Engineering topics
Errichello, Robert
Publications and source records attributed to Errichello, Robert.
Gearbox Reliability Collaborative Analytic Formulation for the Evaluation of Spline Couplings
Gearboxes in wind turbines have not been achieving their expected design life; however, they commonly meet and exceed the design criteria specified in current standards in the gear, bearing, and wind turbine industry as well as third-party certification criteria. The cost of gearbox replacements and rebuilds, as well as the down time associated with these failures, has elevated the cost of wind energy. The National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC) was established by the U.S. Department of Energy in 2006; its key goal is to understand the root causes of premature gearbox failures and improve their reliability using a combined approach of dynamometer testing, field testing, and modeling. As part of the GRC program, this paper investigates the design of the spline coupling often used in modern wind turbine gearboxes to connect the planetary and helical gear stages. Aside from transmitting the driving torque, another common function of the spline coupling is to allow the sun to float between the planets. The amount the sun can float is determined by the spline design and the sun shaft flexibility subject to the operational loads. Current standards address spline coupling design requirements in varying detail. This report provides additional insight beyond these current standards to quickly evaluate spline coupling designs.
Gear-SCouP
Gear-SCouP is an analytical model for the rating analysis of articulated spline coupling designs. Articulated splines are commonly used in the planetary stage of wind turbine gearboxes as the means of transmitting the driving torque while also improving load sharing. Direct measurement of spline loads and performance is extremely challenging because of limited accessibility and spline design standards are limited. For a given torque and shaft misalignment, Gear-SCouP quickly yields physical insights into relationships between the spline design parameters and resulting loads, bending, contact, and shear stresses, and safety factors considering various heat treatment methods. Results of this analytical model are compared well against several computational approaches under moderate misalignment. The computational time of Gear-SCouP is significantly less than other FE-based tools.