Fuel Economy and Cabin Heating Improvements Thanks to Thermal Management Solutions Installed in a Diesel Hybrid Electric Vehicle



Authors Abstract

With the aim of reducing CO2 emissions, several solutions exist presenting different performances and costs. Hybrid electric vehicle is one of the most efficient solutions and lead to fuel consumption and CO2 emissions reduction of 10 to 60 % compared to conventional vehicle and depending on the level of hybridization and the considered speed cycle.

In the context of the European project Hi-CEPS (Highly integrated Combustion Electric Propulsion System), several thermal management solutions have been investigated with the aim of increasing the global vehicle efficiency and tackling hybrid-vehicle-specific cabin comfort challenges such as cabin heating.

Intermittent operation of the engine in a hybrid electric vehicle (Stop & Start, pure electric vehicle mode) has detrimental effects on engine and cabin warm-up. Indeed, a longer time is usually required to reach operating coolant and oil temperatures, hence a longer time before the engine friction is minimized and before the thermal steady-state combustion efficiency is reached.

Models of the vehicle thermal systems have been developed and coupled to Ricardo's vehicle systems model enabling the estimation of fuel consumption and CO2 emissions.

The coupled model was used to assess systems and strategies (like latent or sensible heat storage tank for coolant or lubricant, zero coolant flow-rate inside engine during warm-up but also electric thermostat during thermal steady-state driving conditions) in terms of fuel consumption and/or cabin comfort improvements.

The article will present the simulation's methodology, how the simulation can help to understand the thermal issues encountered on a hybrid electric vehicle and also the fuel consumption and CO2 emissions decrease thanks to different thermal management solutions.

Andrew Sutherland, Ricardo Inc.

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Mar 7, 2012
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