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Nacelle Data

Description

The nacelle data file defines the inertial properties of a wind turbine nacelle, as well as the geometric relations between its coordinate frames. The nacelle is modeled as a lumped mass, with its inertia and center of mass defined relative to the tower top.

Parameters

Name Description Value Unit
overhang Distance along shaft from tower centerline to rotor apex. Real scalar [m]
Twr2Shft Vertical distance from tower top to drive shaft. Real scalar [m]
tilt Tilt of rotor drive shaft. Real scalar [deg]
m_nacelle Nacelle mass. Real scalar [kg]
cm_nacelle_x Center of mass, x-coordinate. Real scalar [m]
cm_nacelle_y Center of mass, y-coordinate. Real scalar [m]
cm_nacelle_z Center of mass, z-coordinate. Real scalar [m]
I_xx Principal moment of inertia about x-axis. Real scalar [kg.m²]
I_yy Principal moment of inertia about y-axis. Real scalar [kg.m²]
I_zz Principal moment of inertia about z-axis. Real scalar [kg.m²]
I_xy Product of inertia. Real scalar [kg.m²]
I_xz Product of inertia. Real scalar [kg.m²]
I_yz Product of inertia. Real scalar [kg.m²]
I_hs_shaft Moment of inertia of high-speed shaft about axis of rotation. Real scalar [kg.m²]
I_ls_shaft Moment of inertia of low-speed shaft about axis of rotation. Real scalar [kg.m²]
gb_ratio Gearbox ratio. Real scalar [-]

Notes

The center of mass vector, cm_nacelle, should be expressed with respect to tower top frame.
The inertia tensor, I, should be expressed about the nacelle center of mass, using the coordinate vectors from the tower top frame.
The overhang is expressed in the pitched frame of the drive shaft. The overhang distance is measured along the drive shaft, from directly above the tower centerline to the rotor apex. It is typically negative, since the positive x-axis points downwind.
The lumped mass of the nacelle includes the yaw system, generator, and other components of the rotor-nacelle assembly (RNA), besides the hub and blades.

The nacelle data is stored in a .txt file that can easily be produced using the Data Generation Tool or by populating a .txt file manually. If the file is created manually, parameters must be defined in the format name = value;, where name is the parameter name and value is a number of type Real. Comments can be inserted in the file using double slash: //. See below for an example. 


    // =============================================
    // Inertial properties
    // =============================================
    m = 123.456; // mass [kg]
    I_xx = 1.23e4; // mass moment of inertia [kg.m²]

    // =============================================
    // Geometric properties
    // =============================================
    l = 12.345; // length [m]

The diagram shows a cross-section of a nacelle, with 3 coordinate frames defined. The subscript “T” frame is defined at the tower top, with the x-axis pointing downwind and the z-axis vertical along the tower centerline. The subscript “S” frame is defined along the drive shaft, translated vertically from the tower top and pitched along the positive y-axis. The vertical translation is Twr2Shft and the pitch angle is tilt. The subscript “R” frame is defined at the rotor apex, translated along the pitched drive shaft by the parameter overhang. The center of mass of the nacelle system is given by the vector cm_nacelle, which is resolved in the tower top frame.

Diagram of a wind turbine nacelle cross section, with annotated coordinates