This research investigates the potential of gasoline compression ignition (GCI) to achieve low engine-out NOx emissions with high fuel efficiency in a heavy-duty diesel engine.
The experimental work was conducted in a model year (MY) 2013 Cummins ISX15 heavy-duty diesel engine, covering a load range of 5 to 15 bar BMEP at 1375 rpm. The engine compression ratio (CR) was reduced from the production level of 18.9 to 15.7 without altering the combustion bowl design. In this work, four gasolines with research octane number (RON) ranging from 58 to 93 were studied. Overall, GCI operation resulted in enhanced premixed combustion, improved NOx-soot tradeoffs, and similar or moderately improved fuel efficiency compared to diesel combustion. A split fuel injection strategy was employed for the two lower reactivity gasolines (RON80 and RON93), while the RON60 and RON70 gasolines used a single fuel injection strategy.
Building on the GCI experimental results at 15.7 CR and by performing closed-cycle, 3-D computational fluid dynamics (CFD) combustion simulations across several key engine operating points, an initial combustion recipe for high efficiency, low NOx GCI operation was conceptualized for a RON80 gasoline, including a new piston bowl design, tailored injector spray pattern, increased compression ratio, and engine thermal boundary conditions development.