Investigation on the Accuracy of Superposition Predictions of Film Cooling Effectiveness

2018 ◽  
Vol 35 (2) ◽  
pp. 181-192
Author(s):  
Tong Meng ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Jian-sheng Wei
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Superposition Method ◽  
Flat Plates ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Staggered Arrangement ◽  
Infrared Measurement ◽  
Experimental Values

Abstract Film cooling effectiveness on flat plates with double rows of holes has been studied experimentally and numerically in this paper. This configuration is widely used to simulate the multi-row film cooling on turbine vane. Film cooling effectiveness of double rows of holes and each single row was used to study the accuracy of superposition predictions. Method of stable infrared measurement technique was used to measure the surface temperature on the flat plate. This paper analyzed the factors that affect the film cooling effectiveness including hole shape, hole arrangement, row-to-row spacing and blowing ratio. Numerical simulations were performed to analyze the flow structure and film cooling mechanisms between each film cooling row. Results show that the blowing ratio within the range of 0.5 to 2 has a significant influence on the accuracy of superposition predictions. At low blowing ratios, results obtained by superposition method agree well with the experimental data. While at high blowing ratios, the accuracy of superposition prediction decreases. Another significant factor is hole arrangement. Results obtained by superposition prediction are nearly the same as experimental values of staggered arrangement structures. For in-line configurations, the superposition values of film cooling effectiveness are much higher than experimental data. For different hole shapes, the accuracy of superposition predictions on converging-expanding holes is better than cylinder holes and compound angle holes. For two different hole spacing structures in this paper, predictions show good agreement with the experiment results.

Accuracy of Superposition Predictions of Film Cooling Effectiveness on a Flat Plate With Double Rows of Holes

2016 ◽  
Author(s):  
Tong Meng ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Qiang Yu ◽  
Jian-sheng Wei
Keyword(s):  
Film Cooling ◽  
Suction Side ◽  
Superposition Method ◽  
Flat Plates ◽  
Ansys Fluent ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Main Work ◽  
Measure Surface Temperature ◽  
Staggered Arrangement

Multi-row film cooling is widely used on both suction side and pressure side of turbine vane, and the coolant behavior is considerable for engine design. Main work of this paper is to find out the accuracy of superposition predictions. Experiments were conducted on flat plates with double rows of cooling holes. The method of stable infrared measurement technique was used to measure surface temperature. Four factors, including hole shape, hole arrangement, row-to-row spacing and blowing ratio were simulated. Numerical simulation using commercial software ANSYS Fluent was also performed to observe the flow structure and film cooling mechanisms between each row. Result showed that the blowing ratio within the range of 0.5 to 2 has an obvious influence on the accuracy of superposition prediction. At low blowing ratio, results obtained by superposition method agreed well with the experimental data while the increase of blowing ratio caused a decrease in accuracy. Another significant factor is hole arrangement, results obtained by superposition prediction was nearly the same as experimental values on staggered arrangement plates while it was much higher on in-line arrangement plates. For different hole shapes, the accuracy of superposition prediction on converging-expanding holes was better than cylinder holes and compound angle holes. For both two hole spacing in this paper, prediction results show good agreement with the experiment results.

Leading Edge Film Cooling: Computations and Experiments Including Density Effects

1996 ◽  
Author(s):  
Pingfan He ◽  
Dragos Licu ◽  
Martha Salcudean ◽  
Ian S. Gartshore
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Stokes Equations ◽  
Leading Edge ◽  
Variable Density ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

The effect of varying coolant density on film cooling effectiveness for a turbine blade-model was numerically investigated and compared with experimental data. This model had a semi-circular leading edge with four rows of laterally-inclined film cooling orifices positioned symmetrically about the stagnation line. A curvilinear coordinate-based CFD code was developed and used for the numerical investigation. The code used a domain segmentation strategy in conjunction with general curvilinear grids to model the complex blade configuration. A multigrid method was used to accelerate the convergence rate. The time-averaged, variable-density, Navier-Stokes equations together with the energy or scalar equation were solved. Turbulence closure was attained by the standard k–ε model with a near-wall k model. Either air or CO2 was used as coolant in three cases of injection through single rows and alternatively staggered double raws of holes. Two different blowing rates were investigated in each case and compared with experimental data. The experimental results were obtained using a wind tunnel model, and the mass/heat analogy was used to determine the film cooling effectiveness. The higher density of the carbon dioxide coolant (approximately 1.5 times the density of air) in the isothermal mass injection experiments, was used to simulate the effects of injection of a colder air in the corresponding adiabatic heat transfer situation. Good agreement between calculated and measured film cooling effectiveness was found for low blowing ratio M ≤ 0.5 and the effect of density was not significant. At higher blowing ratio M > 1 the calculations consistently overpredict the measured values of film cooling effectiveness.

