Butanol or DEE blends with either straight vegetable oil or biodiesel excluding fossil fuel: Comparative effects on diesel engine combustion attributes, cyclic variability and regulated emissions trade-off

This work investigates comparatively the effects of using as base fuels straight vegetable oil (SVO) and its biodiesel in blends with 10% or 20% of either n-butanol or DEE as supplements, excluding fossil fuel. The combustion attributes, cyclic variability, and all regulated emission trade-offs are examined in an experimental, 'Hydra' diesel engine at three loads. Cylinder pressure diagrams and related heat release rate analysis disclose and aid the interpretation of the differences observed in combustion attributes among all bio-fuels blends. Since low ignition quality fuels, such as the present bio-fuel supplements, may give rise to unstable engine operation and so detrimental performance, this work focuses also on the comparative examination of the strength of cyclic combustion variations as reflected in the cylinder pressure diagrams, by analyzing for maximum pressure and rate, indicated mean effective pressure, and ignition delay, using statistical analysis tools for averages and coefficients of variation (COV). The above results and the different physical and chemical properties of bio-fuels are used to aid the interpretation of engine stability differences observed among all bio-fuels examined, as well as the balance of all four exhaust emissions. The latter reveal defeat of smoke-NOx trade-off and interesting CO-HC adverse trade-off. (C) 2016 Elsevier Ltd. All rights reserved.