Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering

Physics-based fluid mechanics models are proposed to predict load-independent (spin) power losses of gear pairs due to oil churning and windage. The oil churning power loss model is intended to simulate spin losses in dip-lubricated conditions while the windage power loss model is intended to simulate spin power losses under jet-lubrication conditions. The total spin power loss, in either case, is defined as the sum of (i) power losses associated with the interactions of individual gears with the environment surrounding the gears, and (ii) power losses due to pumping of the oil or air-oil mixture at the gear mesh. Power losses in the first group are modeled through individual formulations for drag forces induced by the fluid, which is the lubricant in the case of oil churning power losses and air or air-oil mixture in the case of windage power losses, on a rotating gear body along its periphery and faces, as well as for eddies formed in the cavities between adjacent teeth. Gear mesh pocketing/pumping losses are predicted analytically as the power loss due to squeezing of the fluid as a consequence of volume contraction of the mesh space between mating gears as they rotate. The pocketing losses are modeled through means of an incompressible fluid flow approach in the case of oil churning power losses. When the gear pairs rotate under windage conditions, a compressible fluid flow methodology is considered for predicting the pocketing losses. The power loss models are applied to a family of unity-ratio spur gear pairs to quantify the individual contributions of each power loss component to the total spin power loss. The influence of operating conditions, gear geometry parameters and lubricant properties on spin power loss are also quantified. The oil churning and windage power loss models are validated through comparisons to extensive experiments performed on spur gear pairs under dip- and jet-lubricated conditions, over wide ranges of gear parameters and operating co (open full item for complete abstract)

Committee: Ahmet Kahraman PhD (Advisor); Vish Subramaniam PhD (Committee Member); Gary Kinzel PhD (Committee Member); Robert Siston PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2013, Mechanical Engineering

In this study, load-independent (spin) power losses of a gearbox operating under dip-lubrication conditions are investigated experimentally. A family of final drive helical gear pairs from an automotive transmission is considered as the example for this investigation. A dedicated gearbox is designed and fabricated to operate a single gear or a gear pair under given speed conditions. The test gearbox is incorporated with a high-speed test bed with power loss measurement capability. A test matrix that consists of sets of tests with (i) single spur, helical gears, or disks with no teeth, and (ii) helical gear pairs of varying gear ratios is executed with three different transmission fluids at various temperatures and immersion depths. Power losses from single gear and gear pair tests at identical operating conditions are compared to break down the total spin loss to its main components, namely gear drag loss, gear mesh pocketing loss, and bearing/seal loss. In addition, the space around the gears within the gearbox will be altered to quantify any influences of enclosures and peripheral shrouds on the spin losses of a rotating gear.

Committee: Ahmet Kahraman Dr. (Advisor); Donald Houser Dr. (Committee Member) Subjects: Mechanical Engineering