Seungmok Choi

The effects of the combustion chamber geometry and a double-row nozzle on the diesel engine emissions:

This paper presents how injector nozzle distributions and the combustion chamber geometry affect the emission characteristics of diesel engines. The number of nozzle holes was increased from seven to 12 by a using double-row nozzle distribution to enhance the air–fuel mixing and the spatial distribution of the spray while avoiding spray overlap. The combustion chamber geometry was modified to have a wide shallow two-step bowl, which ensured adequate spray penetration with the double-row nozzle, to observe the influence of the spray–piston interaction on the combustion and emissions. Three hardware combinations (a seven-hole single-row nozzle with a conventional piston, a 12-hole double-row nozzle with a conventional piston, and a two-step piston) were tested in a single-cylinder direct-injection diesel engine under three boost and exhaust gas recirculation conditions. The injection timing was adjusted to result in a similar power by maintaining 50% of the total fuel mass fraction burned points for each hardware combination. For a conventional boost pressure (1.10 bar) and 30% exhaust gas recirculation, the 12-hole double-row nozzle with a conventional piston exhibited the best emission characteristics with a significant reduction in the particulate matter emissions. For a high boost pressure (1.30 bar) and 30% conventional exhaust gas recirculation, the nitrogen oxide emissions slightly increased and the particulate matter emissions decreased for the 12-hole double-row nozzle with a conventional piston compared with those for the seven-hole single-row nozzle. The two-step piston resulted in decreased particulate matter emissions but increased nitrogen oxide emissions under a high boost pressure. For 60% high exhaust gas recirculation, which is characterized by low-temperature combustion, the particulate matter emissions, the carbon monoxide emissions, and the total hydrocarbon emissions decreased simultaneously without an increase in the nitrogen oxide emissions using the 12-hole double-row nozzle with a two-step piston.

Detailed Investigation of Filtration and Regeneration Processes in a Diesel Particulate Filter System

This experimental work focuses on examining the detailed filtration and regeneration processes of diesel particulate filter (DPF) system under reaction with various gas emissions. To visualize these processes, we fabricated a unique thermal reactor visualized through a quartz plate, in which a 2-inch diameter × 6-inch long cordierite filter was placed. The cylindrical filter was bisected to examine internal microstructures. Other major components consist of a series of 6 kW electric heater units and a microscopic imaging system. This bench-scale DPF system is connected to the engine exhaust pipe, from where engine-out exhaust emissions were bypassed to the DPF system at a constant flow rate. The filtration and regeneration processes were then visualized to examine soot loading and oxidation phenomena on the channel surfaces, along with measurements of pressure drops across the filter. The mass of soot loading was accurately measured at the DPF inlet by a tapered element oscillating microbalance (TEOM). As a result, three consecutive filtration stages were identified from the pressure drop data and soot loading video images: (1) deep-bed filtration in which the pressure drop significantly increased, (2) transitional filtration, and (3) soot cake formation in which the pressure drop gradually increased to the end of filtration. The mass of soot loading was also measured at each stage. In the DPF regeneration experiment followed by the completion of soot loading, three different regeneration stages were identified, where the degree of pressure drop tended to be different each other. For regeneration, both raw exhaust emissions and NO2-added exhaust emissions were used as reactants for soot. The regeneration with NO2-added emissions was performed at two different DPF inlet temperatures, 400 and 500 °C. The results showed that the NO2-added exhaust emissions significantly enhanced regeneration by reducing the total regeneration time, while overall regeneration behaviours turn out to be similar between the two different reactant mixtures, both cases showing three different regeneration stages and a similar pressure drop trend.

Development of a Virtual CFR Engine Model for Knocking Combustion Analysis

The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (Argonne). Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory, is operated under Contract No. DEAC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in the said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. This research was partially funded by DOEs Office of Vehicle Technologies and Office of Energy Efficiency and Renewable Energy (EERE) under Contract No. DE-AC02-06CH11357. The authors wish to thank Gurpreet Singh, Kevin Stork, and Leo Breton, program managers at DOE, for their support. This research was conducted as part of the Co-Optimization of Fuels and Engines (Co-Optima) project sponsored by the U.S. DOE Office of EERE, Bioenergy Technologies and Vehicle Technologies Offices