What is one purpose of a thrust bearing in a large reaction steam turbine?

A thrust bearing in a large reaction steam turbine primarily serves to absorb axial loads or thrust generated during operation. This is crucial because these axial loads can arise from differential pressure on the turbine blades and can potentially cause movement of the rotor along the shaft.

While the correct function is not about supporting the dummy piston, it's essential to understand that thrust bearings allow the rotor to stay in a stable position by absorbing these forces. The design and installation of thrust bearings ensure that the turbine's rotating components remain aligned and do not experience excessive wear or potential damage due to misalignment.

Thus, the correct understanding of thrust bearings is that they are integral to managing the axial forces, allowing the turbine to run smoothly and efficiently, which is critical for the turbine's performance and longevity.