Nozzle guide vane cooling design for the gas turbine engines

Abstract

Compressor, combustion chamber, and turbine are main parts of gas turbine engines. Air enters from the compressor. The compressor works on the air. The pressure and temperature of the air is increased. Air has high temperature and high pressure enters the combustion chamber. Combustion occurs and the temperature of the gas is increased. After the combustion chamber air enters the turbine section. The first stop is the nozzle guide vane which is stationary airfoil in the high-pressure turbine location after the combustion chamber. Using the high pressure and temperature of the flow, the turbine drives the compressors. Gas turbine engines work with the Brayton cycle. According to the Brayton cycle, when the turbine entering temperature that is named with $T_{4}$ is increased, the efficiency of the Brayton cycle is increased. Therefore, $T_{4}$ temperature should be increased as possible as. High temperatures have negative effects on the nozzle guide vane in terms of strength, and life. Besides, the material service temperature limits the $T_{4}$ temperatures. Therefore, engineers thought of another solution. They found cooled vane and blade design. Compressed and relatively colder air according to the turbine section is used for the cooling of the vane. This air is provided by compressors at different stages. There are different ways of cooling of vane. Also, vane can be cooled inside or outside. The main philosophy of cooling is managing the heat transfer coefficient. Heat transfer coefficient distribution differs pressure side and suction side of the outside of the vane. Therefore, the location of film cooling holes is important in terms of the outside heat transfer coefficient distribution. The heat transfer coefficient is proportional to the increase of the Nusselt number. The increase in the heat transfer coefficient in the external flow, and therefore the increase in the Nusselt number, causes the gases coming from the combustion chamber to increase the temperature of the metal. Therefore, if the location of the film cooling holes is designed to locations where the heat transfer coefficient increases, better cooling is achieved. In order to increase the performance of the coolant flow inside the vane, it is necessary to increase the heat transfer coefficient. Moreover, as the turbulence of the coolant flow increases, heat transfer coefficient of increases for the inside of the nozzle guide vane. That's way various turbulator geometries are used inside of the nozzle guide vane. In this study, sample nozzle guide vane coolant geometry is designed. Part has film cooling holes for outside of the cooling. Also, impingement holes are located in leading edge of the part. Also, pin-fins are located in trailing edge of the part. That pin-fins increase the turbulence of air. Geometry is designed and checked with computational fluid dynamics software. Temperature distributions are found.