Lukas Moeltner

To comply with stringent emission regulations, the deployment of hybridized powertrains is continuously expanding. However, architectures such as plug-in and parallel hybrids intrinsically reduce the overall runtime of the internal combustion engine (ICE). Because the battery state-of-charge (SOC) dictates intermittent engine activation, this operational strategy inevitably induces frequent cold-start events. This study investigates the thermal dynamics of commercial catalyst geometries (300–1200 cpsi, 2–8 mil) via 1D numerical simulations under real-world driving conditions. Without active heating, high-thermal-mass substrates unexpectedly outperform ultra-thin-wall variants by buffering against convective quenching during prolonged idling. However, integrating start–stop functionality halts cold exhaust flow, elevating mean temperatures and marginalizing geometric disparities. Evaluating electrically heated catalysts (EHCs) reveals that discrete preheating is highly inefficient due to rapid heat dissipation. Conversely, continuous closed-loop heating coupled with start–stop functionality sustains operational temperatures for over 90% of the cycle. Under continuous heating, substrate geometry ceases to dictate thermal performance; instead, it governs electrical efficiency. Low-thermal-mass monoliths minimize cumulative energy demand to 213 kJ (versus 277 kJ for high-mass variants), incurring a negligible CO₂ penalty. Consequently, future hybrid architectures must integrate lightweight EHCs to ensure sustainable emission control.

This study investigates the geometric parameters of commercially available or recently published models of catalyst substrates for passenger vehicles and provides a numerical evaluation of their influence on thermal behavior for use in urban areas. To ensure the plausibility of the results, a range of scenarios have been meticulously designed to replicate real operational conditions. To ensure a reliable basis for comparison, all geometries were standardized to the same gas-solid exchange surface by adapt the total monolith length. The simulation experiments conducted revealed that the primary role in question is played by the mass of the monolith and its internal surface area, while the heat transfer coefficient plays a secondary role. The necessity of adapting the geometry to the deployment scenario was demonstrated by comparing the performance of different scenarios. The employment of contemporary technologies, such as start-stop systems and automatic catalytic converter preconditioning, has also been factored. The study's findings suggest that geometries characterized by high cell density and low wall thickness, in conjunction with modern materials and intelligent engine control, are ready to become the norm for future ICE applications. This claim is particularly salient in the context of the requirements of mobile exhaust gas purification systems.

Fatty acid methyl esters (FAME) are the most frequently used substituent to fulfill the legally obliged addition of biofuels to fossil diesel aiming the reduction of greenhouse gas emissions in the transportation sector. Due to the chemical structure of FAME, the storage stability is limited and oxidation reactions can occur under certain circumstances, which can cause difficulties

In the field of emission control, the thermal behavior of catalytic converters plays a dominant role and is a determining factor for achieving current and future emission limits. This abstract reflects upon the potential of electrically heated catalytic converters exemplified by an exhaust gas after-treatment system for passenger vehicles. The demanding technical framework

The potential of direct heating of reactors is in this study exemplified by an aftertreatment system for passenger vehicles. Experimental and numerical investigations on thermal characteristics of catalyst supports were conducted for both a cordierite and a conductive hybrid ceramic substrate, whereby the latter offers the possibility of electric heating. A considerable reduction of critical heat‐up time after engine startup is evident for the conductive hybrid ceramic carrier, which consequently allows an increase in emission reduction efficiency.

This study investigates geometric parameters of commercially available or recently published models of catalyst substrates for passenger vehicles and provides a numerical evaluation of their influence on heat-up behavior. Parameters considered to have a significant impact on the thermal economy of a monolith are: internal surface area, heat transfer coefficient, and mass of the converter, as well as its heat capacity. During simulation experiments, it could be determined that the primary role is played by the mass of the monolith and its internal surface area, while the heat transfer coefficient only has a secondary role. Furthermore, an optimization loop was implemented, whereby the internal surface area of a commonly used substrate was chosen as a reference. The lengths of the thin wall and high cell density monoliths investigated were adapted consecutively to obtain the reference internal surface area. The results obtained by this optimization process contribute to improving the heat-up performance while simultaneously reducing the valuable installation space required.

Diesel engines, in combination with modern turbocharging and common rail injection systems, feature comparably high efficiencies coupled with favorable torque characteristics. Therefore, besides the utilization in commercial vehicles, diesel engines gained large market shares within the passenger car sector. The European Union regulates the deployment of biofuels and has issued several targets throughout the years; focusing on the urge to reduce carbon dioxide emissions, as well as on the growing demand for independence of fossil energy sources. This contribution presents investigations on fuel blends containing different shares of biomass to liquid, hydrotreated vegetable oils, and fatty acid methyl ester applied in a state of the art light-duty diesel engine. In general, the reviewed fuel blends exhibit good applicability for the utilization in the test engine with default settings of injection timing and exhaust gas recirculation; adjustments on the just mentioned parameters unveil further potential in terms of emissions and efficiency. Particularly the potential of biomass to liquid blends to partly mitigate the tradeoff between particulate matter and nitrogen oxides deserves distinct attention.