Measured Film Cooling Effectiveness of Three Multihole Patterns

2005 ◽  
Vol 128 (2) ◽  
pp. 192-197 ◽  
Author(s):  
Yuzhen Lin ◽  
Bo Song ◽  
Bin Li ◽  
Gaoen Liu
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Film Cooling ◽  
Row Spacing ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Analogy Method ◽  
Blowing Ratio ◽  
The Third ◽  
Coolant Injection

As an advanced cooling scheme to meet increasingly stringent combustor cooling requirements, multihole film cooling has received considerable attention. Experimental data of this cooling scheme are limited in the open literature in terms of different hole patterns and blowing ratios. The heat-mass transfer analogy method was employed to measure adiabatic film cooling effectiveness of three multihole patterns. Three hole patterns differed in streamwise row spacing (S), spanwise hole pitch (P), and hole inclination angle (α), with the first pattern S∕P=2 and α=30°, the second S∕P=1 and α=30°, and the third S∕P=2 and α=150°. Measurements were performed at different blow ratios (M=1-4). Streamwise coolant injection offers high cooling protection for downstream rows. Reverse coolant injection provides superior cooling protection for initial rows. The effect of blowing ratio on cooling effectiveness is small for streamwise injection but significant for reversion injection.

Film Cooling Effectiveness From Two Rows of Compound Angled Cylindrical Holes Using Pressure-Sensitive Paint Technique

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Nian Wang ◽  
Mingjie Zhang ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Pressure Sensitive Paint ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Pressure Sensitive ◽  
Staggered Arrangement ◽  
Cylindrical Holes

This study investigates the effects of blowing ratio, density ratio, and spanwise pitch on the flat plate film cooling from two rows of compound angled cylindrical holes. Two arrangements of two-row compound angled cylindrical holes are tested: (a) the first row and the second row are oriented in staggered and same compound angled direction (β = +45 deg for the first row and +45 deg for the second row); (b) the first row and the second row are oriented in inline and opposite direction (β = +45 deg for the first row and −45 deg for the second row). The cooling hole is 4 mm in diameter with an inclined angle of 30 deg. The streamwise row-to-row spacing is fixed at 3d, and the spanwise hole-to-hole (p) is varying from 4d, 6d to 8d for both designs. The film cooling effectiveness measurements were performed in a low-speed wind tunnel in which the turbulence intensity is kept at 6%. There are 36 cases for each design including four blowing ratios (M = 0.5, 1.0, 1.5, and 2.0), three density ratios (DR = 1.0, 1.5, and 2.0), and three hole-to-hole spacing (p/d = 4, 6, and 8). The detailed film cooling effectiveness distributions were obtained by using the steady-state pressure-sensitive paint (PSP) technique. The spanwise-averaged cooling effectiveness are compared over the range of flow parameters. Some interesting observations are discovered including blowing ratio effect strongly depending on geometric design; staggered arrangement of the hole with same orientation does not yield better effectiveness at higher blowing ratio. Currently, film cooling effectiveness correlation of two-row compound angled cylindrical holes is not available, so this study developed the correlations for the inline arrangement of holes with opposing angles and the staggered arrangement of holes with same angles. The results and correlations are expected to provide useful information for the two-row flat plate film cooling analysis.

Comparison of Four Different Two-Equation Models of Turbulence in Predicting Film Cooling Performance

2006 ◽  
Author(s):  
Jawad S. Hassan ◽  
Savas Yavuzkurt
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Turbulence Models ◽  
Accurate Solution ◽  
Diameter Ratio ◽  
Lateral Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Blowing Ratio

