The Film Cooling Effectiveness of Double Rows of Holes

1980 ◽  
Vol 102 (3) ◽  
pp. 601-606 ◽  
Author(s):  
W. O. Afejuku ◽  
N. Hay ◽  
D. Lampard
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Coolant Flow ◽  
Row Spacing ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The film cooling effectiveness provided by two rows of holes separated by a range of distances has been studied experimentally using a mass transfer technique. The blowing rates at the two rows were varied independently. The results are presented in forms suitable for design purposes. Spanwise and area averaged effectivenesses are given for a range of blowing rates. Thus optimum blowing rates for a given row spacing and total coolant flow can be established. Comparisons with a simple superposition theory show that this can be used with safety for design purposes if the holes in the two rows are staggered, but restrictions apply if they are in-line.

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 Downstream of a Row of Discrete Holes With Compound Angle

2000 ◽  
Vol 123 (2) ◽  
pp. 222-230 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Mass Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Compound Angle

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle and 45 deg compound angle with 3d hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetric vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Heat (Mass) Transfer and Film Cooling Effectiveness With Injection Through Discrete Holes: Part II—On the Exposed Surface

1995 ◽  
Vol 117 (3) ◽  
pp. 451-460 ◽  
Author(s):  
H. H. Cho ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Saturated Vapor ◽  
Back Surface ◽  
Exposed Surface ◽  
Transfer Coefficients ◽  
Lateral Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The heat (mass) transfer coefficient and the film cooling effectiveness are obtained from separate tests using pure air and naphthalene-saturated vapor injected through circular holes into a crossflow of air. The experiments indicate that Sherwood numbers around the injection hole are up to four times those on a flat plate (without injection holes) due to the interaction of the jets and the mainstream. The mass transfer around the injection holes is dominated by formations of horseshoe, side, and kidney vortices, which are generated by the jet and crossflow interaction. For an in-line array of holes, the effectiveness is high and uniform in the streamwise direction but has a large variation in the lateral direction. The key parameters, including transfer coefficients on the back surface (Part I), inside the hole (Part I), and on the exposed surfaces, and the effectiveness on the exposed surface, are obtained so that the wall temperature distribution near the injection holes can be determined for a given heat flux condition. This detailed information will also aid the numerical modeling of flow and mass/heat transfer around film cooling holes.

Film-Cooled Turbine Endwall in a Transonic Flow Field: Part I—Aerodynamic Measurements

2001 ◽  
Vol 123 (4) ◽  
pp. 709-719 ◽  
Author(s):  
Friedrich Kost ◽  
Martin Nicklas
Keyword(s):  
Flow Field ◽  
Transonic Flow ◽  
Film Cooling ◽  
Coolant Flow ◽  
Pressure Probe ◽  
Thermal Methods ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Oil Flow ◽  
Oil Flow Visualization

Thermodynamic and aerodynamic measurements were carried out in a linear turbine cascade with transonic flow field. Heat transfer and adiabatic film-cooling effectiveness resulting from the interaction of the flow field and the ejected coolant at the endwall were measured and will be discussed in two parts. The investigations were performed in the Windtunnel for Straight Cascades (EGG) at DLR, Go¨ttingen. The film-cooled NGV endwall was operated at representative dimensionless engine conditions of Mach and Reynolds number Ma2is=1.0 and Re2=850,000 respectively. Part I of the investigation discusses the aerodynamic measurements. Detailed aerodynamic measurements were carried out in the vicinity of a turbine stator endwall using conventional pressure measurements and a Laser-2-Focus (L2F) device. The L2F served as a velocimeter measuring 2D-velocity vectors and turbulence quantities and as a tool to determine the concentration of coolant ejected through a slot and through holes at the endwall. Pressure distribution measurements provided information on the endwall pressure field and its variation with coolant flow rate. Pressure probe measurements delivered cascade performance data. Oil flow visualization and laser velocimetry gave a picture of the near endwall flow field and its interference with the coolant. A strikingly strong interaction of coolant air and secondary flow field could be identified. The measurement of coolant concentration downstream of the ejection locations provided a detailed picture of the coolant flow convection and its mixing with the main flow. The relative coolant concentration in the flow field is directly comparable to the adiabatic film-cooling effectiveness measured by thermal methods at the wall.

