Abstract
In this article, a compound unit of swirl and impingement cooling techniques is designed to study the performance of flow and heat transfer using multi-conical nozzles in a leading-edge of a gas turbine blade. Reynolds Averaged Navier-Stokes equations and the Shear Stress Transport model are numerically solved under different nozzle Reynolds numbers and temperature ratios. Results indicated that the compound cooling unit could achieve a 99.7% increase in heat transfer enhancement by increasing the nozzle Reynolds number from 10,000 to 25,000 at a constant temperature ratio. Also, there is an 11% increase in the overall Nusselt number when the temperature ratio increases from 0.65 to 0.95 at identical nozzle Reynolds number. At 10,000 and 15,000 of nozzle Reynolds numbers, the compound cooling unit achieves 47.9% and 39.8% increases and 63.5% and 66.3% increases in the overall Nusselt number comparing with the available experimental swirl and impingement models, respectively. A correlation for the overall Nusselt number is derived as a function of nozzle Reynolds number and temperature ratio to optimize the results. The current study concluded that the extremely high zones and uniform distribution of heat transfer are perfectly achieved with regard to the characteristics of heat transfer of the compound cooling unit.
Highlights
Heavy-duty gas turbines are always being subjected to new challenges to be efficient with the increasing energy demands [1]
The results revealed that there was a 5.2% increase in the heat transfer due to using film holes bleeding compared to the case without it
The fluid flow is studied at different nozzle Reynolds numbers to predict the variation The flow structure inside the compound cooling unit can be deeply described using the areaof theThe flow characteristics
Summary
Heavy-duty gas turbines are always being subjected to new challenges to be efficient with the increasing energy demands [1]. Achieving the highest power and efficiency requires a high turbine entry gas temperature [2], which is excessively higher than the thermal resistance of the blade material. In order to provide a reasonable uniform temperature of the blade material, various complex cooling techniques are required to protect it. The blade leading-edge is the most critical part, which is directly forced by a very high gas temperature. Over the past years, many cooling techniques have been developed by various researchers to overcome this problem. The impingement cooling and swirl cooling are the only common methods to cool down the leading edge of a blade. Due to the great impact of those two cooling methods on cooling performance, deep investigations are required to optimize the cooling method
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