Our customer required support for the design of a large marine propeller and shaft line for a new fleet of naval vessels. This project required specialist technical capabilities, including 3D finite element modelling, shaft dynamics and propeller performance.
Stirling provided a whirl frequency analysis to identify resonant shaft frequencies near propeller operating speeds that can cause excessive vibration, loads and noise that must be addressed during design. A 3D finite element model of the propeller, shaft, journal bearings and supporting structures was created from a detailed CAD model using Ansys to yield the Campbell diagram (also known as an interference diagram), mapping resonant frequencies to shaft speeds and identifying conditions for further investigation.
The effectiveness of Ansys for the modelling of rotational shaft dynamics, contact mechanics and complex 3D geometries proved invaluable in this project for carrying out sensitivity studies on the influence of the flexibility of supporting structures, journal bearing clearances, added mass of entrained seawater and gravitational effects. Stirling provided the customer with an assessment of shaft whirl resonance and the influence of supporting structures so that they could progress to the next stage in the design process.