The capabilities of four two-equation turbulence models in predicting film cooling effectiveness were investigated and their limitations as well as relative performance are presented. The four turbulence models are the standard, RNG, and realizable k-ε models as well as the standard k-ω model all found in the FLUENT CFD code. In all four models, the enhanced wall treatment has been used to resolve the flow near solid boundaries. A systematic approach has been followed in the computational setup to insure grid-independence and accurate solution that reflects the true capabilities of the turbulence models. Exact geometrical and flow-field replicas of an experimental study on discrete-jet film cooling were generated and used in FLUENT. A pitch-to-diameter ratio of 3.04, injection length-to-diameter ratio of 4.6 and density ratios of 0.92 and 0.97 were some of the parameters used in the film cooling analysis. Furthermore, the study covered two levels of blowing ratio (M = 0.5 and 1.5) at an environment of low free-stream turbulence intensity (Tu = 0.1%). The standard k-ε model had the most consistent performance among all considered turbulence models and the best centerline film cooling effectiveness predictions with the results deviating from experimental data by only ±10% and about 20–60% for the low (M = 0.5) and high (M = 1.5) blowing ratio cases, respectively. However, centerline side-view and surface top-view contours of non-dimensional temperature for the standard k-ε cases revealed that the good results for film cooling effectiveness η compared to the experimental data were due to a combination of an over-prediction of jet penetration in the normal direction with an under-prediction of jet spread in the lateral direction. The standard k-ω model completely failed to produce any results that were meaningful with under-predictions of η that ranged between 80 and 85% for the low blowing ratio case and over-predictions of about 200% for the high blowing ratio case. Even though the RNG and realizable models showed to have better predicted the jet spread in the lateral direction compared to the standard k-ε model, there were some aspects of the flow, such as levels of turbulence generated by cross-flow and jet interaction, that were not realistic resulting in errors in the η prediction that ranged from −10% to +80% for the M = 0.5 case and from −80% to +70% for the M = 1.5 case. As a result of this study at this point it was concluded that the standard k-ε model have the most promising potential among the two-equation models considered. It was chosen as the best candidate for further improvement for the simulation of film cooling flows.

Investigation of Film Cooling Effectiveness of Full-Coverage Inclined Multihole Walls With Different Hole Arrangements

2003 ◽  
Author(s):  
Yuzhen Lin ◽  
Bo Song ◽  
Bin Li ◽  
Gaoen Liu ◽  
Zhiyong Wu
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Film Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Full Coverage ◽  
Inclination Angles ◽  
Combustor Liner ◽  
Compound Angle

An experimental and numerical investigation of adiabatic film cooling effectiveness was conducted on four full-coverage inclined multihole walls with different hole arrangements. The hole geometrical patterns and the test conditions were chosen to be representative of film cooling designs for modern aeroengine combustor liners. The four hole arrangements were grouped into two types based on lateral hole pitch ( P ) and streamwise row spacing ( S ). One type included two test plates which had the same S and P (S/P = 2) and compound angle (β = 0 deg) but different hole inclination angles ( α ) (30 and 150 deg ). The other type included two test plates which had the same S and P (but S/P = 1) and inclination angle (α = 30 deg) but different compound angles (0 deg and 50 deg). Heat-mass transfer analogy method was employed to investigate the adiabatic film cooling effectiveness of these multihole walls with typical blowing ratios for aeroengine combustors. The numerical simulation was performed to characterize the flowfield and temperature distribution, aiming to further understand the film cooling mechanisms. The experimental results indicated that blowing ratio within the range from 1 to 4 had negligible influence on adiabatic film cooling effectiveness (η) in the case of concurrent coolant injection while hole arrangement had large effect on η. But the blowing ratio within the range from 1 to 4 had large effect on the film cooling effectiveness for the counterflow film cooling scheme. The numerical results were compared with experimental data and fairly good agreement was obtained. The numerical simulation revealed the flow structure, particularly exhibiting significant influence of the interaction between mainstream flow and coolant jets on η. With validation by experimental data, film cooling numerical simulation seems quite helpful in selecting optimum multihole arrangement for modern combustor liner design.

Numerical Investigations of Wake and Shock Wave Effects on Film Cooling Performance in a Transonic Turbine Stage: Part 1 — Methodology Development and Qualification Over Stationary Stators and Rotors

2013 ◽  
Author(s):  
Huazhao Xu ◽  
Jianhua Wang ◽  
Ting Wang
Keyword(s):  
Experimental Data ◽  
Mach Number ◽  
Film Cooling ◽  
Suction Side ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Numerical Investigations ◽  
Blowing Ratio

To understand the unsteady shock wave and wake effects on the film cooling performance over a transonic 3-D rotating stage, a series of numerical investigations have been conducted and are presented in this two-part paper. Part 1 is focused on the development of the computational model and methodology of the system setup and model qualification; Part 2 is to investigate the unsteady effects of shock waves and wakes on film cooling performance in a transonic rotating stage. In Part 1, the film cooling experimental conditions (non-rotating) and test sections of Kopper et. al. and Hunter are selected for model qualification. The numerical computation is carried out by the commercial software Ansys/Fluent using the pressure based compressible flow governing equations. The effects of four turbulence models are carefully compared with the experimental data. The Realizable k-ε turbulence model is found to match the experimental data better than the other models and is thus used for the rest of the study, including Part 2. The results show that 1) the weak shock emanating from the neighboring stator’s trailing edge results in a temperature rise and a reduction of film cooling effectiveness on the suction side near the trailing edge, 2) cooling ejection from the trailing edge reduces the shock strength in the stator passage, 3) an increase in Mach number from 0.84 to 1.50 can reduce the total pressure losses of fluid flow near the end-walls, 4) the film cooling effectiveness increases with increasing blowing ratio and becomes more even on the stator with a higher blowing ratio, and 5) an increase in Mach number from 0.84 to 1.50 gives rise to a higher cooling effectiveness in the region from the cooling holes to 80% of the chord length of the stator on the pressure side, but becomes lower after this up to the trailing edge. However, on the stator’s suction side, higher Mach number results in a lower cooling effectiveness region around the film holes from 30% to 55% of the chord length, but cooling effectiveness increases downstream.

