An ultrasound-based water-cut meter for heavy fuel oil

Abstract

In order to have on-line measurement of water content in heavy fuel oil (HFO), the so-called water-cut meters are used. Typically, measurements performed by these devices are based on capacitive principle, in which the water-in-oil emulsion acts as the insulation material. In this case, variations in the water/oil ratio affect the dielectric, which causes the capacitance to vary. By contrast, in our approach, water-in-oil emulsions act as the material medium for propagation of ultrasound waves so that the variations in water/oil ratio affect their frequency components. Since we keep the transmitter transducer excitation the same, the received ultrasound signal will vary according to the current characteristics of the fluid. As it is not known in advance which components will be affected by the presence of water, we present a methodology consisting in laboratory experiments in conjunction with Principal Component Analysis (PCA). This methodology leads to an expression that relates the score value issued from PCA and the water content information. In addition to presenting the development of an ultrasound-based water-cut meter, this paper presents some results obtained from both laboratory and field measurements. We could also compare the proposed system with a PCB-based capacitive sensor under field conditions. We verified a maximum difference of 0.2 percentage point between both approaches.