Design and Testing of a New Smoke Concentration Meter

摘要

The design of a new smoke concentration meter based on light-extinction measurements with a He-Ne laser is described. The measurement allows the determination of the mass-generation rate of smoke and smoke yield during a fire test with little more time or labour than is required for performing heat-release-rate and mass-loss-rate measurements. The new smoke concentration meter was motivated by the finding from several studies of a nearly universal value of the specific extinction coefficient of post-flame smoke produced by over ventilated fires. Key design features include the use of a stabilized laser, purge flow to eliminate smoke deposition on the optics, U channel construction to minimize the effect of heating on the optical alignment and beam correction optics. The facility was fabricated almost entirely from commercially available components to allow this design to be easily reproduced by fire research and testing laboratories. The smoke concentration meter was able to measure a smoke yield as small as 0.005 for a propane fire to as large as 0.10 for a toluene pool fire. A detailed uncertainty assessment was made. The result for a 50 cm diameter heptane pool fire agrees well with previous smoke yield measurements made for the same fuel and pool diameter based on filter collection and weighing.