A Three-Regime Based Method for Correlating Film Cooling Effectiveness for Cylindrical and Shaped Holes

2015 ◽  
Author(s):  
Lieke Wang ◽  
Mats Kinell ◽  
Hossein N. Najafabadi ◽  
Matts Karlsson
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Transition Regime ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

To cope with high temperature of the gas from combustor, cooling is often used in the hot gas components in gas turbines. Film cooling is one of the effective methods used in this application. Both cylindrical and fan-shaped holes are used in film cooling. There have been a number of correlations published for both cylindrical and fan-shaped holes regarding film cooling effectiveness. Unfortunately there are no definitive correlations for either cylindrical or fan-shaped holes. This is due to the nature of the complexity of film cooling where many factors influence its performance, e.g., blowing ratio, density ratio, surface angle, downstream distance, expansion angle, hole length, turbulence level, etc. A test rig using infrared camera was built to test the film cooling performance for a scaled geometry from a real nozzle guide vane. Both cylindrical and fan-shaped holes were tested. To correlate the experimental data, a three-regime based method was developed for predicting the film cooling effectiveness. Based on the blowing ratio, the proposed method divides the film cooling performance in three regimes: fully attached (or no jet lift-off), fully jet lift-off, and the transition regime in between. Two separate correlations are developed for fully attached and full jet lift-off regimes, respectively. The method of interpolation from these two regimes is used to predict the film cooling effectiveness for the transition regime, based on the blowing ratio. It has been found this method can give a good correlation to match the experimental data, for both cylindrical and fan-shaped holes. A comparison with literature was also carried out, and it showed a good agreement.

A Film-Cooling Correlation for Shaped Holes on a Flat-Plate Surface

2008 ◽  
Author(s):  
Will F. Colban ◽  
Karen A. Thole ◽  
David Bogard
Keyword(s):  
Experimental Data ◽  
Flat Plate ◽  
Film Cooling ◽  
Empirical Correlation ◽  
Cooling Effectiveness ◽  
Physical Relationship ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Current Correlation ◽  
Film Cooling Holes

A common method of optimizing coolant performance in gas turbine engines is through the use of shaped film-cooling holes. Despite widespread use of shaped holes, existing correlations for predicting performance are limited to narrow ranges of parameters. This study extends the prediction capability for shaped holes through the development of a physics-based empirical correlation for predicting laterally-averaged film-cooling effectiveness on a flat plate downstream of a row of shaped film-cooling holes. Existing data was used to determine the physical relationship between film-cooling effectiveness and several parameters, including; blowing ratio, hole coverage ratio, area ratio, and hole spacing. Those relationships were then incorporated into the skeleton form of an empirical correlation, using results from the literature to determine coefficients for the correlation. Predictions from the current correlation, as well as existing shaped hole correlations and a cylindrical hole correlation were compared to the existing experimental data. Results show that the current physics-based correlation yields a significant improvement in predictive capability, by expanding the valid parameter range and improving agreement with experimental data. Particularly significant is the inclusion of higher blowing ratio conditions (up to M = 2.5) into the current correlation, whereas the existing correlations worked adequately only at lower blowing ratios (M ≈ 0.5).

Numerical Simulation of Single, Double, and Multiple Row Film Cooling Effectiveness and Heat Transfer

1984 ◽  
Author(s):  
Kevin L. Miller ◽  
Michael E. Crawford
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Cooling ◽  
Numerical Procedure ◽  
Linear Superposition ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Transfer Data ◽  
Coolant Injection ◽  
Experimental Values

A numerical procedure previously developed to simulate heat transfer with full-coverage film cooling has been successfully applied to film cooling geometries that incorporate single, double, and multiple rows of cooling holes. The procedure is based on the STAN5 boundary layer program with models added to simulate film coolant injection and turbulence augmentation. Experimental data for comparison have been extracted mostly from the open literature, and the data represent a wide variety of film cooling geometries. Both spanwise-averaged film cooling effectiveness and heat transfer data are considered. Linear superposition theory for film cooling is tested by comparing superposition predicted effectiveness with the experimental values.

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