scholarly journals Prediction of Film Cooling by Discrete-Hole Injection

1993 ◽  
Author(s):  
Jian-ming Zhou ◽  
Martha Salcudean ◽  
Ian S. Gartshore
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Computational Method ◽  
Hole Injection ◽  
Main Stream ◽  
Cooling Process ◽  
Double Row ◽  
Local Flow ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

This paper presents a study on film cooling performance resulting from injection through a single row and alternatively through two staggered rows of holes onto a flat plate. The objective is to use an appropriate computational method for the simulation of the film cooling process in order to improve our understanding of the complex flow and heat transfer phenomena downstream of the coolant injection holes. A multi-grid and segmentation method is used to solve the transport equations of the film cooling process to achieve good local flow resolution and rapid convergence. The turbulence is represented by the k-ϵ model combined with a nonisotropic eddy-viscosity formulation and a near-wall k model. New experimental results are obtained for comparison with the numerical simulations. Cooling through single and double rows of orifices is investigated computationally; for the same overal mass injection, the double row cooling has better spanwise averaged film cooling effectiveness for the range of parameters investigated. The effects of mass flow ratios and injection angles on the double row cooling performance are investigated computationally. Comparison between the predicted and measured spanwise averaged effectiveness shows good agreement for mass flow ratios of 0.2 and 0.4 but also shows that the numerical values are consistently lower than the measured results for mass flow ratios of 0.8. This difference suggests that the k-ϵ turbulence model under-predicts the turbulence production resulting from the shear flow between the main stream and jets when the cross flow momentum is high and the associated streamwise vorticity is strong and therefore that the turbulence stresses and scalar fluxes are not correctly predicted in these cases. Some possible improvements are suggested.

Numerical Investigation of the Cooling Performance on the Endwall With and Without Fillet

2018 ◽  
Author(s):  
Qingzong Xu ◽  
Qiang Du ◽  
Pei Wang ◽  
Jun Liu ◽  
Guang Liu
Keyword(s):  
Secondary Flow ◽  
Turbulence Model ◽  
Film Cooling ◽  
Computational Method ◽  
Inlet Temperature ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Numerical Predictions ◽  
Turbine Vane

High inlet temperature of turbine vane increases the demand of high film cooling effectiveness. Vane endwall region was extensively cooled due to the high and flat exit temperature distribution of combustor. Leakage flow from the combustor-turbine gap was used to cool the endwall region except for preventing hot gas ingestion. Numerical predictions were conducted to investigate the flow structure and adiabatic film cooling effectiveness of endwall region in a linear cascade with vane-endwall junction fillet. The simulations were completed by solving the three-dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with shear stress transport(SST) k-ω turbulence model, meanwhile, the computational method and turbulence model were validated by comparing computational result with the experiment. Three types of linear fillet with the length-to-height ratio of 0.5, 1 and 2, named fillet A, fillet B and fillet C respectively, were studied. In addition, circular fillet with radius of 2mm was compared with linear fillet B. The interrupted slot, produced by changing the way of junction of combustor and turbine vane endwall, is introduced at X/Cax = −0.2 upstream of the vane leading edge. Results showed that fillet can significantly affect the cooling performance on the endwall due to suppressing the strength of the secondary flow. Fillet C presented the best cooling performance comparing to fillet A and fillet B because a portion of the coolant which climbs to the fillet was barely affected by secondary flow. Results also showed the effect of fillet on the total pressure loss. The result indicated that only fillet A slightly decreases endwall loss.

Film Cooling of the Gas Turbine Endwall by Discrete-Hole Injection

1996 ◽  
Vol 118 (2) ◽  
pp. 278-284 ◽  
Author(s):  
M. Y. Jabbari ◽  
K. C. Marston ◽  
E. R. G. Eckert ◽  
R. J. Goldstein
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Hole Injection ◽  
Qualitative Information ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Density Ratios

Film cooling performance for injection through discrete holes in the endwall of a turbine blade is investigated. The effectiveness is measured at 60 locations in the region covered by injection. Three nominal blowing rates, two density ratios, and two approaching flow Reynolds numbers are examined. Analysis of the data reveals that even 60 locations are insufficient for the determination of the field of film cooling effectiveness with its strong local variations. Visualization of the traces of the coolant jets on the endwall surface, using ammonium-diazo-paper, provides useful qualitative information for the interpretation of the measurements, revealing the paths and interaction of the jets, which change with blowing rate and density ratio.

