Acoustic pyrometry for flow velocity estimation: preliminary analysis

Abstract

Acoustic pyrometry uses the variations of the speed of sound in a medium to determine its temperature. One of the assumptions at the base of this technique is that the flow velocity component in the direction of the acoustic path is negligible in comparison to the speed of sound. However, if the temperature of the medium is known, the acoustic pyrometry approach can be used to determine flow speed, as long as the flow is not perpendicular to the acoustic path. The combined approach of temperature and velocity determination is also known as acoustic tomography. This technique allows the determination of velocity and temperature maps in a flow region. Even though this is an interesting result, the mathematical approach to solve the velocity and temperature fields might be very complex and sensitive measurement set-up. In this study, a preliminary investigation is carried out to determine the flow velocity by starting from the time of flight of an acoustic signal moving along different acoustic paths in a constant temperature field. For this purpose, a simplified geometry is considered. The developed mathematical approach at the base of the methodology is presented in this study.

Acoustic tomography for velocity estimation in high temperature flows

“…Recently, several studies investigated the feasibility of using acoustic pyrometry in turbomachinery applications, as reported in [17]- [20]. In a previous study the authors investigated the potential of velocity estimation in a simplified arrangement [21]. The purpose of this study is to investigate the influence of some design parameters in the capability of the acoustic tomography to reconstruct a temperature and velocity map.…”