Wednesday, May 6, 2009

Prime Mover of Passenger Ship

When designing a passenger ship, naval architects have to come to a decision whether to choose steam turbine or diesel engine as the ship's prime mover. In the past, most of the passenger ships used steam turbine as their prime mover. The choice of this kind of marine engine was based on a consideration that steam engine has relatively very low vibration. Therefore, steam engine was more suitable for passenger ships. However, steam turbine installation needs more spaces for boiler, condenser, turbines, reduction gears and piping installation.
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Improvements in the design of marine diesel engines have led to the application of diesel engine to passenger ships. Marine diesel engines are specially designed to have low RPM to adapt to the diameter of the propeller. This design constraints led to the development of low speed diesel engines for big ships. The lower the speed of the main engine, the better will be the efficiency and the larger will be the diameter of the ship's propellers. In smaller ships where low speed diesel engines are not available, reduction gears are needed to lower the RPM to match it to the RPM of the propeller at its optimum efficiency.

The vibration of marine diesel engine, as the prime mover of a ship, has to be kept lower to make the ship comfortable to all the passengers and crews. If the vibration of a vessel is high, passenger will not be able to sleep well or to enjoy the cruise. Marine engineers and Naval Architects have to work hand in hand to analyze the vibration of a ship before applying damping devices such as rubber and bearings to propeller shaft and engine bed foundation. Now the use of marine diesel engines in passenger ships is a common thing. by Charles Roring in Manokwari of West Papua Indonesia