Influence of conditions in the combustion chamber of small-scale installation on smoke generating ability of wood

Introduction. In order to calculate the time for blocking escape routes by loss of visibility, the value of the smoke ­generation coefficient, which is determined in a small-scale experimental installation, is critical. However, the parameters of the smoke formation process depend on a variety of factors whose influence has not been sufficiently studied. Therefore, scientific justification of test conditions for determination of specific smoke formation factor is necessary. 

Aims and purposes. The aim of this work is to study the influence of conditions in the combustion chamber on the smoke generating ability of wood. To achieve this aim: a modification of the existing experimental installa­tion was performed, which allowed determining the optical density of smoke inside the exposure chamber; experi­mental studies of burning of wood were carried out, during which the optical density of the smoke was measured on the different distances between the electric heating emitter in the combustion chamber of the installation and the surface of the sample of the material under study.

Methods. Measurements of temperature and heat flux density inside the combustion chamber were carried out at different distances from the electric radiator, using certified equipment in a conditionally sealed volume of the experimental installation.

Results. The experiments showed that the specific smoke generation coefficient significantly depends on the test conditions in the combustion chamber. The smoke generation coefficient obtained at the modified installation ­during the burning of coniferous wood varies within 22.1–56.9 Np·m²/kg in the combustion mode and 82.9–134.5 Np·m²/kg in the smoldering mode. For coniferous wood materials, the value of this coefficient used in modeling fires is 57–61 Np·m²/kg, which is comparable with the range of its changes in the experiments. The va­lues of the smoke generation coefficient obtained at the standard installation GOST 12.1.044–2018 significantly exceed the values of the above coefficient obtained at the developed installation. The difference in smoke generation coefficients obtained by the proposed method and the standard method exceeded 233.1 Np·m²/kg in the combustion mode and 640.5 Np·m²/kg in the smoldering mode.

Conclusion. The design features of the experimental installation and the test conditions, significantly change the conditions in the combustion chamber. This fact has a strong effect on the specific smoke generation coeffi­cient of the combustible material. Therefore, in order to calculate reliably the time of blocking evacuation routes due to loss of visibility, further investigations are necessary to substantiate scientifically the method for determin­ing the above mentioned coefficient.

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