A term used to describe a diesel engine in which air flows into the engine by means of only.

Related Terms


The blades of a turbine in the outlet exhaust flow of an engine are driven by the gases flowing over them. Compressor blades at the other end of the same axle are spun in the inlet flow, drawing large volumes of air into the cylinders. This enables faster combustion than naturally aspirated engines and increases power of the engine.


A system having a helical groove in the plunger which covers or uncovers openings in the barrel of the pump; most usually applied in diesel engine fuel-injection systems.


  1. A steel chamber fitted with auxiliary equipment to raise its air pressure to a value two to six times atmospheric pressure; used to relieve a diver who has decompressed too quickly in ascending. 2. Such a chamber in which conditions of high atmospheric pressure can be simulated for experimental purposes.


Low-pressure air compressor that takes suction from a region below atmospheric pressure (turbine condenser) and discharge into the atmosphere.


An engine test made in a singlecylinder Caterpillar diesel engine to determine the oiliness of an engine oil. Also known as scoring test.


Gasoline and diesel engine oil quality levels established jointly by API, SAE, and ASTM, and sometimes called SAE or API/SAE categories; formerly called API Engine Service Classifications.


  1. Explosions of mixtures of air and lubricating oil in the compression chambers or in other parts of the air system of a compressor. 2. Continuation of running by a gasoline spark-ignition engine after the ignition is turned off. Also known as run-on.


Ignition of a charge of fuel vapor and air in an internal combustion engine by passing a high-voltage electric electron flow.


The diesel engine is a type of internal combustion engine which ignites the fuel by injecting it into hot, high-pressure air in a combustion chamber.
The marine diesel engine is a type of diesel engine used on ship. The principle of its operation is as follow: A charge of fresh air is drawn or pumped into the engine cylinder and then compressed by the moving piston to very high pressure.
When the air is compressed, its temperature rises so that it ignites the fine spray of fuel injected into the cylinder. The burning of the fuel adds more beat to the air charge, causing it to expand and force the engine piston to do work on the crankshaft which in turn drive the ship’s propeller.
The operation between two injections is called a cycle, which consists of a fixed sequence of events. This cycle may be achieved either in four strokes or two. In a four-stroke diesel engine, the cycle requires four separate strokes of the piston, i.e. suction, compression, expansion and exhaust. If we combine the suction and exhaust operations with the compression and expansion stroke, the four-stroke engine will be turned into a two-stroke one.
The two-stroke cycle begins with the piston coming up from the bottom of its stroke, i.e. bottom dead center (BDT), with the air inlet ports or scavenge ports in the sides of the cylinder being opened. The exhaust ports are uncovered also. Pressurized fresh air charges into the cylinder, blowing out any residual exhaust gases from the last stroke through the exhaust ports. As the piston moves about one-fifth of the way up, it closes the inlet ports and the exhaust ports. The air is then compressed as the piston moves up.
When the piston reaches the top of its stroke, i.e. the top dead center (TDC), both the pressure and the temperature of the air rise to very high values. The fuel injector injects a fine spray of fuel oil into the hot air and combustion takes place, producing much higher pressure in the gases.
The piston is forced downward as the high-pressure gases expand until it uncovers the exhaust ports. The burnt gases begin to exhaust and the piston continues down until it opens the inlet ports. Then another cycle begins.
In the two-stroke engine, each revolution of the crankshaft makes one power or working stroke, while in the four-stroke cycle engine, it takes two revolutions to make one power stroke, that is why a two-stroke cycle engine will theoretically develop twice the power of a four-stroke engine of the same size. Inefficient scavenging and other losses, however, reduce the power advantage to about 1.8.
Each type of engine has its application on board ship. The low speed (i.e. 90 to 120 r/min) main propulsion diesel operates on the two-stroke cycle. At this low speed the engine requires no reducing gearbox between it and propeller. The four-stroke engine (usually rotating at medium speed, between 250 to 750 r/min) is used for alternators and sometimes for main propulsion with a gearbox to provide a propeller speed of between 90 to 120 r/min.


In an auxiliary diesel engine bypass type lubricating oil system, the main lube oil pump forces some of the oil used by the engine through a filter.

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