Herbert Akroyd-Stuart was an English inventor. He was born on January 28, 1864, and died on February 19, 1927. He is known for inventing the hot bulb engine, also called the heavy oil engine.

Life

Akroyd-Stuart was born in Halifax, Yorkshire, but lived in Australia for some time during his early years. He attended Newbury Grammar School, which is now called St. Bartholomew's School, and later studied at Finsbury Technical College in London. He was the son of Charles Stuart, who started the Bletchley Iron and Tinplate Works. Akroyd-Stuart joined his father's business in 1887.

Oil engines

In 1885, Akroyd Stuart accidentally spilled paraffin oil (kerosene) into a pot of molten tin. The paraffin oil turned into vapor and caught fire when it touched a paraffin lamp. This inspired him to explore using paraffin oil (similar to modern diesel) in an engine. Unlike petrol, paraffin oil was hard to vaporize in a carburetor because it did not evaporate easily.

His first engine prototypes were built in 1886. In 1890, he worked with Charles Richard Binney to file Patent 7146 for Richard Hornsby and Sons in Grantham, Lincolnshire, England. The patent was titled: Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air. One engine was sold to Newport Sanitary Authority, but it had a low compression ratio and needed a heat poultice to start.

From 26 June 1891, Richard Hornsby and Sons built the Hornsby Akroyd Patent Oil Engine under license. It was first sold commercially on 8 July 1892. This engine was the first internal combustion engine to use a pressurized fuel injection system.

The Hornsby–Akroyd engine had a low compression ratio, so the air in the combustion chamber did not get hot enough to start combustion. Instead, fuel was sprayed into a separate chamber called the vaporizer (or hot bulb), which was attached to the cylinder. The vaporizer was heated by coolant or exhaust gases. A blowtorch was used to start the engine. Fuel and air mixed in the vaporizer, and the hot walls caused the mixture to ignite. The narrow neck of the vaporizer created turbulence, helping the ignited gases move into the cylinder. As the engine’s load increased, the vaporizer’s temperature rose, causing ignition to happen earlier. To prevent early ignition, water was added to the air intake.

Hot bulb engines were made until the late 1920s and were sometimes called semi-diesels, even though they were less efficient than diesel engines. They were simpler because they did not need an air compressor, and fuel was injected mechanically at lower pressure than diesel engines.

In 1896, Richard Hornsby and Sons built the world’s first oil-powered railway locomotive, LACHESIS, for the Royal Arsenal in Woolwich, England. They also built the first compression-ignition automobile. Similar engines were made by Bolinder in Sweden and some are still used in canal boats.

In the United States, the De La Vergne Company (later the New York Refrigerating Company) built hot bulb engines and invented the modern refrigerator in 1930. They obtained a license to use the design in 1893.

Both the Diesel engine and the Akroyd engine used petroleum oil as fuel, leading to debates about whether the Diesel engine was based on the Akroyd engine. However, the Diesel engine’s operating method differs from what Rudolf Diesel described in his essay Theory and Construction of a Rational Heat Motor. The Akroyd engine was the first working internal combustion engine to use petroleum oil as fuel. It operated in 1891, six years before the Diesel engine first ran. After the Diesel engine became popular, the term Diesel engine was used for all oil-powered engines, and the Akroyd engine was called semi-Diesel. The name Akroyd fell out of use, so Herbert Akroyd Stuart tried to replace Diesel engine with Akroyd engine in the early 1900s.

Herbert Akroyd Stuart held two patents: No. 7146 (Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air) and No. 15994. In Patent 7146, the Akroyd engine’s process was described as: "…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 used this method. Rudolf Diesel had a patent for the combustion process described in his essay (DRP 67207). The Diesel engine does not use the process in the Akroyd patent or DRP 67207. Instead, it uses a different method patented by Diesel in 1893 (DRP 82168), which is why he is credited as the inventor. Diesel claimed his engine used the process described in DRP 67207, even though this was not possible.

The main difference between the Akroyd and Diesel engines is how they ignite fuel. In an Akroyd engine, a hot bulb or vaporizer ignites the fuel because the compression is too low for compression ignition (less than 300 kPa). A Diesel engine has no separate ignition device. Instead, fuel ignites due to the high heat from piston compression (over 3000 kPa). Because Diesel engines use higher compression, they are more efficient. The lower-pressure Akroyd engine uses about 80% more fuel to do the same work as a Diesel engine.

Death

In 1900, he moved to Australia and established a company called Sanders & Stuart with his brother Charles. He passed away on 19 February 1927 in Perth, Australia, due to throat cancer. His body was sent back to England and buried in All Souls Cemetery in Boothtown, Halifax, Yorkshire. All Souls Church was built entirely at the expense of his maternal uncle, Edward Akroyd.

The University of Nottingham has held the Akroyd-Stuart Memorial Lecture in his honor on occasion since 1928. One lecture was given by Sir Frank Whittle in 1946. Akroyd-Stuart worked with Professor William Robinson in the late 19th century. Professor Robinson served as a professor of engineering at University College Nottingham from 1890 to 1924.

Akroyd-Stuart also left money to the Institution of Mechanical Engineers, Royal Aeronautical Society, and Institute of Marine Engineering. These organizations use the funds to provide their respective bi-annual Akroyd-Stuart Prizes.