Adiabatic film-cooling effectiveness is examined on a high-pressure turbine blade by varying three critical engine parameters, viz., coolant blowing ratio, coolant-to-mainstream density ratio, and freestream turbulence intensity. Three average coolant blowing ratios (BR=1.2, 1.7, and 2.2 on the pressure side and BR=1.1, 1.4, and 1.8 on the suction side), three average coolant density ratios (DR=1.0, 1.5, and 2.5), and two average freestream turbulence intensities (Tu=4.2% and 10.5%) are considered. Conduction-free pressure sensitive paint (PSP) technique is adopted to measure film-cooling effectiveness. Three foreign gases—N2 for low density, CO2 for medium density, and a mixture of SF6 and argon for high density are selected to study the effect of coolant density. The test blade features two rows of cylindrical film-cooling holes on the suction side (45 deg compound), 4 rows on the pressure side (45 deg compound) and 3 around the leading edge (30 deg radial). The inlet and the exit Mach numbers are 0.24 and 0.44, respectively. The Reynolds number of the mainstream flow is 7.5×105 based on the exit velocity and blade chord length. Results suggest that the PSP is a powerful technique capable of producing clear and detailed film-effectiveness contours with diverse foreign gases. Large improvement on the pressure side and moderate improvement on the suction side effectiveness is witnessed when blowing ratio is raised from 1.2 to 1.7 and 1.1 to 1.4, respectively. No major improvement is seen thereafter with the downstream half of the suction side showing drop in effectiveness. The effect of increasing coolant density is to increase effectiveness everywhere on the pressure surface and suction surface except for the small region on the suction side, xss/Cx<0.2. Higher freestream turbulence causes effectiveness to drop everywhere except in the region downstream of the suction side where significant improvement in effectiveness is seen.
It has been suggested by researchers that ingestion, through rim seals, of mainstream gas into axial-flow turbine disk cavities is a consequence of the prevailing unsteady three-dimensional flow field. The cause–effect relationship is complex—to help understand it, experiments were performed in a model single-stage turbine rig using two different vane-blade configurations. Selected measurements from one of the configurations were reported earlier (1999–2001). The second configuration is new, featuring smaller numbers of vanes and blades and a larger vane turning angle. Selected measurements are presented and compared to those from the first configuration. The measurements include unsteady and rotor revolution time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were the main airflow rate, the purge/seal airflow rate, and the rotor speed. Unsteady three-dimensional CFD simulation may be helpful in identifying the roles of the many intertwined phenomena in the ingestion process.
This paper is focused on the effect of film-hole configurations on platform film cooling. The platform is cooled by purge flow from a simulated stator-rotor seal combined with discrete-hole film cooling within the blade passage. The cylindrical holes and laidback fan-shaped holes are assessed in terms of film-cooling effectiveness and total pressure loss. Lined up with the freestream streamwise direction, the film holes are arranged on the platform with two different layouts. In one layout, the film-cooling holes are divided into two rows and more concentrated on the pressure side of the passage. In the other layout, the film-cooling holes are divided into four rows and loosely distributed on the platform. Four film-cooling hole configurations are investigated totally. Testing was done in a five-blade cascade with medium high Mach number condition (0.27 and 0.44 at the inlet and the exit, respectively). The detailed film-cooling effectiveness distributions on the platform were obtained using pressure sensitive paint technique. Results show that the combined cooling scheme (slot purge flow cooling combined with discrete-hole film cooling) is able to provide full film coverage on the platform. The shaped holes present higher film-cooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The hole layout affects the local film-cooling effectiveness. The shaped holes also show the advantage over the cylindrical holes with lower total pressure loss.
The film-cooling effectiveness on the surface of a high pressure turbine blade is measured using the pressure sensitive paint technique. Compound angle laidback fan-shaped holes are used to cool the blade surface with four rows on the pressure side and two rows on the suction side. The coolant injects to one side of the blade, either pressure side or suction side. The presence of wake due to the upstream vanes is simulated by placing a periodic set of rods upstream of the test blade. The wake rods can be clocked by changing their stationary positions to simulate progressing wakes. The effect of wakes is recorded at four phase locations along the pitchwise direction. The freestream Reynolds number, based on the axial chord length and the exit velocity, is 750,000. The inlet and exit Mach numbers are 0.27 and 0.44, respectively, resulting in a pressure ratio of 1.14. Five average blowing ratios ranging from 0.4 to 1.5 are tested. Results reveal that the tip-leakage vortices and endwall vortices sweep the coolant on the suction side to the midspan region. The compound angle laidback fan-shaped holes produce a good film coverage on the suction side except for the regions affected by the secondary vortices. Due to the concave surface, the coolant trace is short and the effectiveness level is low on the pressure surface. However, the pressure side acquires a relatively uniform film coverage with the multiple rows of cooling holes. The film-cooling effectiveness increases with the increasing average blowing ratio for either side of coolant ejection. The presence of stationary upstream wake results in lower film-cooling effectiveness on the blade surface. The compound angle shaped holes outperform the compound angle cylindrical holes by the elevated film-cooling effectiveness, particularly at higher blowing ratios.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.