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Tuesday, 11 March 2014
16:30 - 18:00 Advanced drive trains technologies
Hardware Technology  


Room: Tramuntana
Session description

In recent years several alternative drive train solutions have been proposed and also introduced on prototypes and in larger series. The new solutions seek to reduce the cost of energy by improving the reliability and service costs while keeping the initial costs competitive. Only a few of the new solutions have found their way into the competitive onshore market. The session will look into some of the potential incremental improvements that can be foreseen on the mainstream onshore market, but also look at some more radical concepts that may hold potential.

Learning objectives

  • Get an understanding of the options for journal bearings when used in the gearbox
  • See how field experience and numerical analysis can be used to optimise the performance of gearbox solutions
  • Learn more about the potential of magnetically geared solutions for wind application
  • See some of the potential improvements that can be implemented on drivetrains with gearboxes
Lead Session Chair:
Steffen Haslev Sørensen, RCA Engineering, Denmark

Co-chair(s):
Andreas Reuter, Fraunhofer IWES
James Packer
Ricardo, , United Kingdom

Abstract

Geared wind turbine drivetrains offer many advantages over direct drive arrangements but in service reliability continues to be a major focus especially for large offshore machines. Intensive research and development work continues within the industry to develop reliable geared drivetrain designs. Some current design approaches that attempt to manage the effects of peak and stochastic wind loading within the gearbox and drivetrain will be reviewed. In particular, this paper will describe some new novel approaches to load management under development by Ricardo applicable to both onshore and offshore turbines.

The paper will review past and current observations about geared drivetrain reliability. Focusing on the management of loads within the drivetrain and gearbox, the paper will discuss how inadequate load management leads to some typical geared drivetrain failure modes. Some common industry solutions to these failure modes will be summarised. Finally the paper will then focus on research and development work ongoing at Ricardo and describe how a novel new mechanical load management system can isolate the drivetrain from both impulsive torque and non-torque loads.

Failure investigations supported by rig test results confirm that planet gear bearings in low-speed high-load planetary geartrains are susceptible to torque overload. Deflections in the rotor shaft and support structure caused by lateral forces and bending moments (so called non-torque loads) are often not adequately isolated from the gearbox resulting in gear and bearing misalignment and the risk of early failure.
Some proprietary design approaches that have been proposed to mitigate gearbox damage from peak and non-torque loading due to extreme and stochastic wind loads will be reviewed. Optimum loadshare and alignment of gears and bearings is critical and floating or flexible components in the gearbox can improve load share. External to the gearbox, stiffer close coupled nacelle structures offer reduced misalignment in the drivetrain and some drivetrain systems use flexible couplings to isolate non-torque loads from the gearbox, and slipping clutches to limit peak drivetrain torques.

The paper will conclude that effective management of loads within the drivetrain and gearbox using a combination of existing and new techniques will increase drivetrain reliability and can also be beneficial to the durability of other areas of the turbine structure. The paper will also show that whilst many of these innovations are being driven by the increased need for reliability offshore, they may also help to further optimise design and improve reliability of new and existing onshore turbines.