Self - monitoring Ultrasonic Vortex and Correlation Gas Flow Meter

Ultrasound is predestined for gas flow velocity measurements on account of its high sensitivity to all kinds of turbulences in the streaming fluid. Cross-correlation methods as well as vortex measurements behind a bluff body have been proved good. The most important problem is the ultrasound signal processing. The complex modulated signal can be demodulated by undersampling. The real and imaginary parts of the complex signal can be determined by Hilbert transformation. The demodulated phase signal can be applied to cross-correlation functions for the detection of flow velocity. The vortex frequency can be detected by a simple analog signal processing device. The combination of vortex and cross-correlation measurements results in a self-monitoring system. The pattern of a group of vortices is used to determine the transition time between two sensor pairs. Measurement results show that the uncertainty of gas flow velocity with bluff body is evidently smaller than that without bluff body