Page 69 - Introduction to Marine Engineering
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56 Steam turbines and gearing
Low pressure
turbine
Turning
gear
Gearbox
High pressure
turbine
Figure 3.4 Cross compound turbine arrangement
single cylinder unit which would be usual for turbo-generator sets,
although some have been fitted for main propulsion service.
Reheat
Reheating is a means of improving the thermal efficiency of the
complete turbine plant. Steam, after expansion in the high-pressure
turbine, is returned to the boiler to be reheated to the original superheat
temperature. It is then returned to the turbine and further expanded
through any remaining stages of the high-pressure turbine and then the
low-pressure turbine.
Named turbine types
A number of famous names are associated with certain turbine types.
Parsons. A reaction turbine where steam expansion takes place in the
fixed and moving blades. A stage is made up of one of each blade type.
Half of the stage heat drop occurs in each blade type, therefore
providing 50% reaction per stage.
