Diesel engine runaway

Last updated

Diesel engine runaway is an occurrence in diesel engines, in which the engine draws extra fuel from an unintended source and overspeeds at higher and higher RPM, producing up to ten times the engine's rated output until destroyed by mechanical failure or bearing seizure due to a lack of lubrication. [1] Hot-bulb engines and jet engines can also run away via the same process.

Contents

Causes

In a diesel engine, the torque and the rotational speed are controlled by means of quality torque manipulation. This means that, with each intake stroke, the engine draws in air which is not mixed with fuel; the fuel is injected into the cylinder after its contents have been compressed during the compression stroke. The high air temperature near the end of the compression stroke causes spontaneous combustion of the mixture as the fuel is injected. The output torque is controlled by adjusting the mass of injected fuel; the more fuel injected, the higher the torque produced. Adjusting the amount of fuel received per stroke alters the quality of the air-fuel-mixture, and adjusting the amount of the mixture itself is not required, negating the need for a throttle valve. [2] [3]

Diesel engines can combust a large variety of fuels, including many sorts of oil, petrol, [4] and combustible gases. [5] This means that if there is any type of leak or malfunction that increases the amount of oil or fuel unintentionally entering the combustion chamber, the quality of the air-fuel-mixture will increase, causing torque and rotational speed to increase.

Fuel and oil leaks causing engine runaways can have both internal and external causes. Broken seals or a broken turbocharger may cause large amounts of oil mist to enter the inlet manifold, whereas defective injection pumps may cause an unintentionally large amount of fuel to be injected directly into the combustion chamber. If a diesel engine is operated in an environment where combustible gases are used, a gas leak may result in an engine runaway if the gas can enter the engine's inlet manifold. [6]

Stopping a runaway engine

Several ways to stop a runaway diesel engine are to block off the air intake, either physically using a cover or plug, or alternatively by directing a CO
2
fire extinguisher into the air intake to smother the engine. [7] Engines fitted with a decompressor can also be stopped by operating the decompressor, and in a vehicle with a manual transmission it is sometimes possible to stop the engine by engaging a high gear (i.e. 4th, 5th, 6th etc.), with foot brake and parking brake fully applied, and quickly letting out the clutch to slow the engine RPM to a stop, without moving the vehicle. This should be the last option because it can result in catastrophic damage to the whole transmission, mainly the gearbox, but this operation can save the engine.

Notable incidents involving diesel engine runaway

In the Texas City refinery explosion, an instance of diesel engine runaway is thought to have provided the ignition source that triggered the massive explosion. After the refinery's blowdown stack malfunctioned and started releasing a cloud of raffinate vapor into the air, a pickup truck that had been parked near the stack with its engine idling was engulfed by the vapor cloud released and the engine began to race. As staff at the refinery attempted to stop the truck's now-overheating engine, it backfired, igniting the vapor cloud and triggering the disaster. [8]

Related Research Articles

<span class="mw-page-title-main">Compression ratio</span> Ratio of the volume of a combustion chamber from its largest capacity to its smallest capacity

The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.

<span class="mw-page-title-main">Diesel engine</span> Type of internal combustion engine

The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.

<span class="mw-page-title-main">Fuel injection</span> Feature of internal combustion engines

Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines.

<span class="mw-page-title-main">Exhaust gas recirculation</span> NOx reduction technique used in gasoline and diesel engines

In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. The exhaust gas displaces atmospheric air and reduces O2 in the combustion chamber. Reducing the amount of oxygen reduces the amount of fuel that can burn in the cylinder thereby reducing peak in-cylinder temperatures. The actual amount of recirculated exhaust gas varies with the engine operating parameters.

A stratified charge engine describes a certain type of internal combustion engine, usually spark ignition (SI) engine that can be used in trucks, automobiles, portable and stationary equipment. The term "stratified charge" refers to the working fluids and fuel vapors entering the cylinder. Usually the fuel is injected into the cylinder or enters as a fuel rich vapor where a spark or other means are used to initiate ignition where the fuel rich zone interacts with the air to promote complete combustion. A stratified charge can allow for slightly higher compression ratios without "knock," and leaner air/fuel ratio than in conventional internal combustion engines.

