The distribution issue of turbine radial bearings

At the shaft position between the rotor and stator of the steam turbine, shaft bearings are used, as well as at the front and rear shaft journals of the turbine. It is generally made of plastic and gold materials; the material is soft enough to be scraped with a spatula. Its main function is to create an oil film and protect the journal. The thrust bearings are located at the nose of the engine; they are usually divided into upper and lower sections, with 6 bearings on each side, for a total of 12 bearings. (There are also designs with 8 bearings on one side, resulting in 16 bearings in total.) Simply put… The function of the thrust bearing is to determine the axial position of the rotor within the cylinder. Under normal operation, the working pads in the thrust bearings of the turbine are subjected to force, which prevents the turbine rotor from shifting toward the generator side. However, under load reduction conditions, especially during sudden load shedding, due to factors such as inertia, the turbine tends to shift toward the turbine head side. At this time, it is the non-operating tiles within the thrust tiles that bear the force, thereby ensuring that the axial relative position of the turbine rotor within the cylinder does not change.

This is related to the load-bearing capacity of radial sliding bearings; the common arrangement is three at the bottom and two at the top. When the equipment starts up and operates, the load is mainly borne by the lowest bearing pad. Due to the pre-load on the other bearing pads and its uneven distribution, this leads to a reduction in the stability of the bearings； In the top-three-bottom-two arrangement, the load is primarily borne by the two tiles at the bottom; these two tiles have the same preload, which helps to stabilize the rotor and significantly improves its stability as well as its load-bearing capacity. Therefore, the top-three-bottom-two arrangement is superior to the bottom-three-top-two arrangement.