Controle de velocidade em uma linha de ar utilizando microcontrolador

Abstract

Currently, automated processes have become increasingly indispensable, whether they are to increase productivity, reduce losses or guarantee the quality of a process or product. In industry, many applications require speed control, among which drying and pneumatic conveying operations stand out. In a dryer, speed is very important in controlling the drying rate of materials, while in dilute phase pneumatic conveyors there is a minimum transport speed that changes depending on the material. Therefore, the use of speed controllers becomes very important for some industrial processes, motivating many educational institutions to work with these systems in order to provide students with practical activities that refer to real cases in the industry. Thus, the objective of this work was to build an experimental bench that would allow users to control the air speed in a line through a centrifugal fan. For this, a supervisor was developed in order to monitor the process control in real time. A pitot was installed in the center of the pipeline, and velocity data was measured at this point. It was found, as presented in the literature, that the installation of a pitot in the center of the pipe is sufficient to determine the average velocity. In the experiments carried out, six rotations of the centrifugal fan were defined (1688, 1990, 2300, 2620, 2945 and 3480 rpm) in order to evaluate the differences in the velocity profiles, but what was identified is that for the experimental conditions studied there was no significant variation. Thus, it is possible to conclude that for the range of speeds studied, a single equation to determine the average speed is sufficient. This study, therefore, confirms the ease of determining the volumetric flow of air transport in ducts, given the simplicity of determining the average velocity, especially when dealing with flow in a turbulent regime, with Re (Reynolds number) > 4000, in that the velocity profiles do not suffer significant differences. The experimental unit with the data acquisition and air velocity control system on the line will attend the Electrical Engineering and Control and Automation courses at the Federal Institute of Goiás, Campus Itumbiara, contributing to the improvement of the industrial process laboratory.