NDLI: Experimental and Numerical Investigation on Windage Power Losses in High Speed Gears

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Massini, D. Fondelli, T. Andreini, A. Facchini, B. Tarchi, L. Leonardi, F.
Copyright Year	2017
Abstract	Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. The transmission system in fact has a direct impact on the engine overall efficiency by means of its weight contribution, internal power losses and lubrication requirements. Thus, an evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Gears are among the most efficient power transmission systems, whose efficiencies can exceed 99 %, nevertheless in high speed applications power losses are anything but negligible. All power dissipated through losses is converted into heat that must be dissipated by the lubrication system. More heat leads to a larger cooling capacity, which results in more oil, larger heat exchangers which finally means more weight. Mechanical power losses are usually distinguished in two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid-dynamics of the environment which surrounds the gears, namely windage, fluid trapping and squeezing between meshing gear teeth and inertial losses resulting by the impinging oil jets, usually adopted in high speed transmission for cooling and lubrication purposes. The relative magnitude of these phenomena is strongly dependent on the operative conditions of the transmission. While load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. Among fluid-dynamic losses, windage is extremely important and can dominate the other mechanisms. In this context, a new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry measurements for investigating the flow-field surrounding the rotating gear. The experiment has been computationally replicated, performing RANS simulations in the context of conventional eddy viscosity models. The numerical results were compared with experimental data in terms of resistant torque as well as PIV measurements, achieving a good agreement for all of the speed of rotations.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791850886
DOI	10.1115/GT2017-64948
Volume Number	Volume 5B: Heat Transfer
Conference Proceedings	ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
Language	English
Publisher Date	2017-06-26
Publisher Place	Charlotte, North Carolina, USA
Access Restriction	Subscribed
Subject Keyword	Viscosity Torque Temperature Fuel consumption Turbomachinery Industrial lubrication systems Aircraft engines Engines Design Fluids Torquemeters Weight (mass) Eddies (fluid dynamics) Spur gears Lubrication Engineering simulation Cooling Fluid dynamics Heat exchangers Flow (dynamics) Pressure Stress Heat Gears Gear teeth Simulation Reynolds-averaged navier–stokes equations Particulate matter Jets
Content Type	Text
Resource Type	Article

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