*Article* **Electric Turbocharging for Energy Regeneration and Increased Efficiency at Real Driving Conditions**

### **Pavlos Dimitriou 1,\*, Richard Burke 1, Qingning Zhang 1, Colin Copeland 1 and Harald Stoffels 2**


Academic Editor: Jose Ramon Serrano Received: 23 January 2017; Accepted: 14 March 2017; Published: 1 April 2017

**Abstract:** Modern downsized internal combustion engines benefit from high-efficiency turbocharging systems for increasing their volumetric efficiency. However, despite the efficiency increase, turbochargers often lack fast transient response due to the nature of the energy exchange with the engine, which deteriorates the vehicle's drivability. An electrically-assisted turbocharger can be used for improving the transient response without any parasitic losses to the engine while providing energy recovery for increasing overall system efficiency. The present study provides a detailed numerical investigation on the potential of e-turbocharging to control load and if possible replace the wastegate valve. A parametric study of the optimum compressor/turbine sizing and wastegate area was performed for maximum torque, fast response time and energy regeneration across the real driving conditions speed/load area of the engine. The results showed that the implementation of a motor-generator could contribute to reducing the response time of the engine by up to 90% while improving its thermal efficiency and generating up to 6.6 kWh of energy. Suppressing the wastegate can only be achieved when a larger turbine is implemented, which as a result deteriorates the engine's response and leads to energy provision demands at low engine speeds.

**Keywords:** turbocharger; e-turbo; boosting; electrically-assisted; turbo-compound; energy regeneration; internal combustion engines; 1D simulation
