Analysis of a SuperTurbocharged Downsized Engine Using 1-D CFD Simulation 2010-01-1231
The VanDyne SuperTurbocharger (SuperTurbo) is a turbocharger with an integral Continuously Variable Transmission (CVT). By changing the gear ratio of the CVT, the SuperTurbo is able to either pull power from the crankshaft to provide a supercharging function, or to function as a turbo-compounder, where energy is taken from the turbine and given to the crankshaft. The SuperTurbo's supercharger function enhances the transient response of a downsized and turbocharged engine, and the turbo-compounding function offers the opportunity to extract the available exhaust energy from the turbine rather than opening a waste gate.
Using 1-D simulation, it was shown that a 2.0-liter L4 could exceed the torque curve of a 3.2L V6 using a SuperTurbo, and meet the torque curve of a 4.2-liter V8 with a SuperTurbo and a fresh-air bypass configuration. In each case, the part-load efficiency while using the SuperTurbo was better than the baseline engine. For the bypass configuration, the full-load efficiency was better as well. Also shown was the transient response of the system was similar to a naturally aspirated (N/A) engine, even at low engine speeds. Downsizing from a 3.2L improved fuel economy 17%, and downsizing from a 4.2L improved 36% on the NEDC driving cycle
When implemented with a close coupled catalyst and an air bypass configuration, where some fraction of the boost air bypasses the engine and is inserted into the exhaust in front of the turbine, the exhaust temperatures were air cooled so that fuel enrichment was not necessary. The result was a gasoline engine that could run at high brake mean effective pressure (BMEP) at low engine speeds, and because of the special bypass configuration, can go to high loads with a single compressor. A bypass arrangement would not be possible without the supercharger function of the SuperTurbo.