<span class="mw-page-title-main">Four-stroke engine</span> Internal combustion engine type

A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:

  1. Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum in the cylinder through its downward motion.
  2. Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
  3. Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
  4. Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust port.

In spark-ignition internal combustion engines, knocking occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but when one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel–air charge is meant to be ignited by the spark plug only, and at a precise point in the piston's stroke. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive.

<span class="mw-page-title-main">Nitrous oxide engine</span> Automotive supplement

A nitrous oxide engine, or nitrous oxide system (NOS) is an internal combustion engine in which oxygen for burning the fuel comes from the decomposition of nitrous oxide, N2O, as well as air. The system increases the engine's power output by allowing fuel to be burned at a higher-than-normal rate, because of the higher partial pressure of oxygen injected with the fuel mixture. Nitrous injection systems may be "dry", where the nitrous oxide is injected separately from fuel, or "wet" in which additional fuel is carried into the engine along with the nitrous. NOS may not be permitted for street or highway use, depending on local regulations. N2O use is permitted in certain classes of auto racing. Reliable operation of an engine with nitrous injection requires careful attention to the strength of engine components and to the accuracy of the mixing systems, otherwise destructive detonations or exceeding engineered component maximums may occur. Nitrous oxide systems were applied as early as World War II for certain aircraft engines.

<span class="mw-page-title-main">Gasoline direct injection</span> Mixture formation system

Gasoline direct injection (GDI), also known as petrol direct injection (PDI), is a mixture formation system for internal combustion engines that run on gasoline (petrol), where fuel is injected into the combustion chamber. This is distinct from manifold injection systems, which inject fuel into the intake manifold.

<span class="mw-page-title-main">Hydrolock</span> Type of hydraulic compression system failure

Hydrolock is an abnormal condition of any device which is designed to compress a gas by mechanically restraining it; most commonly the reciprocating internal combustion engine, the case this article refers to unless otherwise noted. Hydrolock occurs when a volume of liquid greater than the volume of the cylinder at its minimum enters the cylinder. Since liquids are nearly incompressible the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.

<span class="mw-page-title-main">Bourke engine</span> Type of internal combustion engine

The Bourke engine was an attempt by Russell Bourke, in the 1920s, to improve the two-stroke internal combustion engine. Despite finishing his design and building several working engines, the onset of World War II, lack of test results, and the poor health of his wife compounded to prevent his engine from ever coming successfully to market. The main claimed virtues of the design are that it has only two moving parts, is lightweight, has two power pulses per revolution, and does not need oil mixed into the fuel.

<span class="mw-page-title-main">Crankcase ventilation system</span> System to relieve pressure in a combustion engines crankcase

A crankcase ventilation system (CVS) removes unwanted gases from the crankcase of an internal combustion engine. The system usually consists of a tube, a one-way valve and a vacuum source.

<span class="mw-page-title-main">Hot-bulb engine</span> Internal combustion engine

The hot-bulb engine, also known as a semi-diesel or Akroyd engine, is a type of internal combustion engine in which fuel ignites by coming in contact with a red-hot metal surface inside a bulb, followed by the introduction of air (oxygen) compressed into the hot-bulb chamber by the rising piston. There is some ignition when the fuel is introduced, but it quickly uses up the available oxygen in the bulb. Vigorous ignition takes place only when sufficient oxygen is supplied to the hot-bulb chamber on the compression stroke of the engine.

A six-stroke engine is one of several alternative internal combustion engine designs that attempt to improve on traditional two-stroke and four-stroke engines. Claimed advantages may include increased fuel efficiency, reduced mechanical complexity, and/or reduced emissions. These engines can be divided into two groups based on the number of pistons that contribute to the six strokes.

<span class="mw-page-title-main">Scavenging (engine)</span> Process used in internal combustion engines

Scavenging is the process of replacing the exhaust gas in a cylinder of an internal combustion engine with the fresh air/fuel mixture for the next cycle. If scavenging is incomplete, the remaining exhaust gases can cause improper combustion for the next cycle, leading to reduced power output.

<span class="mw-page-title-main">Hornsby–Akroyd oil engine</span> Early internal combustion engine design using heavy oil.

