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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).

Diesel engines are the most commonly used power plant of freight and public transportations in the world. Also, the newly developed injection system, Common Rail system, increases the demands for both light and heavy duty diesel vehicles. On the other hand, stringent emission regulations are being proposed with growing concern on NOx and PM emissions from diesel engines. Future emission regulations require advanced emission control technologies, such as EGR and SCR. Exhaust gas recirculation (EGR) is a commonly used technique to reduce NOx emission. In this paper, a model-based investigation was conducted to compare the effect of high pressure loop (HPL) EGR and low pressure loop (LPL) EGR system on NOx level and BSFC of a heavy-duty diesel engine. A WAVE model was created to simulate EURO 3 engine and each component of the engine was modeled using CATIA and WaveMesher.

NO2 is an effective soot oxidizer operating at lower temperatures than O2. The effect of pure NO2 on soot oxidation was evaluated and compared with the gas treated by plasma, which initially consisted of NO, O2, and hydrocarbons. The cutout of a commercial DPF was used and the pressure difference across the DPF was monitored for an hour. The concentration of NO/NO2, CO, CO2 at the outlet of the DPF was measured as a function of time. CO and CO2 concentration was measured periodically by gas chromatography. The experiment was performed at 230, 250, 300, 350°C. When NO2 only was used as an oxidizing agent, there was a close relationship between the decrease of the pressure difference across the DPF, the CO and CO2 concentration at the outlet of the DPF, and the back conversion of NO2 to NO.

In this study, compositions, size distributions and activation energy in oxidation of diesel PM were investigated. Benzene (C6H6) was mixed to diesel fuel as a promoter of PM formation, and further, ferrocene (Fe(C5H5)2) was added as a promoter for oxidation processes during in-cylinder combustion and after-treatment. The effect of those additions on the PM characteristics was discussed on the basis of measured results such as SOF and dry-soot ratio in PM, primary and aggregate particle size distributions of PM, activation energy of PM oxidation, and PM components with elemental analysis. As a result, it was shown that ferrocene had special effect on the PM size distribution and the activation energy.

For gasoline engine, thermal efficiency can be improved by using lean burn. However, combustion instability occurs when gasoline engine is operated on lean condition. Hydrogen has features that can be used for improving combustion stability of gasoline engine. In this paper, an experimental study of hydrogen effect on lean limit was carried out using a four-cylinder 2.0L turbo gasoline direct injection engine. The engine torque was fixed at 110Nm on 1600RPM, 2000RPM and 2400RPM. The results showed that lean limit was extended and brake thermal efficiency was improved by hydrogen addition. Especially, at lower engine speed, the large improvement of lean limit was achieved. However, improvement of brake thermal efficiency was achieved at high speed. HC and CO2 emissions were decreased and NO emissions increased with hydrogen addition. CO emissions were slightly reduced with hydrogen addition.

CARS temperature measurements were carried out both in a constant volume combustion chamber and in a spark-ignition engine. The CARS temperature measurement under engine-like condition was validated by comparing the unburned gas temperatures for premixed propane-air flame in a constant volume combustion chamber obtained by CARS with predicted temperatures of 2-zone flame propagation simulation model. There was good agreement between the predicted temperatures and the mean values of 10 CARS measurements. The standard deviation of 10 measurements at each measuring timing was about ±40 K. End-gas temperatures were measured by CARS technique in a conventional 4-cylinder DOHC spark-ignition engine with the engine motoring and firing. The measured motoring temperature matched well with the adiabatic core temperature calculated from the measured cylinder pressure. The engine was fueled with primary reference fuel (PRF80) of 80% iso-octane and 20% n-heptane by volume.

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.

Plasma-catalyst (Ag, Au/Al2O3) systems were applied to NOx reduction in a model lean-burn engine exhaust gas. Also, DeNOx test of real diesel exhaust gas was performed by plasma-Ag/Al2O3 system. In the case of model exhaust gas, the catalytic activity for NOx reduction was enhanced by the assistance of plasma in the wide temperature range. The NOx conversion efficiency of plasma-Ag/Al2O3 was 40∼90% under the condition of C3 H6 3200ppm (C1/NOx = 5.96) and 10% O2 over the temperature range of 250∼400°C. The plasma-Au/Al2 O3 system showed remarkable low temperature NOx reduction activity at 100∼250°C. The real engine full flow test was performed for 70% of the full load and at engine speed of 1500rpm. NOx removal of 46% from the diesel exhaust gas was achieved by the plasma-Ag/Al2O3 catalyst system at 364°C(C1/NOx = 6). In the case of higher C1/NOx = 10, the NOx conversion increased up to 73% at 381°C. Also, DeNOx engine tests were performed for full load of 1500, 2000 and 2500rpm.

The oxidation of soot (carbon black) which is assisted by Pt/CeO2 catalyst is studied using a flow reactor system simulating the condition of diesel exhaust. In this study, the temperature programmed oxidation (TPO) scheme is mainly used for different NO and O2 concentrations and soot oxidation rate is evaluated by monitoring both CO and CO2 concentrations. Pt/CeO2 catalyst lowers the temperature of the peak CO/CO2 concentrations significantly when there is either NO or O2. Oxidation starts at 200°C and the peak CO2 concentration is observed at 360°C, which depends on the amount of catalyst and NO concentration. The effect of catalyst on NO2 recycling is also investigated. For this purpose, two different types of sample have been prepared. For the mixed case, 10mg of carbon black is mixed with 50mg of Pt/CeO2 catalyst under conditions of loose contact. For the unmixed case, the catalyst layer is placed on top of soot layer without mixing.

Among the recent research ideas to reduce hydrocarbon emissions emitted from SI engines till light-off of catalyst since cold start are those exploiting non-thermal plasma technique and photo-catalyst that draws recent attention by virtue of its successful application to practical use to clean up the atmosphere using the feature of its relative independence on temperature. Based on the previous research results [6] obtained with model exhaust gases using an experimental emissions reduction system that utilizes the non-thermal plasma and photo-catalyst technique, further investigation was conducted on a production N/A 1.5 liter DOHC gasoline engine during cold start to warm-up. For the effects of non-thermal plasma-photocatalyst combined reactor, 10% concentration reduction was achieved with the fuel component paraffins, and the large increase in non-fuel paraffinic components and acetylene concentrations were similar to those of base condition.