George Brayton (October 3, 1830 – December 17, 1892) was born in Rhode Island, son of William H. and Minerva (Bailey) Brayton.[1] He was an American mechanical engineer who lived with his family in Boston, and who is noted for introducing the continuous combustion process that is the basis for the gas turbine, and which is now referred to as the Brayton cycle.
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In 1872 Brayton patented an internal combustion stationary engine initially using gas but more commonly liquid fuels such as kerosene and petroleum known as Brayton's Ready Motor,[2] which had one cylinder for compression, a receiver reservoir, and a separate power cylinder in which the products of combustion expanded for the power stroke. The significant difference from other piston driven internal combustion engines is that the two cylinders are arranged so that the fuel/air mixture burns progressively at constant pressure as it is transferred from the compressor cylinder and reservoir to the working cylinder. In the original engine a gas/air mixture was compressed, and metal gauze/mesh was used to prevent the combustion running back to the compressor. However the consequences of a break in the mesh, leading to flash-back were a problem, so the engine was switched to using liquid fuel introduced as the air passed from the compressor to the working cylinder. The principle was referred to as constant pressure combustion, and had been attempted without success by Sir William Siemens c1861 using a 4-cylinder engine with separate combustion chamber. Brayton not only achieved success in making the constant pressure cycle work, but he also made and marketed a commercial product.
The engine's cycle of operations including sectional drawings, indicator diagrams (for both gas and petroleum fuelled versions) and details of the way the liquid fuel was introduced are described over 11 pages of Dugald Clerk's book "Gas and Oil Engines"[3]. The petroleum engine in these tests was made by the "New York and New Jersey Ready Motor Company". This is followed by a similar analysis of Simon's engine which was an adaptation of the Brayton engine made by Louis Simon & Sons, in Nottingham, UK and marketed as The Eclipse Silent Gas Engine. The Simon engine had an added complexity in that it injected some of the water/steam heated by the engine/exhaust into the engine. The indicator diagrams for this engine are also reported by Dugald Clerk and show that the addition of the water has little merit in terms of power production, the cooling of the gases and expansion of the steam compensating for each other.
Because the Brayton engine had a slow progressive burn of the fuel/air mixture it was possible to maintain a pilot flame, and so the engine, once lit, needed no form of ignition system.[4] The measured efficiency of the gas engine was intermediate between that of the Lenoir/Hugon engines, and the Otto & Langen atmospheric engine, but the liquid fuelled Brayton engine had an advantage in not requiring a gas supply.
The early Brayton gas engine had the engine speed governed by varying the point of cut-off for the admission of the combusted gases into the power cylinder, and the admissions of gas and air to the pump was similarly regulated to maintain the reservoir pressure. The liquid fuelled engine reported by Clerk[3] only regulated the cut-off to the power cylinder, and used a pressure relief valve to limit the reservoir air pressure. The reservoir on the Brayton engine allowed it to be readily started if it remained pressurised, though Clerk[3] states that "that leakage and loss were so frequent that the apparatus was of little use."
Brayton's engine was displayed at the Centennial Exposition in Philadelphia in 1876, and the Simon variant was displayed at the 1878 Paris Exhibition, and for a few years was well regarded, but within a short time the Otto engine became more popular. However, it was considered the first safe and practical oil engine and also served as inspiration to George B. Selden. As a production engine the design evolved over time, and according to Henry de Graffigny in "Gas and Petroleum Engines",[5] it was available in both vertical and horizontal forms.
A Brayton Engine is preserved in the Smithsonian in the American History museum, and a later Brayton engine which powered one of John Philip Holland's early submarines is preserved in the Paterson Museum in the Old Great Falls Historic District of Paterson, New Jersey.[6]