Heat transfer through impingement cooling of a rotating cylinder
Engineering Design, Machine Elements, Product Development
Final Report Abstract
The cooling of critical components, which have to withstand high heat loads, is a current challenge in the engineering community. An effective cooling method is impingement cooling with the potential to withdraw large heat fluxes at a precise location. Liquid impingement cooling with oil has the additional benefit that the oil can lubricate the component, e.g. in a gearbox. Many studies focused on the impingement cooling of static surfaces can be found in the literature, but very little research is available with respect to moving target surfaces. The aim of this study is the thorough investigation of liquid impingement cooling of a rotating cylinder using an oil jet. An analysis on the flow behavior was performed using high-speed images of the jet impingement area. The input parameters oil temperature, oil flow rate, rotational speed of the cylinder and nozzle diameter were varied. Subsequently, the images were classified into flow regimes. Four different flow regimes were identified and characterized. A cylinder instrumented with thermocouples was used for the thermal analysis of the impingement process. A newly developed correction algorithm was able to reduce systematic measurement uncertainties. The effect of the parameters mentioned above on the heat transfer was studied in a parameter study. The measured temperatures were evaluated in a finite-element-analysis to evaluate the heat flux at the cylinder surface. The evaluation revealed that viscous dissipation significantly influences the heat transfer and has to be accounted for. The use of the superposition principle allows for the calculation of the adiabatic wall temperature and the corresponding Nusselt number. The applicability of the superposition principle to liquid oil flows was analytically examined using a similarity solution to a simplified Blasius flow. Correlations for the target parameters recovery factor, Nusselt number and oil film width were derived over a large operational parameter range. In the last part of the project, a possible applicability towards the cooling of gears was investigated. Previous investigations revealed that the wetted area and the impingement process dominate the heat transfer on gears. A simple analytical tool was developed to approximate the wetted surface. The tool was validated against high fidelity CFD results. The heat transfer correlations from the cylinder were applied to the wetted surface of the gears by keeping the necessary non-dimensional parameters constant. A comparison with experimental measurements on gears showed good agreement. The detailed results from this study can now be used in a wide variety of applications with liquid jet impingement on moving target surfaces.
Publications
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„Experimental Investigation of the Oil Jet Heat Transfer on a Rotating Cylinder for an Aero Engine Gearbox,“ in 25th Conference of the International Society for Air Breathing Engines, Ottawa, Canada
C. Kromer, E. Ayan, C. Schwitzke & H.-J. Bauer
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Similarity solutions of a Blasius flow with variable fluid properties and viscous dissipation. Heat and Mass Transfer, 59(12), 2285-2298.
Kromer, Christian; Schwitzke, Corina & Bauer, Hans-Jörg
