Analysis and Simulation of Hybrid Electric Turbocharger and Application on ICE and HEV

Abstract

Hybrid electric turbocharger (HET) has been proven to be an effective pathway to eliminate turbo-lag and improve ICE fuel economy. But HET is not appropriate for traditional vehicles. It is because that the low voltage electrical system (12 V) of these vehicles is not capable of handling the electrical current in excess of 150 A. While HEV has achieved considerable market share in recent years, this provide more flexibility for the application of HET, particularly as while energy recovered by HET can effectively applied on HEVs. The improvement of fuel economy by the combined HET and HEV is investigated in this chapter. For the purpose of exhaust energy recovery, the relevant exhaust gas temperature and availability from a Higer hybrid bus were analysed. An exhaust energy recover model based on the availability balance method is developed to evaluate the potential energy which can be recovered in a practical hybrid implementation. Experimental ICE data are used as inputs for the model. The ICE with HET was modelled and validated by experimental data. And the steady-state fuel benefits of the HET were studied. Finally the engine model was implemented to HEV model in GT-DRIVE to predict the potential of the HET benefit for fuel economy benefits in UDDS driving cycle. The exhaust availability calculation results show that 10~15 % of the exhaust energy could be recovered, which is slightly higher than the prototype vehicle. This may be caused by the constant load conditions for the ICE in the HEV, and this is a potential advantage for the implementation of HET on HEV. The low-speed steady-state characteristic of ICE is improved by increasing volumetric efficiency. The transient simulation shows that HET could effectively improve ICE turbo-lag. The simulation under driving cycle indicates that combined HET/HEV technology could reduce fuel consumption by 25 %, which is slightly higher than middle-hybrid vehicle. Since the ultra-high speed motor is not commercialized, combined HEV and HET could only be applied on commercial vehicles because of the relatively low turbocharger speed required. Because of the high exhaust temperature, cooling system design of the high speed motor is very important and is now under investigation. Combined HET/HEV technology could significantly improve fuel economy without extra weight and cost. This novel configuration also provides new flexible energy utilization method. The HEV diesel engine’s exhaust temperature and availability characteristics were studied. HET is a more applicable technology on HEVs than traditional vehicles due to the high voltage of the on-board electric system and HEV engine working characteristic. Simulated results show that HET could effectively balance engine working by improving engine low speed torque output and high speed exhaust heat recovery. Combined HET/HEV technology could significantly improve ICE fuel consumption. Simulation results show that this novel configuration could improve ICE fuel consumption by 25 % during UDDS driving cycle.