STUDY ON HEAT TRANSFER ENHANCEMENT OF GAS TURBINE BLADES
Farah Nazifa Nourin, Ryoichi S. Amano
Abstract
It is crucial to perform high thermal efficiency in a gas turbine. Increasing the inlet temperature in the combustor is the way to achieve this goal for a gas turbine. Nonetheless, increasing the heat causes a significant difference in the temperature gradient within the blade material, thus resulting in thermal stresses. These effects must be reduced to achieve higher thermal efficiency. The two-pass cooling channels have been studied due to their performance in heat transfer. The dimpled surface on a pass wall cooling technology gets popular in recent years as it shows a low-pressure loss penalty. It is also advantageous to the turbine stages where lower pressure cooling is employed. This study is going to investigate turbulent flow and heat transfer in a two-pass duct. The duct is represented by small cooling channels drilled inside modern gas turbine blades to assist with the heat removal from the hot surfaces of the blade. The modeled channel in this study has a square cross section with a size of 50.8 mm, and the first and second passage lengths of 514 mm and 440 mm, respectively. The dimples are imprinted in the bottom wall of the channel with a depth of 10 mm. Also, results are compared with the elimination of the bend crossflow feed system. The two passes are connected with each other by three cylindrical holes along a partition wall. The airflow rate is set such that the maximum Reynolds number of 25,000 can be achieved. Several computational fluid dynamics simulations are carried out to understand the effect of the dimples on flow and heat transfer in channels with and without bend under various operating conditions. The results show that a dimpled cooling path is more advantageous than the smooth wall channel, and by eliminating bend, a higher heat transfer is achieved without affecting the first pass heat transfer enhancement.