Lubrication system for gas turbine

A turbine essentially comprises a mechanical generating system including a combustion chamber (2) providing useful mechanical work on a high-speed shaft (8), a speed step-down system (18-20) for receiving rotational energy from the high-speed shaft and an output system including a low-speed shaft (17) receiving rotational energy from the speed step-down system for delivering mechanical from the turbine to a load. The high-speed shaft is cantilever mounted on a pair of bearings (9A-9B) in the cold region and is provided with a longitudinal duct and an array of fine orifices (27) in the wall of the shaft which direct pressurized oil in the duct in the form of jets which impinge on the bearings with little relative speed, thereby increasing wetting of the bearing components. Oil is supplied to the duct by means of a positive-displacement pump (23) directly driven by the shaft. The output pressure of the pump provides a signal which is indicative of turbine speed and hence used to control the turbine start-up sequence.