Evaluation of Physicochemical Properties and Combustion Performance of Linseed Oil-DEE Mixtures for Diesel Engines

Abstract

This study focuses on the physicochemical and combustion properties of linseed oil (LO) blended with diethyl ether (DEE) and investigates its potential for application in diesel engines. While similar research exists for rapeseed oil (RO) and DEE blends, a detailed analysis of LO-DEE mixtures has been lacking. Linseed oil, a colourless to yellowish edible oil extracted from flax seeds, is notable for its high content of polyunsaturated fatty acids, especially α-linoleic acid. These properties make it suitable for multiple applications, including the chemical, biomedical, and fuel industries. However, LO's unique chemical composition presents opportunities and challenges for its use as a biofuel. Experimental results demonstrate a significant linear relationship between DEE concentration and the physicochemical properties of LO-DEE blends. For instance, density and surface tension decreased with increasing DEE content, leading to improved spray characteristics and atomization during fuel injection. The LHV of the blends was slightly reduced compared to diesel fuel (DF) but remained comparable to rapeseed oil-DEE mixtures. While LO's viscosity is lower than many vegetable oils, it remains higher than that of conventional diesel fuel, which can impact spray angle and atomization efficiency. The addition of DEE effectively reduced viscosity, enhancing the combustion process. Combustion analysis revealed that LO has a longer ignition delay compared to DF, primarily due to its high polyunsaturated fatty acid content. Blending with DEE significantly reduced the ignition delay, narrowing the gap between LO blends and DF, especially at higher engine speeds. Additionally, the high unsaturated fatty acid content contributes to increased NOx emissions and potential deposition issues on engine components. Preheating and engine modifications may help address these challenges but require further research. Statistical analysis using linear regression models confirmed the significance of the observed trends, with confidence intervals validating the reliability of the experimental data. The study emphasizes the importance of understanding the interplay between fuel properties, combustion behaviour, and engine performance to optimize the use of LO-DEE blends as a renewable alternative to diesel fuel.