Conjugate Heat Transfer From a Flat Plate With Combined Impingement and Film Cooling

2012 ◽  
Author(s):  
Rajesh Kumar Panda ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Fluid Dynamic ◽  
Impinging Jets ◽  
Experimental Investigations ◽  
Thermochromic Liquid Crystal ◽  
Dynamic Features ◽  
Conducting Material ◽  
Film Cooling Effectiveness ◽  
Combined Cooling

Computational and experimental investigations are reported on a flat plate subjected to combined impingement and film cooling with a (14 × 14) matrix of impingement holes and three (6 × 4) staggered arrays of 35° inclined film holes. Conjugate flow and thermal computations are carried out, by using shear stress transport (SST) κ-ω turbulence model. The combined thermo fluid dynamic features of impinging jets and the coolant-mainstream interactions in presence of impingement and film cooling plates are described. Local values of Nusselt number are presented on the impingement surface and film cooling effectiveness values are plotted along the interaction surface. The computed surface temperature distribution is validated by thermochromic liquid crystal measurements. A comparison between the film cooling and the combined impingement and film cooling shows that the surface effectiveness values for the combined cooling are higher as well as more uniform. As the blowing ratio is increased from M = 0.6 to 1.0, the local streamwise effectiveness values show an increasing trend for both the cases. The effectiveness values are higher for higher conducting material at all blowing ratios. However, in case of lower conducting material, local patches of higher effectiveness are observed close to the jet exit.

Experimental Investigations of a Comb-Like Film Cooling Scheme

2019 ◽  
Author(s):  
Hao-Ming Li ◽  
Wahid Ghaly ◽  
Ibrahim Hassan
Keyword(s):  
Film Cooling ◽  
Structural Integrity ◽  
Vortex Pair ◽  
Experimental Investigations ◽  
Published Data ◽  
Thermochromic Liquid Crystal ◽  
Film Cooling Effectiveness ◽  
Comb Structure ◽  
Perfect Performance ◽  
Crucial Effect

Abstract The performance of a simple slot is perfect, but it does not have structural integrity. A new advanced cooling scheme with perfect performance and practical structural integrity is presented. Based on the crucial effect of the counter-rotating vortex pair (CRVP) on the film cooling effectiveness (η), the new scheme is composed of a comb-like structure and a blind slot, in which the comb structure maintains the mechanical strength, and the blind slot is intended to eliminate the CRVP and produce a smooth coolant film. The new scheme is investigated experimentally with the transient thermochromic liquid crystal (TLC) technique. Two classic geometries, the cylindrical hole and the simple slot, were also measured. The agreement of their results with the published data validated the present experimental facilities. The experimental results of the Comb scheme demonstrated that, with practical structural integrity, the new scheme has perfect performance, which bears comparison with the simple slot. Consequently, the success of the Comb scheme proved the crucial CRVP effect on η.

Film Cooling With Swirling Coolant Flow on a Flat Plate and the Endwall of High-Loaded First Nozzle

2014 ◽  
Author(s):  
Kenichiro Takeishi ◽  
Yutaka Oda ◽  
Shinpei Kondo
Keyword(s):  
Wind Tunnel ◽  
Flat Plate ◽  
Film Cooling ◽  
Wind Tunnel Test ◽  
Impinging Jets ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes ◽  
Cooling Air

This paper describes an experimental study on the film cooling effectiveness of circular and fan-shaped film cooling holes with a swirling film coolant injected through a flat plate and the endwall of a high-loaded first nozzle. The experiments were conducted using a flat plate wind tunnel and a two-dimensional vane cascade, which is designed based on the first-stage vane of an Energy Efficient Engine (E3) studied under a NASA project. The film cooling effectiveness on a flat plate wind tunnel and the endwall of the enlarged first nozzle of the E3 turbine was measured using pressure sensitive paint (PSP) techniques. The experimental results indicate that the film cooling effectiveness of a circular hole improved by increasing the angle θ of two impinging jets inside the cavity, which are used both for cooling the internal wall and generating a swirling motion in the film coolant. In contrast, it was found that there exist optimal jet angles of θ = 20° for a circular film cooling hole, θ = 5–10° for a flat plate wind tunnel test, and θ = 15° for the cascade test conducted using a fan-shaped film cooling hole. Thus the new film cooling method using swirling cooling air has been demonstrated to maintain high film cooling effectiveness even under such a complicated flow field.

