Mesures hydrodynamiques pour des jets dans un ecoulement transversal dans le cas du refroidissement par film des aubes de turbines a gaz

Hydrodynamic measurements of jets in crossflow for gas turbine film cooling application.

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow with a density ratio of injectant to freestream of two. Laser Doppler anemometry was used to measure the vertical and streamwise components of velocity for a jet-to-freestream mass flux ratio of 0.5. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and freestream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer.Copyright © 1989 by ASME

Effects of density ratio on the hydrodynamics of film cooling

Experimental and numerical studies on film cooling with reverse/backward coolant injection

Gas turbines are widely used in the areas of air propulsion, electric power generation, ship propulsion, external driving units, and other industrial applications. Efficient coating and cooling methods are often essential for the gas turbine surfaces to further achieve higher turbine inlet temperature and output efficiency. The thermal barrier coating (TBC) is the type of multilayered coating applied on rotating and stationary surfaces of the gas turbine components to safeguard them against the attack of high stream thermal loads and pressure gradients of the hot mainstream flows. TBC can also assist in surface-modified film cooling of gas turbine components. In this paper, the thermal barrier coated surface-modified film cooling methods for gas turbine components, viz. leading edge, pressure side, suction side, end wall, flat surfaces of stator guide vane and rotor blade, were reviewed and discussed in detail. The surface-modified film cooling methods for gas turbine components are grouped into three broad categories based on their geometric appearance. Each group was reviewed in detail for geometric and flow parameters, measurement techniques, flow characteristics, and performance parameters. Further, this study provides an overview of geometric and flow parameters of the compound angled film hole. Finally, the areas required for future research on the application of surface-modified film cooling methods are recommended in this review.

Thermal barrier coated surface modifications for gas turbine film cooling: a review

Double-row discrete-hole cooling arrangements offer several advantages over single-row systems yet the detailed cooling mechanism is less completely understood than for the single-row. This is partly because there have been fewer studies of this geometry and partly because the flow structure is more complex. The present paper presents detailed flow-field and concentration measurements around the injection holes for double-row injection on a flat plate at 30 deg to the mainstream. The experiments span values of the blowing injection mass velocities from 0.25 to 1.0 times the free stream mass velocity and for two boundary layer thicknesses just upstream of the injection. In contrast to single-row injection the cooling effectiveness rise monotonically with M over the range studied. Computer simulation of these flows and similar experiments of [7] has been made using a three-dimensional finite-difference code that embodies a semi-elliptic treatment of the flow field in the neighborhood of the injection holes in conjunction with a two-equation turbulence model with non-isotropic effective transport coefficients. It emerged from the calculations, that, for injection velocities up to 50 percent of the free stream value, levels of film-cooling effectiveness are extremely well predicted beyond about 10 diameters behind the leading row of holes. Around the holes themselves, however, there are certain discrepancies which become more serious as the injection level is raised.

Double-row discrete-hole cooling: An experimental and numerical study.

Enhanced film cooling performance of a row of cylindrical holes embedded in the saw tooth slot

Mechanism of Film Cooling with One Inlet and Double Outlet Hole Injection at Various Turbulence Intensities

Film cooling performance about a row of dual-fanned holes with injection angles of 30°, 60 ° and 90° were experimentally investigated at blowing ratios of 1.0 and 2.0. Dual-fanned hole is a novel shaped hole which has both inlet expansion and outlet expansion. A transient thermochromic liquid crystal technique was used to reveal the local values of film cooling effectiveness and heat transfer coefficient. The results show that injection angles have strong influence on the two dimensional distributions of film cooling effectiveness and heat transfer coefficient. For the small injection angle of 30 degree and small blowing ratio of 1.0, there is only a narrow spanwise region covered with film. The increase of injection angle and blowing ratio both leads to the enhanced spanwise film diffusion, but reduced local cooling ability far away from the hole. Injection angles have comprehensive influence on the averaged film cooling effectiveness for various x/d locations. As injection angles are 30 and 60 degree, two bands of high heat transfer coefficients are found in mixing region of the gas and coolant. As injection angle increases to 90 degree, the mixing leads to the enhanced heat transfer region near the film hole. The averaged heat transfer coefficient increases with the increase of injection angle.

Film cooling performance of a row of dual-fanned holes at various injection angles

Effect of cross-flow direction of coolant on film cooling effectiveness with one inlet and double outlet hole injection

Abstract Film cooling performance of one row of cylindrical holes integrated with saw-tooth slots was numerically studied at blowing ratios of 0.5, 1.0 1.5 and 2.0 respectively. The saw-tooth slot concept combines the advantages both of easy machining for the slot and of the high film cooling effectiveness caused by the anti-vortex induced by the shaped hole. The film holes have an inclination angles of 30°, length to diameter ratio of 4 and pitch to diameter ratio of 3. The corner angles of the saw-tooth are 60°, 90°, 120°, 150° and 180° respectively. The 180° corner angle corresponds to a standard transverse slot. The emphasis of this other is on the influence of the corner angles of the saw-tooth on film cooling effectiveness. The flow field and thermal field were obtained to explain the mechanism of film cooling performance improvement by the saw-tooth slot. The results show that the numerical data agrees with the experimental values for the cylindrical holes. Relatively small corner angles generate uniform local film cooling effectiveness and high spanwise averaged film cooling effectiveness due to the coolant ejected from the hole smoothly flowing into the slot. The effect of corner angles strongly depends on blowing ratios. The increase of x/D decreases the differences of film cooling effectiveness between various corner angles. At low blowing ratios, an anti-vortex can be found with the spanwise angle of 60° and 120°. At high blowing ratios, an anti-vortex can be found with the spanwise angle of 60°.

Kou Zhihai

Papers

Enhanced film cooling performance of a row of cylindrical holes embedded in the saw tooth slot

Mechanism of Film Cooling with One Inlet and Double Outlet Hole Injection at Various Turbulence Intensities

Film cooling performance of a row of dual-fanned holes at various injection angles

Effect of cross-flow direction of coolant on film cooling effectiveness with one inlet and double outlet hole injection

Film Cooling Mechanism of Combined Hole and Saw-tooth Slot