Análise de gasolina adulterada por etanol através do método vibracional e FFT

Abstract

The increasing scenario of automobile production drives the search for solutions that minimize the impacts of internal combustion engines on the environment. In this context, the National Agency of Petroleum, Natural Gas, and Biofuels (ANP) promotes the regulation and monitoring of the ethanol percentage in gasoline, aiming to maintain emissions levels of harmful gases into nature within limits established by law. However, cases of fuel composition adulteration using imperceptible means to the naked eye are not uncommon, leading to increased profit margins for sellers. Additionally, fuel adulteration can cause performance loss and severe damage to the structural integrity of the engine, resulting in high repair costs for affected parts. Automobiles lack a device that can indicate whether the fuel being used is adulterated or not, with this diagnosis being currently performed by the ANP through laboratory tests. Given this circumstance, there is a need for a real-time, non-invasive diagnostic method capable of determining whether the fuel meets ANP resolutions. This study aims to investigate the correlation between the vibration mode of the operating engine and the percentage of ethanol in the blend. Experimental tests were conducted using ten samples with different compositions, from which the engine vibration signal was collected. This signal was then processed and used to calculate three statistical metrics: kurtosis, root mean square (RMS), and shape factor, which were subsequently used to calculate the correlation coefficient with the ethanol percentage, yielding the following results: 0.6054, 0.7082, and 0.7967, respectively. These results indicate that the shape factor metric may potentially be more effective in diagnosing fuel adulteration compared to the other statistical metrics. Additionally, the Fast Fourier Transform (FFT) was computed for each signal, revealing a peak frequency around 1088 Hz for all samples, correlating at 0.9922 with the ethanol percentage in the blend. Indicating a possible new methodology for adulterated fuel diagnosis.