The results of experimental studies on determination of the effect of the deflector-type sprinkler geometric parameters on the air-mechanical foam formation process are presented in the article. A collapsible sprinkler was developed for the experiment. The elements of the collapsible sprinkler which allow creating its various configurations in a fairly wide range of geometric parameters were made from polylactide (PLA-plastic) with the help of 3D printing. The dependencies of the air-mechanical foam expansion rate and stability on the sprinkler holder length, as well as the external diameter, the taper angle and the ledges height of the sprinkler sprayer were established. The ranges of optimal values along the holder length L = 45÷55 mm and the sprayer ledges height h = 1÷3 mm of the sprinkler for generation of foam with the greatest expansion rate and stability were determined, as well as the ranges of values of these parameters at which the change in the quality characteristics does not occur (L = 90÷150 mm, h = 5÷15 mm). A decrease in the foam quality characteristics with an increase in the sprayer taper angle of the sprinkler was established. Approximate dependencies of the foam expansion rate and stability on the sprayer taper angle of the sprinkler in the range α = 30÷135° were obtained. In addition, it is determined that an increase in the sprayer external diameter in the range from 20 mm to 100 mm results in a gradual deterioration in the foam qua lity. The results of the conducted researches will allow optimizing geometrical parameters of existing designs of deflector-type sprinklers with the aim to increase their fire extinguishing efficiency.
The wind force acting on full-grown pine trees as they free fall was calculated based on comparison of the results of the field experiment and numerical simulation (Borisevich and Vikhrenko 2018). A number of improvements were proposed in order to increase the accuracy of the method. Field experiments of the free fall of five pine trees previously cut were carried out. Then, computer simulations of their motion assuming the linear dependence of drag force on air velocity were performed. Comparisons of the data of the field experiments and computer simulations showed that the linear dependence with a constant scaling parameter gives a good approximation of the drag force at a wide range of air velocity values. Error analysis was carried out to assess the quality of the numerical model. At all times during the movement, the deviations in the center mass positions observed in the field experiment and obtained in the numerical experiment do not exceed the diameter of the tree stem. The scaling parameter for five full-grown Scots pines (Pinus sylvestris L.) growing in stands ranged between 25.5 to 90.0 kg/s.
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