|Model of the working prototype. The engine is packaged as a research engine, with easy access for instrumentation, a balancer shaft, etc., not as a production unit. Click to enlarge.|
The Scuderi Group unveiled a cutaway model of the first proof-of-concept prototype for its Scuderi Split-Cycle Engine (earlier post) at the SAE World Congress in Detroit. The engine cutaway is an exact duplicate of the prototype undergoing testing and analysis by SwRI in San Antonio, Texas. First firing of the working prototype is slated for May, according to President Sal Scuderi.
The prototype is of the naturally-aspirated Split Cycle gasoline engine, and is intended to be a proof of the basic technology of the split cycle with firing after Top Dead Center (one of the key attributes of the engine and cycle). Subsequent implementation of the Split Cycle will be a turbocharged split cycle unit, an air hybrid version of the engine, and a diesel-fueled version.
|“Our efficiencies right now are running higher than anything that is on the market .”|
The one-liter, naturally-aspirated gasoline prototype is expected to produce up to 80% fewer criteria pollutants than a typical internal combustion engine. When fully developed with its turbocharged and air-hybrid components, the engine is expected to achieve significant gains in fuel efficiency.
The Scuderi Engine is a split-cycle design that divides the four strokes of a conventional combustion cycle over two paired cylinders: one intake/compression cylinder and one power/exhaust cylinder. By firing after top-dead center (TDC), it produces highly efficient, cleaner combustion with one cylinder and compressed air in the other.
The Scuderi engine achieves compression ratios in excess of 100:1 in its compression cylinder, Sal Scuderi said. The high pressure air flows into the crossover chamber, where it receives its fuel load from two direct-injection injectors, and then flows into the combustion chamber with a great deal of turbulence and concomitant rapid mixing of the fuel air charge. As a result, Scuderi said, combustion is four times faster than in a conventional engine.
The Scuderi engine also uses the high pressure air generated on the compression side to run accessories of the engine. The inlet and outlet valves are all pneumatically actuated valves. There is no throttle on the engine to control the load, rather “we control load with the intake and exhaust valves that are being fed from the compression side of the engine,” Scuderi said. The engine uses air springs to return the high speed valves in the crossover; those are also fed by the compression side of the engine.
Combustion starts 15 degrees after TDC and ends 23 degrees after ignition. This results in higher average temperatures but lower peak temperatures than conventional engines—one unanticipated benefit of this is low NOx formation.
The Scuderi engines offer high power density—the turbocharged split-cycle engine is projected to deliver 140 hp/liter.
Unlike conventional engines that require two crankshaft revolutions to complete a single combustion cycle, the Scuderi Engine requires just one. Besides the improvements in efficiency and emissions, studies show that the Scuderi Engine is capable of producing more torque than conventional gasoline and diesel engines. (Earlier post.)
With the assembly of the naturally aspirated Scuderi Engine now complete, the Scuderi Group and its independent laboratory continue to work on the next prototypes. Completion of the turbocharged Scuderi Engine and the Scuderi Air-Hybrid are expected in 2010.
|Select Attributes of First Two Scuderi Prototypes|
Split Cycle Engine
Split Cycle Engine
|Engine speed||Up to 6,000 rpm||Up to 6,000 rpm|
|Power||Similar to conventional engine||Up to 140 hp/L|
|Efficiency (full load)||Similar to conventional engine||10-15% higher than conventional engine|
|Emissions||Up to 80% less NOx than conventional engine||Up to 80% less NOx than conventional engine|
|Air pressure levels||50-60 bar||110-130 bar|
|Fuel injection pressure||Up to 200 bar||Up to 200 bar|
|BMEP||9 bar/L displacement||22 bar/L displacement|
|Displacement (approx. 1 liter)||.58: compression side
.52: power side
|.48: compression side|
.52: power side
The company intends to license its technology to engine manufacturers. The Scuderi Group expects further advancement of the technology once the greater engineering community begins working with the engine, making their own modifications that will most likely take the efficiency to even higher levels. According to Scuderi, the company is in discussions with 14 of the largest 20 engine manufacturers in the world.