Philippe le Bon (or Lebon) (D'Humbersin) (May 29, 1767 – December 1, 1804) was a French engineer, born in

Brachay Brachay () is a Communes of France, commune in the Haute-Marne Departments of France, department in northeastern France. Population See also *Communes of the Haute-Marne department References

Communes of Haute-Marne {{HauteMarne ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

. There is much confusion about his life and accomplishments. His main contributions were improvements to

steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...

s and industrializing the extraction of lighting gas from wood. Following details published in readings for young people, Lebon has long been purported to have been assassinated on the eve of

Napoleon Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader who ...

's crowning ceremony, at the beginning of December 1804.Fetter, Johann. ''Lehrgang der französischen Sprache'' 211pp (1897). ''(in french)''.
Available online a
archive.org

p 85: "''Philippe Lebon mourut assassiné, on ne sait par qui, en 1804.''" While the actual time of death seems to be December 1 at 10 am, there are no contemporary evidence to sustain the story: legal documents produced by the Archives Nationales upon the 150th jubilee of Lebon make it clear that neither the engineer's servant, Euphrasie Hubert, nor the justice practitioner committed to the post mortem inventory did mention any criminal circumstance, nor any wound on the body. Joseph Gaudry, Lebon's nephew and heir, only mentions family rumors in his 1856 writing. Lebon's correspondence during the last months of his life make it clear he had been suffering from illness and lack of medical assistance for weeks before his untimely death. He also designed, though apparently did not build, a wood gas engine. (Not the first.) Like other early engines, it had no compression in its main cylinder. It has three mechanically connected cylinders, each double-acting, one to compress the air, one to compress the gas, and one driven by the burned mixture. This engine resembles an internal combustion engine, but the combustion actually takes place in a combustion chamber separated by mechanically controlled valves from the cylinders. This makes it a steam engine running on combustion products instead of on steam, or the piston equivalent of a gas turbine. Hardenberg's analysis shows a theoretical efficiency and specific power much less than those of the earlier

Street engine A street is a public thoroughfare in a built environment. It is a public parcel of land adjoining buildings in an urban context, on which people may freely assemble, interact, and move about. A street can be as simple as a level patch of dirt, ...

, but this assumes that the intake valve stays open during the whole power stroke. Assuming that the inventor had more in his mind than what he wrote on paper and therefore allowing arbitrary valve timing, its idealized

thermodynamic Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of ther ...

cycle is similar to that of a

gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...

, which can have a high

compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...

and relatively high efficiency. This assumes, contrary to what Hardenberg seems to assume, that the combustion chamber would have been big enough to act as a pressure reservoir. Of course, one's place in history depends on what one does and writes more than on what one can be assumed to have thought. Certainly, all but possibly Hardenberg must have seen that it would give more room for optimization than the Street engine did. The reasons that it has never been used must be the obvious thermal and mechanical problems, such as heat loss from the combustion products to the containing structures. In 1801, Philippe Lebon invented an engine that improved on Robert Steele's design. It used coal gas ignited by an

electric spark An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael F ...

. This was the first internal combustion engine. Although very inefficient, it would later be improved, as internal combustion is used in modern cars.

Notes and references

Further reading