PR-457-14201-R04 Variable NG Composition Effects on LB 2SC Integral Engines

Abstract

The overall goal of this project is to improve upon existing engine control strategies of large bore, fuel-lean natural gas engines in order to increase efficiency and maintain emissions compliance during variable fuel composition events. This will be done by simulating the effects of variable fuels in a natural gas engine, and if necessary, develop engine control methods. Phase III builds upon the work of previous phases by implementing detailed cylinder-level geometry, increasing the number of alkane species in the laminar flame speed and ignition delay solutions, and incorporating a prechamber model into the full-scale engine simulation of a Cooper-Bessemer GMWH-10C. The piston motion and port profiles were calculated from known engine geometry as a way to simulate cylinder compression and expansion as well as cylinder scavenging. The species considered were increased from binary mixtures of methane and ethane to quinary mixtures of methane, ethane, propane, butane, and pentane in order to capture the effects of heavier hydrocarbons. The laminar flame speed and ignition delay equations were developed using the same method utilized in the previous phase, but the laminar flame speed was implemented differently. Two predictive combustion simulations were developed in GT-Power. The first simplifies the combustion chambers into just one open chamber. The second includes the actual cylinder volumes: two small prechambers attached to the main chambers. Both of these models were tuned and validated against experimental data.