Marine Main Engine

Marine Main Engine<b>Marine Main Engine</b> The main component of the entire propulsion system of a ship is the power generation unit (main engine). As a rule, these are diesel or electric motors, gas or steam turbines, gas motors or dual-fuel engines, motors that can be supplied with both conventional diesel fuels and liquefied natural gas (LNG) for operation. If the power is often transmitted directly from the main engine to the shaft to the propeller, combined systems are often used, especially in cruise and naval shipbuilding. The combined systems include: <b>CODAD</b> propulsion (Combined Diesel and Diesel): This propulsion concept is used when a lot of power is required but no gas turbines are used. Two - also different - diesel engines are switched to the drive shaft via a clutch and a gearbox. The advantage of this type of propulsion is the low fuel consumption, the disadvantage is the complicated gearbox. <b>CODOG</b> propulsion (Combined Diesel or Gas): A concept in which a diesel engine for cruising or a gas turbine for maximum speed can be switched to the drive shaft. The advantage of the CODOG propulsion is the relatively simple design of the main drive. Disadvantages are both the additional weight of the drive component that is not in operation and the reduction gear required for the gas turbine. The German Navy's class F122 frigates, for example, have such a propulsion system. Two General ELectric LM2500 gas turbines with 15 MW each, two drive diesel engines with 3820 kW each on two shafts with controllable pitch propellers are installed on them. <b>CODAG</b> propulsion (Combined Diesel and GAS): Propulsion concept in which two diesel engines and a gas turbine are switched together on the drive shaft with controllable pitch propellers. The interconnection takes place via multi-stage gears and a so-called cross-connect gear via coupling systems. A reduction gear is required to switch on the gas turbine. The first ships to be built with this system were F120 class frigates of the German Navy. The advantage of this drive concept lies in the lower fuel consumption due to the drive diesel in connection with short-term switchable gas turbines for maximum speed. The complicated design of the collective drive is disadvantageous, since very different services have to be processed at the same time. <b>CODLAG</b> propulsion (Combined Diesel-Electric and Gas): This is a further development of the CODAG system. Diesel generators provide electricity for the electric drive motors. A gas turbine is switched on via gears and clutches to achieve maximum speed. The advantage of this system is that only one type of diesel generator is required for the entire power supply of the ship, which minimizes maintenance and repair work. Furthermore, this drive concept has the further advantage that the diesel generator sets (electric diesel engines) are not directly connected to the drive shaft and can therefore be installed in the most suitable places inside the ship. <b>COGLA</b> propulsion (Combined Gas Turbine and Gas Turbine): This system is installed, for example, in the new Japanese destroyer class 25DD. Gas turbines are used. When the energy requirement is low (slow travel), electricity is generated that drives the drive shaft via the e-drive motors. At “full speed”, the gas turbine is switched directly to the drive shafts via a gearbox and clutch system. This type of drive is supposed to save fuel at low speeds and reduce the signature (heat radiation and noise signature) <b>COGOG</b> propulsion (Combined Gas or Gas): Propulsion system in which two different gas turbines can be switched to the drive shaft by means of reduction gearboxes. A less powerful turbine is used for cruising (cruise gas turbine), a more powerful turbine is used for high speeds (high-speed gas turbine). The advantage is the reduced fuel consumption, since a small turbine, which is designed for cruising, uses less fuel at 100% power than a twice as powerful one (for high-speed), which is then only driven at 50% power during cruising . The expensive gearbox is a disadvantage. <b>COGAG</b> propulsion (Combined Gas Turbine and Gas Turbine): With this type of propulsion, two turbines with the same power are switched off the drive shaft in contrast to the COGOG system. This propulsion provides high performance. Up to 80 MW of power can be generated. However, due to the transmission, the system is very complex and consumes a lot of fuel. <b>IEP</b> drive (Integrated Electric Propulsion): In contrast to the CODLAG system, a system of diesel engines and / or gas turbines that only generate electricity for the traction motors and has no mechanical connection to the propeller shafts is called an integrated electric drive. The “AIDAALuna”, for example, is equipped with this type of drive. The Hapag-Lloyd ship “Orizaba” was the first cargo ship with a turbo-electric propulsion. <b>Diesel Engine</b> Even today, mostly inexpensive, unpurified diesel oil or heavy oil is used as fuel in large diesel engines. Due to resolutions of the IMO to reduce emissions from combustion engines, however, low-sulfur diesel fuels (“marine diesel”) are increasingly being used in order to make it possible to drive into the so-called Emission Control Areas (ECAs), in which only 1% sulfur is allowed in the fuel is; in EU ports even stricter requirements apply: 0.1% sulfur content in fuel. In particular, the larger marine diesel engines with an efficiency of up to 50% are designed for operation at low speeds. Four-stroke engines are used for small and medium outputs (up to 24 MW at 400 rpm to a maximum of 2000 rpm, so-called medium-speed motors) and for large and larger outputs, two-stroke engines (up to 100 MW per motor, rotation 60-250 rpm, so-called slow-speed motors ) used. High-speed runners with speeds of > 2000 rpm are particularly common in the sport and recreational boating sector, but are also used in the Fast Rescue Boats on board professional and naval vessels, although jet propulsion is already used and more and more prevalent for these boats . The term “diesel” is derived from the work process that takes place in the machine - not from the fuel. The engine developed by Rudolf Diesel (1893 - 1898) is the unequaled heat engine in terms of efficiency. The engine owes this to the high compression achieved during compression in the working area, which is made possible by the fact that, in contrast to the Otto engine, it compresses pure air and no air-fuel mixture; In the diesel process, the combustible mixture is only created at the end of compression by injecting the fuel into the cylinder. The injected fuel normally burns independently under the effect of the high compression temperature without a special ignition device. In this respect, the diesel engine is also referred to as a compression ignition engine. In contrast to this, in Otto engines, the fuel-air mixture is ignited by an externally controlled ignition device. Electrically operating spark plugs are generally used here, which ignite the intake mixture at the set point in time.