Novo sensor de vazão de fluidos com foco em aplicações biomedicas / New fluid flow sensor aimed at biomedical applications

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Spirometer is a device that evaluates pulmonary ventilation. This paper presents a preliminary study of a new electromechanical sensor, focused on the biomedical application of spirometry. The sensor is composed of a bluff body positioned inside a tube trough a hole, being a part of the body inside and another part outside of the tube, and an accelerometer positioned on the outside part. Within a fluid flow, the bluff body causes vortex shedding, and the vortexes induce vibrations on the body. Also, the viscous force of the flow drags the bluff body. Both movements are captured by the accelerometer and correlated with the flow. One important feature of this sensor is that the fluid does not contact any of the electronics, easing tube lumen sterilization procedures. Three types of bluff bodies were studied: two blades (with and without additional mass), and one cylinder. The experimental procedure consisted of establishing six different air flows and then capturing the accelerometer response in all of its three axes. Each of the collected signals from the accelerometer was divided in 24 parts, and these parts where analyzed through statistics; finally the mean response of the sensor was plotted. Best results were found in the accelerometer axis parallel to the air flow. In the blade tests, the RMS value of the AC component was proportional to the air flow, with linearity and correlation varying, respectively, from 19% and R2 = 0.99058 for the blade without mass, to 8.4% and R2 = 0.9741 for the blade with additional mass. It was observed that the mass addition reduced in a meaningful way the response variances. Yet the viscous force (DC value) did not respond in a monotonic way with the increase of air flow. On the other hand, the viscous force was the most expressive regarding the experiments with the cylinder (linearity of 0.17% and R2 = 0.96347), but the RMS value did not respond in a monotonic way. Finally, although further studies are needed to prove that the proposed sensor is efficient to be used in spirometry equipment, this study demonstrates that this sensor responds proportionally to the flow input, within (0 to 14 l/s) and without (up to 21 l/s) the spirometer operation range, with high correlation and linearity, as well as varying responses, given different inputs (flow), as verified by ANOVA test (p <10-15).

ASSUNTO(S)

arrasto (aerodinamica) vortex sensor accelerometer resonant vibration vibração ressonante drag (aerodynamics) spirometer dinamica de vortices acelerometros espirometria

ACESSO AO ARTIGO

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