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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.

HC-SCR is more convenient when compared to urea-SCR, since for HC-SCR, diesel fuel can be used as the reductant which is already available onboard the vehicle. However, the DeNOX efficiency for HC-SCR is lower than that of urea-SCR in both low and high temperature windows. In an attempt to improve the DeNOX efficiency of HC-SCR, the effect of hydrogen were evaluated for the fresh and aged catalyst over 2 wt.% Ag/Al₂O₃ using a Euro-4 diesel engine. In this engine bench test, diesel fuel as the reductant was injected directly into the exhaust gas stream and the hydrogen was supplied from a hydrogen bomb. The engine was operated at 2,500 rpm and BMEP 4 bar. The engine-out NOX was around 180 ppm-200 ppm. H₂/NOX and HC₁/NOX ratios were 5, 10, 20, and 3, 6, 9, respectively. The HC-SCR inlet exhaust gas temperatures were around 215°C, 245°C, and 275°C. The catalyst volumes used in this test were 2.5L and 5L for both fresh and aged catalysts.

Biogas has been used as a fuel because of its lean-burn capability, low cost, and direct application to current engine systems. However, some performance loss occurs when using biogas as a fuel in a typical gas engine. To compensate that performance loss, hydrogen can be added to enhance combustion. Given the increasing need to substitute energy sources, many studies have been performed to examine the performance of biogas-hydrogen blends. In this study, experiments and simulations of a gas engine fueled with biogas were compared to confirm the accuracy of the simulation model under a fixed excess air ratio of 1.2 and spark timing of 16 CA BTDC. Performance predictions were made numerically for various spark timings, excess air ratios, and amounts of added hydrogen. With increased amounts of added hydrogen, the cylinder pressure and heat release rate increased and the ignition delay was reduced.

Soot particles accumulated in a DPF should be removed after a certain service time due to high pressure drop. The most common method is oxygen active regeneration which sometimes DPF cracking or melting. In this study, the authors aim to investigate the low temperature regeneration with hydrogen, which could prolong the DPF lifespan and facilitate CDPF regeneration efficiency. The DPF used in this research was coated with Pt/Al₂O₃ 25 g/ft₃ and all experiments were performed on engine test bench. Results showed that DPF regeneration can be realized at about 150°C or even lower. During regeneration, the inside temperature at front part (about 20 mm) of DPF was about 40°C higher than the other parts during regeneration. The maximum inside temperatures during regeneration depend only on the hydrogen concentration and soot oxidation can be calculated simply from the Arrhenius equation using the experimental temperatures.

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.