Finding the Optimal Funnel Configuration to Enhance Gas Sensor Readings

Overview

This research was conducted with the intent of designing and testing a gas funneling system for use in a non- invasive blood alcohol content detection system. The design goal was to identify the optimal method for gas transfer between a user's finger and the MiCS-5524 gas sensor embedded within the steering wheel. After initial prototyping with designs from vortex-funnels to proximity based arrays, a venturi funnel was identified as a candidate for further exploration. By altering two variables, length and closing diameter, a set of nine venturi funnels were created ranging from 30-60mm in length and 16-28mm in diameter. To provide airflow, a 27mm fan was installed for testing. The MiCS-5524 gas sensor was placed ¾ of an inch away from the rear opening to detect gas concentration levels. For each test, a cotton swab soaked in a 91% isopropyl alcohol solution was applied to a 5mm hole at the smallest cross-sectional area of the funnel. After multiple repetitions, a correlation between longer funnels with midsized closing diameters and high concentration readings became apparent. To add validity to these results, two more tests were done to examine the qualities of funnels <30mm in length and the effect o f enclosing the sensor. Both of these trials supported the idea of a “goldi-locks zone” near the 60x22mm configuration. This research has the potential to be applied to numerous industry applications utilizing the venturi effect, including everything from jet pumps, to fuel injectors, and passive flow control valves in liquid propellant rocket engines.