This study aims to find a function describing the sulfur-associated particle emissions arising from the lubricant in heavy-duty diesel engines, hypothesizing that the sulfur consumed is multiplied by a linear transfer function (LTF).
Several studies have examined the impact of fuel sulfur on particulate matter emitted by heavy-duty diesel engines, finding a linear relationship between fuel sulfur and sulfur-associated particles. For every gram of sulfur in the fuel, the sulfur-associated particulate emissions increase by approximately 0.15 gram, higher engine loads increasing such emissions.
The LTF calculated for the fuel sulfur (0.15) is applied to the sulfur in the lubricant. The lubricant sulfur LTF is likely lower than the fuel sulfur LTF since, first, the lubricant is less exposed to combustion and high temperatures and, second, the molecules in the lubricant are longer hydrocarbons that are harder to combust/oxidize, i.e., 0.15 is an upper estimate of the LTF slope for the lubricant sulfur.
Normal engine oil will at most contribute 0.15 mg/kWh to the production of sulfur-associated particles (given an engine without after treatment). A given total particle volume will result in the maximum number of particles detected in the Particulate Measurement Program (PMP) setup if the particles are approximately 20 nm in diameter (assumed to be spherical). If the volatile particle remover in the PMP setup removes 99% of the sulfur-associated particles and they are 20 nm in diameter, the number of sulfur-associated particles originating from the lubricant will be in the range of 1011 particles/kWh. After-treatment devices promoting oxidation could potentially increase the production of sulfur-associated particles by 50 times.
Stockholm: KTH , 2010. , 18 p.