Trilateral correlation of spray characteristics, combustion parameters, and deposit formation in the injector hole of a diesel engine running on preheated Jatropha oil and fossil diesel fuel

Abstract

The long term use of pure vegetable oil in diesel engines should be thoroughly evaluated from different perspectives including engine performance, deposit formation, etc. to ensure its compatibility. In line with that, the trilateral correlation of spray characteristics, combustion parameters, and deposit formation in the injector hole of a high-speed, 4-stroke, direct injection diesel engine fueled with pure Jatropha oil and diesel fuel (DF) was studied. Jatropha oil was investogated at room temperature 30 °C (SJO30) and in preheated form at 90 °C (PSJO90). The expertimental tests were conducted in two phases: (i)- investigation of the spray characteristics of the fuels including cone angle and penetration length at 200 bar of injection pressure, (ii)- investigation of the combustion characteristics (i.e., thermal efficiency and engine emissions) and deposits formation in the injector hole of the diesel engine at 0 h and 300 h of operation. The results obtained showed large differences between the spray characteristics of SJO30 and the other fuels investigated. Moreover, this fuel led to significant reductions in NOx emissions (14.69-20.30%) and thermal efficiency (3.04-4.41%) but large increases in CO emissions (26.36-77.57%), HC emissions (48.98-77.85%), and smoke (58.43-131.71%). It also resulted in huge deposits formed in the injector hole after 300 h of the endurance test compared to DF and PSJO90 as revealed by optical observations using scanning electron microscopy analysis. Overall and compared to DF, SJO30 cannot be recommended for long term use in diesel engines while preheating or in better words, PSJO90 may only be considered as an alternative fuel in the short term.