scholarly journals Film Cooling on a Gas Turbine Rotor Blade

1991 ◽  
Author(s):  
Kenichiro Takeishi ◽  
Sunao Aoki ◽  
Tomohiko Sato ◽  
Keizo Tsukagoshi
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Rotor Blade ◽  
Turbine Rotor ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Rotor Blade ◽  
Pressure Surface ◽  
Rotating Blade

The film cooling effectiveness on a low-speed stationary cascade and the rotating blade has been measured by using a heat-mass transfer analogy. The film cooling effectiveness on the suction surface of the rotating blade fits well with that on the stationary blade, but a low level of effectiveness appears on the pressure surface of the rotating blade. In this paper, typical film cooling data will be presented and film cooling on a rotating blade is discussed.

Effects of Axial Row-Spacing for Double-Jet Film-Cooling on the Cooling Effectiveness

2011 ◽  
Author(s):  
Zhan Wang ◽  
Jian-Jun Liu ◽  
Bai-tao An ◽  
Chao Zhang
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Inlet Guide Vane ◽  
Row Spacing ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Cylindrical Holes ◽  
Compound Angle

The effects of axial row-spacing for double jet film-cooling (DJFC) with compound angle on the cooling characteristics under different blowing ratios were investigated numerically. First, the flow fields and cooling effectiveness of DJFC on flat plate with different axial row-spacing were calculated. Film-cooling with fan-shaped or cylindrical holes was also calculated for the comparison. The results indicate that a larger axial row-spacing is helpful to form the anti-kidney vortex and to improve the cooling effectiveness. The DJFC was then applied to the suction and pressure surface of a real turbine inlet guide vane. Comparisons of film-cooling effectiveness with the cylindrical and fan-shaped holes were also conducted. The results for the guide vane show that on the suction surface the DJFC with a larger axial row-spacing leads to better film coverage and better film-cooling effectiveness than the cylindrical or fan-shaped holes. On the pressure surface, however, the film-cooling with fan-shaped holes is superior to the others.

Research on Film Cooling Mechanism of Vortex Reconstruction Induced by Swirling Coolant Flow

2017 ◽  
Author(s):  
Guoqiang Yue ◽  
Ping Dong ◽  
Yuting Jiang ◽  
Jie Gao ◽  
Qun Zheng
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Mechanism ◽  
New Type ◽  
The Difference ◽  
Momentum Region

In this paper, a new-type coolant chamber with higher film cooling effectiveness is proposed based on the vortex reconstruction. Three different kinds of coolant chamber configuration based on the cylindrical hole are selected to develop the swirling flow structure of coolant, and the comparative investigations have been carried out to study the effect of different coolant chambers at blowing ratios ranging from 0.5 to 2.0. The results show that the coolant jet momentum is small at low blowing ratio, and the difference of the film cooling effectiveness for three kinds of coolant chamber configuration is little, but the advantage of swirling inflow coolant film cooling becomes obviously with the increase of blowing ratio. When the blowing ratio is 2.0, the jet momentum with original coolant chamber configuration is large and uniform, which leads to the lowest cooling effectiveness due to the formation of a strong kidney vortex. The first coolant chamber configuration has a low jet momentum region at upstream of the film hole, the coolant in this region interacts with high temperature mainstream and bypasses the large jet momentum coolant to attach cooling surface at downstream, the cooling effect is obvious at downstream. The second coolant chamber configuration is sprayed with the structure of unidirectional vortex, which forms a vortex pressing on other vortex, making the coolant in pressed vortex attach surface better. The coolant laterally velocity is large, producing the best coverage and the higher film cooling effectiveness. The average film cooling effectiveness of the first and second coolant chamber configuration are larger than original by about 10% and 25%, respectively (M = 1.0), or 50% and 550% (M = 1.5). From the distribution of average film cooling effectiveness of different blowing ratios, it can be concluded that the optimal blowing ratio of swirling coolant flow film cooling is in the range of 1.8 to 2.1.

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