Analysis Research On Turbo Generating System For IC Engine Waste Heat Recovery

From the perspective of internal combustion engine (ICE) heat balance, only 30% to 40% of the energy generated by the fuel is used as power output while about 60% to 70% of the energy is eliminated into the atmosphere. In the real life situation, the lost is nearly 80%. The combination of ICE and turbo generator is an effective way to increase the system overall efficiency and reduce fuel consumption. The main difficulties of ICE turbo generating technology include the low efficiency of the combined cycle and poor adaptability under driving conditions.A through-flow turbo generating model is used to analyses the interaction process between ICE and turbine. And a turbo-generating performance test bed is established to validate the model. On the basis of this turbo generating model, an integrated simulation platform about ICE turbo generating system is established by the re-development of a commercial software GT-Power.There are two existing turbo generating schematics: one schematic with an electric turbocharger and another schematic with a turbo generator in series with turbocharger. Based on the simulation platform, a detailed comparative study on existing schematics is carried out in this paper on a turbocharged gasoline engine. It is found that the system efficiency under low and middle load cannot be increased by using existing turbo generating schematics.A schematic which has a power turbine in parallel with the turbocharger is proposed to overcome the shortcoming of existing schematics. Besides, the influence of power turbine on the whole system and the design requirement of the power turbine is studied. A power turbine which features high efficiency at low mass flow rate is designed. Simulation result shows that ICE fuel economy can be improved greatly by using the paralleled turbo generator. The highest efficiency improvement is more than 8%. And the fuel economy improvement is 4.7% under US06 driving cycle and 1.8% under FTP75 driving cycle, compared with the original prototype engine.