Influence of Cabin Heating Strategies on Fuel Consumption and Emission Behavior of an Automotive Diesel Engine

Even in actual, combustion-engine powered vehicles, cabin-heating in winter conditions is mainly provided by the heat rejection of the drivetrain. Consequently, development goals to achieve higher effective efficiency and lower fuel consumption entail decreasing waste heat production. As a result, diesel engine-driven vehicles, in particular, have to deal with insufficient heat supply to the vehicle cabin under low ambient temperatures. In order to satisfy the thermal needs of the passengers under those conditions, it is common practice to install electrical heaters in the climate control system of the vehicle. Though real driving emissions are targeted in media reporting nearly every day, the interactions between emissions, fuel consumption and cabin heating are not addressed. The next logical question is, how heating strategies of conventional and hybrid vehicles have to be designed to keep fulfilling future legal requirements. As there is a strong dependency on the operational strategy of the powertrain and heat-up behavior of the vehicle cabin, present investigations discuss the influence of different engine operation modes of a state-of-the-art automotive diesel engine on its energy balance and its emissions. Due to the fact that heat rejection is mostly deficient under low-load conditions, the present study focuses on those operating points. Experiments on an engine test bench are used to gain knowledge about thermal behavior. Primarily, the effect of parameters affecting the combustion process and the intake system are investigated. Additionally, load point shifting due to electrical loads is examined. As an evaluation criterion, a new kind of efficiency factor is introduced. Finally, this paper outlines how engine concepts and operation modes have to be designed to reduce emissions and fuel consumption on the one hand, and to maintain passenger comfort inside the vehicle cabin on the other.