Session: 11-14-01 Heat Transfer in Gas Turbines

Paper Number: 71713

Start Time: Wednesday, 01:40 PM

71713 - Velocity and Heat Transfer Studies of an Impinging Jet Using Magnetic Resonance Velocimetry and Infrared Thermometry 

Modern gas turbine engines require advanced cooling techniques to operate at the high temperatures that are required to achieve performance targets. One method for improving thermal management is to implement impingement cooling on the interior surface of engine components. In this study, heat transfer performance of a single cylindrical orthogonal jet impinging on a flat plate was obtained through steady-state infrared (IR) thermometry. The flat plate, constructed from a stainless-steel (SS) shim with a thickness of 0.13 mm, was painted matte black to improve the emissivity of the surface and secured horizontally between two copper bus bars. An electrical current uniformly distributed across the bus bars was passed through the shim to create a constant heat flux boundary condition. A single pipe with constant diameter was used to direct an impingement jet orthogonally at the center of the SS shim. One Reynolds number of 23,000 based on pipe exit diameter was considered. The ambient air passed through a flow meter before being routed through a sufficiently long and smooth pipe to ensure fully developed turbulent flow conditions were achieved prior to the exit of the impinging jet. The distance of the impingement jet exit plane from the shim varied from two to eight times the impingement jet diameter in increments of two diameters. The observed temperature and constant heat flux boundary condition allowed for the calculation of a Nusselt number distribution to estimate the heat transfer performance of the impingement jet. The smallest separation distance of two diameters exhibits maximum heat transfer performance at the stagnation point followed by a minimum and a second peak occurring at a radial distance less than three diameters from the stagnation point. At a separation distance of six diameters, the greatest magnitude of Nusselt number was observed at the stagnation point. No second peak radial from the impingement stagnation point was observed at separation distances of greater than six diameters. A paired fluids experiment using Magnetic Resonance Velocimetry (MRV) techniques collected extensive hydrodynamic data of a single impinging jet. The MRV experiments utilized dilute aqueous copper sulfate solution as the working fluid and developed three-dimensional, three-component velocity data at a matching Reynolds number of 23,000 and jet exit plane distances. The MRV technique utilized the capabilities of a Magnetic Resonance Imaging (MRI) scanner which provided high fidelity measurements of the three-dimensional velocity fields. Temperature and Nusselt number distribution data obtained from the IR experiment along with the flow field velocity data obtained from the MRV experiment were compared. This study provides a unique in-depth analysis of the fluid mechanics and heat transfer characteristics of a single impinging jet using coupled experimental velocity and heat transfer methods to improve cooling performance in gas turbines, as well as improving broader applications in thermal management applications.

Presenting Author: Nathan Humbert United States Military Academy

Authors:

Nathan Humbert United States Military Academy
Jack Galante United States Military Academy
F. Todd Davidson United States Military Academy
David B. Helmer United States Military Academy
Christopher J. Elkins Stanford University
Gunnar O. Tamm United States Military Academy
Michael J. Benson United States Military Academy