Steam turbines Nikola Budimir Brodostrojarstvo

1.Introduction 1.1. Definition A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Main advantages of steam turbines as propulsion plants are: - high power - simple, low weight and compact propulsion plants - good manoeuvring abilities - low request in space for their location - relatively easy and simple plant maintaining and handling

1.2.Application Steam turbines are used as a main propulsion plant on board some of today most famous vessels USS Ronald Regan Propulsion: 4 x nuclear reactors 4 x steam turbines 260,000 shp (194 MW) 4 x shafts Length: 333 m Displacement: 101,400 long tons Vessel speed: 30 knots (56 km/h)

Typhoon class submarine ( Russian ballistic missile submarine ) Propulsion: 2 x pressurized-water nuclear reactors, 190 MW (254,800 hp) each 2 x VV-type steam turbines, 37 MW (49,600 hp) each Length: 175 m Beam: 23 m Speed: 22.22 knots (41.15 km/h) Submerged endurance: 120 days submerged Test depth: 400 m

on board some fast container ships (they also could be converted from destroyers or cruisers) - on board LNG and LPG carriers (they can use cargo - gas, or fuel oil for boiler heating)

1.3. Steam turbine propulsion plant essential components: - steam generator - turbine - condenser - feed pumps - pipelines, boiler fittings One of twenty 6.0 or 8.5 MW steam turbine packages supplied to a Danish shipyard (maersk).

- electro generator could be used instead of reduction gear Reductor gear is essential to reduce high number of RPM - electro generator could be used instead of reduction gear (in that case the reversing turbine is not necessary)

1.4.Turbine designs: Most common design – with two casings ( low and high pressure steam turbine) 3000 – 12000 RPM power 800 – 2000 kW design with one casing – on board certain container ships design with three casings (low, intermediate and high pressure turbine)

2.Steam turbine main components Rotor It is designed with the number of discs equipped with blades Blades Different in size (from short to large, depending on pressure) Nozzles - steam conducting canals placed inside of turbine casing

Bearings - only sliding bearings = plummer block Labyrinth seals (glands) - to prevent steam to exude in atmosphere Coupling (clutch) - flexible coupling enables connecting of main turbine with the reductor gear

- to condense steam, de – aerating of condensate and to cool it down Condenser (steam) - to condense steam, de – aerating of condensate and to cool it down Reversing turbine - usually designed with two Curtis wheels Reductor gear - most common design – double reduction gears Common reductor gear position on board

Control and protection system - to control steam turbine operation and its protection from overload Steam turbine regulation - to maintain constant number of revolutions (by regulating valves = by hydraulic or servo motor) Turbine casing (housing) - its function is to make supporting structure, to make canals (passages) for steam

3.Conclusion . Steam turbines operate at silent and quiet conditions. They develop high powers and enable high speeds for large vessels. Because of high costs of fuel they do not have wider application on board (in merchant - flag marine) In case of navy, there is practically a rule, that any larger vessel is powered by steam turbine, because the diesel engine can not follow the turbine characteristics. .

4.Literature http://www.ehow.com/how_7218252_calculate-power-output-steam-turbine.html http://www.energy.siemens.com/hq/en/services/power-generation/performance-enhancement/steam-turbine.htm http://www.ori.milano.it/admin/tmp/files/Sito/turbine%20marine Introduction to marine engineering, D. A. Taylor, Elsevier Ltd, 1996