What is meant by flame speed?

What is meant by flame speed?

For coordinates centered in the flame, the velocity at which unburned gases move through the combustion zone in the direction normal to the flame front is defined as the flame velocity. For laboratory coordinates, the flame speed is the velocity of the flame through the unburned gases.

What is turbulent flame speed?

The turbulent burning velocity is defined as the average rate of propagation of the flame through the turbulent premixed gas mixture. In the turbulent case it is not clear that a turbulent speed is indeed a well- defined notion.

What is the flame speed of hydrogen?

The laminar flame speeds of hydrogen/air mixture and natural gas/air mixture reach their maximum values 2.933 and 0.374 m/s when equivalence ratios equal to 1.7 and 1.1, respectively.

Which has the highest flame speed?

The highest laminar flame speed results for all of these mixtures are found to be at ϕ = 1.1, and the values are within a range of 40–42 cm/s, while the lowest flame speeds for all mixtures were measured at ϕ = 0.7 to be in the range of 20–22 cm/s.

How fast does a flame travel?

In normal atmospheric conditions in air, typical flame speeds are 10 – 100 cm/s relative to the unburned gas , or roughly 5-7 times that relative to the burned gas. In your situation, where you have a spark in a non-moving flammable mixture, the speed relative to the burned gas is the relevant one.

How do you find the speed of a flame?

The burning velocity, also referred as the displacement speed, is denoted as . In laminar regimes, the flame speed writes S D = S L for any laminar stretched flame and S D = S L 0 for the unstretched flames configuration, such as obtained from 1D laminar premixed flame calculations or from theoretical solutions.

What is turbulent flame propagation?

Turbulent flame speed is a characteristic of the rate of propagation of a flame in a turbulent flow field, such as that in a gas turbine combustor or a reciprocating internal combustion engine.

What is the most important single factor affecting flame speed?

There are several factors which affect the flame speed, to a varying degree, the most important being the turbulence and the fuel-air ratio.

Does flame front exist in CI engine?

Abnormal combustion in SI and CI engines : Spark knock occurs when the end gas ahead of combustion flame front ignites and substantial pressure rise takes place due to instant heat release.