Athanasios Dimaratos

Combustion and Emissions of a Common-Rail Diesel Engine Fueled with HWCO

Hydrotreated vegetable or waste cooking oils (HVOs or HWCOs) are considered second-generation biofuels and are regarded as a promising alternative to current market diesel because they mainly consist of paraffinic hydrocarbons. This paper presents an experimental investigation conducted in order to examine the potential of HWCO as a substitute of diesel fuel. The HWCO used was produced from waste cooking oils through a catalytic hydrotreatment process. The main target of the study was the investigation of the emissions and combustion characteristics of the HWCO in comparison with conventional diesel. To that aim, a light-duty common-rail Euro 5 diesel engine, running on neat HWCO, was tested over the New European Driving Cycle (NEDC) at the engine test bed. The results showed lower CO₂, CO, and hydrocarbon emissions, but increased NOₓ emissions. Combustion analysis, performed at specific steady-state operating points, revealed the differences in the combustion mechanism between HWCO and market diesel, forming a basis for the interpretation of emissions results.

Evaluation of a Hydrotreated Vegetable Oil (HVO) and Effects on Emissions of a Passenger Car Diesel Engine

In the coming years, the application of paraffinic biofuels, such as Hydrotreated Vegetable Oils (HVO), in the transportation sector is expected to increase. However, as the composition of HVO is different compared to conventional diesel, the engine optimized for conventional fuel cannot take full advantage of the HVO beneficial properties. Suitable adjustment of a number of engine parameters, if not complete engine re-calibration, will enable the full exploitation of such fuels’ potential for lower exhaust emissions and reduced fuel consumption. In the present work, the emission characteristics of HVO fuel in a light-duty Euro 5 diesel engine have been studied, under steady-state operation, as well as during the New European Driving Cycle (NEDC). The study was expanded to the investigation of exhaust emissions under modified Main Injection Timing (MIT) and EGR rate. The NEXBTL fuel, produced by Neste, was considered in the study and was compared with conventional market diesel. Emissions of nitric oxides (NOx), soot, carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) were studied. At default MIT and EGR settings the use of HVO resulted in a significant reduction of all regulated emissions. In addition, it was observed that the adjustment of MIT and EGR can enhance the exploitation of HVO potential for emissions reduction, highlighting the differences with the conventional diesel fuel.