Die Zeit is a national weekly newspaper in Germany that has an estimated readership of more than 1.4 million. It’s one of the most highly respected newspapers in Germany. On January 4, Die Zeit published a comprehensive article about the Scuderi Group and the Scuderi Air-Hybrid Engine. We’ve included an English translation of the article below:
(Or read the original article in German at www.zeit.de/2007/02/T-Drucklufthybrid).
FUEL EFFICIENT DOUBLE CYLINDERS
Hybrid technology with compressed air should make buses in the future cleaner and more efficient
By Burkhard Strassmann
Compared to the private car and considering the number of passengers, even an old bus is an environmentally friendly vehicle. Now though, the real environmentally friendly buses have arrived; the twin motorized hybrids. An example is the Urbino 18 bus from Poland; a city bus with a diesel engine and two electric engines. The promise: up to 43% less usage, nearly 40% less NOx and barely any more fine dust. Some of these buses are already being driven in Dresden and Bremen.
The Hybrid Question is not new, but the momentous consequences are just being understood now. Back in 1969 Mercedes Benz experimented with the Electric Trial Bus OE 302. In 1996 four Hybrid Buses were tested in traffic. Two years later the low-floor, mid-size Cito bus with diesel-electric powertrain was launched. However the main disadvantage of all Hybrid concepts is that, like with passenger cars, there is a high price. The demanding regulations, the additional engines and the rechargeable batteries amounts to an additional cost of Euros 7,000 - 10,000. Thus, insiders are watching with interest a slightly different hybrid concept by the U.S. company Scuderi; the air hybrid engine, which should only be a couple of hundred Euros more expensive than a conventional diesel engine. Albeit, the engine only exists now as a computer simulation.
The inventor of this engine, Camillo Scuderi, from West Springfield, MA., based his theory on a ninety year old, from time to time revived, idea to reinvent the Otto engine.
In their split-cycle engine, the four classical strokes (intake, compression/firing, power and exhaust) don’t happen in one cylinder, but in two. One cylinder creates compressed air through compression, whilst in the other cylinder, the fuel/air mixture is combusted. Due to an ingenious choice of valves, and an invention which delays the firing of the gas as long as possible (provoking the engineers: firing after top dead center!), Camillo Scuderi managed to design, at least theoretically, an amazingly efficient and clean engine. His son Sal, who heads the young company, added a tank for compressed air and the result: a hybrid engine.
In a relaxed mode, the system directs parts of the compressed air, which is generated in the compression cylinder, into this tank. If the driver wants to speed up; he uses the energy from the tank. The best part: if the vehicle brakes, additional compressed air will be pumped into the tank. It is at this moment when the hybrid technology makes sense. Stop-and-go in city traffic or downhill driving means no more hot brake shoes, but fully recharged batteries. Or, at Scuderi, a full tank of compressed air.
This would mean in the real life of a bus driver, that he would be able to drive with the contents of a small tank of compressed air, perhaps for 2 or 3 minutes, before refilling the air tank by diesel or brake pressure. One suspects that the real saving of fuel is dependent on the way one drives and where one drives. The numbers should be looked at positively, but with caution: usage halved and emissions reduced by up to 80%. Because of the late firing, the combustion temperature decreases so much that one can count on significantly less NOx in the exhaust fumes.
The Southwest Research Institute in San Antonio, TX, is entrusted with the building of the first prototype. Their goal is to create a two cylinder and a six cylinder in split cycle technology by the end of 2007. Significant Funding by the Ministry of Defense shows that the Institute is well respected in the U.S. For military purposes, but also for commercial vehicles, this way of generating compressed air on-board is interesting. It can be integrated into the present compressed air systems, with which valves can be controlled or brakes actuated. With the energy from the hybrid tank, it is possible to start the engine and to operate tools.
If the air hybrid works not only from a technical point of view, but also from an economical point of view, it could create shock waves in both the domains of commercial vehicle power trains and stationary engines, one example being, by making a couple of expensive components redundant or cheaper. A turbo charger wouldn’t be necessary anymore, as the split cycle engine takes care of it instead. Because firing is only done in every second cylinder, one saves expensive injection systems. Possibly, but one has to wait for the first test-runs, the engine will run so cleanly that the after treatment of the exhaust fumes will be much more inexpensive.
The question not yet clarified by experts, is if a car with two engines can drive more fuel efficiently and cleanly than a car with a conventional engine, has long been answered by the consumer, as: “Never mind, hybrid is cool!” Famous actors have bought twin engine Toyotas and now everyone wants one. If the air hybrid prevails, at least in the small segment of public transport, then even the economists will finally understand the hybrid.
