Measurement of Exhaust Emissions of Small Gasoline Engines Under Real-World Driving Conditions

The paper focuses on portable “on-board” instrumentation and methods for evaluation of exhaust emissions from scooters and various small machinery under real-world driving conditions. Two approaches are investigated here. In one, a miniature on-board system mounted on the equipment itself performs online measurements of the concentrations of the pollutants of interest (HC, CO, CO₂, NO_x, some property of particulate matter), and measurement or computation of the intake air flow. This approach has been used on a 50 cm³ scooter fitted with a 14-kg on-board system and driven on local routes. Measured concentrations of gaseous compounds, particle mass and total particle length were multiplied with the corresponding intake air flow computed from measured engine rpm, intake air manifold pressure and temperature. In the second approach, a full-flow dilution tunnel, gas analyzers and particle measurement or sampling devices are mounted on an accompanying hand cart or vehicle. This approach has been used with weedeaters, chainsaws, and lawnmowers. An improvised high-volume atmospheric sampler was used to collect milligrams of particulate matter from a lawmnower for subsequent analysis of polyaromatic hydrocarbons. Preliminary results suggest that measurement of real-world emissions from small engines with on-board or “coupled off-board” systems could be feasible.