What Are The Common Types Of Spark Plugs?

According to the calorific value, there are cold type and hot type; according to the electrode material, there are nickel alloy, silver alloy, platinum alloy, etc.; if it is more professional, the types of spark plugs are generally as follows:
1. Quasi-type spark plug: The insulator skirt is slightly retracted into the end face of the shell, and the side electrode is outside the end face of the shell. It is the most widely used type [5].
2. Spark plug with protruding rim: the insulator skirt is longer and protrudes beyond the end face of the casing. It has the advantages of large heat absorption and good anti-fouling ability, and can be directly cooled by the inlet air to reduce the temperature, so it is not easy to cause hot fire, so it has a wide thermal adaptability range [5].
3. Electrode type spark plug: Its electrode is very thin, characterized by strong sparks and good ignition ability. It can ensure the engine starts quickly and reliably even in severe cold seasons. It has a wide thermal range and can meet a variety of purposes [5].
4. Seat-type spark plug: Its shell and screw thread are made into a tapered shape, so it can maintain a good seal without a gasket, thus reducing the size of the spark plug, which is more beneficial to the engine design [5].
5. Polar type spark plug: Generally there are two or more side electrodes. The advantage is reliable ignition and the gap does not need to be adjusted frequently. Therefore, it is often used in some gasoline engines where the electrode is easy to ablate and the spark plug gap cannot be adjusted frequently [5].
6. Surface spark plug: that is, surface gap type. It is the coldest type of spark plug. The gap between the center electrode and the shell end face is concentric [5].
7. Standard and protruding spark plugs
The standard spark plug is a single-sided electrode spark plug with the skirt end of the insulator slightly lower than the threaded end face of the housing. It adopts the traditional firing end structure most widely used in side-valve engines. To distinguish it from the "protruding type" that appeared later, this structure is called the "standard type" [6].
Protruding spark plugs were originally designed for overhead valve engines. Its insulator skirt protrudes from the threaded end face of the housing and extends into the combustion chamber. It absorbs more heat in the burning mixture, and has a higher operating temperature at rest speed to avoid fouling; at high speed, due to the top position of the valve, the inhaled airflow is directed at the skirt of the insulator, cooling it, so that the maximum temperature does not increase. More, so the thermal range is larger. Protruding spark plugs are not suitable for side-valve engines due to the many turns in the intake duct and the airflow has little effect on cooling the insulator skirt [6].
8. Single-side pole and multi-side pole spark plugs
The traditional single-side electrode spark plug has an obvious flaw, that is, the side electrode covers the center electrode. When a high-voltage discharge occurs between the two poles, the mixture at the spark gap will absorb the heat of the spark and be activated by ionization to form a "fire core". The place where the fire core is formed is generally close to the side electrode, and the heat will be absorbed more by the side electrode, that is, the "flame suppression effect" of the electrode, which reduces the spark energy and the flashover performance [6].
Therefore, in the 1920s, three-side pole spark plugs appeared. Compared with the single-side pole, the spark gap of the multi-side pole is composed of the cross-sections of multiple side electrodes (punched into circular holes) and the cylindrical surface of the center electrode. This side-by-side spark gap eliminates the problem of the side electrodes covering the center electrode. The disadvantage is that it increases the "accessibility" of the spark. The spark energy is larger and it is easier to penetrate deep into the cylinder, which helps to improve the combustion condition of the mixture and reduce exhaust emissions. Since the multi-side poles provide multiple sparkover channels, the service life is extended and the ignition reliability is improved. It must be pointed out here that only one channel can flash over at the moment of discharge, and it is impossible for multiple side poles to flash over at the same time. High-speed photography of the discharge process demonstrates this [6].
The suffix letters (letters after the calorific value) D, J, and Q in domestic spark plug models represent double-sided poles, three-sided poles, and four-sided poles respectively [6].
9. Nickel-based alloy and copper core electrode spark plugs
The most basic requirements for electrodes extending into the combustion chamber are resistance to ablation (electrical and chemical corrosion) and good thermal conductivity. With the development of materials science and process technology, electrode materials have experienced the evolution of iron, nickel, nickel-based alloys, nickel-copper composite materials, and precious metals. The most commonly used alloys today are nickel-based alloys. Generally, pure metals have better thermal conductivity than alloys, but pure metals (such as nickel) are more sensitive to the chemical corrosion of combustion gases and the solid deposits they form than alloys. Therefore, the electrode material uses a nickel base with elements such as chromium, manganese, and silicon added. Chromium improves the resistance to electrical corrosion, and manganese and silicon improve the resistance to chemical corrosion, especially the corrosion resistance to harmful sulfur oxides [6].
10. Ordinary and resistance spark plugs
As a spark discharge generator, the spark plug is a broadband continuous electromagnetic radiation interference source. In order to suppress the strong interference to radio fields caused by electromagnetic radiation caused by flashover, protect radio communications and prevent malfunctions of vehicle-mounted electronic devices, countries around the world have accelerated the development of resistive spark plugs since the 1960s. Our country has also issued a series of national standards for mandatory electromagnetic compatibility, which impose strict restrictions on the radio interference characteristics of vehicle devices driven by spark plug ignition engines. Therefore, the demand for resistive spark plugs has also greatly increased. There is no big difference in structure between the resistance type spark plug and the ordinary type. It is just that the conductor sealant in the insulator is changed to a resistance sealant.