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Bearing Analysis
Bearings influence the dynamic behavior of the rotor in a
significant way. User has been given the facility to input
bearing dynamic coefficients using three different options.
First one is defining the bearing coefficients directly. Second
option is to provide a table of non-dimensional bearing
dynamic coefficients vs. Sommerfeld number. From this
table, the bearing coefficients at a particular speed are
obtained by linear interpolation. Finally, there is a third
option to compute bearing coefficients for a specified
bearing geometry.
THE INPUT INCLUDES
- Direct input of bearing dynamic damping and stiffness coefficients
including cross-coupling terms (isotropic or orthotropic) for
different speed ranges, if necessary.
- Table of non-dimensional bearing dynamic coefficients with
respect to Sommerfeld number for interpolation at any other
speed.
- Computation of bearing dynamic coefficients for a given bearing
specification data such as load on bearing, shaft diameter, length
to diameter ratio, bearing clearance and viscosity of the lubricant.
An independent program is incorporated into NISA/ROTOR
module to compute the bearing dynamic coefficients. The program
utilizes linearized Reynold's equation about a steady state position.
The equation is solved to arrive at the stiffness and damping
coefficients using FEM with 2D discretization of the fluid film
surface, for plain cylindrical journal bearing and 2 and 4 tilting pad
journal bearings. Closed form expressions are used to compute
Dynamic coefficients for Rolling element, Squeeze film damper and seals
THE OUTPUT INFORMATION INCLUDES
- Bearing dynamic coefficients stiffness and damping
- Sommerfield vs non dimensional coefficients output to an ascii file
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