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Scale Modeling in Fire Reconstruction

NCJ Number
Date Published
June 2017
160 pages
After reviewing scaling theory used in fire research, this research project developed scaling rules for design fires and enclosure material boundaries, followed by the full-scale testing of a gas burner, heptane pool fire, pine wood crib, and polyurethane foam, and the scaling theory was applied to the full- scale scenario and a 1/8 scale compartment.
Gas temperature scaling results for the natural gas burner and heptane pool fire were generally well scaled. Distance was a factor in scaling accuracy due to the material boundaries. The best results were directly above the fire. The burner scaled better than the heptane pool due to the prescribed mass flow rate of the fuel. The transient temperature measurements showed similar trends for both fuels. Some discrepancy existed in the model because a more temperature-sensitive thermocouple was used. The heptane pool yielded excellent flame height results. The behavior, shape, color, and turbulence of the flame were also successfully scaled. The smaller gas burner fires produced laminar flames in the scale model, which resulted in a lower flame height. The larger gas burner experiments in the scale model produced flame heights that were in good agreement with the full scale. Using pure methane instead of natural gas had some effect on the flame height. The steady state comparisons of temperature between the full and 1/8 scale models showed that the scaling laws applied are accurate close to the fire. In locations far from the fire, the full scale temperatures were higher than the scale model due to the heat transfer differences in the boundary materials. Future research will include the scaling of the pine wood crib and the polyurethane foam blocks. 42 figures, 20 tables, 20 references, and appended details

Date Published: June 1, 2017