Propeller shaft enclosure system

By Keith Henderson at July 09, 2010 16:34
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There is a patented device claiming to give between 6 to 10 per cent increased efficiency to the propulsion system applying mainly to planning hulls with inboards. The BOSS (Bolt On Shaft System) as it is called, basically is a tube that encloses the immersed part of the propeller shaft and combines it with a seal and thrust bearing that is mounted directly on to the hull. The self contained unit eliminates through hull sealing and alignment difficulties, and allows the gearbox and engine to be mounted free of thrust considerations. The propeller end of the tube is supported by a P-bracket type of arrangement. For the boat builder, installation times are substantially reduced and the built-in watertight shaft seal ensures a dry bilge. For the user, the reduced losses give the benefits of lower fuel consumption, improved range or a higher top speed. It’s available for shaft diameters of one to four inches (25 – 102mm) and is claimed to lower propulsion noise and vibration.
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Engine cooling systems optimization

By Keith Henderson at June 20, 2010 13:17
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One of the many areas of interest as part of the Danish Greenship Project is reducing the energy consumption of the engine cooling systems. For the investigation, a MAN B&W engine in a 35,000 dwt bulk carrier is used to study both sea water and lubrication oil cooling systems. Project studies indicate that there is an unnecessarily high pressure drop and therefore flow resistance in the sea water cooling circuit resulting in wasteful energy consumption. By specifying a larger capacity heat exchanger the flow resistance would decrease permitting the use of smaller pumps with an energy saving that could be as much as 90 per cent and save 160 tons of CO2 per pump per year! Using a different type of oil pump and / or optimizing the flow through the lubricating oil recirculation system, around five per cent of energy can be saved, equivalent to more than 110 tons of CO2 per annum.
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