Using Variable
Valve Timing to Reduce Spark-Ignition Engine Hydrocarbon Emissions
Abstract:
The
objective of this study is to investigate the use of EVO to
reduce cold-start HC emissions. Experimental and computational
tools are being used to access how EVO affects in-cylinder and
exhaust port temperatures, HC oxidation, as well as catalyst
light-off time.
Background:
Driven by health and environmental concerns, automotive HC emission
standards continue to be tightened by the EPA and other regulatory
agencies. Although HC emissions per mile have been reduced to
2-3% of 1965 levels, further reductions continue to be mandidated
by the EPA. As these new standards are implemented, new technologies
must be developed.
Goals
of the work:
Since a warmed-up catalytic converter oxidizes nearly all engine-out
HC emissions, the first 30 seconds, before the catalytic converter
is warmed-up, represents the majority of the total HC emissions
for a US FTP75 cycle. One design option which may prove effective
in reducing initial HC emissions is to advance exhaust valve opening
(EVO). An advanced EVO increases exhaust gas temperature which
may "light off" the catalyst faster and promote exhaust
port HC oxidation. |
Researchers:
Stani Bohac
Dennis Assanis
Sponsors:
Ford Motor Company
Accomplishments:
Analytical models of combustion, exhaust flow, heat transfer,
and HC oxidation are being developed to suggest strategies of
using EVO, A/F ratio, and spark advance to reduce cold-start HC
emissions.
A
Ford V6 engine has been instrumented and is being run to test
the HC reduction strategies. It is currently possible to measure
exhaust HC concentration and temperature in various place in the
exhaust system on either a time or cycle-resolved basis. |
