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Optimization of air transport in the fan chamber with a free impeller
Cakl, Dominik ; Bašta, Jiří (referee) ; Cifrinec, Ivan (referee) ; Rubina, Aleš (advisor)
The work deals with the improvement of the hydraulic properties of air transport in fan chambers with free impeller wheels, which are equipped in every larger central air handling system. Every larger central air handling system is equipped with a fresh air intake that transports the air into a fan chamber, which contains a free-wheel fan that provides air transport and provides kinetic energy to the air stream. From the fan chamber, the air is further transported by the air handling system to the individual distribution elements. Similiary, the extraction of polluted air is solved through the fan chamber. The turbulent flow of air at the outlet of the impeller causes a pressure loss in the discharge chamber of the air handling unit, as the air is transported in pulses according to the slip of the blades. In practice, fans with smaller performance parameters measured in laboratories under ideal boundary conditions are installed in air handling units, which do not solve the problem of the difference in real traffic pressure between the supply and exhaust air ducts, with the result that the installed fans in the real fan box do not reach the parameters specified by the manufacturer. Reduction the pressure losses in fan chambers is correlated with the reduction of energy consumption of equipment ensuring air transport in the context of sustainable construction. Based on the development of aerodynamic efficiency of fans and European legislation, the current trend of a significant reduction in energy consumption was described, among other things, for equipment providing air transport, through repairs, reuse, repurposing and recycling of used materials, and through extending the life of products and buildings. Furthermore, three research principles and methods of improving the efficiency of equipment in order to reduce the energy demand of equipment ensuring air transport are presented, the authors of which approach the research numerically and experimentally. The goal of the original technical solutions presented in this work is to present a development that optimizes the pressure losses of a fan chamber with a free impeller. The first solution describes the principle of lead-in plates, where the goal is to help the air stream eliminate the negative effects of swirling and facilitate the outflow of air from the fan chamber by means of a smooth slide along an inclined surface, which reduces the specific power of the fan, under the given marginal conditions, by up to 5.9 %. The essence of the second innovative technical solution is to present a free impeller, which is based on the connection of two rows of curved blades of concave and convex shape, which serves to optimize the pressure loss of the fan chamber with a free impeller, which produces smaller, more uniform, mutually interacting currents that help the flow of air to more smoothly change the direction of swirling in the fan chamber and which found practically no value for the specific measured boundary conditions. The essence of the third innovative technical solution is the introduction of modern production of products from "sustainable" materials with the help of 3D printing, in the form of a free impeller for fans with a free impeller. The results of geometric copies of free impellers made of lighter material reflect that there was a reduction in the average specific power of the fan by up to 4.4 %, while at the same time there was a reduction in the total sound level.
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