Investigation of impact of fuel injection strategy and biodiesel fueling on engine emissions and performance

Open Access
- Author:
- Ye, Peng
- Graduate Program:
- Fuel Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 04, 2011
- Committee Members:
- Andre Louis Boehman, Dissertation Advisor/Co-Advisor
Randy Lee Vander Wal, Committee Member
Daniel Connell Haworth, Committee Member
Yaw D Yeboah, Committee Member - Keywords:
- biodiesel
engine
efficiency
emissions
fuel injection strategy
fuel injection pressure - Abstract:
- Both biodiesel fueling and changes of fuel injection pressure have significant impacts on diesel engine emissions. The investigations of their impacts on engine exhaust NOx and particulate matter emissions were conducted with an 8-cylinder common-rail turbocharged direct injection diesel engine using ultra low sulfur diesel fuel and soybean methyl ester (SME) – based biodiesel blends. The engine was running at moderate speed and different loads. Three fuel injection parameters: start of injection, fuel injection pressure and fuel injection duration were investigated to investigate their impact on engine emissions. With the control of fuel injection strategy, it is shown in this work that the biodiesel engine NOx emission penalty can be eliminated. A fuel spray, mixture stoichiometry field and lift-off length model was employed to explain the variations of NOx emission from biodiesel fueling and change of fuel injection strategy. Linear correlations between the average oxygen equivalence ratio of the fuel-air mixture at the autoignition zone near the lift-off length and brake specific NOx emissions were observed for all load conditions, regardless of fuel type. This confirms that the dominant factor that determines NOx emissions is the ignition event controlled by the oxygen equivalence ratio at the autoignition zone. The impact of late in-cylinder (post) injection combustion with biodiesel on lubricating oil dilution was investigated in this work. It is shown that this injection strategy could effectively decrease engine NOx emissions, while increase the CO and unburned hydrocarbon emissions. The lubricating oil dilution depends on the post injection timing: an increase in the lubricating oil dilution can be only observed if the post injection timing is later than 45º after top dead center. The impacts of fuel injection pressure on diesel and biodiesel soot morphology and oxidative reactivity were investigated. It is shown that compared with engine condition and fuel injection pressure, biodiesel has much less significant impact on soot morphology. For soot oxidative reactivity, it is found that both diesel and biodiesel soot from higher fuel injection pressure have higher reactivity, and biodiesel soot has higher reactivity than diesel soot when both of them are obtained from the same injection pressure. The optimized apparent heat release pattern for improved engine thermal efficiency was investigated with a zero-dimensional engine thermodynamic simulation. The results suggest that the optimized apparent heat release is a “wide and low” peak. The reason for this kind of heat release is that it can decrease the in-cylinder temperature and consequently decrease heat loss.