Herbert Akroyd-Stuart (28 January 1864 – 19 February 1927) was an English inventor who is noted for his invention of thehot bulb engine, orheavy oil engine.
Akroyd-Stuart was born inHalifax,Yorkshire, but lived inAustralia for a period in his early years. He was educated atNewbury Grammar School (nowSt. Bartholomew's School) andFinsbury Technical College inLondon. He was the son of Charles Stuart, founder of the Bletchley Iron and Tinplate Works, joining his father in the business in 1887.[1]
In 1885, Akroyd Stuart accidentally spiltparaffin oil (kerosene) into a pot of moltentin. The paraffin oil vaporised and caught fire when in contact with aparaffin lamp. This gave him an idea to pursue the possibility of using paraffin oil (very similar to modern-daydiesel) for an engine, which unlikepetrol proved difficult to vaporise in a carburettor because itsvolatility is insufficient.
His first prototype engines were built in 1886. In 1890, in collaboration with Charles Richard Binney, he filed Patent 7146 forRichard Hornsby and Sons ofGrantham,Lincolnshire, England. The patent was entitled:Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air.[2] One such engine was sold to Newport Sanitary Authority, but the compression ratio was too low to get it started from cold, and it needed a heat poultice to get it going.[3]
Akroyd-Stuart's engines were built from 26 June 1891 byRichard Hornsby and Sons as theHornsby Akroyd Patent Oil Engine under licence and were first sold commercially on 8 July 1892. It was the first internal combustion engine to use a pressurisedfuel injection system.[4]
The Hornsby–Akroyd engine used a comparatively low compression 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, thevaporizer (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 vaporizer.[5] 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.[6]
Hot bulb engines were produced until the late 1920s, often being calledsemi-diesels, even though they were not as efficient as compression ignition engines. They had the advantage of comparative simplicity, since they did not require the air compressor used by early Diesel engines; fuel was injected mechanically (solid injection) near the start of the compression stroke, at a much lower pressure than that of Diesel engines.[5]
Richard Hornsby and Sons built the world's first oil-enginedrailway locomotiveLACHESIS for theRoyal Arsenal,Woolwich, England, in 1896. They also built the first compression-ignition powered automobile.
Similar engines were built by Bolinder inSweden and some of these still survive incanal boats.
Hot bulb engines were built in the USA by theDe La Vergne Company ofNew York City, later the New York Refrigerating Company – inventing themodern refrigerator in 1930, who purchased a licence in 1893.
Both theDiesel engine and the Akroyd engine run the same kind of fuel,petroleum oil, which has led to a dispute about whether or not the Diesel engine is based upon the Akroyd engine.[7] The fact that the Diesel engine's operating principle differs from the operating principleRudolf Diesel describes in his essayTheory and Construction of a Rational Heat Motor further contributed to this. The Akroyd engine was the first functional internal combustion engine that could use petroleum oil as fuel.[8] It was operational in 1891, six years before the Diesel engine first ran. However, after the Diesel engine had proven successful,Diesel engine became the synonym for an engine that ran on any sort of petroleum oil.Oil engines that used the Akroyd operating principle were calledsemi-Diesel, and the nameAkroyd, which had been associated with oil engines, fell out of use. Therefore, Herbert Akroyd Stuart sought to replace the term Diesel engine with Akroyd engine in the early 20th century.[9]
Herbert Akroyd Stuart had two patents, No. 7146Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air, and No. 15994. In the former, the Akroyd engine's operating principle is described as follows: "... at the desired part of this compression stroke, the supply of liquid hydrocarbon is forced, in a spray form, on to the heated vaporiser, which almost instantly changes it into a gas...". Early Akroyd engines indeed operated on this principle.[8] Rudolf Diesel had a patent on the combustion process described in his essay (DRP 67207). The Diesel engine neither operates on the process described in the Akroyd patent, nor on the process described in the DRP 67207 patent. It operates instead on a different operating principle, also invented by Rudolf Diesel (patented in 1893, DRP 82168), which is why Diesel is in fact the Diesel engine's inventor. However, Diesel never admitted that his engine operated on asecret operating principle, and claimed that the Diesel engine operates on the (impossible) operating process described in the DRP 67207 patent.[10]
The key difference between the Akroyd and Diesel engines is the ignition: In an Akroyd engine, an ignition device – thehot bulb, orvaporiser – ignites the fuel, because the compression is too low for compression ignition (<300 kPa). A Diesel engine on the other hand has no discrete ignition devices. The fuel instead ignites due to high heat caused solely by piston compression inside the cylinder (>3000 kPa).[11] Since higher compression leads to better efficiency, the lower-pressure Akroyd engine consumes ~ 80% more fuel than a Diesel engine doing the same work.[12]
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In 1900, he moved to Australia and set up a company Sanders & Stuart with his brother Charles. He died on 19 February 1927 in Perth, Australia ofthroat cancer. His body was transported back to England and was buried inAll Souls Cemetery inBoothtown,Halifax, Yorkshire. All Souls Church was built at the sole expense of his maternal uncle, Edward Akroyd.
TheUniversity of Nottingham has hosted the Akroyd-Stuart Memorial Lecture on occasional years in his memory since 1928. One was presented bySir Frank Whittle in 1946. Akroyd Stuart had worked with Professor William Robinson in the late 19th century, who was professor of engineering from 1890 to 1924 at University College Nottingham.
Akroyd-Stuart also left money to theInstitution of Mechanical Engineers,Royal Aeronautical Society andInstitute of Marine Engineering, which provided for their respective bi-annual Akroyd-Stuart Prizes.
