In order to increase overall energy efficiency of road vehicles, new systems that are able to recover vehicle's kinetic energy usually lost in dissipating process of frictional braking are being developed. This study was done to look at the effects of integrating Mechanical Flywheel-based Kinetic Energy Recovery System (KERS) into an automotive vehicle. Possible system architectures, due to different connection point of the KERS into the vehicle driveline, were proposed and investigated. Interaction of the system main components (IC engine, vehicle Gearbox, KERS subsystems) was analyzed and explained. In particular, three plots are proposed to introduce a graphical representation that can help the project manager to understand the effect of different parameter values related to the main system components on the overall system behavior during energy transfer from the vehicle to KERS and back.
Thermal Management Strategies for SCR After Treatment Systems
Nicolo Cavina, Giorgio Mancini, Enrico Corti, Davide Moro, Matteo De Cesare, Federico Stola
While the Diesel Particulate Filter (DPF) is actually a quasi-standard equipment in the European Diesel passenger cars market, an interesting solution to fulfill NOx emission limits for the next EU 6 legislation is the application of a Selective Catalytic Reduction (SCR) system on the exhaust line, to drastically reduce NOx emissions.
In this context, one of the main issues is the performance of the SCR system during cold start and warm up phases of the engine. The exhaust temperature is too low to allow thermal activation of the reactor and, consequently, to promote high conversion efficiency and significant NOx concentration reduction. This is increasingly evident the smaller the engine displacement, because of its lower exhaust system temperature (reduced gross power while producing the same net power, i.e., higher efficiency).
The proposal of the underlying work is to investigate and identify optimal exhaust line heating strategies, to provide a fast activation of the catalytic reactions on SCR. The main constrain is to limit the potential fuel consumption increase, and possibly to even increase global efficiency, and the chosen application is a small EU5-compliant diesel engine.
After an initial investigation, the research has been focused on main combustion control parameters, rather than on post-oxidation processes associated with late injections, in an effort to reduce eventual fuel penalties. The effect of each relevant engine control parameter has been analyzed on the test bench, observing the results in terms of exhaust system temperature and fuel efficiency. After this preliminary identification phase, different calibration strategies have been tested on the vehicle, executing several NEDC cycles. The most relevant comparisons are illustrated and critically discussed in the paper.