Numerical Simulation and Experiments of Reformed Fuel Blends in a Lean-Burn Spark-Ignited Engine

Premixed, lean burn combustion research has focused for years on extending the lean flammability limit while maintaining both stables ignition and turbulent flame propagation. Operating with a leaner air-fuel mixture results in a lower temperature conversion of reactants to products (i.e. reduced NOx) while maintaining thermal efficiency. The lean limit, at some level, is dependent on both the fuel transport and chemical properties. This work sets out to numerically explore the effect of reformed fuels on both fundamental flame stability and the performance/emissions tradeoffs of the engine. The numerical simulations were conducted for a range of reformed fuel blends (10–40%) as well as mixture equivalence ratios (0.35–0.6). The laminar flame speed results clearly define the regime of stable flame propagations for equivalence ratio/reformed fuel blend combinations. Subsequently, a validated and predictive quasi-dimensional engine simulation is used to simulate the performance/emissions characteristics of the complete engine system operating on the reformed fuel blends (10–50%) for a range of ignition timings, and air-fuel ratios. The performance trends define not only the misfire and detonation limits associated with the air-fuel blends but also the thermal efficiency/NOx tradeoffs.