Leading Edge Film Cooling of a Turbine Blade Model Through Single and Double Row Injection: Effects of Coolant Density

1994 ◽  
Author(s):  
M. Salcudean ◽  
I. Gartshore ◽  
K. Zhang ◽  
Y. Barnea
Keyword(s):  
Turbine Blade ◽  
Mass Flow ◽  
Film Cooling ◽  
Leading Edge ◽  
Spanwise Direction ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Staggered Arrangement

Experiments have been conducted on a large model of a turbine blade. Attention has been focussed on the leading edge region, which has a semi-circular shape and four rows of film cooling holes positioned symmetrically about the stagnation line. The cooling holes were oriented in a spanwise direction with an inclination of 30° to the surface, and had streamwise locations of ±15° and ±44° from the stagnation line. Film cooling effectiveness was measured using a heat/mass analogy. Single row cooling from the holes at 15° and 44° showed similar patterns: spanwise averaged effectiveness which rises from zero at zero coolant mass flow to a maximum value η* at some value of mass flow ratio M*, then drops to low values of η at higher M. The trends can be quantitatively explained from simple momentum considerations for either air or CO2 as the coolant gas. Close to the holes, air provides higher η values for small M. At higher M, particularly farther downstream, the CO2 may be superior. The use of an appropriately defined momentum ratio G collapses the data from both holes using either CO2 or air as coolant onto a single curve. For η*, the value of G for all data is about 0.1. Double row cooling with air as coolant shows that the relative stagger of the two rows is an important parameter. Holes in line with each other in successive rows can provide improvements in spanwise averaged film cooling effectiveness of as much as 100% over the common staggered arrangement. This improvement is due to the interaction between coolant from rows one and two, which tends to provide complete coverage of the downstream surface when the rows are placed correctly with respect to each other.

Film Cooling of the Gas Turbine Endwall by Discrete-Hole Injection

1994 ◽  
Author(s):  
M. Y. Jabbari ◽  
K. C. Marston ◽  
E. R. G. Eckert ◽  
R. J. Goldstein
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Hole Injection ◽  
Qualitative Information ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Density Ratios

Film cooling performance for injection through discrete holes in the endwall of a turbine blade is investigated. The effectiveness is measured at sixty locations in the region covered by injection. Three nominal blowing rates, two density ratios, and two approaching flow Reynolds numbers are examined. Analysis of the data reveals that even sixty locations are insufficient for the determination of the field of film cooling effectiveness with its strong local variations. Visualization of the traces of the coolant jets on the endwall surface, using ammonium-diazo-paper, provides useful qualitative information for the interpretation of the measurements, revealing the paths and interaction of the jets which change with blowing rate and density ratio.

Background-Grid Based Mapping Approach to Film Cooling Meshing: Part III — Applications in a Full-Cooled Turbine Vane

2020 ◽  
Author(s):  
Ruiqin Wang ◽  
Xin Yan
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Mass Flow ◽  
Flow Rate ◽  
Film Cooling ◽  
Design Flow ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Structured Grids

Abstract To cool a high-pressure gas turbine blade, many rows of cooling holes with different arrangements and configurations are manufactured to achieve higher cooling effect and lower aerodynamic loss. To evaluate the heat transfer and film cooling effect in the full-cooled turbine blade, efficient numerical simulations are required in the design and performance optimization processes. From the view of numerical accuracy, the structured grids have to be employed because of higher resolution in flow and heat transfer than the unstructured grids. Because many splitting, attaching and merging manipulations are involved in meshing the cooling features and curved boundaries, it is very complex and time-consuming for a researcher to generate multi-block structured grids for a full-cooled gas turbine blade. As a result, in the industrial applications, almost all researchers preferred to generate unstructured grids instead of structured grids for the full-cooled blade. Unlike the previous research, the aim of this study is to apply the Background-Grid Based Mapping (BGBM) method proposed in Part I to generate multi-block structured grids for a full-cooled gas turbine vane. With the strategy of BGBM method, meshes were conveniently generated in the computational space with simple geometrical features and plain interfaces, and then were mapped back into physical space to obtain the multi-block structured grids which can be used for numerical simulations. With the experimental data, the present numerical methods and BGBM strategy were carefully validated. Then, the flow and film cooling performance in the full-cooled NASA GE-E3 nozzle guided vane were numerically investigated. The effects of coolant mass flow rate and land extensions on film cooling effectiveness were discussed. The results show that film cooling effectiveness near the stagnation point is the lowest and film cooling effectiveness on the pressure side is slightly higher than that on the suction side. When the coolant mass flow rate increases up to the value of 1.5 design flow, the relative outflow mass flow rates of cooling hole arrays and slots are no longer affected by the increase of the coolant flow rate. At half design flow, the outflow mass flow rates of No.5 hole-array to No.10 hole-array are almost zero, and the area-averaged film cooling effectiveness on vane surface is as low as 0.268. Compared with the cases of half design flow and double design flow, better film cooling performance is obtained in the cases of design flow and 1.5 design flow. Compared with the vane without lands, the area-average cooling effectiveness on vane surface is slightly higher for the vane with lands. Land extensions have a considerable influence on film cooling performance in the cutback region.

