Abstract
Keywords - Passenger Car, Heat Management, Auxiliaries, Fuel Consumption, Comfort
Abstract - Rising requirements on safety, comfort and emissions constantly raise the number of the auxiliaries, their space requirement, total weight and above all their energy consumption. To limit additional fuel consumption the management of auxiliaries has to be optimized.
With the legally regulated NEDC cycle, on which the consumption data published by the car manufacturers is based, the auxiliaries are considered only insufficiently or not at all. Thus e.g. for the currently valid cycle the cabin heating is not operated. For the determination of the customer-relevant fuel consumption and the impact on the environment, regarding CO2 emissions, also heating and air conditioning must be considered. Taking this aspect into account an optimization is possible only with consideration of a customer-relevant driving behavior. With the help of transient numeric simulation the influence of auxiliaries on consumption and comfort can be examined. Beside vacuum pump, water pump, fan and generator also different heater configurations and the air conditioning are regarded. New concepts like an AC system in cooling mode and in heat pump mode are also investigated.
With the help of the heat management simulation software KULI, developed at MAGNA STEYR, a simulation model for a vehicle can be provided, which includes the engine, cooling system, heating and air conditioning systems and which is aligned with measurement data. The model enables the determination of the engine operating points for different vehicle configurations and thus the computation of fuel consumption and the examination of the heat balance. Using efficiency chains the fuel consumption of a certain benefit can be traced.
It is shown that for passenger cars auxiliaries such as water pump and vacuum pump have only a relatively small influence on fuel consumption and thus possess only a comparatively small potential for a reduction of fuel consumption. On the other hand for comfort-relevant accessories, like heating or AC, easily an increased consumption of 30 % can occur. In this range an optimization is promising, since the aggregates are usually dimensioned to cover the maximum requirements. From the simulation it also can be derived, with which concept the best efficiencies can be obtained in compliance with the given boundary conditions.