Accuracy of cross correlation velocity measurements in two-phase gas-solid flows

The paper presents a detailed discussion of the errors of quantisation and sampling (conversion) caused by AID converters and brought up for discussion on the basis of some original formulae derived. These converters are implemented in analogue-digital parts of measuring systems designed and produced to be in operation according to the cross correlation method of measurement of mean flow velocity of solid particles especially in pipelines of pneumatic transport. The discussion is based on an analysis of a real measuring system in which electrostatic flow probes were used to detect the smallest changes in charge carried by solid particles in pipes of pneumatic transport and in the air during their two-phase gas-solid flows. In the cross correlation of signals induced in electrostatic flow probes a non-intrusive electrostatic method is employed which is based on the phenomenon of electrostatic induction brought about by the time-varying charge of particulates in conveying pipes or by the so-called electrostatic flow noise. The conclusion of the discussion can be spread among other kinds of cross correlation method including the capacitive or electromagnetic methods based on the types of sensors named after the names of the methods. Certain excerpts in the paper are taken from or based in part on some passages from the author's monograph (Gajewski, 2010 [1]). (C) 2013 Elsevier Ltd. All rights reserved.