B. Yao

Interaction of water mists with a diffusion flame in a confined space

Abstract This paper describes the study of the interaction of water mists with a diffusion flame in a confined space with proper ventilation control. Water mist was generated by a single pressure nozzle and diffusion flames were produced from ethanol and pine samples, respectively. The LDV/APV system was employed to determine the water mist characteristics. The Cone Calorimeter was used to measure the heat release rate, oxygen and carbon monoxide concentrations and other important parameters of the interaction under various conditions. The test results showed that water mist suppressed the diffusion flame in the confined space through oxygen displacement, evaporative cooling and heat radiant attenuation, and enhanced the combustion through expansion of the mixture and chain reaction as well. Suppression played the dominating role when the water mists with enough volume flux were applied to the diffusion flame in confined space. The poorer was the ventilation, the easier the suppression. The water mists had a more complex effect on the solid sample than the liquid, and affected the smoke release rate and movement.

Numerical modeling for interaction of a water spray with smoke layer

Interaction of a water spray with a smoke layer was studied numerically. A one-dimensional model was developed by taking smoke and air as two quasi-steady layers. W ater droplets of the spray were divided into several typical classes based on the droplet distribution function. Spray characteristics such as droplet diameter and velocity, shape of the spray envelope, gas temperature, and flow rate inside the spray envelope were calculated with heat and mass transfer to the induced air flow. The simulated results agreed with the experiments on full cone water spray in a normal atmospheric environment, and indicated some physical principles for using water spray to minimize smoke damage.Interaction of a water spray with a smoke layer was studied numerically. A one-dimensional model was developed by taking smoke and air as two quasi-steady layers. W ater droplets of the spray were divided into several typical classes based on the droplet distribution function. Spray characteristics such as droplet diameter and velocity, shape of the spray envelope, gas temperature, and flow rate inside the spray envelope were calculated with heat and mass transfer to the induced air flow. The simulated results agreed with the experiments on full cone water spray in a normal atmospheric environment, and indicated some physical principles for using water spray to minimize smoke damage.

A Comparative Experimental Study on Heat Release Rates of Charring and Noncharring Solid Combustible Materials

Two commonly used solid combustible materials in China, PMMA(Polymethyl Methacrylate) and Red Pine of Northeast China, are selected as typical noncharring and charring material respectively. Bench-scale experiments were carried out to measure the heat release rates of these two materials under various external radiant heat fluxes. A comparison of similarity and difference was made between the Heat Release Rate (HRR) of PMMA and that of Red Pine and the influence of external radiant fluxes on HRR was analyzed. Bubble layers and char layers formed near the heated surface of burned noncharring and charring materials, respectively, make them differ greatly in pyrolysis and combustion processes as indicated by different HRR profiles, which are closely related to the materials original structural properties and greatly influenced by external radiant heat flux.