The Hornsby-Akroyd oil engine, named after its inventor Herbert Akroyd Stuart and the manufacturer Richard Hornsby & Sons, was the first successful design of an internal combustion engine using heavy oil as a fuel. It was the first to use a separate vapourising combustion chamber and is the forerunner of all hot-bulb engines, which are considered predecessors of the similar Diesel engine, developed a few years later.

<span class="mw-page-title-main">Carbureted compression ignition model engine</span> Type of carbureted engine

A carbureted compression ignition model engine, popularly known as a model diesel engine, is a simple compression ignition engine made for model propulsion, usually model aircraft but also model boats. These are quite similar to the typical glow-plug engine that runs on a mixture of methanol-based fuels with a hot wire filament to provide ignition. Despite their name, their use of compression ignition, and the use of a kerosene fuel that is similar to diesel, model diesels share very little with full-size diesel engines.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance. This process transforms chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

<span class="mw-page-title-main">M-System</span>

The MAN M-System, also referred to as M-Process and M combustion process, is a direct injection system for Diesel engines. In M-System engines, the fuel is injected onto the walls of the combustion chamber that is solely located inside the piston, and shaped like a sphere. The M-System was rendered obsolete by modern fuel injection systems for Diesel engines. Due to its particularities, the M-System was only used for stationary applications and commercial vehicle engines, passenger car engines with this design have never been made. The letter M is an abbreviation for the German word Mittenkugelverfahren, meaning centre sphere combustion process.

Manifold injection is a mixture formation system for internal combustion engines with external mixture formation. It is commonly used in engines with spark ignition that use petrol as fuel, such as the Otto engine, and the Wankel engine. In a manifold-injected engine, the fuel is injected into the intake manifold, where it begins forming a combustible air-fuel mixture with the air. As soon as the intake valve opens, the piston starts sucking in the still forming mixture. Usually, this mixture is relatively homogeneous, and, at least in production engines for passenger cars, approximately stoichiometric; this means that there is an even distribution of fuel and air across the combustion chamber, and enough, but not more air present than what is required for the fuel's complete combustion. The injection timing and measuring of the fuel amount can be controlled either mechanically, or electronically. Since the 1970s and 1980s, manifold injection has been replacing carburettors in passenger cars. However, since the late 1990s, car manufacturers have started using petrol direct injection, which caused a decline in manifold injection installation in newly produced cars.

References

  1. Wellington, B.F.; Alan F. Asmus (1995). Diesel Engines and Fuel Systems . Longman Australia. ISBN   0-582-90987-2.
  2. Stefan Pischinger, Ulrich Seiffert (ed.): Vieweg Handbuch Kraftfahrzeugtechnik. 8th edition, Springer, Wiesbaden 2016. ISBN   978-3-658-09528-4. p. 348.
  3. Morton Lippmann (ed.): Environmental Toxicants – Human Exposures and Their Health Effects, 3rd edition, Wiley, Hoboken 2009, ISBN   9780470442890. p. 553: ″Because the air entering diesel engines is not throttled, the engines can operate at air–fuel ratios other than that required for stoichiometric combustion. Fuel is injected under pressure into the combustion chamber in variable amounts to achieve different engine speeds and power outputs.″
  4. Hans Christian Graf von Seherr-Thoß (auth): Die Technik des MAN Nutzfahrzeugbaus, in MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus, Springer, Berlin/Heidelberg, 1991. ISBN   978-3-642-93490-2. p. 436
  5. Richard van Basshuysen (ed.): Erdgas und erneuerbares Methan für den Fahrzeugantrieb in H. List: Der Fahrzeugantrieb, Springer, Wiesbaden 2015, ISBN   978-3-658-07158-5, p. 418
  6. Donald Launer: Lessons from My Good Old Boat, Sheridan House, Inc., 2007, ISBN   9781574092509, p. 161
  7. Launer, Donald; William G. Seifert; Daniel Spurr (2007). Lessons from My Good Old Boat. Sheridan House, Inc. pp. 161–162. ISBN   978-1-57409-250-9.
  8. U.S. Chemical Safety and Hazard Investigation Board. Investigation Report - Refinery Fire and Explosion and Fire. BP Texas City March 23, 2005, para 2.5.13 Ignition Source, p66

Bibliography

See also