Development of a Cycle-Resolved Mechanism for Carbon Monoxide Formation

Abstract

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.