Review of soot measurement in hydrocarbon-air flames

Soot, which is produced in fuel-rich parts of flames as a result of incomplete combustion of hydrocarbons, is the No. 2 contributor to global warming after carbon dioxide. Developing soot measurement techniques is important to understand soot formation mechanism and control soot emission. The various soot measurement techniques, such as thermophoretic sampling particles diagnostics followed by electron microscopy analysis, thermocouple particle densitometry, light extinction, laser-induced incandescence, two-color method, and emission computed tomography, are reviewed in this paper. The measurement principle and application cases of these measurement methods are described in detail. The development trend of soot measurement is to realize the on-line measurement of multi-dimensional distributions of temperature, soot volume fraction, soot particle size and other parameters in hydrocarbon-air flames. Soot measurement techniques suitable for both small flames in laboratories and large-scale flames in industrial combustion devices should be developed. Besides, in some special situations, such as high-pressure, zero gravity and micro-gravity flames, soot measurement also should be provided.