TheHornsby–Akroyd oil engine, named after its inventorHerbert Akroyd Stuart and the manufacturerRichard Hornsby & Sons, was the first successful design of aninternal combustion engine usingheavy oil as a fuel. It was the first to use a separate vapourising combustion chamber and is the forerunner of allhot-bulb engines, which are considered predecessors of the similarDiesel engine, developed a few years later.
Early internal combustion engines were quite successful running on gaseous and light petroleum fuels. However, due to the dangerous nature of petroleum and light petroleum fuel, legal restrictions were placed on their transportation and storage.[clarification needed] Heavier petroleum fuels, such askerosene, were quite prevalent, as they were used for lighting, but posed specific problems when used in internal combustion engines: Oil used for engine fuel must be turned to a vapour state and remain in that state during compression. Furthermore, the combustion of the fuel must be powerful, regular, and complete, to avoid deposits that will clog the valves and working parts of the engine.[citation needed]
The earliest mention of anoil engine was by Robert Street, in his English patent no. 1983 of 1794, and according to Horst O. Hardenberg there is evidence that he built a working version.[1][2] Other oil engines were subsequently built byEtienne Lenoir,Siegfried Marcus, Julius Hock of Vienna andGeorge Brayton in the 19th century. In 1807Nicéphore Niépce built a working moss and coal powder powered engine, thePyreolophore, which powered a boat upstream on the River Saône. All of these engines with the exception of Brayton's were non-compression.
Others made refinements to the oil engine;William Dent Priestman[3] and Emile Capitaine[4] are some of the more notable. However, it wasHerbert Akroyd Stuart's design that was the most successful.
Herbert Akroyd Stuart's first prototype engines were built in 1886. In 1890, in collaboration withCharles Richard Binney, he filed Patent 7146 forRichard Hornsby & Sons ofGrantham,Lincolnshire, England. The patent was entitled:Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air.[5]
Stuart's oil engine design was simple, reliable and economical. It had a comparatively lowcompression ratio, so that the temperature of the air compressed in the combustion chamber at the end of the compression stroke was not high enough to initiate combustion. Combustion instead took place in a separated combustion chamber, thevapouriser (also called thehot bulb) mounted on the cylinder head, into which fuel was sprayed. It was connected to the cylinder by a narrow passage and was heated either by the cylinder's coolant or by exhaust gases while running; an external flame such as a blowtorch was used for starting. Self-ignition occurred from contact between the fuel-air mixture and the hot walls of the vapouriser.[6]
By contracting the bulb to a very narrow neck where it attached to the cylinder, a high degree of turbulence was set up as the ignited gases flashed through the neck into the cylinder, where combustion was completed. As the engine's load increased, so did the temperature of the bulb, causing the ignition period to advance; to counteract pre-ignition, water was dripped into the air intake.[7]
The Stuart engine is offour cycle design. During the intake stroke (1), fresh air is inducted into the cylinder through a mechanically operated intake valve. Simultaneously, oil is injected into the vapouriser. The vapour of the oil is almost entirely confined to the vapouriser chamber. This cloud of hot oil vapour is too rich to support combustion. On the compression stroke (2) of the piston, the fresh air is forced through the narrow neck and into the vapouriser. Just as compression is completed, the mixture is just right to support combustion and ignition occurs to push the piston during expansion stroke (3). Exhaust gas is released then during stroke (4).
Some years later, Akroyd-Stuart's design was further developed in theUnited States by the German emigrants Mietz and Weiss, who combined thehot-bulb engine with thetwo-strokescavenging principle, developed byJoseph Day to provide nearly twice the power, as compared to a four-stroke engine of same size.Similar engines, for agricultural and marine use, were built by J. V. Svensons Automobilfabrik,Bolinders, Lysekils Mekaniska Verkstad,Pythagoras Engine Factory and many other factories in Sweden.
Akroyd-Stuart's engine was the first internal combustion engine to use a pressurisedfuel injection system[8] and also the first using a separate vapourising combustion chamber. It is the forerunner of allhot-bulb engines, which are considered kind of predecessors of the similarDiesel engine, developed a few years later.
However, the Hornsby–Akroyd oil engine and other hot-bulb engines are distinctly different fromRudolf Diesel's design, where ignition occurs alone through the heat of compression: An oil engine will have a decentcompression ratio between 3:1 and 5:1, where a typicaldiesel engine will have a much harder achieved compression ratio ranging between 15:1 and 20:1, making it a lot more efficient.Also the fuel is injected easily during the early intake stroke and not at the peak of compression with a high-pressureDiesel injection pump.[9]
Akroyd-Stuart's engines were built from 26 June 1891 byRichard Hornsby & Sons inGrantham, a large manufacturer of steam engines and agricultural equipment, as theHornsby Akroyd Patent Oil Engine under licence and were first sold commercially on 8 July 1892. Other engineering companies had been offered the option of manufacturing the engine, but they saw it as a threat to their business, and so declined the offer.
In 1892, T. H. Barton at Hornsbys enhanced the engine by replacing the vaporiser with a newcylinder head and increased thecompression ratio to make the engine run on compression alone pre-dating Rudolph Diesel's engine.[10] This Hornsby–Akroyd oil engine design was hugely successful: during the period from 1891 through 1905, a total of 32,417 engines were produced. They would provide electricity for lighting theTaj Mahal, the Rock of Gibraltar, the Statue of Liberty (chosen after Hornsby won the oil engine prize at theChicago World's Fair of 1893), manylighthouses, and for poweringGuglielmo Marconi's firsttransatlantic radio broadcast.
