Abstract
Gas turbines have been widely used in power generation and aircraft propulsion. To improve the gas turbine performance, the turbine inlet temperature is usually elevated higher than the metal melting point. Therefore, cooling of gas turbines becomes very critical for engines’ safety and lifetime. One of the effective methods is film cooling, in which the coolant air from the discrete holes blankets the surface from the hot gas flow. The major issues related to film cooling are its poor coverage, aerodynamic loss, and increase of heat transfer coefficient due to strong flow mixing. To improve the cooling performance, this paper examined film cooling with backward injection. It is observed that film cooling with backward injection can produce much more uniform cooling coverage under different conditions, which include cases on flat surface with low or high pressure and temperature. The backward injection also performs better in the presence of blade curvature. The effect of other parameters on the film cooling is also reported. The numerical results are validated by simple experimental test in this study.
Highlights
Based on the principle of thermodynamics, a higher turbine inlet temperature leads to a higher thermal efficiency in gas turbine engines, which are widely used for power generation and propulsion due to the compact structure and ease of operation
To compare the performance of backward injection with forward injection, the forward injection case is simulated with otherwise the same geometry
The interaction of the coolant jet with main flow makes the cooling in the spanwise direction much higher and more uniform when compared to the forward injection case
Summary
Based on the principle of thermodynamics, a higher turbine inlet temperature leads to a higher thermal efficiency in gas turbine engines, which are widely used for power generation and propulsion due to the compact structure and ease of operation. As part of effort to increase the engine efficiency, the operating temperatures of a gas turbine can be elevated as high as 2000K, which is much higher than the melting point of metal in use. Generation gas turbines are expected to operate at even higher temperature. The operation of these engines becomes impossible if the hot components are not provided with proper thermal protection. One of these components is turbine blades. There are few other cooling techniques available, film cooling has been extensively studied and applied over years
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