Heat Transfer Committee Best Paper of 1995 Award: Distribution of Film-Cooling Effectiveness on a Turbine Endwall Measured Using the Ammonia and Diazo Technique

1996 ◽  
Vol 118 (4) ◽  
pp. 613-621 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Surface Concentration ◽  
Surface Flow ◽  
Turbine Cascade ◽  
Cooling Effectiveness ◽  
Ammonia Gas ◽  
Film Cooling Effectiveness ◽  
Complete Representation ◽  
A New Technique

The distribution of adiabatic film-cooling effectiveness on the endwall of a large-scale low-speed linear turbine cascade has been measured using a new technique. This technique is based on an established surface-flow visualization technique, and makes use of the reaction between ammonia gas and a diazo surface coating. A new method of calibration has been developed to relate the result of the reaction to surface concentration of coolant. Using the analogy that exists between heat and mass transfer, the distribution of film-cooling effectiveness can then be determined. The complete representation of the film-cooling effectiveness distribution provided by the technique reveals the interaction between the coolant ejected from the endwall and the secondary flow in the turbine blade passage. Over- and undercooled regions on the endwall are identified, illustrating the need to take these interactions into account in the design process. Modifications to the cooling configuration examined in this paper are proposed as a result of the application of the ammonia and diazo technique.

scholarly journals Distribution of Film-Cooling Effectiveness on a Turbine Endwall Measured Using the Ammonia and Diazo Technique

1995 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Surface Concentration ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Cooling Effectiveness ◽  
Ammonia Gas ◽  
Film Cooling Effectiveness ◽  
Complete Representation ◽  
A New Technique

The distribution of adiabatic film-cooling effectiveness on the endwall of a large-scale low-speed linear turbine cascade has been measured using a new technique. This technique is based on an established surface-flow visualisation technique, and makes use of the reaction between ammonia gas and a diazo surface coating. A new method of calibration has been developed to relate the result of the reaction to surface concentration of coolant. Using the analogy that exists between heat and mass transfer the distribution of film-cooling effectiveness can then be determined. The complete representation of the film-cooling effectiveness distribution provided by the technique reveals the interaction between the coolant ejected from the endwall and the secondary flow in the turbine blade passage. Over- and under-cooled regions on the endwall are identified, illustrating the need to take these interactions into account in the design process. Modifications to the cooling configuration examined in this paper are proposed as a result of the application of the ammonia and diazo technique.

Systematic Study on the Fluid Dynamical Behaviour of Streamwise and Laterally Inclined Jets in Crossflow

1997 ◽  
Author(s):  
R.-D. Baier ◽  
W. Koschel ◽  
K.-D. Broichhausen ◽  
G. Fritsch
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Large Scale ◽  
Computational Study ◽  
Dynamical Behaviour ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

The design of discrete film cooling holes for gas turbine airfoil applications is governed by a number of parameters influencing both their aerodynamic and thermal behaviour. This numerical and experimental study focuses on the marked differences between film cooling holes with combined streamwise and lateral inclination and film cooling holes with streamwise inclination only. The variation in the blowing angle was chosen on a newly defined and physically motivated basis. High resolution low speed experiments on a large scale turbine airfoil gave insights particularly into the intensified mixing process with lateral ejection. The extensive computational study is performed with the aid of a 3D block-structured Navier-Stokes solver incorporating a low-Reynolds-number k-ε turbulence model. Special attention is paid to mesh generation as a precondition for accurate high-resolution results. The downstream temperature fields of the jets show reduced spanwise variations with increasing lateral blowing angle; these variations are quantified for a comprehensive variety of configurations in terms of adiabatic film cooling effectiveness.

Unsteady Analysis of Adiabatic Film Cooling Effectiveness Behind a Row of Circular Holes Fed by Internal Crossflow

2019 ◽  
Author(s):  
Mohamed Qenawy ◽  
Wenwu Zhou ◽  
Han Chen ◽  
Hongyi Shao ◽  
Di Peng ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Main Role ◽  
Test Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Entry Length ◽  
Circular Holes

Abstract The adiabatic film cooling effectiveness behind a single row of circular holes fed by internal crossflow was measured by fast-response pressure-sensitive paint technique. During the experiment, the coolant flow was discharged from the coolant holes via either plenum or crossflow channel. The test model has a row of circular holes with 3D spacing, 6.5D entry length, and 35° inclination angle. Two blowing ratios (M = 0.40 and 0.80) were tested with a density ratio of 0.97. A numerical steady-state RANS simulation, using SST k-ω and Realizable k-ε turbulence models, was conducted to understand the internal crossflow behaviors. The unsteadiness caused by the flow structures (counter-rotating vortex pair (CRVP) and horseshoe vortex) was quantified by the root mean square and the cross-correlations. In addition, the proper orthogonal decomposition was used to identify the large-scale unsteady coherent structures and their contributions. The fluctuations of the crossflow feed were asymmetric, which were significantly weaker compared with the plenum case. The CRVP, as the most significant coherent structures, were demonstrated to play the main role in the unsteadiness of the crossflow feed.