Numerical modeling of innovative film cooling hole schemes

2021 ◽  
Author(s):  
Siavash Khajehhasani
Keyword(s):  
Flat Plate ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Lateral Spread ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Mainstream Flow ◽  
Hole Geometry

A numerical investigation of the film cooling performance on novel film hole schemes is presented using Reynolds-Averaged Navier-Stokes analysis. The investigation considers low and high blowing ratios for both flat plate film cooling and the leading edge of a turbine blade. A novel film hole geometry using a circular exit shaped hole is proposed, and the influence of an existing sister holes’ technique is investigated. The results indicate that high film cooling effectiveness is achieved at higher blowing ratios, results of which are even greater when in the presence of discrete sister holes where film cooling effectiveness results reach a plateau. Furthermore, a decrease in the strength of the counter-rotating vortex pairs is evident, which results in more attached coolant to the plate’s surface and a reduction in aerodynamic losses. Modifications are made to the spanwise and streamwise locations of the sister holes around the conventional cylindrical hole geometry. It is found that the spanwise variations have a significant influence on the film cooling effectiveness results, while only minor effects are observed for the streamwise variations. Positioning the sister holes in locations farther from the centerline increases the lateral spreading of the coolant air over the plate’s surface. This result is further verified through the flow structure analysis. Combinations of sister holes are joined with the primary injection hole to produce innovative variant sister shaped single-holes. The jet lift-off is significantly decreased for the downstream and up/downstream configurations of the proposed scheme for the flat plate film cooling. These schemes have shown notable film cooling improvements whereby more lateral distribution of coolant is obtained and less penetration of coolant into the mainstream flow is observed. The performance of the sister shaped single-holes are evaluated at the leading edge of a turbine blade. At the higher blowing ratios, a noticeable improvement in film cooling performance including the effectiveness and the lateral spread of the cooling air jet has been observed for the upstream and up/downstream schemes, in particular on the suction side. It is determined that the mixing of the coolant with the high mainstream flow at the leading edge of the blade is considerably decreased for the upstream and up/downstream configurations and more adhered coolant to the blade’s surface is achieved.

Effect of Density Ratio on Film-Cooling Effectiveness Distribution and Its Uniformity for Several Hole Geometries on a Flat Plate

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Jiaxu Yao ◽  
Jin Xu ◽  
Ke Zhang ◽  
Jiang Lei ◽  
Lesley M. Wright
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spread ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Density Ratios ◽  
Compound Angle

The film cooling effectiveness distribution and its uniformity downstream of a row of film cooling holes on a flat plate are investigated by pressure sensitive paint (PSP) under different density ratios. Several hole geometries are studied, including streamwise cylindrical holes, compound-angled cylindrical holes, streamwise fan-shape holes, compound-angled fan-shape holes, and double-jet film-cooling (DJFC) holes. All of them have an inclination angle (θ) of 35 deg. The compound angle (β) is 45 deg. The fan-shape holes have a 10 deg expansion in the spanwise direction. For a fair comparison, the pitch is kept as 4d for the cylindrical and the fan-shape holes, and 8d for the DJFC holes. The uniformity of effectiveness distribution is described by a new parameter (Lateral-Uniformity, LU) defined in this paper. The effects of density ratios (DR = 1.0, 1.5 and 2.5) on the film-cooling effectiveness and its uniformity are focused. Differences among geometries and effects of blowing ratios (M = 0.5, 1.0, 1.5, and 2.0) are also considered. The results show that at higher density ratios, the lateral spread of the discrete-hole geometries (i.e., the cylindrical and the fan-shape holes) is enhanced, while the DJFC holes is more advantageous in film-cooling effectiveness. Mostly, a higher lateral-uniformity is obtained at DR = 2.5 due to better coolant coverage and enhanced lateral spread, but the effects of the density ratio on the lateral-uniformity are not monotonic in some cases. Utilizing the compound angle configuration leads to an increased lateral-uniformity due to a stronger spanwise motion of the jet. Generally, with a higher blowing ratio, the lateral-uniformity of the discrete-hole geometries decreases due to narrower traces, while that of the DJFC holes increases due to a stronger spanwise movement.

