Concentration Sensor for Hydrogen-Methane Mixed Gas Based on Quartz Oscillator

Abstract

Quartz is used in various devices, since it can be easily vibrated by the piezoelectric effect and controlled in an electric circuit. The force, which acts on the vibrating body, follows the principles of fluid dynamics; this phenomenon is explained in detail by the Navier-Stokes equation that is a fundamental equation of motion of a flow system. The authors measured the drag acting on a vibrating body (i.e., a quartz oscillator) settled within a hydrogen-methane mixed gas. The quartz oscillator is sensitive to temperature, pressure, and viscosity. It was placed in a constant temperature bath to control the temperature accurately. A pressure gauge was also placed into the same bath, and the pressure inside the tube was controlled by using a piezo valve. This drag is measured and converted into a physical property by using an approximate solution of the Navier-Stokes equation. The drag changes depending on gas conditions, because the property of a gas differs under different conditions. If a quartz oscillator can detect this difference, it can be used as a sensor for a gas. In this study, the authors attempted to ascertain the possibility of using a quartz oscillator as a concentration sensor for a hydrogen-methane mixed gas. The large-scale project on hydrogen-methane mixed gas that has begun in Europe shows the increasing concern for devices using hydrogen-methane mixed gas among the countries because of environmental issues. Differences in the mixture ratio of the hydrogen-methane mixed gas were successfully determined by this sensor.