Blade vibration viewed in experimental turbine

SOME of the difficulties experienced with early superposed steam-electric turbogenerator units indicated a need for a better understanding of the conditions affecting the operation of turbine impulse blades in these machines. To obtain good economy at partial loads the incoming steam is fed to the first turbine wheel at only a portion of its periphery, and the blades passing into and out of this steam jet receive a most violent shock each revolution of the turbine. This method of loading has been used for many years with turbines operating at lower pressures, and it has been only on those few machines of the large superposed class, which operate at a pressure of approximately 1,200 pounds per square inch and a temperature of some 900 degrees Fahrenheit, that its use has caused some blades to break at the root where they are fastened to the spindle.