Comparison of Supercharging Concepts for SI Engine Downsizing

The paper reviews the design of the supercharging system for a strongly downsized engine, to be installed on a sport car. Design is supported by cfd-1d engine simulations, using an experimentally calibrated model. The goal of the supercharging system is to deliver the required values of boost pressure at steady operating conditions, and to maintain or improve the full size engine response during acceleration (one of the most critical issues for downsized engines). Two options have been considered: 1) two-stage turbocharging, with two small turbochargers as a high-pressure stage, and one big turbo as low pressure stage (referred to as "TRITURBO"; 2) two-stage supercharging made up of one low pressure stage turbocharger and one electric supercharger (referred to as "E-SUPER"). It was found that both configurations not only allow the downsized engine to comply with the performance targets at wide open throttle, steady conditions, but they are also able to improve the transient response in comparison to the full size engine. TRITURBO is less expensive than E-SUPER, but also less fuel efficient and more difficult to install on the vehicle.