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Technical Paper

Characterization of Catalyzed Soot Oxidation with NO2, NO and O2 using a Lab-Scale Flow Reactor System

2008-04-14
2008-01-0482
Today's diesel PM reduction systems are mainly based on catalyzed particulate filter(CPF) systems. However, most of their reaction kinetics remain unresolved. Among others, the soot oxidation rate over catalyst is particularly important in the evaluation of the performance of the catalysts and the efficient control of CPF regeneration. This study, therefore, investigated the oxidation rate of carbon black (Printex-U) over various Pt supported catalysts using a flow reactor setup simulating diesel exhaust conditions. Compared to non-catalyzed soot oxidation, the oxidation rate of carbon black over Pt catalysts was to an extent shifted towards low temperatures. This activity enhancement of soot oxidation over a catalyst can be attributed principally to NO to NO2 conversion because NO2 oxidizes soot with much lower activation energy (Ea=60kJ/mol) than O2 (Ea=177kJ/mol).
Technical Paper

Experimental Investigation of Soot Oxidation Characteristic with NO2 and O2 using a Flow Reactor Simulating DPF

2007-04-16
2007-01-1270
Characteristics of soot oxidation were investigated with a carbon black (Printex-U). A flow reactor system which can simulate the condition of diesel particulate filter and diesel exhaust gas (1 bar, O2 0 ∼ 10%, NO2 200 ∼ 900ppm) was designed and used with the temperature programmed oxidation (TPO) and constant temperature oxidation (CTO) techniques. The temperature increase rate was 5°C/min for TPO experiments. From the experiments, the apparent activation energy for carbon oxidation with nitrogen dioxide was determined as 60 ± 3 kJ/mol with the first order of carbon in the range of 10∼90% oxidation and the temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of oxygen oxidation which was 177 ± 1 kJ/mol. When oxygen exists with nitrogen dioxide, the reaction rate increased with the concentration of oxygen. Its rate of increase was faster for low oxygen concentration and slower for high concentration.
Technical Paper

Flame Propagation and Knock Detection Using an Optical Fiber Technique in a Spark-Ignition Engine

1993-11-01
931906
In this research, an optical system for the detection of the flame propagation under the non-knocking and knocking conditions is developed and applied to a mass produced four cylinder SI engine. The normal flames are measured and analyzed under the steady state operating conditions at various engine speeds. For knocking cycles, the flame front propagations before and after knock occurrence are simultaneously taken with cylinder pressure data. In non-knocking and knocking cycles, flame propagation shows cycle-by-cycle variations, which are quite severe especially in the knocking cycles. The normal flame propagations are analyzed at various engine speeds, and show that the flame front on the exhaust valve side becomes faster as the engine speed increases. According to the statistical analysis, knock occurence location and flame propagation process after knock can be categorized into five different types.
Technical Paper

Low Temperature Active Regeneration of Soot Using Hydrogen in a Multi-Channel Catalyzed DPF

2010-04-12
2010-01-0562
Diesel particulate filter (DPF) systems are being used to reduce the particulate matter emissions of diesel vehicles. The DPF should be regenerated after certain driving hours or distance to eliminate soot in the filter. The most widely used method is active regeneration with oxygen at 550~650°C. Fuel penalty occurs when the exhaust gas temperature is increased. The low temperature oxidation technique is needed to reduce fuel consumption. In this study, we found that hydrogen could be used to decrease the PM oxidation temperature significantly on a catalyzed DPF (CDPF). The oxidation characteristics of PM with hydrogen supplied to CDPF were studied using a partial flow system. The partial flow system was used to control temperature and a flow rate independently. The CDPF was coated with Pt/Al₂O₃ 25g/ft₃, and a multi-channel CDPF (MC CDPF) with a square cross section of 1.65 cm width and length of 10 cm was used.
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