Effects of polyoxymethylene dimethyl ether (PODEn) blended fuel on diesel engine emission: Insight from soot-particle aerosol mass spectrometry and aethalometer measurements

Abstract

Polyoxymethylene Dimethyl Ether (PODE_n) is a promising diesel additive that can reduce particulate matter (PM) emission effectively, yet the changes in chemical and physical characteristics of PM emissions due to the application of PODE_n-diesel blended fuel remain largely unexplored. This laboratory study investigates the effects of PODE₃–diesel blended fuels (10, 20, and 30 vol% of PODE₃ mixed with diesel, denoted as P10, P20, and P30, respectively) on diesel engine emissions at 30% and 60% engine loads. Black carbon (BC) and organic aerosol (OA) were characterized in real time by a combination of a soot-particle aerosol mass spectrometer (SP-AMS) and a seven-wavelength aethalometer. Our results show that PODE₃ can significantly reduce both OA and BC emissions at both engine loads, with P20 producing the largest total PM mass reductions (>84%). The changes in the contribution of refractory oxygenated fragments to BC mass (i.e., C₃O₂⁺/C₃⁺ and C₃O⁺/C₃⁺) indicate that PODE₃ can reduce the functionality of soot surface/nanostructure. This is the first work showing that PODE₃ can affect the mixing state of BC and OA in diesel engine exhaust. Increasing PODE₃ blended volume can reduce the total fraction contribution of particle types that were composed of notably amounts of BC by mass. Furthermore, clustering analysis of single-particle data can identify two OA-dominated particle classes that were dominated by hydrocarbon fragments (C_xH_y⁺), and one of them had higher signal contribution from high molecular weight compounds. Lastly, the absorption Ångström exponent of BC (AAE_BC) can be enhanced with PODE₃ blended volume for both engine loads, and brown carbon (i.e., a light absorbing fraction of OA) can contribute up to ∼5% to the total aerosol absorption at the wavelength of 370 nm. Overall, this work provides insights into the potential impacts of PODE_n blended fuel application on the chemical and optical properties of BC and OA emitted from diesel engine combustion.