Numerical Investigation of Heat Retention and Warm-Up with Thermal Encapsulation of Powertrain



WCX SAE World Congress Experience
Authors Abstract
Powertrain thermal encapsulation has the potential to improve fuel consumption and CO2 via heat retention. Heat retained within the powertrain after a period of engine-off, can increase the temperature of the next engine start hours after key-off. This in turn reduces inefficiencies associated with sub-optimal temperatures such as friction. The Ambient Temperature Correction Test was adopted in the current work which contains two World-wide harmonised Light duty Test Procedure (WLTP) cycles separated by a 9-hour soak period. A coupled 1D - 3D computational approach was used to capture heat retention characteristics and subsequent warm-up effects. A 1-D powertrain warm-up model was developed in GT-Suite to capture the thermal warm-up characteristics of the powertrain. The model included a temperature dependent friction model, the thermal-hydraulic characteristics of the cooling and lubrication circuits as well as parasitic losses associated with pumps. A 23°C WLTP cycle was run via the 1D model, key fluids and solids temperatures around the engine bay calculated at the end of the 1st WLTP cycle were then imported into a 3D heat retention model, in which the transient 3D computational fluid dynamics and heat transfer coupled simulation was initiated to model the full-geometry vehicle for a 9 hours static soak period. The cool-down behaviors of the coolant and oils were predicted from the 3D model and the temperatures at the end of the soak were fed back to the 1D warm-up model to carry out the second WLTP cycle simulation at 14°C ambient condition.
A coupled 1D-3D heat retention modelling method predicted both warm-up and cooldown characteristics to within circa ±3 °C of vehicle test data over the entire ATCT test. The impact of thermal encapsulation was clearly shown, whereby coolant and oil temperatures at the end of the 9 hour soak period were 6°C and 10°C higher with encapsulation respectively, which led to a fuel consumption improvement in the order 1% over the post-soak 14°C WLTP through retaining heat.
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Yuan, R., Price, C., Kasurkar, R., Spenley, M. et al., "Numerical Investigation of Heat Retention and Warm-Up with Thermal Encapsulation of Powertrain," SAE Technical Paper 2020-01-0158, 2020,
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Apr 14, 2020
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Technical Paper