Film Cooling Superposition Theory for Multiple Rows of Cooling Holes With Multiple Coolant Temperatures

2020 ◽  
Author(s):  
Matthew N. Fuqua ◽  
James L. Rutledge
Keyword(s):  
Film Cooling ◽  
Classical Method ◽  
Fluid Dynamic ◽  
Coolant Temperature ◽  
Double Row ◽  
Design Work ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Different Temperatures ◽  
Cooling Hole

Abstract The classical method of superposition has been used for several decades to provide an estimate of the adiabatic effectiveness for multiple sets of already well-characterized film cooling hole rows. In this way, design work is aided by classical superposition theory prior to higher fidelity experiments or simulations that would account for fluid dynamic interaction for which superposition cannot account. In the present work, we consider the additive effects of multiple rows of coolant holes, but now also with coolant issuing at different temperatures. There are a number of ways that coolant may issue from different cooling hole rows at different temperatures, one of which is simply the necessarily different internal channels through which the coolant must pass. The film cooling effectiveness is investigated for double rows of cooling holes wherein the two rows have different coolant temperatures. A double row consisting of an upstream slot and a downstream row of 7-7-7 cooling holes were first evaluated with a single coolant temperature to demonstrate that classical superposition theory applies well to the present configuration. Superposition theory is then extended to the context of multiple coolant temperatures and a new non-dimensional parameter is identified, which governs cooling performance. The theory is experimentally evaluated by independently varying the coolant temperatures of the two rows. Circumstances are identified in which a second row of cooling holes may be detrimental to cooling performance.

Effect of Hole Exit Shaping on Film Cooling Performance for Tripod Hole Injection Over a Flat Surface

2013 ◽  
Author(s):  
Christopher N. LeBlanc ◽  
Sridharan Ramesh ◽  
Srinath V. Ekkad ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Operating Conditions ◽  
Hole Injection ◽  
Bottom Surface ◽  
Main Stream ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The effect of hole exit shaping on both heat transfer coefficient and film cooling effectiveness of tripod injection holes is examined experimentally on a flat plate. Previously, it has been clearly proven that tripod hole configurations provide at least 50–60% more cooling effectiveness while using 50% less coolant than standard cylindrical and shaped hole exit geometries. Temperature data is collected using infrared thermography at different operating conditions to determine the benefit of shaping the hole exits for an already proven tripod hole configuration. The test rig consists of a rectangular test section with a main stream flow at 7.9 m/s and coolant flow injected through the bottom surface through the film cooling injection holes. A unique transient IR technique has been used to determine both the adiabatic film effectiveness and heat transfer coefficient from a single test. Two different exit shaping have been considered, one with a 5° flare and layback and one with a 10° flare and layback. Results show that exit shaping improves the performance of these tripod holes compared to the cylindrical hole exits. The 10° flare and layback exit performs slightly better than the 5° flare and layback exit.

Numerical Study of the Film Cooling With Discrete-Hole Arrangement on a Cut Back Squealer Blade Tip

2015 ◽  
Author(s):  
Xiang Zhang ◽  
Zhong Yang ◽  
Shuqing Tian ◽  
Haiteng Ma
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Numerical Study ◽  
Pressure Side ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blade Tip ◽  
Cavity Floor

