Performance of a common-rail diesel engine fuelled with rapeseed and waste cooking oils

The EU energy strategy for 2020 forces scientists and industries to develop new generation of bio-fuels and increase the use of the ones available nowadays. Straight vegetable oils (SVO) and waste cooking oils (WCO) could represent an interesting alternative fuel for Diesel engines, representing a good solution in some niches sectors (i.e., public transportation, hybrid or marine propulsion, etc.). As a matter of fact the use of SVO as fuel do not requires large production plants as in the case of biodiesel, thus it can be used in a large number of countries without requiring new costs. On the other hand SVO has some shortcomings due to the different characteristics comparing with the gasoil fuel. Main differences are related to its smaller heating value, a different density, and a larger viscosity, and this may provoke some problems to the injection system and power loss in a Diesel engine. Aim of this work is to analyse the behaviour of a Diesel engine in automotive configuration when fuelled with SVO and WCO, to study the feasibility of use them in small public transport hybrid vehicles. To this aim a series of bench tests are performed; results are here presented. Tests are performed using a turbocharged, four stroke, four cylinders, water cooled, common-rail multijet Diesel engine operating on Diesel fuel, rapeseed oil (RO) and waste cooking oil (WCO) are presented. The influence of fuel used on engine power, specific consumption, efficiency, and exhaust opacity, are compared with those obtained fuelling with Diesel fuel.