A robust Doppler shift-based velocimetry via using tuable diode laser absorption spectroscopy

In this paper, the WMS-2f method was introduced to determine the Doppler shift in tunable diode laser spectroscopy (TDLAS) velocimetry. The peak shift caused by the velocity was achieved from the cross correlation of amplitude peaks in two separate laser paths. In this way, the peak position in the WMS-2f signal can be located precisely, and the standard deviation of the measured velocity can be only one half of the classical peak picking method. As a result, the resolution and robustness of the velocity measurement were improved and the applications in low-speed flowing medium and harsh environment can be more feasible. Numerical simulations in cases of both uniform and nonuniform velocity profiles verified the feasibility and effectiveness of the proposed method.