G - Physics – 01 – N
Patent
G - Physics
01
N
G01N 15/02 (2006.01)
Patent
CA 2272758
The present invention relates to a method and apparatus for applying laser induced incandescence (LII) to determine a primary particle size of submicron sized particles. The present invention has found that in addition to volume fraction information, particle size can be determined using LII due to the fact that transient cooling is dependent on the diameter of the particle. The ratio of a prompt and a second time integrated measurement from the same laser pulse has been found to be a function of the particle size. A modeling process involves a solution of the differential equations describing the heat/energy transfer of the particle and surrounding gas, including parameters to describe vaporization, heat transfer to the medium, particle heating etc. The solution gives temperature and diameter values for the particles over time. These values are then converted to radiation values using Planck's equation. Thus the technique in accordance with the invention is able to provide a more accurate particle measurement than previous LII techniques, particularly where time averaging is not possible and size measurements must be obtained from a single laser pulse. Simultaneously a particle volume fraction can be obtained in accordance with the invention. Calibration is needed to obtain a quantified volume fraction measurement. In a further embodiment of the present invention, a technique for providing absolute intensity calibration is included in the method.
Gulder Omer L.
Smallwood Gregory J.
Snelling David R.
Freedman Gordon
Gulder Omer L.
National Research Council Of Canada
Smallwood Gregory J.
Snelling David R.
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