Early fire smoke movements and detection in high large volume spaces

The maximum rise equation was obtained by differential solution of the integral equations of a plume in linearly thermally stratified environment and its applicability in piecewise linearly stratified environment was discussed. To better understand early fire smoke movements in thermally stratified environments in large volume spaces, a detailed study of smoldering cotton wick and flaming diesel oil smoke plumes in thermally stratified environments in a small scale enclosure was investigated by experimental measurements and CFD simulations. The reasonably good agreements of the experimental results and the simulated results indicate that the thermally stratified environment intensifies the decreases of the axial temperature and velocity of a fire smoke plume until makes it stop at a maximum height. Comparisons of the maximum plume heights between the experimental measurements and the integral equation results show that the available equation underestimates the actual maximum heights of fire smoke plumes and is unable to predict the influence of smoke density upon the maximum heights. A new smoke detection method of light section image detection was suggested to overcome the shortcomings of conventional beam-type smoke sensors and detect the early fire effectively.