The Potential Benefits of Intake Air Oxygen Enrichment in Spark Ignition Engine Powered Vehicle

A production spark ignition engine powered vehicle (3.1-L Chevrolet Lumina, model year 1990) was tested with oxygen-enriched intake air containing 25 and 28% oxygen by volume to determine if (1) the vehicle would run without difficulties and (2) there would be emissions benefits. Standard Federal Test Procedure (FTP) emissions test cycles were run satisfactorily without vehicle performance anomalies. The results of catalytic converter-out (engine with a three-way catalytic converter in place) emissions showed that both carbon monoxide and hydrocarbons were reduced significantly in all three phases of the emissions test cycle, compared with normal air (21 % oxygen). Carbon monoxide emissions from the engine (with the three-way catalytic converter removed) were significantly reduced in the cold-phase of the test cycle. The catalytic converter also had an improved carbon monoxide conversion efficiency under the oxygen-enriched air conditions. Detailed results of hydrocarbon speciation indicated large reductions in 1,3-butadiene, formaldehyde, acetaidehyde, and benzene from the engine with the oxygen-enriched air. The catalytic converter-out ozone was reduced by 60% with the 25%-oxygen-content air. Even though there was a significant increase in NOx both from the engine-out and the catalytic converter-out emissions, we believe that they can be ameliorated in the near future with new control technologies. On the basis of estimates made from current data, several production vehicles that had low NO_x emissions could meet the 2004 Tier II emissions standards with the 25%-oxygen-content air. The results indicate that by adding oxygen to the intake air instead of adding it to the fuel (as in oxygenated gasoline), the same emissions reduction goal can be achieved.