Runaway diesel engine is a rare condition affecting diesel engines, where the engine pulls extra fuel from unwanted sources and excess speed at higher and higher RPMs and generates up to 10 times the output value of the engine up to destroyed by mechanical failure or foreclosure due to lack of lubrication.
Video Diesel engine runaway
Cause
The gasoline engine is fed by a carburetor with a butterfly valve or an air receiver with a throttle valve and fuel injector. In both cases, the operated valve (in case of car, gas pedal), controls the volume of air-fuel mixture captured into the engine and controls the engine speed. Finally, the combustion cycle requires a system of ignition in the form of electric sparks, which are connected to a switch (in the case of a car, ignition key). Thus in rare cases of throttle relationship splits, it is very easy to carry a gasoline engine that runs to a halt by turning off the ignition.
The speed of a diesel engine is controlled by varying the amount of fuel supplied to the cylinder in the injector unit and since there is no air restriction (and also accelerated by a turbocharger-driven exhaust or compressor mechanism) the unlimited supply of air permits. There are two different mechanisms that cause escape.
Excess fuel supply
As stated above, the cylinder in a diesel engine is fed by the injector unit, which in turn is fed by a crankshaft injection pump or charger driven. The maximum RPM pump (and thus the fuel pressure supplied to the injector) is governed by the centrifugal governor. The operator manages the cleaning of the injector nozzle and the governor thereby adjusting the fuel pressure to keep the RPM stable. Failure of any part of the mechanism, especially the governor may cause an uncontrolled amount of fuel to enter the nozzle creating a positive feedback loop.
Oil supply to intake
In many vehicles, the respiratory pipe of the crankcase enters the air intake to vent the crankcase without releasing the crude hydrocarbon vapor into the atmosphere. In very worn-out engines, hot gases, including unburned fuel, can travel past the piston ring and into the crankcase. This creates an excess oil mist, which is then taken from the crankcase to the air intake through the breath. Diesel engines will easily burn this oil mist as fuel, because engine oil has the same energy and combustion properties as diesel fuel. The extra fuel causes increased engine speed, causing more oil mist to be forced out of the crankcase and into the engine, and a positive feedback loop is created. The machine quickly reaches the point where it generates so much fuel from its own crankcase oil that it can sustain operations even with normal dead fuel supply, and it will run faster and faster until destroyed.
Runaway conditions can also be generated from oils supplied by oil seal failure in turbocharged diesel engines, from crankcase overload with oil, or certain other mechanical problems such as faulty internal fuel pipelines or worn or poorly installed throttle connections. On vehicles or installations using diesel and bottled gas (eg propane, natural gas, acetylene) or operating in areas where steam can accumulate, gas leaks that are recalled to the engine air intake may supply unwanted fuel.
Diesel engines used in industrial environments are subject to external hydrocarbons introduced into the atmosphere and then sucked into the air intake system. This dangerous situation occurs in chemical plants, refineries, drilling sites or environments where hydrocarbons are being produced. The BP Texas City facility was destroyed when this occurred in 2005. The federal law mandates the use of air-shutting valves or ESD valves on diesel engines used on offshore drilling rigs.
Maps Diesel engine runaway
Stopping the escape engine
Some ways to stop the runaway diesel engine is to block air intake, either physically using a cover or plug, or alternatively by directing CO
2 fire extinguisher into the air intake to choke the machine. Machines equipped with decompressors can also be stopped by operating decompressors, and in vehicles with manual transmissions it is sometimes possible to stop the machine using high gear (ie 4th, 5th, 6th, etc.), with the foot brake and the parking brake is fully applied, and releases the clutch quickly to slow the machine's RPM to a halt, without moving the vehicle.
The famous incident involved a runaway diesel engine
- In the explosion of the Texas City Refinery, an example of a run of a diesel engine is thought to have provided an ignition source that triggered a massive explosion. After the blowdown stack of refineries fails and starts releasing the raffinate into the air, a pickup truck that has been parked near the blowdown pile with its idling engine is engulfed by a steam cloud that is released and the engine starts to race. When the staff at the refinery tried to stop the now overheated truck engine, it backfired, triggering a cloud of steam and triggering a disaster.
References
Bibliography
-
Offshore Sailing: 200 Important Tips for Upcoming Cities . McGraw-Hill Professional. ISBN: 0-07-137424-8.
See also
- Rev limiter
External links
- Locomotive General Electric ES44AC is in the process of escape
- South Norfolk diesel locomotive on the run
Source of the article : Wikipedia
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