Failure of fuel injectors in a medium speed diesel engine operating on bio-oil

The residue of a fatty acid distillation was used as a diesel fuel in a medium speed diesel engine. This bio-oil was heated to 110 °C to decrease the viscosity to 8 mPa s. The injectors working with the bio-oil failed prematurely with operation times ranging from 50 to 1500 h. The injectors and the fuel were investigated in order to know the reasons of the failure and to improve the operation of the engine. The investigation revealed different causes, including plastic deformation and clogging of the injector’s passages, as well as micro cracks, erosion and cavitation damage. The failed injectors were compared with non affected ones from the same engine and injectors from fossil diesel fuelled engines. It was found that the chemical and physical composition of the fuel enforced the failure of the injectors.

► Injector failing occurred by a fatty acid distillation residue as diesel fuel.
► SEM analysis show details of the failures.
► Main damage was caused by the alkalis, water and contamination content of the fuel.
► Surface treatment can improve erosion & oxidation resistance.