Yaw System Modelling Options

The yaw system in Bladed is a versatile model. It covers a wide range of features by including or excluding properties in the input JSON. The basic model covers only the yaw bearing. This can be extended by adding a gearbox ratio and actuation properties. Furthermore, the high-speed shaft flexibility can be modelled and dual load banks can be added. The mass and static inertia properties are part of the Nacelle Mass and Inertia.

Note

In the following multibody diagrams, the node and component names are presented without the prefix “Yaw 1“. The prefix number corresponds to the associated yaw system, as multiple yaw systems can coexist.

Yaw Bearing

The yaw bearing functions as the rotatable interface connecting the rotor nacelle assembly (RNA) to the tower top. By incorporating a YawSystem with a Bearing definition in the input JSON, it is possible to include a rotational joint between the Tower component and the DrivetrainAndNacelle component. The properties of the Bearing are:

• Damping: The rotational damping coefficient and is modeled as viscous damping.
• Friction: The total kinetic friction torque expressed in \(\bunit{N}/\bunit{m}\), when the bearing is moving.
• Stiction: The total rotational stiction torque (expressed in \(\bunit{N}/\bunit{m}\)) occurs when the rotor nacelle assembly remains stationary. This value needs to exceed the specified friction, as it represents the total stiction during standstill. If only the Bearing component is included in the "YawSystem", the multibody representation assumes a gearbox component with a gear ratio of 1, as shown in Figure 1.

An example of a yaw bearing only YawSystem:

"YawSystem": {
    "Bearing": {
        "Damping": 100000.0,
        "Friction": 100000.0,
        "Stiction": 100000.0
    },
}

Note

The yaw angle is set to 0 degrees and locked for Steady Operational Loads calculation.

Figure 1: Multibody diagram for a yaw bearing with friction.

Yaw Gearbox and Actuation

To include the gearing and actuator motors in a simulation use the Actuation property in the YawSystem. A gear ratio can be defined as well as motor inertias.

The gearbox is represented by the gearbox component which has a few special properties, see Figure 2. That is two distal nodes: YB(Yaw Bearing) and YBGS(Yaw Bearing Gearbox Side). For every one rotation of the YB node, the YGBS or high-speed shaft (HSS) experiences \(\bscalar{N_g}\) rotations, which is set by the EffectiveGearRatio property.

A load bank can be defined by adding the LoadBanks array property. This allows for individual properties to be specified for each load bank. For a rigid load bank, only the motor’s inertia is necessary, which can be included using the MomentOfInertiaOfMotor property (\(\bunit{kg}\cdot \bunit{m^2}\)).

Here’s an example of a single rigid load bank YawSystem:

"YawSystem": {
    "Bearing": {
        "Damping": 100000.0,
        "Friction": 100000.0,
        "Stiction": 100000.0
    },
    "Actuation": {
        "EffectiveGearRatio": 20000.0,
        "LoadBanks": [
            {
                "MomentOfInertiaOfMotor": 1.0
            }
        ]
    }
}

Note

The external loads DLL is not supported for Steady Operational Loads calculation.

Figure 2: Multibody diagram for a yaw gearbox and single rigid load bank.

High-speed Shaft Flexibility

To account for the flexibility of the high-speed shaft, two properties need to be added to the LoadBanks array:

• HighSpeedShaftStiffness: The stiffness (\(\frac{\bunit{N}}{\bunit{m}}/\bunit{rad}\)) of the high-speed shaft, associated with the flexible hinge: "HSS Yaw Flexibility".
• HighSpeedShaftDamping: The damping coefficient (\(-\)) of the high-speed shaft, associated with the flexible hinge: "HSS Yaw Flexibility".

The node, YBH1, will be created by connecting the inertia defined by MomentOfInertiaOfMotor through the flexible high-speed shaft to the gearbox. See Figure 3 for the corresponding multibody diagram.

An example of a single flexible load bank YawSystem:

"YawSystem": {
    "Bearing": {
        "Damping": 100000.0,
        "Friction": 100000.0,
        "Stiction": 100000.0
    },
    "Actuation": {
        "EffectiveGearRatio": 20000.0,
        "LoadBanks": [
            {
                "HighSpeedShaftStiffness": 1000000.0,
                "HighSpeedShaftDamping": 100.0,
                "MomentOfInertiaOfMotor": 3.0
            }
        ]
    },
}

Figure 3: Multibody diagram for a yaw gearbox and single flexible load bank.

Dual Load Banks

An additional load bank can be added by introducing a second entry to the LoadBanks array. This enables the possibility to have different load bank properties. The additional banks simply connect to the YBGS node as shown in Figure 4 (rigid load banks) and Figure 5 (flexible load banks). It is supported to have a dual bank consisting of both a rigid and a flexible load bank.

An example of a dual flexible load bank YawSystem:

"YawSystem": {
    "Bearing": {
        "Damping": 100000.0,
        "Friction": 100000.0,
        "Stiction": 100000.0
    },
    "Actuation": {
        "EffectiveGearRatio": 20000.0,
        "LoadBanks": [
            {
                "HighSpeedShaftStiffness": 1000000.0,
                "HighSpeedShaftDamping": 100.0,
                "MomentOfInertiaOfMotor": 3.0
            },
            {
                "HighSpeedShaftStiffness": 100000.0,
                "HighSpeedShaftDamping": 100.0,
                "MomentOfInertiaOfMotor": 1.0
            }
        ]
    },
}

Figure 4: Multibody diagram for a yaw gearbox and dual rigid load banks.

Figure 5: Multibody diagram for a yaw gearbox and dual flexible load banks.