Characterization of the Ethanol-Water Blend by Acoustic Signature Analysis in Ultrasonic Signals

The use of ethanol as fuel in Brazil stimulated the competition between distribution companies and resellers, which aggravated the practice of adulteration of fuels, aiming for illicit gains and tax evasion. The most common practice of adulteration in fuel alcohol is the addition of water. The classic techniques for measuring the water content in ethanol offer good precision and good detailing as to the presence of water. However, they present disadvantages such as the need for sample collection, long analysis time, in addition to the need for specialized laboratory and labor. This work aims to propose digital signal processing techniques to analyze and quantify the presence of water in ethanol fuel using a combination of Principal Component Analysis (PCA), and Singular Spectrum Analysis (SSA) applied on ultrasonic signals. This method resulted in the proposal of a new score, which relates to the ethanol/water ratio information present in the mixture. The results were promising when relating the proposed score to the presence of moisture in ethanol to a greater or lesser degree. Experiments performed prove the technique’s feasibility and pave the way for a new method for real-time monitoring.