Burn rate (chemistry)
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In chemistry, the burn rate (or burning rate) is a measure of the linear combustion rate of a compound or substance such as a candle or a solid propellant. It is measured in length over time, such as "mm/second" or "inches/second". Among the variables affecting burn rate are pressure and temperature.
One device for measuring burning rate is a V shaped metal channel about 1–2 feet long wherein a sample is placed, with a cross-sectional dimension of approximately 6 mm or 1/4". The sample is ignited on one end and time is measured until the flame front gets to the other end. Burn rate (typically expressed in 'mm/s' or 'in/s') is the sample length over time at a given pressure and temperature. For solid fuel propellant, the most common method of measuring burn rate is the Crawford Type Strand Burning Rate Bomb System (also known as the Crawford Burner or Strand Burner), as described in MIL-STD-286C.
A substance is characterized through burn rate vs pressure chart and burn rate vs temperature chart.
- Higher burn rate than the speed of sound in the material (usually several km/s): "detonation"
- A few meters per second: "deflagration"
- A few centimeters per second: "burn" or "smolder"
- 0.01 mm/s to 100 mm/s: "decomposing rapidly" to characterize it.
- http://www.ditusa.com/strand_burner.php Crawford Burner System (Strand Burner) for Testing Burn Rate