Particle Emissions from a Small Two-Stroke Engine: Effects of Fuel, Lubricating Oil, and Exhaust Aftertreatment on Particle Characteristics

Abstract

The effects of fuel and lubricating oil formulation and exhaust catalytic aftertreatment on physical and chemical characteristics of two-stroke engine exhaust particles were studied. The exhaust particles were produced with a professional chainsaw engine. The employed fuels were a 98-octane oxygenated, low-sulfur, low-aromatic reformulated gasoline, which served as a reference, and a 95-octane nonoxygenated alkylate gasoline that had no aromatics and olefins. The applied lubricating oils were a semisynthetic mineral-based oil and a biodegradable ester-based oil. In total eight fuel-lubricating oil-catalyst combinations were studied. The test runs were conducted on a test bench and exhaust was diluted in a full-flow dilution tunnel. The size and number emissions of the exhaust particles were measured with a scanning mobility particle sizer (SMPS). The organic carbon (OC) and elemental carbon (EC) composition of the particles were analyzed with a thermal-optical transmission analyzer (TOT). In addition, the inorganic ion and metal composition of the particles were quantified, and the gaseous total hydrocarbon (THC), carbon monoxide (CO), and nitrogen oxide (NOx) emissions were measured. The volatility characteristics of the exhaust particles were studied with a thermal desorption unit combined with the SMPS. The particle mass (PM) emissions ranged without catalyst from 2.9 to 3.4 g/kWh and with catalyst from 1.7 to 2.4 g/kWh, the catalytic converter thus reducing PM emissions by 19-50%. Without catalyst the alkylate fuel-biodegradable oil combination gave the highest particle mass emissions, but with catalyst with the same fuel-oil mixture the emissions were the lowest. The count median diameter (CMD) of the particles ranged from 57 to 123 nm. Without catalyst, the alkylate fuel-biodegradable oil combination gave the lowest number emissions, but with catalyst with the same fuel-oil combination the emissions were the highest. The catalytic converter reduced the particle size by 22-56 nm, but it also increased the number emissions by a factor of 1.3-2.6. In thermal analysis 88-98% of the exhaust particle volume proved to be volatile, the solid fraction consisting of elemental carbon and metal residues. With the mineral-based lubricating oil, the metal residues appeared in two modes at the evaporation temperatures of 350 • C and higher, while in the particles produced with the biodegradable oil the residues were unimodally distributed.

Fine Particulate Matter Emissions Inventories: Comparisons of Emissions Estimates with Observations from Recent Field Programs

“…Alander et al 48 found that PM emissions from a single two-stroke chain saw could vary by 4% to 16% even when tested under a single set of operating conditions. When conditions such as presence of a catalyst and fuel type and lubricating oil type were varied, the emissions differed by almost a factor of two.…”

Is Alaska Truly the Great Escape from Air Pollution? - Long Term Source Apportionment of Fine Particulate Matter in Fairbanks, Alaska

“…For diesel emission, EC was higher compared to the gasoline vehicle profile. Zn and Ca are additives in motor oil, and Fe is released from brake pads and muffler ablation (Garg et al, 2000;Maykut et al, 2003;Alander et al, 2005;Wahlin et al, 2006;Zhao and Hopke, 2006). The winter contributions were higher than other seasons.…”

The Difference Between the Physical Properties of Petrol and Alkylate Petrol and Impact on the Exhaust Gas of a Two-Stroke Engine

“…Part-load tests were run on an engine and the exhaust gas emission measured, like in other similar tests [13,16]. Fractional distillation characteristics were carried out with test fuels as well as the test for assessing lubrication properties [12].…”

“…In these cases, the difference between fuels lies in the fact that in the alkylate petrol produced specifically for two-stroke engines, the lubrication additive is selected and added by the manufacturer company. Alander et al (2005) states that in comparison to the use of regular petrol, the proportions of, for example, CO and HC in the exhaust gas decrease when alkylate petrol for a two-stroke engine is used [13]. Magnusson et al (2000Magnusson et al ( , 2002 draws the conclusion that the exhaust gas emission increases as alkylate petrol is used [14,15].…”

“…For that reason, the exhaust gas emission of two-stroke engines without catalysts might significantly differ from the exhaust gas of engines equipped with one. The impact of alkylate petrol and blends of alkylate petrol and oil produced specifically for two-stroke engines on the exhaust gas of two-stroke engines has been studied as well [13]. In these cases, the difference between fuels lies in the fact that in the alkylate petrol produced specifically for two-stroke engines, the lubrication additive is selected and added by the manufacturer company.…”