Experimental study on ultrasonic signal measurement and longitudinal wave transfer in air-CH4 mixture space

Abstract

This current work offers the experimental method which is capable of measuring the air-methane gas using L-wave by an ultrasound sensor in a constant volume chamber (CVC). For experimental method, a constant volume chamber is integrated with of a high-sensitive ultrasound sensor, a conventional ultrasound sensor, a non-resistance cable, a temperature sensor, a pressure sensor and two mounted zigs. The main conditions, for the experiment defined in this work, are composed of 2 bar of initial pressure, 296 K of temperature, air-CH4 mixture of gas fuel, 25 V of input voltage, 3 Hz of pulse rate and 0.2-2 of measurement distance (m) for two different ultrasonic sensors. The resonant frequency is set 67.6, 70.6, 73.6 and 76.6 kHz by adjusting wavelength inside the circuit system. It is shown that sensitivity in ethylene vinyl acetate matching layer (EVAM) type is remarkably increased comparing with the chemical wood matching layer (CWM) type. Moreover, in comparison to the conventional CWM type, the amplitude height of EVAM type shows 1.19 V at 1st, 1.05 V at 2nd, 0.63 V of 3rd, 0.40 V at 4th and 0.27 V at 5th in CVC. With regards to the average percentage, the EVAM type is shown up to 116, 250, 270,263 and 350 % for 1st, 2nd, 3rd, 4th and 5th comparing with the conventional. Consequently, the voltage characteristics improved by EVAM type layer is demonstrated that energy transfer is higher than CWM type in CVC and efficiently led to increasing the ultrasonic sensitivity in an air-methane mixture.