PR-457-18204-R01 Variable Fuel Effects on Legacy Compressor Engines Phase IV – Predictive NOx Modeling

The ultimate goal of this work is to improve the current control methods for large bore, lean burn natural gas engines in order to combat performance and emissions issues during variable fuel composition events. This will be achieved in the long term by simulating the effects of variable fuel composition on a large bore, natural gas engine and developing engine control strategies which work to mitigate adverse effects. The work of Phase IV adds onto previous work by enabling the prediction of NOxemissions in the validated, full-scale engine simulation of a Cooper-Bessemer GMWH-10C developed in Phase III. A sweep of fuel composition was also performed to assess the effect that variable fuel composition has on in-cylinder properties and NOxemissions.

Engine-out NOxwas predicted via a chemical kinetic mechanism which was implemented into the existing engine simulation. The mechanism dictates the composition of combustion products in each cylinder, including NO and NO2(NOx). NOxlevels were measured at the simulation exhaust to compare with the experimental NOxdata acquired as part of the data collection carried out in Phase III of this project. The prediction was tuned in order to achieve the closest prediction to real measured NOxvalues.

A preliminary sweep of fuel composition was completed by varying the mole fractions of ethane and propane within the natural gas compositions used in the simulation. Changes in in-cylinder pressure, location of peak pressure, in-cylinder temperature, and engine-out NOxwere evaluated based on their trend-wise behavior and compared qualitatively to expected results.