|The VanDyne SuperTurbo. Click to enlarge.
The US Army SBIR Program has competitively selected and awarded a Phase 1 research contract to VanDyne SuperTurbo, Inc. for a project developing a waste heat recovery system using VanDyne’s SuperTurbocharger technology.
VanDyne’s 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 concept. Click to enlarge.
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. Effectively, says VanDyne, the SuperTurbocharger can create a “hybrid engine”—the combination of a piston engine working together with a turbine engine.
Work on the Army SBIR contract is scheduled to begin immediately and will be conducted in three phases; each phase award is pending the success of the previous phase. The program goal of Phase 1 and Phase 2 is to achieve a 7% increase in fuel efficiency as well as a corresponding 7% increase in maximum horsepower over the traditional turbocharged diesel engines within the US Army fleet.
In a paper being presented this week at the SAE 2010 World Congress, Chris Chadwell and Mark Walls from the Southwest Research Institute (SwRI) used 1-D simulation to show that a 2.0-liter I4 using a SuperTurbo could exceed the torque curve of a 3.2L V6, and meet the torque curve of a 4.2-liter V8 by using 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. 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.
Christopher James Chadwell, Mark Walls (2010) Analysis of a SuperTurbocharged Downsized Engine Using 1-D CFD Simulation. (SAE 2010-01-1231)