History

In 1885, the English inventor Herbert Akroyd Stuart began investigating the possibility of using paraffin oil (very similar to modern-day diesel) for an engine, which unlike petrol would be difficult to vaporise in a carburettor as its volatility is not sufficient to allow this.

His hot bulb engines, first prototyped in 1886 and built from 1891 by Richard Hornsby and Sons, used a pressurised fuel injection system.[8] 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, the "vaporizer" or "hot bulb" mounted on the cylinder head, into which fuel was sprayed. Self-ignition occurred from contact between the fuel-air mixture and the hot walls of the vaporizer.[9] 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.