Ship engines: types, characteristics, maintenance
The first ship engines began to appear only at the beginning of the 20th century. One of the first to be installed on Zeeland, a Danish vessel built in 1912. The unit consisted of two diesel plants, the total power of which was 147.2 kW. Today, ships are also equipped with internal combustion engines. All of them must be equipped in accordance with the requirements of the River Register or the Register of Russia to drive the ship propulsion or auxiliary units. Consider the main types of engines, their characteristics and maintenance.
Classification of internal combustion engines for ships
As intended, ship engines can be divided into main units and auxiliary units. The first is the main driving force. Auxiliary units are designed to ensure the operation of a variety of mechanisms. So, motors are used as a drive for electric generators, additional equipment.In addition to the appointment, internal combustion engines are divided into types and power.
Another ship units can be divided by the way the fuel burns in them. Marine diesel engines can be both two-and four-stroke. The first can be identified models where the combustion is mixed - they provide a constant level of pressure. We can distinguish models where the fuel mixture burns under constant volume conditions. There are ICE, equipped with supercharged and without it.
Types of marine engines power
According to the materials of the Central Research Institute, the motors in power characteristics can be divided into four main groups. So, low-power units are considered below 74 kW. Machines with average power characteristics - from 74 to 736 kW. Powerful ICE machines are read, issuing from 736 to 7360 kW. Heavy-duty engine is capable of producing 7360 kW and more. Basically, ship engines, mass-produced, develop about 1600 kW of energy. This option is most common.
Motors for burning fuel mixture
Four-stroke engines, like their two-stroke counterparts, operate on the basis of a cycle, where the combustion of the air-fuel mixture is mixed.How does this happen? One part burns at a constant volume. The second portion burns under the influence of constant pressure. There are exceptions. The process can be in conditions of constant volume (for example, the mixture burns entirely when the pistons are at TDC).
Engine and air intake
Depending on how the combustion chambers are filled with air, ship engines can be equipped with a pressure boosting system and without it. So, ICE is equipped with supercharged or works without it.
Charging allows you to create pressure, due to which more air will fit into the chambers. This also leads to an increase in the amount of fuel that burns in one cycle. Thus, power, torque and other characteristics increase.
Compressors are used as pressurization in four-stroke diesel ship units. They serve air under pressure. The compressor in such motors is connected to the crankshaft and is driven from it. This is a mechanical system. Air enters the valves through the charge manifold.
Due to the fact that the compressor is driven by the crankshaft, the engine loses useful power.This reduces the cost. This is especially noticeable when the system is under high pressure. Mechanical boost for this reason is rarely used. There is only one type of engine with supercharged mechanical type. This is the M400, which is installed on the river transport.
Some models of ship assemblies can be equipped with an external boost system. Here, the air is pre-compressed by a compressor that is driven from an independent source. The most commonly used marine diesel engines with a gas turbine charge system. Thus, the exhaust gases flow into the collector, and then into the gas turbine. They ensure the rotation of the rotor, on the shaft of which the drive wheel of the compressor is mounted. Air that is drawn from the atmosphere is supplied to the collector. Then he enters the cylinders.
In the two-stroke internal combustion engine, where the air supply system is contoured and straight-through, a combination of pressurization is used. Depending on how the compressor drives are connected, there can be three boost schemes. So, distinguish:
- Serial-parallel connection of compressor systems.
Types by type of fuel
Like automobile engines, units for ships can also work on "light" fuel and on "dark." ICEs capable of operating on fuel of various fractions without significant changes in their design are multi-fuel. Distinguish and dual-fuel systems that run on liquid types of fuel, as well as gas. During operation, you can transfer the car from one type of fuel mixture to another.
According to the ignition method
In engines, where the mixture is formed inside the unit, the ignition process occurs due to high temperatures in the combustion chamber due to compression. In low compression models, the auto ignition process is not possible. It uses a forced ignition, similar to the car. These can be candles.
Modern industry also produces convertible types of ship engines. With minimal design changes, they are converted into diesel engines or engines with forced spark ignition.
By type of mixture formation
In gas internal combustion engines, as well as in those intended for operation on liquid light fuel, external mixture formation systems are used. So, in the combustion chamber comes ready-to-use mixture.It is prepared in the carburetors.
