BLADE FAILURES IN THE H.P. TURBINES OF R.M.S. QUEEN ELIZABETH 2 AND THEIR RECTIFICATION

The history of the operation of the engines up to the time of failure is recorded, and the damage sustained is described as being due to fatigue. The blade vibration aspects are reviewed, establishing the theoretical background and discussing the response to external and steam excitation. The determination of the blade frequencies in the affected stages on the basis of past research and recent measurements in the laboratory on groups of blades is treated at some length, and it is deduced that one or other of these stages would reach a state of resonance with the nozzle wake impulse frequency within the range from half shaft speed to full speed. The particular modes of vibration are tangential batch modes known as clamped-pinned. It is concluded that such vibration is the prime cause of failure, aggravated by stress concentrations. The rectification of the fault by a redesign, incorporating a binding wire, is described.