Estimation and reduction of errors in flow measurements which use cross-correlation techniques

Propagation of inherent inhomogeneities or tracers in flowing liquids is used to measure flow. The peak value obtained from a cross-correlation analysis of downstream and upstream sensor signals is used to determine the tracer transit time and hence the flow. Performance of a “clamp-on” ultrasonic cross-correlation flowmeter developed by Canadian General Electric under contract from Atomic Energy of Canada Limited (AECL) was evaluated at the Chalk River Nuclear Laboratories of AECL. During this work, the effects of: (1) cross-correlation parameters, (2) filtering of correlator output and (3) use of an add-only polarity coincidence correlator on the standard deviation of transit time measurements were investigated both theoretically and experimentally. Comparison of ultrasonic cross-correlation flowmeter readings against gravimetric flow measurements gave a standard deviation of 2% of reading.