Author: Melissa ShallcrossPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
In gas turbine engines, the turbine comes just after the combustor, where fuel is mixed with air and ignited to produce a rapid expansion of hot gases. These turbine blades are thus exposed to an air temperature higher than the melting temperature of the turbine blade material, which threatens to destroy the airfoils. In order to combat this, jet engine manufacturers use several different cooling methods. One of these methods involves bleeding cooler bypass air routed from the upstream compressor through the turbine airfoils where arrays of short cylinders inside the trailing edge promote turbulence, therefore increasing the heat transfer from the blade to the cooling air. The heat transfer of these short pin fins is affected by the close proximity of the endwalls, making them unique compared to long cylinders in crossflow. The current study investigates the instantaneous and time-averaged heat transfer within short aspect ratio pin fin arrays of two streamwise spacings. Understanding the heat transfer characteristics of pin fin arrays will allow engineers to design more efficient arrays to incorporate into gas turbine engines. Using a heat flux microsensor embedded in an isothermal heated cylinder, the heat transfer around the circumference of a test pin is measured at ten-degree intervals. The instantaneous and time-averaged data is then compared for cylinders in multiple locations in the array at Reynolds numbers of 3000, 10000, 20000, and 50000. This data is taken at two streamwise spacings of 1.73 diameters between subsequent rows and 3.46 diameters between subsequent rows in order to compare the pin fin heat transfer at different array densities. The effect of natural convection on these tests was also studied. An experiment was performed in an attempt to find a correlation that could correct the heat transfer data so that only forced convection was reported.