In models where the mixture is formed inside, air and fuel are fed into the combustion chamber separately. Fuel is prepared directly inside the engine cylinder. The process of organizing high-quality mixing of liquid fuel and air with an internal type of mixture formation is quite complicated. And the production of marine engines with the external formation of a mixture for fuel is impossible. In the case of light, light fuel, it evaporates, while the dark remains as a liquid.
Diesel units, where the mixture is formed inside, the spray may be volumetric. In this case, a large portion of the injected mixture is directed to the cylinder walls, forming a film. Only a small part is mixed with air. Also there are volume-film models. Here, one part of the fuel batch is in the volume of the cylinder, while the second is directed to the cylinder walls to create a film.
By the combustion chambers
A sample of the unit where the combustion chamber is located in the piston is a diesel 6XCG 18/22. Here, to create a mixture and burning made one camera. It is located in the head on the piston. The camera connects the piston space, providing air movement. In this design, vortex formation is provided by radially directed air currents.
If the cylinder is located in the head on the piston, in the cylinder head or between the bottom of the pistons, then such a unit is called an internal combustion engine with an open combustion chamber and direct injection system.
Some engines use a precameral mixture formation method. Here the principle of pressure differential due to partial combustion of the fuel mixture is laid. In air-chamber machines, an air jet is used, which is created in an additional air chamber during the compression stroke.
According to GOST 10448-80, the motors can be divided into five main groups. The first consists of units where the operating mode is not controlled in any way, and the shaft rotates at a frequency of more than 1,800 revolutions per minute. The second group - aspirated engines with a crankshaft rotational speed of one and a half thousand and more. The third group includes supercharged models, where the shaft rotates with a frequency of two or more. The fourth group - crankshaft rotational speed from 250 rpm to 1500 rpm. The fifth group consists of engines where the crankshaft rotates at a speed of less than 250 rpm.
Characteristics of four-stroke internal combustion engines
The power of ship engines of the four-stroke type averages 40 kW. They are equipped with pallets with deadwood, and the drive shafts are located above the central chamber.Water pump is missing. Some models are equipped with locking reversing. Sometimes on certain modifications there are gears for reversing.
These units are most often used with transition connectors.
Motors are equipped with a manual starter. The propeller shaft is mounted above the pallet. There are modifications equipped with superchargers. There are no reverse locks on most models.
Models of average power
Four-stroke and two-stroke engines of average power are more often found on vessels intended for passenger traffic. Models differ in volume and number of cylinders. Carburetors on such engines can be found in the rear of the engine block. Most versions have locks for reversing. The shaft may be located above the pallet. Models are equipped with a manual starter.
Heavy Duty Units
These internal combustion engines are manufactured on the basis of the camshaft. The characteristics of a ship engine of this kind are very high. Therefore, in versions there is a silencer. Carburetor systems are located near the pallet. The rotational speed of the crankshaft in such an internal combustion engine is not higher than 2.3 thousand revolutions per minute.
These solutions are more suitable for installation on tankers.
Starter - manual. Tillers are located above the clamp and mounted on the camshaft. In terms of motors are different. It is worth saying that the engine can be equipped with clamps of various types. Oil is supplied using a pump.
Naturally aspirated machines
These units are suitable for transport ships. Many models are equipped with a manual starter. Valves hold pressure up to 5.5 atm. The pallet is made of steel alloys. Some modifications have retainers for reversing and other systems. The ship's engine has a shaft located behind the pinion gear. Characteristics depend on power. Units of this kind are equipped with cooling systems.
Ship Motors and their maintenance
Unlike cars, where they serve the engine through a certain mileage, ship power units serve by engine hours. There are several types of maintenance. The first maintenance should be performed after 60-250 working hours. During maintenance, the filters are cleaned and rinsed, oil performance is checked, sediment is removed from the fuel and oil tanks, and the fittings are inspected.
The second maintenance, which is performed through 250-750 engine hours, checks the valve clearances, the reliability of the mounting of the base frames, the main and connecting rod bearings, and the cylinder heads. The quality of fuel atomization, the condition of pumps, compressors and other attachments is diagnosed.
All subsequent operations include checking the condition of the shafts, coolers, electrical equipment, piston rings, and other important systems. In each case, the frequency, as well as the procedure for servicing the ship’s engine, is established by the ship management services or shipping companies.