Characterization of a two-cycle engine and evaluation of its use as a particle generator

Particulate matter (PM) emissions have been characterized for a two-cycle engine with a subsequent evaluation of the effectiveness of the engine test stand as a laboratory particle generator. The particle generator could be used to produce particles with diameters ranging from less than 0.1 to 5 microns (µm) to assist in the laboratory evaluation of particulate matter air pollution control for small particles.

The two-cycle engine test stand was assembled utilizing a standard string trimmer with a two-cycle engine (25 cubic centimeter capacity) which was modified slightly for use in a laboratory environment. The two-cycle engine was selected given the fact that it uses a gasoline/lubrication oil mixture and is, therefore, a relatively high emitter of submicron particles compared to the 4-cycle engine which bums only gasoline. The particle concentrations emitted from the trimmer exhaust for various scenarios were measured using an optical particle counter (OPC) for particles in the 0.3 - 5.0 µm range and an Electrical Aerosol Analyzer (BAA) for emissions in the 0.01 - 1.0 µm range.

Based on the test runs utilizing the OPC and EAA, the engine PM emissions were characterized by particle number distribution, particle mass distribution, and mass emission rates for particle size ranges of 0.1 to 4.4 µm. Comparisons were also made of engine particle generation and engine speed measured in revolutions per minute (RPM). Parallel to the engine PM emissions characterization, the test stand was evaluated in regards to its practicality as a laboratory particle generator.