High-Load Compression-Ignition Engine Emissions Reduction with Inverted Phi-Sensitivity Fuel using Multiple Injection Strategies 2019-01-0554
Inverted phi-sensitivity is a new approach of NOx reduction in compression-ignition (C.I.) engines. Previously, pure ethanol (E100) was selected as the preliminary test fuel in a single injection compression-ignition engine and has shown good potential for low engine-out NOx emissions under low and medium load conditions due to its inverted ignition sequence. At high load, the near-stoichiometric and non-homogeneous fuel/air distribution removes the effectiveness of the inverted phi-sensibility. Therefore, it is desirable to recover the combustion sequence in the chamber such that the leaner region is burned first and then the near-stoichiometric region. Consequently, the combustion near-stoichiometric region is inhabited, thus the temperature rise of that region is hindered and the formation of NOx is suppressed. To achieve the goal of remedying the mixture preparation thus the combustion mode and emissions when fueling with the target fuel, multiple injection strategies are applied to this study. A 0-D ignition delay analysis is first performed to illustrate ethanol’s potential to generate mixtures with inverted phi-sensitivity. 3-D engine CFD simulations are also conducted with the multiple injection strategies under high-load operations in a compression-ignition engine. The injection characteristics of optimized cases are examined in KIAV-3V coupled with a Genetic Algorithm(GA). An objective function is used to qualify the realization of optimized cases with minimized engine-out NOx, carbon monoxide (CO), soot and unburned hydrocarbon(UHC), while preserving the engine performance.
Suya Gao, Chia-Fon Lee
Univ. of Illinois at Urbana-Champaign, Univ of Illinois at Urbana-Champaign