Turbo-generators

Nuclear technology

All UK nuclear-powered submarines entering service in the last half-century have featured Rolls-Royce turbo-generators. A large number of turbine products have also been designed for naval surface ship applications, many of which remain in service today around the world.

Turbo-generators are designed to convert energy in steam into electrical power, essential for sea-going craft, particularly submarines that must maintain a breathable atmosphere. The turbo-generators run at a fixed speed and are designed to be both quiet and resistant to severe mechanical shocks.

Design & methods

We design bespoke steam turbines using cutting-edge, integrated thermodynamic/mechanical tools that are capable of complex three-dimensional (3D) blade design and performance prediction. 

They feature:

  • Compact, high-efficiency, impulse technology turbine blading.
  • Reversing stages allowing a vessel to be driven backwards.
  • Tolerance to “wet” steam (with a high liquid content).
  • A design that supports a vessel’s 30-year service life.

Steam turbine performance is guaranteed by validation testing of all the turbine systems using a live steam supply ahead of delivery to the shipbuilder.

Turbo-generator components are designed using 3D finite element analysis to ensure external shock resistance. Rotor shafts are assessed using dedicated rotor dynamics software to confirm machine alignment.  Optimum performance of the turbo-generator is maintained while minimising vibration and noise.

Materials

For turbine blade designs stainless steel is chosen to minimise corrosion and erosion in the marine environment. 

A ruggedised design is combined with lacing wire to reduce noise and vibration, while a tapered profile with varied cross section maximises turbine efficiency.

Manufacturing engineering

Turbo-generators are supplied as complete modular packages. They incorporate the turbine, generator and control/oil systems on a single baseplate for simple and rapid installation. This also minimises operational noise and vibration.

Control is achieved through a modularised hydraulic or all-electric system and multiple control valves deliver maximum part-load efficiencies.

This ‘design for manufacture’ approach also includes reduced weld ‘lay-up’ in diaphragms to achieve a manufacturing process that is more rapid than common diaphragm build practice.

Turbo-generators are also designed for supportability – with COTS (commercial off-the-shelf) components utilised where appropriate. Other components such as pump motors and valves are as interchangeable as possible to reduce the amount of spares that have to be held.

Electrical & control systems

A turbine’s throttle control and safety steam valves are commonly powered by hydraulic actuators, calling for a complex and expensive arrangement of pumps, tanks, heaters and coolers.

We have invested in the design, development and testing of an electrically actuated steam valve that can draw on the vessel’s existing electrical supply system. This completely eliminates the hydraulic oil system, reducing cost and complexity, as well as removing a potential fire risk.

The valve design is unique in that it immediately closes in the event of an interruption of the electrical supply.

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