It looks like "explosion" refers to something actually flying apart. The flame front speed of travel game seems to devolve to defining burning, deflagration & detonation.
Burning is in the cm/second range. Deflagration is subsonic flame front propagation (up to 0.34 Km/s), detonation is supersonic flame front propagation ( over .34 Km/s).
Dynamite combustion propagates at about 1.2 Km/s. Faster explosives can achieve nearly 4 Km/s rates.
Gasoline can detonate, usually when "burned" in its lower combustible limits. This makes supersonic shock waves/pressure waves inside the combustion chamber, ie. "knock".
Kevin Cameron in his December 26, 2018 article discusses this phenomenon and a lot more. His fast combustion chamber working numbers cited are about 0.006 to 0.020 Km/sec. Even a 0.34Km/s detonation effect shock wave is still some 17x faster than normal working numbers.https://www.cycleworld.com/how-fuel-efficiency-and-fast-combustion-are-related/#:~:text=Although%20people%20casually%20refer%20to,to%20150%20feet%20per%20second.
https://en.wikipedia.org/wiki/Flammability_limitViolence of combustion
Combustion can vary in degree of violence. A deflagration is a propagation of a combustion zone at a velocity less than the speed of sound in the unreacted medium. A detonation is a propagation of a combustion zone at a velocity greater than the speed of sound in the unreacted medium. An explosion is the bursting or rupture of an enclosure or container due to the development of internal pressure from a deflagration or detonation as defined in NFPA 69.
Lower flammability limit (LFL): The lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in the presence of an ignition source (arc, flame, heat). The term is considered by many safety professionals to be the same as the lower explosive level (LEL). At a concentration in air lower than the LFL, gas mixtures are "too lean" to burn.
Percentage reading on combustible air monitors should not be confused with the LFL concentrations. Explosimeters designed and calibrated to a specific gas may show the relative concentration of the atmosphere to the LFL—the LFL being 100%. A 5% displayed LFL reading for methane, for example, would be equivalent to 5% multiplied by 4.4%, or approximately 0.22% methane by volume at 20 degrees C. Control of the explosion hazard is usually achieved by sufficient natural or mechanical ventilation, to limit the concentration of flammable gases or vapors to a maximum level of 25% of their lower explosive or flammable limit.
Upper flammability limit (UFL): Highest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in the presence of an ignition source (arc, flame, heat). Concentrations higher than UFL or UEL are "too rich" to burn. Operating above the UFL is usually avoided for safety because air leaking in can bring the mixture into combustibility range.
https://en.wikipedia.org/wiki/DetonationDetonation (from Latin detonare 'to thunder down/forth'[1]) is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with speeds in the range of 1 km/sec and differ from deflagrations which have subsonic flame speeds in the range of 1 m/sec.[2]
Detonations occur in both conventional solid and liquid explosives,[3] as well as in reactive gases. The velocity of detonation in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higher resolution).
A very wide variety of fuels may occur as gases (e.g. hydrogen), droplet fogs, or dust suspensions. In addition to oxygen, oxidants can include halogen compounds, ozone, hydrogen peroxide and oxides of nitrogen.
Gaseous detonations are often associated with a mixture of fuel and oxidant in a composition somewhat below conventional flammability ratios.
Applications
When used in explosive devices, the main cause of damage from a detonation is the supersonic blast front (a powerful shock wave) in the surrounding area. This is a significant distinction from deflagrations where the exothermic wave is subsonic and maximum pressures for non-metal dusts are approximately 7 - 10 times atmospheric pressure.[24] Therefore, detonation is a feature for destructive purpose while deflagration is favored for the acceleration of firearms' projectiles. However, detonation waves may also be used for less destructive purposes, including deposition of coatings to a surface[25] or cleaning of equipment (e.g. slag removal[26]) and even explosively welding together metals that would otherwise fail to fuse.
In engines and firearms
Unintentional detonation when deflagration is desired is a problem in some devices. In Otto cycle, or gasoline engines it is called engine knocking or pinging, and it causes a loss of power, excessive heating, and harsh mechanical shock that can result in eventual engine failure.
https://en.wikipedia.org/wiki/Engine_knockingThe phenomenon of detonation was described in November 1914 in a letter from Lodge Brothers (spark plug manufacturers, and sons of Sir Oliver Lodge) settling a discussion regarding the cause of "knocking" or "pinging" in motorcycles. In the letter they stated that an early ignition can give rise to the gas detonating instead of the usual expansion, and the sound that is produced by the detonation is the same as if the metal parts had been tapped with a hammer.[1] It was further investigated and described by Harry Ricardo during experiments carried out between 1916 and 1919 to discover the reason for failures in aircraft engines.[2]
Topic: E-Bike developments (Read 108040 times)