The demands for fuel economy and pollution control (essentially contradictory) have stimulated a number of novel designs of the internal combustion engine, some of them drastically new.
The two-stroke engine may be coming back. As late as a decade ago, the blue smoke emerging from the exhausts of motorcycles formed a tell-tale tail of incomplete fuel combustion: poor fuel economy and disproportionate pollution.
On the other hand, the two-stroke engine was very simple and powerful: simple because it had no real valves (just holes in the cylinder wall closed or freed by the piston itself), and powerful because it did not go " 1-2-3-bang, 1-2-3-bang," but "bang-and-bang-and-bang-and-bang!"
A small British company, Templewall, is now trying to eliminate the two-stroked disadvantages while keeping the power and simplicity. The "stepped piston crossflow" (SPX) engine makes two top-hat-shaped cylinders cooperate, one forcing the air-fuel mixture into the top combustion chamber of the other, much like a supercharger in a conventional engine. Then a spark ignites the mixture, and the rest should be clear from the picture.
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There are other designs in the works to improve fuel economy. The Texaco engine injects fuel from the side of the cylinder and makes it swirl round its walls while the spark plug is sparking, resulting in all of the fuel being consumed in the power stroke. General Motors, too, is playing with the geometry of the ignition; it uses a wedge-shaped combustion space, with the spark plug mounted on the steep side of the wedge.
Prof. Oppenheim of the U. of California at Berkeley has abandoned the spark plug altogether; instead, he shoots a plasma jet (hot, ionized gas) through a nozzle deep into the combustion chamber and achieves a smooth and complete burn of the fuel as the plasma ignites it. So far, however, his work is limited to the combustion space without valves, pistons, or for that matter, an engine.
At the U. of Rhode Island's mechanical engineering department, Prof. G.A. Brown is working on a diesel engine of revolutionary design
¾it abandons the piston (which compresses the air linearly with time and does not make it hot enough to avoid an ignition delay when the fuel is injected). Instead, Brown makes the compression space diminish quadratically by closing an aperture between three triangular slides (called "hedrons") in much the same way as the aperture in the iris of a camera is diminished when the f-stop ring is turned. The entire arrangement is firmly mounted on a crankshaft and works the engine by rotating when the explosion forces the hedrons apart.[More: "Two stroke plus," Economist (London), 29 Sept. 79, p.94; "Shaping an improved diesel," Science News, 27 May 1978; "Combustion research," Popular Science, Sept. 79; "Shaping combustion chambers to save fuel," Search (GM Res. Labs, Warren, Mich.]
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Vol. 7, No. 5
Newsletter: Access to Energy Newsletter Archive Volume: Volume 7 Issue/No.: Vol. 7, No. 5 Date: January 01, 1980 03:04 PM Title: Huxley, not Orwell
Copyright © 2004 - Access to Energy Newsletter Archive
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