Segelstrategien zur Senkung der CO2 Emission von P0 Hybridfahrzeugen

The future of driving will be increasingly electric. The next step will be 48V Mild Hybrid cars. Based on moderate costs and good CO2 saving benefit/cost ratio this allows a high number of cars to be using this system, thus reducing the total CO2 fleet emission substantially. The P0 Hybrid configuration, with the electric machine mounted similar to conventional alternators, allows easy integration in existing powertrains, because there is only little more space needed for the bigger electrical machine and for the water cooling, but it does not increase the length of the powertrain. Therefore it is an advantageous hybridization method for comparatively quick implementation in many car models or platforms. Passive engine-off coasting is known already without 48V Mild Hybrid Systems as an efficient CO2 saving measure in real driving. It is known to save less in WLTP, but unfortunately it does not allow emissions savings in NEDC. On the other side, active coasting, where an electric machine drives the car to hold the speed at a constant level, allows emission savings both in real driving and in test WLTP and NEDC test cycles. But for P0 Hybrids, active coasting requires dragging the internal combustion engine, what at first sight doesn´t seem to be efficient , considering the engine drag losses. Using car energy simulations, we demonstrate that a combination of active and passive coasting in a 48V Mild Hybrid car with P0 configuration saves substantially more fuel and reduces more CO2 emission than other utilization methods of the recuperated energy, such as active or passive coasting alone, or electric torque assist, or consumption of the energy in the electric 12V system. The influence of design variables like e.g. battery size, driving cycles and load scenarios is also evaluated and discussed. Validation of the simulation results is demonstrated by tests on an energy management test stand.

Autor: Dr.-Ing. André Körner
Co-Autor: Sebastian Kahnt
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