Aerodynamic Aspects of Endwall Film-Cooling

1996 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Static Pressure ◽  
Three Dimensional ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Film Cooling Effectiveness ◽  
Blade Passage ◽  
Endwall Film Cooling

This paper describes an investigation of the aerodynamic aspects of endwall film-cooling, in which the flow field downstream of a large-scale low-speed linear turbine cascade has been measured. The integrated losses and locations of secondary flow features with and without end wait film-cooling have been determined for variations of both the coolant supply pressure and injection location. Together with previous measurements of adiabatic film-cooling effectiveness and surface-flow visualisation, these results reveal the nature of the interactions between the ejected coolant and the flow in the blade passage. Measured hole massflows and a constant static pressure mixing analysis, together with the measured losses, allow the decomposition of the losses into three distinct entropy generation mechanisms: loss generation within the hole, loss generation due to the mixing of the coolant with the mainstream, and change in secondary loss generation in the blade passage. Results show that the loss generation within the coolant holes is substantial and that ejection into regions of low static pressure increases the loss per unit coolant massflow. Ejection upstream of the three-dimensional separation lines on the endwall changes secondary flow and reduces its associated losses. The results show that it is necessary to take the three-dimensional nature of the endwall flow into account in the design of endwall film-cooling configurations.

An Experimental Study of Heat Transfer and Film Cooling on Large-Scale Turbine Endwalls

1974 ◽  
Vol 96 (4) ◽  
pp. 524-529 ◽  
Author(s):  
M. F. Blair
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Film Cooling ◽  
Large Scale ◽  
Convective Heat Transfer Coefficient ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Test Models ◽  
Turbine Vane ◽  
Flow Vortex

Experiments were conducted to determine the film cooling effectiveness and convective heat transfer coefficient distributions on the endwall of a large-scale turbine vane passage. The vane test models employed simulated the passage geometry and upstream cooling slot geometry of a typical first stage turbine. The test models were constructed of low thermal conductivity foam and foil heaters. The tests were conducted at a typical engine Reynolds number but at lower than typical Mach numbers. The film cooling effectiveness distribution for the entire endwall and the heat transfer distribution for the downstream one-half of the endwall were characterized by large gapwise variations which were attributed to a secondary flow vortex.

The Experimental and Numerical Research for Linear Cascade Film Cooling With Different Hole Shapes

2010 ◽  
Author(s):  
Yi Lu ◽  
Yinyi Hong ◽  
Zhirong Lin ◽  
Xin Yuan
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Blowing Ratio ◽  
Cylindrical Holes

Detailed film cooling effectiveness distributions were experimentally obtained on a turbine vane platform within a linear cascade. Testing was done in a large scale five-vane cascade with low freestream Renolds number condition 634,000 based on the axial chord length and the exit velocity. The detailed film-cooling effectiveness distributions on the platform were obtained using pressure sensitive paint technique. Two film-cooling hole configurations, cylindrical and fan-shaped, were used to cool the vane surface with two rows on pressure side, two rows on suction side and three rows on leading edge. For cylindrical holes, the blowing ratio of the coolant through the discrete cooling holes on pressure side and suction side ranged from 0.3 to 1.5 (based on the inlet mainstream velocity) while the blowing ratio ranging from 0.15 to 1.5 on leading edge; for fan-shaped holes, the four blowing ratios were 0.5, 1.0, 1.5 and 2.0. Results showed that average film-cooling effectiveness decreased with increasing blowing rate for the cylindrical holes, while the fan-shaped passage showed increased film-cooling effectiveness with increasing blowing ratio, indicating the fan-shaped cooling holes helped to improve film-cooling effectiveness by reducing overall jet liftoff. Fan-shaped holes improved average film-cooling effectiveness by 93.2%, 287.6% and 489.6% on pressure side, −4.1%, 27.9% and 78.2% on suction side over cylindrical holes at the blowing ratio of 0.5, 1.0 and 1.5 respectively. Numerical results were used to analyze the details of the flow and heat transfer on the cooling area with two turbulence models. Results demonstrated that tendency of the film cooling effectiveness distribution of numerical calculation and experimental measurement was generally consistent at different blowing ratio.

