Continuous diesel engine

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As a continuous diesel engine , (English diesel engine runaway ), a runaway diesel engine understood, the excessive amount of fuel burned in an unintended source, thereby exceeds its design-related speed limit. This can lead to destruction through mechanical failure or bearing damage through insufficient lubrication.

A similar phenomenon can unintentional ignition in Otto engines with a carburetor after switching off Dieseling (English this ling ) be. Then the engine chugs on irregularly because fuel accumulates in heated areas such as B. Oil carbon deposits ignited. Countermeasure is a shut-off valve in the fuel supply, as in some Mercedes-Benz / 8 .

principle

In a classic gasoline engine , a finished mixture of air and fuel enters the combustion chamber through the inlet valve. The amount of this mixture is regulated with a throttle valve , whereby the torque delivered by the engine and thus the engine speed is adjusted (change in quantity ). In contrast to this, in the case of a diesel engine, only air enters the combustion chamber through the inlet valve, which, unlike in a gasoline engine, is not throttled by a throttle valve. The torque is only adjusted by the amount of fuel injected, whereby the fuel is only mixed with the air inside the combustion chamber (change in quality ). The more fuel is injected, the more torque the engine delivers and the higher the speed. An uncontrolled fuel supply thus ensures that the speed increases in an uncontrolled manner and the engine exceeds its design-related upper speed limit.

causes

In many engines, a crankcase ventilation pipe runs into the air inlet to vent the crankcase so that the unburned hydrocarbon vapors are not released into the atmosphere. If the engine is badly worn, the gases can enter the crankcase, creating excessive oil mist which is then drawn from the crankcase through the vent into the air inlet. A diesel engine burns this oil mist because engine oil has similar combustion properties to diesel fuel . The additional fuel causes the engine speed to increase, which means that more oil mist is forced out of the crankcase into the combustion chamber and a feedback is created. The engine quickly reaches a point where it is burning enough of its own crankcase oil that it can keep running even if the normal fuel supply is turned off. It now accelerates independently until it reaches its maximum speed, which it maintains until it is destroyed or the oil mist dries up.

A runaway diesel engine can also be caused by oil leaking due to failure of the oil seals in a turbocharger , and also by overfilling the crankcase with oil. In addition, certain other mechanical problems, such as B. a defective internal fuel line or a worn or incorrectly installed throttle linkage cause this phenomenon. If a diesel engine is operated in an environment in which flammable gases are generated or used for industrial applications, gas escaping through gas leaks can be sucked into the intake pipe of the engine, from where it enters the combustion chamber and burns in an uncontrolled manner. This can lead to dangerous situations, especially in chemical plants, refineries , drilling sites or similar facilities. In many countries, shut-off valves for the air supply are therefore mandatory when using diesel engines in offshore drilling.

The ways to stop a continuous diesel engine are either physically blocking the air intake using a cover or valve, or alternatively chemically by spraying carbon dioxide into the air intake to stifle auto-ignition. Engines equipped with a decompression lever can also be stopped by operating it. In vehicles with a manual gearbox, it is possible to stop the engine by engaging the highest gear with the footbrake and parking brake fully applied. When the clutch is abruptly engaged, the engine speed is slowed down until it comes to a stop without the vehicle moving. In addition to possible engine damage, this can also lead to gearbox and clutch damage.

See also

Web links

Individual evidence

  1. ^ BF Wellington: Diesel Engines and Fuel Systems , Longman Australia 1995, ISBN 0-582-90987-2
  2. ↑ Intake air matters . www.primempg.com. Retrieved June 7, 2015.
  3. ↑ FIE system; diesel fuel system; boat fuel system . Tb-training.co.uk. Retrieved June 22, 2012.
  4. ↑ Donald Launer: Lessons from My Good Old Boat , Sheridan House 2007, ISBN 1-57409-250-2 , pp. 161-162