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Marine steam turbine

marine steam turbine

Introduction

During the mid of the 20th century marine steam turbine was used as main engine on different vessels for propulsion. After that, the use of steam turbines was declined because of higher oil price and the introduction of new technologies like Diesel engines and gas turbines. Due to several competitions in markets steam turbine decided to improve the steam turbine efficiency.  Now currently steam turbines are used as the main engine with collaborations of turbo engine or reduction gear in high power required ships mainly nuclear naval and commercial vessels, LNG carriers, super tankers, ice breakers, cruise ships and FPSO vessels etc. Thus day by day the production of steam engine is required too much.

How does marine steam turbine works on ships?

Marine steam turbine is a heat engine which transferred the high pressure steams heat energy into mechanical energy or electrical energy with its fixed and moving the blades and alternators. It commonly used many years as a main engine or auxiliary machine on the land and marine facilities to supply power requirement. And it is a kind of rotational machine which can reaches high rotational speed which about 300rpm. And when it reaches its high speed then it can produce more power and thus efficiency increased.  But ship propeller is more preferable on lower speed, and the conflicts between turbine and propeller can be fixed using reduction gear or turbo alternator. When the steam is supplied from the ships boiler at high pressure and high temperature, superheated steam passes through the turbine at high pressure through the blades and exit at low pressure through a large bore insulated pipe. The lower pressure steam passes through LP turbine blades and exiting from these to suck by vacuum from the last few stages into main condenser. Thus, the HP and LP turbines are generally separate it for their own drives shafts, which are coupled to a double reduction gearbox that decreases their revolutions from several 1000 to about 100 rpm, which is normal operating propeller shafts speed.

Marine steam turbine

The HP turbines rotor also has several rows blade which are uses as an astern turbine, and helps the ships to maneuver when arriving or departing to ports. Simultaneously, the HP and LP steam turbines have glands at each ends which helps to stop the steam from escaping into the engine room from the HP stages and which stop the loss of condenser vacuum through the LP stages. Thus, these glands are known as labyrinth type and as  the name pronounced, are made up of a series of three rings and are supplied with two different pressure, which effectively seals both turbines shafts and end covers, with the supplied steam exiting to the gland cooler. And the common lube oil system is used to lubricate the various components and keep them cool by pumping the oil through a cooler, and the oil drawn from the drain tank through a set of magnetic strainers by the lube oil pumps into set of duplex filters, then onto the main lube oil cooler before supplying oil under pressure to the turbine white metal bearings, gearbox, sprays and thrust blocks. However, the overhead tank usually positioned at the top of the engine room is also supplied by the pump through a bleed off orifices. From the tank there is a vertical overflow pipe incorporating a circular glass windows, which is illuminated from oil and observed flowing back into the system.

Why are Marine turbine engines used on ships?

Marine turbine engines used on ships because it provides power for efficient low-power and cruise operations and these are called CODOG (Combined diesel or gas) turbine system, diesel is used in low power and cruise operations, and the turbine is used when high speeds are needed. Basically, on ships the marine turbine used as a direct propulsion plant in which the turbine shaft is connected to propeller shaft of the ship. And the speed could be thousands rpm, reduction gears and reduction systems are used to get a drop in propeller rpm. And the propelling plant of the ships can be driven by steam turbine through a slow speed motor, the turbine generator directly supplies power to these slow speed motors that are connected to the propeller shaft of the ship.

How big is an industrial and Marine Turbine?

In current situations of energy-hungry world different kinds of energy harnessing system are developing day by day like simple and combined cycle power generations turbine, mechanical drives equipment used in oil and gas industry and  marine propulsion units to provide unique and pure insight into the market. Probably, the full industrial and marine turbines forecast like gas and steam covers turbines ranging from 1200kw to 300 mw.  Whereas gas turbine and machine is mostly diversified and manufacturing in world that are used to meet the diverse power need, including propulsion( air craft, ships and rains), direct drive like( pumps and compressors) and stationary electricity generations.

How does a double reduction steam turbine work?

In marine application the double reduction steam turbine was a popular choice because it was more compact because of capturing less space in ships engine-room, not only that it had the advantage of a built-in astern turbine giving easier astern movement with up to 50% astern output power as that of the ahead turbine and that was a big advantage when the first oil super tankers were built. In this operations, the steam is supplied to the ships boiler as high pressure, high temperature superheated steam and passes into the main high pressure turbine, and expending through the blades and exiting into the low pressure turbine though a large diameter pipe.

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