Method Development and Application of Thermal Encapsulation to Reduce Fuel Consumption of Internal Combustion Powertrains 2019-01-0902
During cold start of an internal combustion engine, fuel consumption (CO2 emissions) is higher due to increased engine friction (Friction Mean Effective Pressure) until the optimum operating temperature of the engine is achieved. With the introduction of the WLTP emissions drive cycle the impact of cold start is recorded twice; once at the start of the 23°C external ambient drive cycle, and a second time at the restart of the 14°C external ambient WLTP drive cycle after the vehicle has soaked for 9 hours at 14°C.
By tackling the impact of the second cold start, the g CO2/km value for a vehicle can be reduced both on the cycle and in the real world. An approach is given to retain the heat generated during the first cycle and maintain engine and key fluid temperature (engine oil, transmission oil and engine coolant) until the start of the second cycle by using under bonnet thermal encapsulation.
Alongside this, a CAE method was developed to simulate the temperature and movement of air within the under bonnet thermal encapsulation zone using Thermal CFD, allowing the temperature decay for the key fluids to be predicted over the full duration of the vehicle soak, and therefore the fluid temperatures at the start of the second cycle to be known, without the need to run real time CFD.
A systems engineering approach was applied to deliver an integrated bill of materials whereby each component met several requirements, minimizing the number of additional parts on the vehicle. By using the new thermal CFD method, the impact of the thermal encapsulation design was analysed in a timely manner, allowing a development cycle for iterative improvements and the maximum g CO2/km reduction to be found.
Richard Owen, Adam Price, Juan Diego Barril Boleto, Suresh Sivasankaran, Wilko Jansen