Detailed numerical investigations of film cooling effectiveness are conducted for the holes on the tip cavity floor and near the tip pressure side. The tested blade tip is a squealer with the trailing rim wall cut to allow the accumulated coolant in the cavity to escape and cool the trailing edge. The heat transfer coefficients on the un-cooled flat and cutback squealer blade tip are studied with numerical and experimental methods. Three dust purging holes with different diameters are arranged along the camber line, which forms the basic cooled case (PG case). Additional six tip cavity holes are arranged on cavity floor near the suction side rim (PG-TF case). Another row of angled twenty-one holes is arranged along the pressure side just below the tip based on the PG case (PG-PSF case). The coolant supply pressure ratios are controlled to be 1, 1.11, and 1.22 respectively, offering local blowing ratio from 0 to 2.5. Results show that the dust purging flow cooling performance increases with the cavity depth. Discrete holes on the cavity floor offer a well-distributed coolant, which refines the cooling effect on the cavity floor. The PG-PSF case with cooling holes on the pressure side has the best overall cooling performance with more coolant consumed, when PR ≥ 1.22. However, maintaining the same coolant mass flow the PG-TF case has the best cooling performance, and the margin between PG-TF and PG-PSF case decreases with mass flow. The moving shroud cases reveal that blade movement will cause significant negative impacts on film cooling effectiveness.

Optimal Arrangement of Combined-Hole for Improving Film Cooling Effectiveness

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Chang Han ◽  
Zhongran Chi ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Positive Influence ◽  
Optimal Arrangement ◽  
Aerodynamic Parameter ◽  
Local Flow ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Compound Angle

Film cooling technique is widely used to protect the components from being destroyed by hot mainstream in a modern gas turbine. Combining round-holes is a promising way of improving film cooling effectiveness. A DoE (design of experiment) simulation of 396 cases focusing on the arrangement of the combined-hole with double holes for improving film cooling performance is carried out in this work, and the influence of an aerodynamic parameter, blowing ratio is considered as well. The dimensionless lateral distance (PoD) and compound angle (CA) of the double holes have relative influence on the film cooling performance of the combined-hole unit. At the low blowing ratio, increasing symmetrical compound angle (SCA) has positive influence on the area-average effectiveness (EFF) of the combined-hole. But at the intermediate and large blowing ratio, the influence of SCA on the area-average EFF depends on the range of PoD. At the small PoD, the area-average EFF ascends basically along SCA axis. However, the area-average EFF first ascends and subsequently descends along SCA axis at the large PoD. Asymmetrical compound angle (ACA) is also considered to fit the antikidney vortexes produced in the combined-hole film cooling compared to their ideal schematic. However, the film cooling effect of the cases with ACA is not as good as expected. The area-average EFF of ACA cases locates in the level between that of the adjacent SCA cases. The optimal arrangement of combined-hole unit for improving film cooling effectiveness is relative to the local flow field. The optimal arrangement of PoD and CA for improving the combined-hole film cooling performance is different at different blowing ratios.

Experimental Study on the Effects of Slot Jet on Film Cooling Performance in the Cascade Endwall With Purge Flow

2019 ◽  
Author(s):  
Yao Yunjia ◽  
Zhu Peiyuan ◽  
Tao Zhi ◽  
Song Liming ◽  
Li Jun
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Ejection Angle ◽  
Purge Flow ◽  
Endwall Film Cooling ◽  
Mass Flow Ratio

Abstract Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE‘s E3 turbine first stage stator blades is selected as the experimental reference blade type in this experiment. In the current experiment, effects of different slot locations, slot ejection angles and slot profiles on the endwall film cooling effectiveness were taken into account. Under the influence of endwall secondary flow, the film cooling is mainly concentrated on the front part of the channel and close to the suction side of the blade, while there is almost no cooling effect close to the pressure side of the blade in the channel. With the increase of the distance between the blade leading edge and the slot, the endwall film cooling performance is reduced. While the distance increasing from 0.15Cx to 0.45Cx, and the peak endwall film cooling effectiveness is reduced by 78%, 68% and 58% respectively when the mass flow ratio (MFR) is 1.0%, 1.5%, and 2.0%. As the slot ejection angle is reduced, the endwall film cooling performance can be effectively improved. When the slot ejection angle increased from 45° to 90°, the peak endwall film cooling effectiveness decreases by 17%, 15%, and 13% respectively at the mass flow ratio (MFR) = 1.0%,1.5% and 2.0%. And the convergent slot can effectively improve the endwall cooling film formed by slot jet compared to the reference slot. When the mass flow ratio are MFR = 1.0%, 1.5%, and 2.0%, the peak endwall film cooling effectiveness at the convergent slot is increased by 50%, 20%, and 15% comparing to the reference slot.

Sign in / Sign up

Export Citation Format

Share Document