Aerodynamic Aspects of Endwall Film-Cooling

1997 ◽  
Vol 119 (4) ◽  
pp. 786-793 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Static Pressure ◽  
Three Dimensional ◽  
Surface Flow ◽  
Film Cooling Effectiveness ◽  
Blade Passage ◽  
Generation Mechanisms ◽  
Endwall Film Cooling

This paper describes an investigation of the aerodynamic aspects of endwall film-cooling, in which the flow field downstream of a large-scale low-speed linear turbine cascade has been measured. The integrated losses and locations of secondary flow features with and without endwall film-cooling have been determined for variations of both the coolant supply pressure and injection location. Together with previous measurements of adiabatic film-cooling effectiveness and surface-flow visualization, these results reveal the nature of the interactions between the ejected coolant and the flow in the blade passage. Measured hole massflows and a constant static pressure mixing analysis, together with the measured losses, allow the decomposition of the losses into three distinct entropy generation mechanisms: loss generation within the hole, loss generation due to the mixing of the coolant with the mainstream, and change in secondary loss generation in the blade passage. Results show that the loss generation within the coolant holes is substantial and that ejection into regions of low static pressure increases the loss per unit coolant massflow. Ejection upstream of the three-dimensional separation lines on the endwall changes secondary flow and reduces its associated losses. The results show that it is necessary to take the three-dimensional nature of the endwall flow into account in the design of endwall film-cooling configurations.

New Techniques for Measuring Film Cooling Effectiveness

1975 ◽  
Vol 97 (4) ◽  
pp. 539-543 ◽  
Author(s):  
M. F. Blair ◽  
R. D. Lander
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Leading Edge ◽  
New Techniques ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Rigid Foam ◽  
Test Models ◽  
Scale Models ◽  
Infrared Radiometer

Techniques to measure local film effectiveness distributions on large-scale models of turbine blade and vane sections were developed for use in subsonic, room-temperature wind-tunnel environments. Highly detailed film cooling effectiveness distributions were obtained on near-adiabatic, cast rigid foam test models using infrared radiometer scanning techniques. Sample results from both flat-plate film cooling studies and airfoil leading-edge film cooling studies are presented.

A Comparison of Cylindrical and Fan-Shaped Film-Cooling Holes on a Vane Endwall at Low and High Freestream Turbulence Levels

2006 ◽  
Author(s):  
W. Colban ◽  
K. A. Thole ◽  
M. Haendler
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Manufacturing Cost ◽  
Freestream Turbulence ◽  
Flat Plates ◽  
Major Drawback ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Film Cooling Holes

Fan-shaped film-cooling holes have been shown to provide superior cooling performance to cylindrical holes along flat-plates and turbine airfoils over a large range of different conditions. Benefits of fan-shaped holes include less required cooling air for the same performance, increased part lifetime, and fewer required holes. The major drawback however, is increased manufacturing cost and manufacturing difficulty, particularly for the vane platform region. To this point, there have only been extremely limited comparisons between cylindrical and shaped holes on a turbine endwall at either low or high freestream turbulence conditions. This study presents film-cooling effectiveness measurements on an endwall surface in a large-scale, low-speed, two-passage, linear vane cascade. Results showed that film-cooling effectiveness decreased with increasing blowing rate for the cylindrical holes, indicating jet lift-off. However, the fan-shaped passage showed increased film-cooling effectiveness with increasing blowing ratio. Overall, fan-shaped holes increased film-cooling effectiveness by an average of 75% over cylindrical holes for constant cooling flow.

Film Cooling Effectiveness Measurements on Trailing Edge Cutback Surface and Lands Following Novel Cross Corrugated Slot Geometry

2016 ◽  
Author(s):  
T. H. Wong ◽  
P. T. Ireland ◽  
K. P. Self
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Scale Model ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Included Angle ◽  
Rectangular Slot ◽  
Turbine Cooling ◽  
Cooling Design

The trailing edge of the high pressure turbine blade presents significant challenges to the turbine cooling engineer. A novel cooling design using cross corrugated slots for the trailing edge has been proposed. This geometry allows blade designers to finely tune pressure loss and consequently coolant flow through the slot, but potentially results in poor film cooling performance downstream of the slot exit, an effect that could be mitigated with exit shaping. The current study is focused on comparing film cooling effectiveness on the cutback surface and lands with a plain rectangular slot under the same conditions. A set of nine cross corrugated internal slot geometries has been investigated in a large scale model of the trailing edge pressure side ejection slot exit. Four geometries used a 90° included angle with variations to the channel alignment at slot exit. Four used a 120° included angle, with the same variations to the exit alignment. The final geometry used a 90° included angle with exit shaping. Pressure sensitive paint was used to measure adiabatic film cooling effectiveness at five blowing ratios ranging from 0.6 to 1.4 in increments of 0.2. High resolution 2D distributions of film cooling effectiveness both on the cutback surface and the top of the lands were recorded. It was found that unmodified cross corrugated slots do result in poor film effectiveness on the cutback surface compared to a plain rectangular slot. However, land cooling is slightly improved, and applying exit shaping to the cross corrugated slot results in effectiveness levels at the trailing edge on par with or even superior to the rectangular slot at blowing ratios of 0.8 or below. Therefore, in this respect, the novel cross corrugated slot design proposed is a viable candidate for blade design, provided exit shaping is used and low blowing ratios are expected.

Sign in / Sign up

Export Citation Format

Share Document