Desempenho de motor diesel com óleo vegetal de Crambe (Crambe abyssinica hochst) pré-aquecido

Abstract

The environmental problems arising from the use of fossil fuels have encouraged the development of renewable energy sources. In this scenario, in relation to the search for possible substitutes for petrodiesel, fuels made from vegetable oils are considered an interesting alternative. However, to use pure vegetable oils as fuel, adaptations must be made to reduce the oil viscosity and minimize the occurrence of performance issues and engine damage. In this study, a long-term test was performed in a single-cylinder, indirect injection diesel engine fueled with crambe oil preheated at 100 °C, with the aim of evaluating the performance of the engine with the use of this vegetable oil as fuel, in comparison to petrodiesel, and also possible contaminations in the lubricant due to the use of crambe oil. The essay had a duration of 100 hours. At specific time intervals, consumption and relative power loss for crambe oil and petrodiesel were measured, and lubricant samples were taken for laboratory analysis. The initial evaluations were at time zero and the subsequent at each 15 hours of engine operation. Also, the thermal efficiency was calculated for both fuels. The consumption of crambe oil was, on average, higher than that of petrodiesel for the four engine operating regimes, and the difference between the fuels consumptions was more evident at load conditions. The relative power loss of crambe fuel was higher than that of petrodiesel in the evaluations in which the load of 51% of rated engine power was applied over the condition of 1,800 rpm load-free and for the application of additional load of 15% over the demand of 51% of rated engine power; however, for the application of load of 66% of rated engine power over the condition of 1,800 rpm load-free, crambe oil presented less relative power loss. There was no difference between the fuels in the thermal efficiency of the engine-generator set, proving that the higher consumption of crambe oil compensates its lower heating value in relation to petrodiesel. In the lubricant analyses, there was no evidence of contamination by the fuel and no changes in its properties, indicating adequate combustion of the crambe oil, but it was observed a marked increase in iron concentration. In general, despite the inferior performance, good results were obtained with preheated crambe oil as fuel. However, more studies are necessary to evaluate the technical and economic feasibility of its use.