Table of Contents

Drivetrain Mounting Flexibility

If desired, hinge flexibility may be specified in the gearbox mounting and/or between the pallet or bedplate and the tower top/yaw system. It adds an additional rotational degree of freedom for each selected flexibility. The different mounting flexibility options will introduce hinge components in the turbine multibody model.

Figure 1

Figure 1: Diagram illustrating the drivetrain flexibility options and their locations. Note that the gearbox mounting flexibility is attached between the mass and inertia of the nacelle and the gearbox. This is also shown in the multibody model diagram.

Flexible mountings introduce a high frequency mode which is liable to result in much slower simulations. If the mountings are relatively stiff, for example if they are intended for noise isolation, then they will not influence loads significantly and are best omitted. If they are intended to modify the rotational dynamics, then they can be approximated by a corresponding reduction in shaft stiffness. This will have little effect on rotor and tower loads, but simulations will run faster.

Pallet Rolling and Nodding

The pallet mounting is situated between either the tower top or yaw system and the nacelle mass as illustrated in the multibody model diagram and in Figure 1. Nodding is the rotational degree of freedom of the y-axis and rolling is about the x-axis as illustrated to the right in Figure 1.

Both PalletNodding and PalletRolling have two properties:

  • Stiffness: The drivetrain pallet's nodding or rolling stiffness.
  • Damping: The drivetrain pallet's nodding or rolling damping.

Example of a PalletNodding and PalletRolling objects:

"MountingFlexibility": {
    "PalletRolling": {
      "Stiffness": 9.26E+08,
      "Damping": 1.562E+07
    },
    "PalletNodding": {
      "Stiffness": 9.26E+08,
      "Damping": 1.562E+07
    },
},

Gearbox Mounting

The gearbox mounting option enables flexibility between the nacelle mass and the gearbox as shown multibody model diagram and in Figure 1. The flexibility is added about the x-axis as illustrated to the right in Figure 1. The MomentOfInertia about the x-axis is not to be included in the inertia of the nacelle.

In the case of a flexible gearbox mounting, the moment of inertia of the gearbox casing. The GearboxMountingRolling have three properties:

  • Stiffness: The gearbox mounting's rolling stiffness about the x-axis.
  • Damping: The gearbox mounting's rolling damping about the x-axis.
  • MomentOfInertia: The gearbox casing's moment of inertia about the x-axis.
"GearboxMountingRolling": {
    "PalletRolling": {
      "Stiffness": 2.4E+09,
      "Damping": 1.54E+07,
      "MomentOfInertia": 40724
    },
},