HEV and PHEV require an improved aftertreatment system to clean the exhaust gas in various driving situations. The efficiency of aftertreatment system is significantly influenced by the residence time of the gas in a catalyst which gas flow has generally strong pulsation. Simulation showed up to 70% reduction of exhaust gas emission if the pulsation could be completely attenuated. A new concept exhaust manifold was designed to minimize pulsation flow by wall impingement, with slight increase of pressure loss. Experimental results with new concept exhaust manifold showed exhaust gas emission were reduced 16% at cold condition and 40% at high-load condition.

Injection of fuel into the exhaust system is used to support the operation of exhaust gas aftertreatment systems. When injecting a fluid into the exhaust system, one major challenge is to design the exhaust system for optimal fuel distribution and to define an appropriate injection pressure. Simulation techniques are a suitable measure to support the corresponding development process. Hence, the project “Exhaust Fuel Injection” was initiated. Project target is the alignment of simulation methods and measurement techniques to predict the HC distribution in radial and axial direction at the inlet of a catalyst. This includes the definition of suitable measurement techniques to determine the hydrocarbon concentrations upstream of a catalyst. Transient 3D Computational Fluid Dynamics (CFD) simulation was used to model the fuel injection into a purpose-built exhaust system. The simulation results of the distribution of hydrocarbons at catalyst inlet in radial and axial direction are compared with measurements performed at an engine test bench. In total 18 variations were simulated and measured and twelve of them showed deviations in the uniformity index (UI) below 2 %. Only two variations resulted in deviations in UI above 3%. The trends in axial distribution showed good correlation between test bench and simulation. Especially the influence of injection pressure and operating point was predicted well by the simulation.

The development of the device and an experimental study was carried out to investigate the effect of liquid fuel on the oxidation characteristics of the DOC. The Ultrasonic generator was used to develop the device which can control the liquid droplet diameter and the number density by changing the frequency and carrier gas flow rate. In this study, a special emphasis was placed on oxidation behaviors of liquid droplet particles of n-Decane (C10H22) and 1-Decene (C10H20) in the order of 100 nm. Thus, oxidation tests were carried out with and without liquid droplets in that order. The previous study suggested that liquid fuel may adversely affect the oxidation characteristics of DOC. However, the experimental results showed no significant difference between the two oxidation characteristics. The reason for this was inferred that the liquid droplets flowing into DOC vaporize instantly, and they didn’t show inhibit behavior. It was concluded that the effect of fuel droplets in 100 nm order on oxidation characteristics of DOC was extremely small, and the experiments for lager droplet (in μm order) were needed to reveal the liquid fuel effect on DOC.

A Hydrocarbon is supplied to a diesel oxidation catalyst installed in an upstream of the diesel particulate filter for burning particulate matter deposited on the diesel particulate filter. In this study, we developed a thermal fluid numerical computation fluid dynamics code including a chemical reaction rate model which shows the influence of a hydrocarbon concentration and a type on the oxidation reaction of a hydrocarbon on a diesel oxidation catalyst. First, oxidation characteristics of four types of hydrocarbon fuels (Decane, Hexadecane, Eicosane, and 1-Methylnaphthalene) were investigated using a straight flow substrate carrying a platinum palladium catalyst. 1-methylnaphthalene greatly deteriorated the oxidizing ability, but there was no significant difference in the three kinds of alkane fuels. The difference of these oxidation characteristics could be reproduced by constructing a sub model expressing the difference between the adsorption characteristics of each hydrocarbon fuel and the oxidation inhibition effect due to adsorption. Further, the oxidation characteristics of the zeolite-containing catalyst were evaluated. As a result of the evaluation, the oxidation characteristics of the decane of the linear hydrocarbon did not change when compared with the catalyst which did not contain the zeolite, but the oxidation characteristics of the aromatic hydrocarbon 1-methylnaphthalene deteriorated. It was assumed that the zeolite had high adsorption capacity of 1-methylnaphthalene and a further inhibition of a reaction by adsorption was accelerated.