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C. Kromer, F. von Plehwe, L. Cordes, C. Schwitzke, H.-J. Bauer
Lower specific fuel consumption as well as noise reduction are the main goals in the sector of civil aeronautics engineering nowadays. One prominent concept of achieving these goals is the geared turbofan engine, in which a planetary gear box is installed between the low pressure spool and the fan. This allows the low pressure turbine as well as the fan to rotate at optimum speeds. This way, the same power can be generated by fewer stages in the faster rotating turbine, which in turn compensates the additional weight of the gear box. The main advantage of the geared turbofan is the possibility to further increase the fan diameter and therefore improve the propulsion efficiency by means of a higher bypass ratio. One crucial feature of the gear box is the cooling system needed to ensure safe operating conditions during all phases of the flight envelope. For an efficient cooling system, optimized with respect to weight and cost, the heat transfer between the cooling fluid and the gears needs to be understood thoroughly. In this study, the impingement cooling of spur gears by oil jets is for the first time examined analytically and compared to experimental results. This provides knowledge about the evolution of the heat transfer coefficient distribution resulting from the cooling fluid flow rate and the gear speed, as well as a deep understanding of the underlying phenomena causing this behavior. The analytical solution process comprises of two calculation steps. First, the size of the oil film is calculated and secondly, the heat transfer across this surface is evaluated while the oil film is flung off the tooth flank by centrifugal forces. The parameters varied in this study were the oil flow rate, the rotational speed of the spur gear and the oil jet angle. The theoretical results are in good agreement with the experimental data. The theoretical approach can therefore be applied as a new and efficient tool to estimate the global heat transfer coefficient of impingement cooled spur gears. Furthermore, the validated tool can be used as boundary condition for thermal models of spur gears and help optimize the impingement cooling oil systems.
Deutscher Luft- und Raumfahrtkongress 2019, Darmstadt
Verlag, Ort:
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2020
Conference Paper
21,0 x 29,7 cm, 11 Seiten
Stichworte zum Inhalt:
Luftfahrtantriebe, Wärmeübergang
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Kromer, C.; von Plehwe, F.; et al. (2020): Heat Transfer by Impingement Cooling of Spur Gears. Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V.. (Text). https://doi.org/10.25967/490085. urn:nbn:de:101:1-2020012410020444143660.
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