A glowplug (alternatively spelled as glow plug or glow-plug ) is a heater used to help power diesel engines. In cold weather, high speed diesels can be difficult to start because the mass of the cylinder block and the cylinder head absorbs the compression heat, preventing ignition (which depends on the heat). The pre-chamber machine uses a small electric heater (glowplugs) inside the pre-chamber. Direct-injected engines have glowplugs in the combustion chamber. Glowplug is a pencil-shaped piece of metal with a heating element at the end. This heating element, when electrified, heats up due to electrical resistance and begins to emit light in the visible spectrum, hence the term glowplug. The visual effect is similar to the heating element in the toaster. The fuel injector spray pattern then pierces directly at the hot end of the light plug during the fuel injection at the top of the die. It ignites the fuel even when the engine is not hot enough for normal operation, which reduces the cranking time to start the engine.
Video Glowplug
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Diesel engines, unlike gasoline engines, do not use spark plugs to induce burning. Instead, they only rely on compression to raise the air temperature to the point where the diesel burns spontaneously when introduced into high-pressure hot air. High pressure and diesel spray patterns ensure complete and controlled combustion. Piston rises, compresses the air in a cylinder; this causes the air temperature to rise. By the time the piston reaches the top of its path, the temperature in the cylinder is very high. Fog fuel is then sprayed onto the cylinder; it instantly burns, forcing the piston down, resulting in power. The pressure required to heat the air to that temperature, however, requires a large and powerful engine block.
The temperature at the top of the compression stroke depends on many factors, especially the compression ratio of the cylinder and the initial temperature of the induced air. When the engine is cold, the air temperature is induced low and receives less heat from the engine cylinder wall. In addition, because the air is compressed and becomes hot, some of this heat is lost to the cold cylindrical wall, further reducing the temperature at the top of the compression. The light plug broke this.
There are two different types of light plugs: various in-cylinders and various manifolds ("Thermostart"). In the case of an in-cylinder, there is a plug in each cylinder that is injected directly (or in the case of indirect injection, the luminous plug is in the prechamber that provides a hot spot to induce ignition.In case of in-manifold, there is only one for all cylinders.
Maps Glowplug
Operation method
Pre-heating
In older generation diesel-powered vehicles, unlike in gasoline-powered vehicles, for 'cold start' the operator not only turns the key to the "start" position and immediately starts the engine. Instead, the operator activates the light plug (s) for the first time. Early diesels use glowplug type 'Thermostart' on inlet manifold. It takes 20 seconds to reach the working temperature and the vehicle operator must manually set the time (or guess) when 20 seconds have elapsed. With glow in-cylinder plugs, technological improvements include a warning light on the dashboard to show how long the initial warm-up should last. The initial heating phase is also created to be activated automatically when the operator turns the key to the "on" position for a long duration; the glowplug relay turns on the glowplug, and the light (see picture on right) on the instrument cluster is on. This process is called "pre-heating" or "shining". Many modern diesel engines automatically activate the incandescent plugs when the operator unlocks the vehicle or opens the door to the car, thus simplifying the process and shortening the operator's waiting time before the engine starts working. According to Bosch: "Older machines with Thermostart type plugs use light periods of up to 20 seconds while more modern machines use about 6 to 8 seconds of hot periods and provide after light at reduced voltage."
Start
Before any attempt is made to start the vehicle engine, the vehicle parking brake should be applied properly and the selection of the tooth should be in Neutral (or Park). Any engine stop control must be returned to the run position and in cold weather, any initial 'excess fuel' aid should be set or used - such as Ki-Gass.
With the glow in-cylinder plug, when the specified time has elapsed, the glowplug relay will turn off the "wait-to-start" lamp. The pre-heating cycle usually lasts for 2 to 5 seconds. The operator then starts turning the key to the "start" position. The relay turns off the incandescent plug after the engine is on (or, in an older car, at the same time the "wait" to go off "lights). In some cars, in order to maintain compliance with emissions regulations, plugs can be operated immediately after the engine is turned on, or during extended idle periods where the engine temperature has decreased, since the combustion efficiency is greatly reduced when the engine is below operating temperature.
With the Thermostart plug in the inlet manifold, within seconds the diesel vapor begins to fill the inlet manifold. As the plug continues to heat up, it opens a valve that allows diesel from a special reservoir mounted directly above the Thermostart into the Thermostart plug. This fresh diesel also evaporates and adds it up in the inlet cuff. At 20 seconds, available air is available, the diesel near the plug blends and when the engine is turned on, the lit diesel is pulled into the combustion chamber - which more diesel is added after the compression stroke. This additional diesel is immediately lit, starting the engine with ease. Vehicles equipped with Thermostart light plugs are usually not activated via normal ignition buttons. A button somewhere else is provided (along with, in some cases, a button to activate the starting motor). When the Thermostart is switched on by the same switch as the ignition key, it is usually activated by turning a clockwise 'notch' switch counterclockwise. After a period of 20 seconds elapses, cranking is achieved by turning the ignition key counter-clockwise. Once the engine is on and running, the ignition switch is released, allowing it to return to the off position. The operator then has to rotate the ignition key to the illuminated position - usually one level clockwise
Start warm machine
If the car has just been running, or if the ambient temperature is hot, the "waiting to start" light may not turn on. In this case, the operator can proceed to turn the key to the "start" position and start the engine without having to wait.
With Thermostart, it is entirely up to the operator to choose whether to activate the light plug. In the case of a Thermostart controlled contact lock, turn the key two notches to the right hot initiate cranking.
Construction
A glowplug resembles a short metal pencil. The heating filament is fitted to the end. Glowplug filaments must be made of certain materials, such as platinum and iridium, which resist oxidation and high temperatures.
Model engine
Glow plugs in model engines are different from those in full size diesel engines. The full-size machine only uses the incandescent plug to start. Engine models use light plugs as an integral part of the ignition system because of the catalytic effect of platinum wires, on which their methanol-base fuel is designed to run.
The model glow plug machine is also used as reusable igniters in theatrical fireworks and special effects industries to spray long-range pyrotechnic devices using flash and smoke composition powder.
See also
- Block heater
References
Source of the article : Wikipedia
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