Computational and Experimental Investigation of Vortex Cooling of a Gas Turbine Blade Using 3-D Stereo-Particle Image Velocimetry and Liquid Crystals PDF Download

Author: Daisy Galeana
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Get Book Here

Book Description
The limiting factor for most gas turbines has been the turbine inlet temperature. Furthermore, higher pressure ratios and turbine inlet temperatures improve the efficiencies on the gas turbine. A big focus has been on new schemes of internal cooling designs of turbine blades, using pressurized air from the engine compressor, and break-through in blade metallurgy, in order to achieve higher turbine inlet temperatures. Significant research has been ongoing for decades to design an internal cooling system for the first stage of the turbine blade consequently higher turbine inlet temperatures can be achieved. The challenging engineering intricacies related to improving the efficiency of a gas turbine engine come with the need to maximize the efficiency of the internal cooling of the turbine blade to withstand the high turbine inlet temperature. Understanding the fluid mechanics and heat transfer of internal blade cooling is therefore of paramount importance. This dissertation presents the impact of swirl flow cooling on the heat transfer of a gas turbine blade cooling passage to understand the mechanics of internal blade cooling. The focus is the continuous cooling flow that must be maintained via nonstop injection of tangential flow, whereby swirl flow is generated. The experimental investigation is presented first with three-dimensional (3-D) Stereo-Particle Image Velocimetry (Stereo-PIV) and second Thermochromic Liquid Crystal (TLC) of a swirl flow that models a gas turbine blade internal cooling configuration. The study is intended to provide an evaluation of the developments of swirl flow cooling methodology utilizing 3-D Stereo-PIV and liquid crystals. The objective of the experimental models is to determine the critical swirl number that has the potential to deliver the maximum axial velocity results with the highest heat transfer at three different Reynolds numbers, 7,000, 14,000, and 21,000. The swirl flow cooling methodology comprises of cooling air channeling through the blade's internal passages lowering the metal temperature, therefore the experimental cylindrical chamber is made of acrylic allowing detailed measurements and includes seven discrete tangential air inlets designed to create the swirl flow. Additionally, a 3D domain fluent setup employing a steady-state pressure-based solver with a standard k-epsilon turbulence model was applied. The energy equations were activated to handle the temperature effect; the gravitational acceleration is accounted for. Important variations of the swirl number are present near the air inlets and decrease with downstream distance as predicted since the second half of the chamber has no more inlets. The axial velocity reaches the maximum downstream in the second half of the chamber. The circumferential velocity decreases downstream distance and reaches the highest towards the center of the chamber. As part of the results relatively low heat transfer rates were observed near the upstream end of the cylindrical chamber, resulting from a low momentum swirl flow as well as crossflow effects. The TLC heat transfer results exemplify how the Nusselt Number (Nu) measured favorably at the midstream of the chamber and values decline downstream. Furthermore, experimental results when compared to the Computational Fluid Dynamics analysis are compatible with each other.