Comparative study of vibration signatures by correlating them with engine oil degradation for diesel and blended fuel DBD20 in a CI engine

The use of biofuels as a sustainable alternative to fossil fuels has garnered significant attention. However, several factors, including oil degradation, can impact the effectiveness of biofuels. It is recommended to regularly change and maintain the oil to minimize the impact of oil degradation on biofuel performance. This can be achieved by monitoring the engine's vibration signature without draining any oil from the engine. This study aimed to investigate the correlation between engine vibration signatures and the degradation of lubricating oil. A 5 horse power (HP) compression ignition (CI) engine fuelled with a mixture of 80% diesel and 20% biodiesel, referred to as diesel biodiesel (DBD)20, was used for the study. The engine operated at a steady load, equivalent to 50% of its rated power at 1500 rpm. The vibration signatures, including amplitude and frequency of vibration in the longitudinal direction, were recorded at regular intervals of 2 hours using an accelerometer placed on top of the engine head. Samples of used lubricating oil were collected every 20 hours of operation, and properties such as viscosity, density, soot content, and moisture were measured and compared with the vibration signatures. The analysis revealed distinguishable differences in vibration signatures and lubricating oil properties between diesel and DBD fuelled engines. The findings indicated a significant decline in oil quality and corresponding vibration signatures after 80 hours of engine operation. Therefore, it is recommended to replace the engine oil every 80 hours of engine run for stationary field engines.