Development of a Cycle-Resolved Mechanism for Carbon Monoxide Formation

This paper presents an investigation into CO formation in large-bore two-stroke cycle (2SC) lean-burn engines. On March 5, 2009, the Environmental Protection Agency (EPA) proposed a new rule to addressing National Emission Standards for Hazardous Air Pollutants (HAP) for existing stationary reciprocating internal combustion engines. Specifically, the 2009 Proposed Rule identifies carbon monoxide (CO) as a surrogate for HAP and requires reductions in CO for 2SC lean-burn engines. This future promulgation has created the need for a comprehensive kinetic CO formation model. The CO model itself integrates equilibrium concentration values of CO with the CO concentration created later in the cycle from the dissociation of equilibrium CO₂. The previously developed variable-geometry multi-cylinder Turbocharged-Reciprocating Engine Compressor Simulation (T-RECS) has been modified with a mechanism to model cycle-resolved CO formation using a calibrated kinetic reaction scheme. The simplified chemical kinetic CO reaction scheme has been tuned and validated with exhaust concentration data collected on a Cooper GMVC large-bore two-stroke cycle engine, and directly relates the impact of engine operating conditions and in-cylinder geometry.