The flame speed is the measured rate of expansion of the flame front in a combustion

Combustion

Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 reaction. Whereas flame speed is generally used for a fuel

Fuel

Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, a related term is explosive velocity

Explosive velocity

Explosive velocity, also known as detonation velocity or velocity of detonation , is the velocity at which the shock wave front travels through a detonated explosive. The data listed for a specific substance is usually a rough prediction based upon gas behavior theory , as in practice it is...

, which is the same relationship measured for an explosive. Combustion engineer

Engineer

An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...

s differentiate between the laminar flame speed

Laminar flame speed

Laminar flame speed is a property of a combustible mixture. It is the speed at which an un-stretched laminar flame will propagate through a quiescent mixture of unburned reactants. Laminar flame speed is given the symbol sL...

 and turbulent flame speed. Flame speed is typically measured in m/s, cm/s, etc.

In engines

In an internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

, the flame speed of a fuel

Fuel

Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 is a property which determines its ability to undergo controlled combustion without detonation

Detonation

Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...

. Flame speed is used along with adiabatic flame temperature

Adiabatic flame temperature

In the study of combustion, there are two types of adiabatic flame temperature depending on how the process is completed, constant volume and constant pressure, describing the temperature the combustion products theoretically reach if no energy is lost to the outside environment.The constant volume...

 to help determine the engine's efficiency. According to one source,

"...high flame-speed combustion processes, which closely approximate constant-volume processes, should result in high efficiencies."

typical 2 m/s for gasoline

See also

• Chemical kinetics
  Chemical kinetics
  Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition...
  
  
• Deflagration
  Deflagration
  Deflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...
  
  
• Burn rate (chemistry)
  Burn rate (chemistry)
  In chemistry, the burn rate is a measure of the linear combustion rate of a compound or substance such as a candle or a solid propellant. Burn rate is measured in length over time, such as "mm/second" or "inches/second". Burn rate is a property of combustible substance and it quantifies the...
  
  
• Wobbe index
  Wobbe index
  The Wobbe Index or Wobbe number is an indicator of the interchangeability of fuel gases such as natural gas, liquified petroleum gas , and town gas and is frequently defined in the specifications of gas supply and transport utilities...
  
  
• Octane rating
  Octane rating
  Octane rating or octane number is a standard measure of the anti-knock properties of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating...