Measured Emissions of Small Engines under Steady State and Transient Operation
Date Published: 1994-09-01
Paper Number:941806
DOI: 10.4271/941806
Citation:
Brereton, G., Morrison, K., Chishty, H., Schwartz, G. et al., "Measured Emissions of Small Engines under Steady State and Transient Operation," SAE Technical Paper 941806, 1994, doi:10.4271/941806.
Author(s):
G. J. Brereton - University of Michigan and Michigan State Univ.
K. Morrison - University of Michigan
H. A. Chishty - University of Michigan
G. Schwartz - University of Michigan
D. J. Patterson - University of Michigan
Abstract:
The exhaust emissions of off-road and utility engines have recently come under increasingly thorough scrutiny and are now becoming the subject of federal regulations. While the most straightforward emissions guidelines relate to steady-state engine performance, it is well known that duty cycles of many small engines have a transient content and that its significance can vary strongly from application to application. Hence, it is important to examine how measured emissions change when the transient content of a test cycle is varied, and what kinds of steady-state and transient test cycles might realistically imitate operational conditions. These questions have been addressed in an experimental study in which several small two- and four-stroke engines have been tested under steady state and transient cycles. The same tests were also carried out when these engines had been adjusted to operate at leaner air-fuel ratios, as might be required by forthcoming regulations. The results of this study reveal some appreciable differences between steady-state and transient emissions of engines, particularly at leaner air-fuel ratios.
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