Masters Theses

Lori M. Snook

Date of Award

8-1993

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

J. W. Hodgson

Committee Members

W. S. Johnson, K. Nguyen, J. R. Parsons

Abstract

Proof-of-concept testing was performed to determine the effectiveness of a computer controlled air pump (CCAP) in reducing the unburned hydrocarbons (UHC) and carbon monoxide (CO) emitted from automobile engines. For the initial phase of testing, a prototype CCAP was designed and evaluated on a dynamometer test-stand at the University of Tennessee. This CCAP maintained the engine's exhaust at a stoichiometric air/fuel ratio by utilizing a second oxygen sensor mounted downstream from the catalyst. In this way, the catalyst's conversion efficiency for CO and UHC was always high, even if the engine was running rich. Results of this steady-state testing indicated that the CCAP was able to reduce UHC and CO emissions without a corresponding increase in oxide of nitrogen (NOx) emissions. Additionally, catalyst temperatures did not increase dramatically. For the second phase of testing, the CCAP was installed on a vehicle and four sets of emission tests were performed at the Environmental Protection Agency's Environmental Research Center Annex in Research Triangle Park, NC. As a result of testing, it was determined that the CCAP has merit as a system to decrease CO and UHC emissions during acceleration and power enrichment. However, the CCAP must be activated after the catalyst has lit-off (or it can delay catalyst light-off and result in poor emissions). NOx emissions remained essentially unchanged and catalyst temperatures did not increase by more than 200 °F. Recomendations for further study are made.

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