Date of Award
5-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Automotive Engineering
Committee Chair/Advisor
Benjamin Lawler
Committee Member
Brian Gainey
Committee Member
Harsh Sapra
Abstract
Gasoline Compression Ignition (GCI) is an advanced compression ignition strategy which utilizes the high octane number of gasoline to improve diesel soot and NOx emissions by enabling partially premixed injections of fuel. GCI work in the literature typically uses single, double, or triple injection strategies, with higher numbers of injections noted for their ability to achieve low MPRRs, improved soot and NOx emissions, and higher efficiency. Thus, this study extends the literature by evaluating quadruple and quintuple injection strategies for continued improvement in engine efficiency and emissions.
The experiments in this work are conducted on a heavy-duty Detroit Diesel DD13 production engine which has been deactivated to a single cylinder and fueled with E10 certification gasoline. The study consists of a sweep of the first injection timing (SOI1) for a double, triple, quadruple, and quintuple injection strategy. All four strategies are PPC-diffusion strategies, where the final injection is an MCCI injection with most (>60%) of the fuel. As the number of injections increased, decreases in MPRR allowed for an increase in the PPC fraction from ~30% to ~39%.
For the double injection strategy, advancing SOI1 decreased the amount of fuel residing in pockets of sufficient local richness to ignite in the initial kinetically-controlled burn event, lowering MPRR, NOx, and soot emissions. Advancing SOI1 also retarded the start of combustion and diminished the size of the initial kinetic peak due to increased mixing, in turn increasing the size of the premixed spike of the main injection. However, advancing SOI1 carried a CO-dominated combustion efficiency penalty related to overmixing of portions of the first injection. Increasing from two to three injections removed a soot penalty seen at the earliest SOI1 in the double injection strategy from wall wetting, and was able to lower the MPRR and raise the efficiency of a heavily ringing double injection point.
For the quadruple and quintuple injection sweeps, the effect of sweeping SOI1 on heat release profile was minimal. However, these strategies did lower soot emissions relative to the triple injection strategy while maintaining comparable NOx emissions and GIFCE. The quadruple and quintuple injection strategies also lowered MPRR and allowed for an increase in PPC fraction. The combustion efficiency of the quadruple and quintuple injection strategies remained constant at 98.5%, which was lower than the triple injection points but higher than the double injection points with earliest SOI1. CO emissions were comparable with the highest values seen from double and triple injection strategies and uHC emissions were between the triple injection points and the worst double injection points.
Recommended Citation
Murray, Joshua, "Increasing the Number of Injections Per Cycle in a Gasoline Compression Ignition Strategy: An Experimental Study" (2026). All Theses. 4754.
https://open.clemson.edu/all_theses/4754
Author ORCID Identifier
0009-0001-6024-0343