A combustion gas sampling system for a study of CO and NO history during engine expansion process

An electronically controlled and electromagnetically actuated combustion gas sampling valve with its operating circuitry has been built and used for a periodic sampling of burned gases from the combustion chamber of a single cylinder variable-compression-ratio spark-ignited reciprocating combustion engine. The sampled gases were instantly cooled and analyzed for 'CO' and 'NOx', concentrations using a nondispersive infrared gas analyzer. Results of single point sampling indicate that 'NOx' concentration apparently freezes in the post-flame region, whereas 'CO' destruction continues in the expansion phase. Measured results have been compared with the computed equilibrium mole fractions for various engine operating conditions.