Ardashir Mohammadzadeh

In photoacoustic spectroscopy, the signal is inversely proportional to the resonant cell volume. Photoacoustic spectroscopy (PAS) is an absorption spectroscopy technique that is suitable for detecting gases at low concentrations. This desirable feature has created a growing interest in miniaturizing PA cell in recent years. In this paper, a simulation of a miniaturized H-type photoa-coustic cell consisting of 2 buffer holes and a resonator is performed in order to detect CO, NH3, NO, and CH4 pollutants. These gases are the main part of the air pollutants that are produced by the automotive industry. The linear forms of the continuity, Navier-Stokes equations, and the energy equation are solved using the finite element method in a gaseous medium. The generated pressure can be measured by a MEMS sensor. Photoacoustic spectroscopy has proved to be a sensitive method for detecting pollutant gases. The objectives of the measurements are: Determine the proper position of the pressure gauge sensor; Measure the frequency response; Frequency response changes at different temperatures; Study the local velocity at the resonant frequency; Calculate the quality factor. The acoustic quality coefficient, acoustic response (pressure), local velocity, frequency response and the effect of different temperatures on frequency response are investigated. Frequency response measurement represents that different gases have different resonance frequencies in which for CO and NO gases have values of 23.131 [kHz] and 23.329 [kHz], respectively. The difference between these gases is 200 [Hz]. NH3 and CH4 gases with values of 21.206 [kHz] and 21.106 [kHz] are separable with a difference of 100 [Hz]. Also, CO and NO gases have a difference of 2000 [Hz] compared to NH3 and CH4, which indicates the characteristic fingerprint of the designed cell in different gases detection. Better access to high frequency acoustic signals is the goal of the presented model in this paper.