Flame rectification is a phenomenon in which a
flame
A flame (from Latin '' flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density the ...
can act as an electrical
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an inve ...
. The effect is commonly described as being caused by the greater mobility of
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary partic ...
s relative to that of positive
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
s within the flame,
and the asymmetric nature of the
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials ...
s used to detect the phenomenon.
This effect is used by rectification flame sensors to detect the presence of flame.
[ The rectifying effect of the flame on an AC voltage allows the presence of flame to be distinguished from a resistive leakage path.
One experimental study suggested that the effect is caused by the ionization process occurring mostly at the base of the flame, making it more difficult for the electrode further from the base of the flame to attract positive ions from the burner,]
See also
* Flame detection
A flame detector is a sensor designed to detect and respond to the presence of a flame or fire, allowing flame detection. Responses to a detected flame depend on the installation, but can include sounding an alarm, deactivating a fuel line (such a ...
* Flame supervision device For gas appliances, a flame supervision device (FSD) – alternative name: flame failure device (FFD) – is a general term for any device designed to stop flammable gas going to the burner of a gas appliance if the flame is extinguished. This is ...
References
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External links
A video of a flame being used as a rectifier in a simple AM radio
Plasma physics