Flame speed

The flame speed is the measured rate of expansion of the flame front in a combustion reaction. Whereas flame velocity is generally used for a fuel, a related term is explosive velocity, which is the same relationship measured for an explosive. Combustion engineers differentiate between the laminar flame speed and turbulent flame speed. Flame speed is typically measured in m/s, cm/s, etc.

In engines

In an internal combustion engine, the flame speed of a fuel is a property which determines its ability to undergo controlled combustion without detonation. Flame speed is used along with adiabatic flame temperature to help determine the engine's efficiency. According to one source,

"...high flame-speed combustion processes, which closely approximate constant-volume processes, should reflect in high efficiencies.[1]"

The flame speeds are not the actual engine flame speeds, A 12:1 compression ratio gasoline engine at 1500 rpm would have a flame speed of about 16.5 m/s, and a similar hydrogen engine yields 48.3 m/s, but such engine flame speeds are also very dependent on stoichiometry[2]

gollark: https://queue.acm.org/detail.cfm?id=3212479
gollark: AMD and Intel CPUs have for some time been JITing x86 into internal RISC microcode.
gollark: Wrong. The ISA is old, but the microarchitectures of high-performant x86 CPUs are absolutely not ancient. They internally do a ton of optimization tricks to pretend to execute code in order with flat undifferentiated memory as fast as possible, even though the CPU is executing things out of order and aggressively caching and prefetching.
gollark: However, you can just not use it and will probably save a lot of time and segfaults.
gollark: Performant because it contorted the design of all modern CPUs to fit its model, useful because all the low-level APIs use it.

See also

References
  1. NASA Technical Note, May 1977, "Emissions and Total Energy Consumption of a Multicylinder Piston Engine Running on Gasoline and a Hydrogen-Gasoline Mixture"
  2. http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html
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