Effects of Environmental Factors on the Emissions Performance of Stoichiometric Natural Gas Engines with Three-Way Catalysts
Engine and catalyst emissions testing were conducted on the Cummins G5.9E, G8.3E and the GA855E stoichiometric engines under development to meet the 2008 NSPS 1048 EPA requirements for engines (2g/bhp-hr NOx, 4g/bhp-hr CO, ad 1g/bhp-hr VOC). The test periods ranged from 2,000 to 4,000 hours at rated or overload conditions. Periodic emission measurements were taken with a four-gas portable analyzer. Test conditions were subject to ambient changes (i.e., temperature, humidity, and variation of pipe line gas constituents). During testing, core samples from the catalyst were collected and sent to the catalyst manufacturer for the determination of deterioration effects. Results indicate that the engine control algorithm was robust and did not require adjustment for the test period. The testing also gave insight into the engine/catalyst deterioration rate and the need for periodic calibration of emission analyzers with certified calibration gas.