For turbines operating above the critical speed, stops are provided to limit the amplitude as they run through the critical speed.
In the turbine of Problem, if the clearance between the 2.54-cm shaft and the stops is 0.0508 cm, and if the eccentricity is 0.0212 cm, determine the time required for the shaft to hit the stops.
Assurne that the critical speed is reached with zero amplitude.
Problem
The rotor of a turbine 13.6 kg in mass is supported at the midspan of a shaft with bearings 0.4064 m apart, as shown in Figure.
The rotor is known to have an unbalance of 0.2879 kg . cm. Determine the forces exerted on the bearings at a speed of 6000 rpm if the diameter of the steel shaft is 2.54 cm.
Compare this result with that of the same rotor mounted on a steel shaft of diameter l.905 cm. (Assume the shaft to be simply supported at the bearings.)