Measurement of Detailed Heat Transfer Coefficient and Film Cooling Effectiveness Distributions Using PSP and TSP

2009 ◽  
Author(s):  
Rebekah A. Russin ◽  
Daniel Alfred ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Optical Filters ◽  
Experimental Investigations ◽  
Transient Temperature ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range

This paper presents the development of a novel experimental technique utilizing both temperature and pressure sensitive paints (TSP and PSP). Through the combination of these paints, both detailed heat transfer coefficient and film cooling effectiveness distributions can be obtained from two short experiments. Using a mass transfer analogy, PSP has proven to be a powerful technique for measurement of film cooling effectiveness. This benefit is exploited to obtain detailed film cooling effectiveness distributions from a steady state flow experiment. This measured film cooling effectiveness is combined with transient temperature distributions obtained from a transient TSP experiment to produce detailed heat transfer coefficient distributions. Optical filters are used to differentiate the light emission from the florescent molecules comprising the PSP and TSP. Although two separate tests are needed to obtain the heat transfer coefficient distributions, the two tests can be performed in succession to minimize setup time and variability. The detailed film effectiveness and heat transfer enhancement ratios have been obtained for a generic, inclined angle (θ = 35°) hole geometry on a flat plate. Distinctive flow features over a wide range of blowing ratios have been captured with the proposed technique. In addition, the measured results have compared favorably to previous studies (both qualitatively and quantitatively), thus substantiating the use of the combined PSP / TSP technique for experimental investigations of three temperature mixing problems.

Numerical Approach at Flat Plate for Predicting the Film Cooling Effectiveness Part A: Effect Blowing Ratio

2018 ◽  
Vol 16 ◽  
pp. 30-44 ◽  
Author(s):  
Farouk Kebir ◽  
Azzeddine Khorsi
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Film Cooling ◽  
Thermal Stresses ◽  
Free Stream ◽  
Turbine Blades ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Blowing Ratio

Film cooling is vital for gas turbine blades to protect them from thermal stresses and high temperatures due to the hot gas flow in the blade surface. Film cooling is applied to almost all external surfaces associated with aerodynamic profiles that are exposed to hot combustion gases such as main bodies, end-walls, blade tips and leading edges. In a review of the literature, it was found that there are strong effects of free-stream turbulence, surface curvature and hole shape on film cooling performance also blowing ratio. The performance of the film cooling is difficult to predict due to the inherent complex flow fields along the surfaces of the airfoil components in the turbine engines. From all what we introducing the film cooling is reviewed through a discussion of the analyses methodologies, a physical description, and the various influences on film-cooling performance. Initially Computational analysis was done on a flat plate with hole inclined at 55° to the surface plate. This study focuses on the efficient computation of film cooling flows with three blowing ratio. The numerical results show the effectiveness cooling and heat transfer behavior with increasing injection blowing ratio M (0.5, 1, and 1.5). The influence of increased blade film cooling can be assessed via the values of Nusselt number in terms of reduced heat transfer to the blade. Predictions of film effectiveness are compared with experimental results for a circular jet at blowing ratios ranging from 0.5, 1.0 and 1.5. The present results are obtained at a free stream turbulence of 10%, which are the typical conditions upstream of the effectiveness is generally lower for a large stream-wise angle of 55°.

