Could an engine design with roots that go back to 1914 revolutionize the way that vehicles are powered in the future? The people at Scuderi Group (www.scuderigroup.com; Springfield, MA) think so. They’ve developed an air-hybrid engine that, unlike traditional internal combustion engines, features a split-cycle configuration. Although the split-cycle design has been continually dismissed for the past 90 years as having inherent problems when it comes to volumetric and thermal efficiency, Scuderi says it has eliminated those issues, thanks to several breakthroughs. Chief among them: A unique disc-valve design that handles both the inlet and outlet valves of the compression cylinder, allowing trapped gases to be removed from the cylinder, which improves volumetric efficiency, while spark plug firing has been configured to occur after top dead center for improved thermal performance. This portion of the system is what Scuderi calls its silver bullet: “The key breakthrough here is the ability to fire after top dead center and still maintain overall pressure,” says Stephen Scuderi. Pressure is also a key factor in improving split-cycle efficiency. Scuderi says its design is able to achieve compression cylinder pressures equal to that of a conventional internal-combustion engine during the combustion cycle, thus creating large amounts of turbulence for improved atomization of the fuel/air mix. This results in a flame speed rate more than two times faster than a conventional engine.
Since the split-cycle configuration produces compressed air during its operation, Scuderi engineers decided it would be ideal if they could capture the air produced during the combustion process and use it to power the engine and auxiliary items. The result is a compressed air tank attached to the engine block that stores the air for use during various operating modes. When braking, the power cylinder is turned off and the air is sent through the crossover passage directly into the tank and stored for use during operation. Engineers developed a high-efficiency operating mode that turns off the compression cylinder while the power cylinder is fed pressurized air from the storage tank, virtually eliminating compression losses. In normal cruising mode, the compression cylinder feeds the air into the tank and only a portion of the air is discharged from the tank into the power cylinder during combustion and the engine returns to high-efficiency mode operation when the tank is full. The switch to an air-hybrid configuration virtually eliminates the need for complex electrical propulsion systems found in today’s electric-hybrid systems, resulting in a significant reduction in weight for the entire powertrain system. “As opposed to a traditional electric hybrid, this system only carries a price premium of a couple hundred dollars, as opposed to several thousand dollars, which results in additional savings for OEMs,” Stephen Scuderi said.
So why aren’t automakers tripping over themselves to get on board? For starters, not a single prototype of the engine has been built, although extensive compute modeling and testing has been completed by Southwest Research Institute (San Antonio, TX), which is also building the two prototypes expected to hit the dyno in 2007. Commercialization is not expected until at least 2010 or 2011. Another key obstacle will be getting automakers to divest of their current long-range internal combustion engine investment plans and switch to the split-cycle design, which could be a monumental task given the fact that most of the world’s automaker’s are not flush with cash and willing to take a serious gamble on something as crucial as engine configurations. Still, Scuderi is confident his team will be able to win over several OEMs, and he’s pitching licensing options throughout the world.—KMK