Gas ignition and ignition of boiler burner
Gas ignition and ignition
The combustion reaction must have certain energy conditions, that is, there must be an endothermic preparation process of energy accumulation. When the heat released by the oxidation reaction is greater than the heat absorbed, it can be called combustion
In addition to spontaneous combustion under certain conditions, the method of forced ignition is more widely used in practical engineering to ignite combustible gas mixtures. Common ignition sources include electric sparks, small flames, and electric heating coils, etc.
If the ignition is to be successful, first the local combustible gas should be ignited and burned to form the initial flame center, and then the initial flame center should be able to spread to other unburned areas.
The following takes electric spark ignition as an example to illustrate the necessary conditions for successful ignition.
Put the two electrodes in the combustible mixture, energize the spark to release a certain amount of energy, and ignite the combustible mixture, which is called spark ignition
The electric spark can make the temperature of the local gas rise sharply, so the spark area can be regarded as a hot gaseous object and become a heat source for ignition
When the concentration, temperature and pressure of the combustible mixture in the discharge electrode gap are constant, if the initial flame center is to be formed, the discharge energy must reach a minimum value. This necessary minimum discharge energy is called the minimum ignition energy Emin.
After the initial flame center is formed, the flame will spread in all directions. If the distance between the electrodes is too small, it will increase the heat dissipation from the center of the initial flame to the electrodes so that the flame cannot spread to the surrounding mixture. Therefore, the distance between electrodes should not be too small
When the distance between the electrodes is so small that the combustible mixture cannot be ignited no matter how much spark energy is, this minimum distance is called the flameout distance dq