Effects of Density and Blowing Ratios on the Turbulent Structure and Effectiveness of Film-Cooling

2018 ◽  
Author(s):  
Zachary T. Stratton ◽  
Tom I-P. Shih
Keyword(s):  
Shear Layer ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Turbulent Structure ◽  
Reverse Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbulent Fluctuations

Large eddy simulations (LES) were performed to investigate film cooling of a flat plate, where the cooling jets issued from a plenum through one row of circular holes of diameter D and length 4.7D that are inclined at 35° relative to the plate. The focus is on understanding the turbulent structure of the film-cooling jet and the film-cooling effectiveness. Parameters studied include blowing ratio (BR = 0.5 and 1.0) and density ratio (DR = 1.1 and 1.6). Also, two different boundary layers (BL) upstream of the film-cooling hole were investigated — one in which a laminar BL was tripped to become turbulent from near the leading edge of the flat plate, and another in which a mean turbulent BL is prescribed directly. The wall-resolved LES solutions generated were validated by comparing its time-averaged values with data from PIV and thermal measurements. Results obtained show that having an upstream BL that does not have turbulent fluctuations enhances the cooling effectiveness significantly at low velocity ratios (VR) when compared to an upstream BL that resolved the turbulent fluctuations. However, these differences diminish at higher VRs. Instantaneous flow reveals a bifurcation in the jet vorticity as it exits the hole at low VRs, one branch forming the shear-layer vortex, while the other forms the counter-rotating vortex pair. At higher VRs, the shear layer vorticity is found to reverse direction, changing the nature of the turbulence and the heat transfer. Results obtained also show the strength and structure of the turbulence in the film-cooling jet to be strongly correlated to VR.

Effectiveness of Normal and Angled Slot Cooling

2004 ◽  
Author(s):  
A. C. Smith ◽  
J. H. Hatchett ◽  
A. C. Nix ◽  
W. F. Ng ◽  
K. A. Thole ◽  
...  
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Fluid Dynamic ◽  
Current Experiment ◽  
Cfd Simulations ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Mach Numbers ◽  
Lift Off

An experimental and numerical investigation was conducted to determine the film cooling effectiveness of a normal slot and angled slot under realistic engine Mach number conditions. Freestream Mach numbers of 0.65 and 1.3 were tested. For the normal slot, hot gas ingestion into the slot was observed at low blowing ratios (M < 0.25). At high blowing ratios (M > 0.6) the cooling film was observed to “lift off” from the surface. For the 30° angled slot, the data was found to collapse using the blowing ratio as a scaling parameter. Results from the current experiment were compared with the subsonic data previously published. For the angle slot, at supersonic freestream Mach number, the current experiment shows that at the same x/Ms, the film-cooling effectiveness increases by as much as 25% as compared to the subsonic case. The results of the experiment also show that at the same x/Ms, the film cooling effectiveness of the angle slot is considerably higher than the normal slot, at both subsonic and supersonic Mach numbers. The flow physics for the slot tests considered here are also described with computational fluid dynamic (CFD) simulations in the subsonic and supersonic regimes.

Geometrical Optimization and Experimental Validation of a Tripod Film Cooling Hole With Asymmetric Side Holes

2014 ◽  
Author(s):  
Zhongran Chi ◽  
Chang Han ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Experimental Results ◽  
Geometrical Parameters ◽  
Vortex System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Optimum Configuration ◽  
Optimization Study ◽  
Cooling Hole

A tripod cylindrical film hole with asymmetric side holes is studied numerically and experimentally on a flat plate for higher film cooling effectiveness. Firstly, the influences of geometrical parameters are studied and the optimum configurations of the asymmetric tripod hole are found in a DoE optimization study based on an improved numerical model for film cooling prediction, in which more than one hundred 3D CFD simulations are carried out. Then one optimum configuration of the asymmetric tripod hole is examined experimentally using pressure-sensitive paint (PSP) measurements, and compared against the experimental results of the simple cylindrical film hole and a well-designed shaped film hole. The flow and heat transfer characteristics of the asymmetric tripod holes were explored from the DoE results. The side holes can form a shear vortex system or an anti-kidney vortex system when proper spanwise distances of them are adopted, which laterally transports the coolant and form a favorable coolant coverage. According to the experimental results, the cooling performance of the optimized asymmetric tripod hole is significantly better than that of the simple cylindrical hole, especially at high blowing ratios. And the optimized asymmetric tripod hole can provide almost the same or even higher film cooling effectiveness on the flat plate compared with the shaped hole in the same flow conditions.

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