The inlet temperature of modern gas turbine engines has been increased to achieve higher thermal
efficiency and increased output. The blade edge regions, including the blade tip, the leading edge, and the
platform, are exposed to the most extreme heat loads, and therefore, must be adequately cooled to
maintain safety.
For the blade tip, there is tip leakage flow due to the pressure gradient across the tip. This leakage
flow not only reduces the blade aerodynamic performance, but also yields a high heat load due to the thin
boundary layer and high speed. Various tip configurations, such as plane tip, double side squealer tip, and
single suction side squealer tip, have been studied to find which one is the best configuration to reduce the
tip leakage flow and the heat load. In addition to the flow and heat transfer on the blade tip, film cooling
with various arrangements, including camber line, upstream, and two row configurations, have been
studied. Besides these cases of low inlet/outlet pressure ratio, low temperature, non-rotating, the high
inlet/outlet pressure ratio, high temperature, and rotating cases have been investigated, since they are
closer to real turbine working conditions.
The leading edge of the rotor blade experiences high heat transfer because of the stagnation flow.
Film cooling on the rotor leading edge in a 1-1/2 turbine stage has been numerically studied for the design
and off-design conditions. Simulations find that the increasing rotating speed shifts the stagnation line
from the pressure side, to the leading edge and the suction side, while film cooling protection moves in the
reverse direction with decreasing cooling effectiveness. Film cooling brings a high unsteady intensity of
the heat transfer coefficient, especially on the suction side. The unsteady intensity of film cooling
effectiveness is higher than that of the heat transfer coefficient.
The film cooling on the rotor platform has gained significant attention due to the usage of low-aspect
ratio and low-solidity turbine designs. Film cooling and its heat transfer are strongly influenced by the
secondary flow of the end-wall and the stator-rotor interaction. Numerical predictions have been
performed for the film cooling on the rotating platform of a whole turbine stage. The design conditions
yield a high cooling effectiveness and decrease the cooling effectiveness unsteady intensity, while the high rpm condition dramatically reduces the film cooling effectiveness. High purge flow rates provide a better
cooling protection. In addition, the impact of the turbine work process on film cooling effectiveness and
heat transfer coefficient has been investigated. The overall cooling effectiveness shows a higher value than
the adiabatic effectiveness does.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4338 |
| Date | 30 October 2006 |
| Creators | Yang, Huitao |
| Contributors | Han, J-C |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 3930644 bytes, electronic, application/pdf, born digital |
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