Numerical Investigation of Adiabatic Film Cooling Effectiveness over Flat Plate with ESCR Shape Ramp Configuration

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.

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

Journal of Turbomachinery ◽

10.1115/1.4041810 ◽

2019 ◽

Vol 141 (5) ◽

Cited By ~ 3

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.

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

Volume 5A: Heat Transfer ◽

10.1115/gt2018-76170 ◽

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.

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CFD Assisted Investigation on Adiabatic Film Cooling Effectiveness over a Flat Plate

Materials Today Proceedings ◽

10.1016/j.matpr.2019.07.305 ◽

2019 ◽

Vol 18 ◽

pp. 3711-3716

Author(s):

Kunal ◽

Apurba Kumar Roy ◽

Kaushik Kumar

Keyword(s):

Flat Plate ◽

Film Cooling ◽

Cooling Effectiveness ◽

Film Cooling Effectiveness

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

Volume 5B: Heat Transfer ◽

10.1115/gt2014-25211 ◽

2014 ◽

Cited By ~ 1

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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