HYDROGEN ASSISTED DIESEL COMBUSTION

Author:

Lilik, Gregory Kenneth

Graduate Program:

Energy and Geo-Environmental Engineering

Degree:

Master of Science

Document Type:

Master Thesis

Date of Defense:

March 24, 2008

Committee Members:

Andre Louis Boehman, Thesis Advisor/Co-Advisor

Keywords:

HCCI
LTC
HYDROGEN ASSISTED DIESEL COMBUSTION
PCCI
Hydrogen
Diesel

Abstract:

In this study, the effect of hydrogen assisted diesel combustion on conventional and advanced combustion modes was investigated on a DDC/VM Motori 2.5L, 4-cylinder, turbocharged, common rail, direct injection light-duty diesel engine, with exhaust emission being the main focus. Hydrogen was substituted for diesel fuel on a percent energy basis of 0%, 2.5%, 5%, 7.5%, 10% and 15%. The conventional combustion modes studied consisted of four engine combinations of speed and load (1800 rpm at 25% of maximum output, 1800 rpm at 75% of maximum output, 3600 rpm at 25% of maximum output, and 3600 rpm at 75% of maximum output). A significant retarding of injection timing by the diesel fuel injection timing map in the engine’s electronic control unit (ECU) was observed during the increased aspiration of hydrogen. The retarding of injection timing resulted in significant emission reductions, however, the same emission reductions were achieved without aspirated hydrogen by manually retarding the injection timing. Subsequently, hydrogen assisted diesel combustion was conducted, with the pilot and main injection timings locked, to study the effects caused directly by hydrogen addition. Hydrogen assisted diesel combustion resulted in a modest increase of NOX emissions and a NO / NO2 trade-off in which NO emissions decreased and NO2 emissions increased, with NO2 becoming the dominate NOX component in some circumstances. Increased aspiration of hydrogen resulted in PM, and HC emissions which fluctuated with speed and load. Predominantly, CO and CO2 decreased with the increase of hydrogen. The aspiration of hydrogen into the engine modestly decreased fuel economy due to the reduction of oxygen in the cylinder charge. In the advanced combustion portion of the study, the engine was operated under a partially-premixed charge compression ignition PCCI mode known as high efficiency clean combustion (HECC), in which NOX and PM emissions dramatically decreased while fuel economy was maintained. Hydrogen assisted diesel combustion was performed while the engine operated in the HECC mode, which resulted in emissions and combustion impacts similar to those observed in the conventional combustion modes.