For the similar device used in model aircraft engines, see Glow plug (model engine). Model Engine was an Alternative rock band based in Santa Barbara, California. For the glow plugs used in automotive diesel engines see Glowplug A glow plug (alternatively spelled glowplug or glow-plug) is a device similar
A glowplug (alternately spelled as glow plug or glow-plug) is a heating device used to aid starting diesel engines. A diesel engine is an Internal combustion engine which operates using the Diesel cycle (named after Dr
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Purpose
Diesel engines, unlike petrol engines, do not use spark plugs to induce combustion. A diesel engine is an Internal combustion engine which operates using the Diesel cycle (named after Dr A Petrol engine or Gasoline engine is an Internal combustion engine with spark-ignition designed to run on petrol ( Gasoline) and similar volatile A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of Instead, they rely solely on compression. The piston rises, compressing the air in the cylinder; this, by natural effect, causes the air's temperature to rise. A cylinder is the central working part of a Reciprocating engine, the space in which a Piston travels By the time the cylinder reaches the top of its travel path, the temperature in the cylinder is very high. The fuel mist is then sprayed into the cylinder; it instantly combusts, forcing the piston downwards, thus generating power. The pressure required to heat the air to that temperature, however, necessitates the use of a large and very strong engine block. The problem posed is that in cold weather, if the engine has not been running (as is the case when the car is left to sit overnight), that large engine block becomes very cold; when one then attempts to start the engine, the cold engine block acts as a heat sink, quickly dissipating the heat generated by the pistons compressing air. A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using Thermal contact (either direct or radiant The engine is then unable to start, because it can not generate and maintain enough heat for the fuel to ignite. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of
One common, and very effective, method for fixing this problem is to fit each cylinder with a glowplug. A cylinder is the central working part of a Reciprocating engine, the space in which a Piston travels For that reason, many smaller diesel engines come pre-fitted from the factory with glow-plugs.
Method of operation
In a diesel-engine car, unlike in a gasoline-engine car, the operator does not simply turn the key to the "start" position and have the engine immediately start. Instead, the operator turns the key to the "on" position; the glowplug relay switches the glowplugs on, and a light (see picture at right) on the instrument cluster illuminates. This process is called "pre-heating" or "glowing".
If the car has been running very recently, or if the ambient temperature is hot, the "wait to start" light may not come on; in this case, the operator may proceed to turn the key to the "start" position and start the engine without having to wait.
A glowplug is a pencil-shaped piece of metal with a heating element at the tip; that heating element, when electrified, heats due to electrical resistance and begins to emit light in the visible spectrum, hence the term "glow" plug; the effect is very similar to that of a toaster. A heating element converts Electricity into Heat through the process of Joule heating. Electrical resistance is a ratio of the degree to which an object opposes an Electric current through it measured in Ohms Its reciprocal quantity is A toaster is a small electric Kitchen appliance designed to Toast slices of Bread. The heat generated by the glowplugs is directed into the cylinders, and serves to warm the of the engine block immediately surrounding the cylinders. This aids in reducing the amount of thermal diffusion which will occur when the engine attempts to start. In thermal physics, heat transfer is the passage of Thermal energy from a hot to a colder body
When internal sensors detect that the core of the engine block has reached a certain designated temperature, or when a certain amount of time elapses, the glowplug relay switches off the "wait-to-start" light. The pre-heating process usually lasts for 10 to 20 seconds (less if the engine is warm). The operator then turns the key to the "start" position, and holds it there until the engine starts. The glowplug relay switches off the glowplugs after the engine is running (or, in older cars, at the same time the "wait to start" light goes out). In some newer cars, the glow plugs will continue operating for up to 180 seconds after starting to keep the engine within emissions regulations, as combustion efficiency is greatly reduced when the engine is very cold.
Construction
A glowplug resembles a short metal pencil. A pencil is a Writing or Drawing instrument consisting of a thin stick of Pigment (usually Graphite, but can also be coloured pigment or The heating filament is fitted into its tip. Glowplug filaments must be made of materials, such as platinum or iridium, which are resistant to both oxidation and high levels of heat. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Iridium (ɪˈrɪdiəm is a Chemical element that has the symbol Ir and Atomic number 77 Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state
Problems
In some cars, including all older cars, it is possible to attempt to start the engine (crank it over) while the glowplugs are switched on (relays in many modern cars prevent this). The heat caused by the engine's combustion, when combined with the heat from being electrified, is destructive to the glowplugs; the overheating can easily cause them to burn out. Thus, it is important to wait for the "wait to start" light to go out before cranking the engine.
Glowplugs have a limited lifespan. Certain factors, such as the aforementioned overheating, can greatly shorten that lifespan. The amount of heat which a glowplug produces diminishes over time; this causes the engine to become progressively harder to start in cold weather.
Glowplugs are inexpensive, and typically easy to replace -- making it worthwhile to replace them annually in areas with a cold winter season.
Modern advancements
Indirect-injection engines are less thermally efficient, due to the greater surface area of their cylinders, and so suffer more from cold-starting issues. They require longer pre-heating times than direct-injection engines, which often do not need glow plugs at all in temperate or hot climates even for a cold start. Most modern diesel cars use direct-injection engines (see Volkswagen TDI). Turbocharged Direct Injection (acronym TDI) is the technology used to describe and name modern turbocharged Diesel engines produced by Volkswagen
Modern automotive diesel engines use various electronic methods of altering the timing and style of the injection process to ensure reliable cold-starting. Glow plugs are still fitted, but are rarely used for more than a few seconds.
Large engines
Large diesel engines, such as those used in heavy construction equipment and locomotives, do not need glow plugs. Their cylinders are large enough that the air in the middle of the cylinder is not in contact with the cold walls of the cylinder, and thus retains enough heat to allow ignition.
See also
External links
A block heater is an electric Heater that heats the Engine of a car to ease starting in cold weatherDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic