Vibration-based diagnosis of adulterated ethanol in internal combustion engines

Abstract

Ethanol adulterations include the addition of hydrated ethanol with anhydrous ethanol, methanol, or even water. These alterations are visually imperceptible but can affect the vehicle’s performance, the concentrations of pollutants emitted, and deterioration levels of parts, leading to high repair costs. There are no current safety devices in vehicles that inform if the fuel is adulterated — this analysis is carried out by regulatory agencies employing instruments. This study develops a method to determine the adulteration of ethanol in real-time and non-invasively. An Arduino-based system acquires the vibration signal emitted by the engine of a running vehicle, and Signal Analysis based on Chaos using Density of Maxima (SAC-DM)is employed to process the signal. Experimental tests were carried out in a combustion engine to develop and validate the method. Currently, there is no existing method to detect the adulteration of ethanol fuel in a running engine, and this is the first study to apply Chaos Theory to this end. There was a long-term correlation for vibration signals obtained from a running engine with adulterated fuel (different proportions of ethanol), which revealed a long-term decay that confirms the chaotic behavior of the signal. Also, the chaotic variable SAC-DM relates linearly with the percentage of ethanol in the fuel, with an average relative error in the estimate of 0.6%.