Patent Page: The Brayton Cycle Engine

The Brayton engine is claimed to be the first commercially successful engine of purely American design.

| August/September 2019

brayton-cycle-engine
A detailed drawing of George B. Brayton's engine as shown in his 1872 patent for "improvement in gas engines".

Students of gas-powered engines know that Nicolaus Otto (1832-1891) is credited as the father of the 4-cycle engine that still serves us today, powering just about every kind of motorized machine imaginable. Introduced in 1876 as the Otto Silent engine, Otto’s engine was a revolution in the making, and its introduction heralded a new age in mechanical power.

Lesser known, however, is the engine scheme designed by one George Bailey Brayton (1839-1892) of Boston, Massachusetts, in 1872. Writing in American Gasoline Engines Since 1872, engine historian C.H. Wendel claims that Brayton’s engine was the “first commercially successful engine of purely American design.”

A 2-stroke engine, Brayton’s patented design hinged on the use of a charging cylinder to pull in and compress the fuel/air charge. The compressed charge was stored in a receiver and then admitted into the combustion chamber. The combined charging cylinder and power cylinder worked simultaneously; a charge being pulled in as the power cylinder dropped to the bottom of its stroke, then compressed as the power cylinder rose on its power stroke.



The compressed fuel/air charge was admitted into the bottom of the power cylinder through a cam-actuated valve. On its way to the power cylinder it passed through a chamber where it was ignited by a constant flame as it entered the power cylinder. Receiver pressure was always greater than combustion pressure, and a series of wire-gauze diaphragms kept the burning charge from reversing directions.

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Brayton's engine as depicted in his 1872 patent. The charging receiver is at the right. Charge volume was controlled by a simple gate valve at the bottom of the receiver, and a linkage-actuated valve (visible between the receiver and the cylinder) admitted the fuel/air charge into the combustion chamber.



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