Measurement of the Percentage of Biodiesel in Blends With a Commercial Dielectric Fuel Sensor Available to Purchase

Biodiesel is a nontoxic, biodegradable, and renewable fuel which can be made from vegetable oils. Most biodiesel used today is blended with petroleum diesel because lower level blends can be used in compression-ignition engines designed for conventional diesel fuel. Blending biodiesel with petroleum based diesel affects the physical properties of the fuel, which can have an impact on the performance of the engine. If the percentage of biodiesel in the fuel tank can be measured easily, it is possible to make engine adjustments to enhance the performance and emissions. In this project, a commercial fuel sensor was evaluated as a possible biodiesel percentage sensor. The Ford flexible fuel sensor was originally designed to measure the amount of ethanol in ethanol/gasoline blends. This resonant electromagnetic cavity sensor was used to determine the correlation between the output frequency and the percentage of biodiesel in blends of soybean oil biodiesel and No. 2 diesel fuel. Pure diesel fuel and soybean B100 were tested to serve as reference points. Soybean B100 from a different distributor and canola B100 were tested to investigate the effect of different biodiesel sources and types on output frequency. The output frequency of vegetable oil was also measured in order to consider the effect of using vegetable oil instead of biodiesel when trying to estimate blend percentage. The Ford flexible fuel sensor was capable of measuring the biodiesel percentage to within about ± 3%, and temperature changes between 10 and 50 °C produced no substantial change in this measurement. Emissions and performance measurements on a production diesel engine suggest that this sensor accuracy is sufficient to provide feedback for making adjustments to the engine operation.