Diesel exhaust emissions and particle hygroscopicity with HVO fuel-oxygenate blend

Fully paraffinic diesel fuel produced from hydrotreated vegetable oils (HVOs) is one alternative to increase the share of renewable energy in the transport sector. HVO fuel has also been shown to reduce exhaust emissions but, as the fuel contains no oxygen, even higher emissions reductions are possible by blending the HVO fuel with suitable oxygenate. From a large number of oxygenates, di-n-pentyl ether (DNPE) was chosen due to its favourable fuel properties (e.g. high cetane number and good solubility to diesel). In this paper, it was studied how fuel blend containing 2 wt.% oxygen (80 wt.% HVO and 20 wt.% DNPE) affects particulate and NOx emissions of a single-cylinder research engine. It was observed that the blend reduced emitted particulate mass 25-30% depending on load while the NOx emissions was changed under 5%. Thus, PM and NOx can possibly be both reduced e.g. by utilising EGR. In addition to emission reductions, the effects of the blend on the hygroscopic properties of produced exhaust particles were studied using a hygroscopic tandem differential mobility analyzer (HTDMA). The addition of oxygen into fuel led to a small increase in the hygroscopicity of exhaust particles.