. The plate downstream of the slot is porous, and air contaminated with propane is bled through it. By measuring the propane concentration very close to the wall using a flame ionization detector, mass transfer measurements are conducted for film cooling mass flow ratios ranging from 0 to 0.5. The mass transfer coefficients are calculated using a wall function correction formula, which corrects the measurements for displacement from the surface, and are then related directly to corresponding heat transfer coefficients using the mass/heat analogy. The validity of the method and the wall function correction formula are checked by examining the case with zero film coolant injection, a situation analogous to the well-known turbulent boundary layer mass/heat transfer with impermeable/unheated starting length. Good agreement with predicted data is obtained for this experiment. For film cooling with low mass flow ratios, heat transfer coefficients close to those of a conventional turbulent boundary layer are obtained. At high values of mass flow ratios quite different trends are observed, reflecting the important effect of the separation bubble, which is present just downstream of the injection slot.

Direct Numerical Simulation and Large Eddy Simulation of Laminar Separation Bubbles at Moderate Reynolds Numbers

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Francois Cadieux ◽  
Julian A. Domaradzki ◽  
Taraneh Sayadi ◽  
Sanjeeb Bose
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Boundary Layer ◽  
Direct Numerical Simulation ◽  
Separation Bubble ◽  
Leading Edge ◽  
Transition To Turbulence ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Large Eddy

Flows over airfoils and blades in rotating machinery for unmanned and microaerial vehicles, wind turbines, and propellers consist of different flow regimes. A laminar boundary layer near the leading edge is often followed by a laminar separation bubble with a shear layer on top of it that experiences transition to turbulence. The separated turbulent flow then reattaches and evolves downstream from a nonequilibrium turbulent boundary layer to an equilibrium one. Typical Reynolds-averaged Navier–Stokes (RANS) turbulence modeling methods were shown to be inadequate for such laminar separation bubble flows (Spalart and Strelets, 2000, “Mechanisms of Transition and Heat Transfer in a Separation Bubble,” J. Fluid Mech., 403, pp. 329–349). Direct numerical simulation (DNS) is the most reliable but is also the most computationally expensive alternative. This work assesses the capability of large eddy simulations (LES) to reduce the resolution requirements for such flows. Flow over a flat plate with suitable velocity boundary conditions away from the plate to produce a separation bubble is considered. Benchmark DNS data for this configuration are generated with the resolution of 59 × 106 mesh points; also used is a different DNS database with 15 × 106 points (Spalart and Strelets, 2000, “Mechanisms of Transition and Heat Transfer in a Separation Bubble,” J. Fluid Mech., 403, pp. 329–349). Results confirm that accurate LES are possible using O(1%) of the DNS resolution.

A note on expansions for the two-dimensional, compressible, laminar boundary layer equations near a point of zero skin friction

1983 ◽  
Vol 94 (1-2) ◽  
pp. 93-96 ◽  
Author(s):  
G. Wilks
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Skin Friction ◽  
Laminar Boundary Layer ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Boundary Layer Equations ◽  
Heat Transfer Coefficients

SynopsisThe first non-arbitrary coefficient, α12, of the Buckmaster expansions is evaluated in the context of the extended Goldstein-Stewartson theory. Leading terms of the next order contributions to the skin friction and heat transfer coefficients are also obtained.

Sign in / Sign up

Export Citation Format

Share Document