Ethanol-fueled engines are considered to be low particulate emitting engines. This study was performed to investigate the potential to achieve even lower particulate emission if a 9-liter Scania diesel engine, running on ethanol fuel is equipped with emission control. State-of-the art technology in emission control was applied, e.g., exhaust gas recirculation, EGR, catalysts and a continuous regenerating particle filter, DPF. Particulate emissions were compared with emissions from a 9-liter Scania diesel engine from the same engine family, running on Swedish environmental class 1 diesel fuel. Tailpipe measurements of particle size and distribution were performed with a scanning mobility particle sizer, SMPS, instrument together with filter sampling.
An evaluation of SMPS measurements was performed for test conditions specified according to a 22-mode test cycle, which included the test modes in the European Stationary Cycle, ESC.
Calculated weighted particle mass from SMPS-data, and in accordance with ESC, showed that the ethanol engine without emission control emitted approx. 1/12 of particle mass compared to the diesel engine. Weighted particulate emissions were reduced by approx. 96%, when the engine was fitted with EGR and DPF. The reduction of weighted particulate emissions was even higher when the diesel engine was fitted with EGR and DPF, as high as 99%. Particle size and distribution measurements revealed that particles emitted from the ethanol engine mainly consisted of ultrafine particles (<100nm), usually had a mean diameter of about 30 nm, while particles emitted from the diesel engine usually had mean diameters of about 60-70 nm and sizes going up to approx. 300 nm. Filter samples analyzed by Scanning electron microscopy and energy dispersive x-ray analysis SEM/EDX showed that the particles, both from the ethanol-fueled engine and the diesel fueled engine mainly consisted of carbon and that they agglomerated, dependent upon running conditions, chainlike or clot-wise. Raman spectroscopy confirmed that the same elemental carbon was present in particles emitted from diesel and ethanol-fueled engines.
The investigations showed that the system used, with EGR and DPF combined, is highly effective in reducing particulate emissions from ethanol and diesel-fueled diesel engines. A general conclusion is also that the ethanol-fueled engine, equipped with emission control system or not, emitted lower particle mass, smaller particle sizes and approx. the same or a greater number of particles in the emissions than the diesel fueled engine.