Assessment of efficient powertrain concepts in real driving conditions
Driven by stringent CO2 constraints, engine friction and thus thermal operating strategies are key levers in the development of efficient powertrains. Conventional approaches for friction assessment are limited with respect to their validity for realdriving conditions. Thus, the potential in terms of fuel consumption and emission reduction cannot be fully exploited.
In order to be able to assess the impact of friction reduction measures on fuel efficiency, the entire vehicle and representative driving cycles have to be taken into consideration. Based on physical models the interaction between temperature dependent component friction and vehicle warmup can be captured properly.
This paper discusses the AVL friction toolbox which is based on physical and semiempirical models. The toolbox creates speed, temperature and load dependent FMEP maps which are input to a global engine and vehicle model. This model is founded on a VTMS (vehicle thermal management system) approach. Amongst others, it covers longitudinal dynamics, gear ratios as well as all thermally relevant systems like cooling and lubrication circuits.
The capabilities of the aforementioned method are demonstrated on a passenger car gasoline engine. The study depicts the impact of measures like piston ring tangential force, switchable piston cooling in combination with variable oil pump, water pump and tailored operating strategies.
KeywordsVehicle Model Driving Cycle Piston Ring Coolant Pump Engine Friction
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