Barsanti-Matteucci engine

The Barsanti-Matteucci engine was the first internal combustion engine. In late 1851 or early 1852 Eugenio Barsanti, a professor of mathematics, and Felice Matteucci, an engineer and expert in mechanics and hydraulics, joined forces on a project to exploit the explosion and expansion of a gaseous mix of hydrogen and atmospheric air to transform part of the energy of such explosions into mechanical energy.

The idea originated almost ten years earlier with Barsanti when, as a young man, he was teaching at St. Michael's College in Volterra. An engineer from Milan, Luigi de Cristoforis, described in a paper published in the acts of the Lombard Royal Institute of Science, Literature and Art, a pneumatic machine (later built and shown to work) that ran on naphtha and an air mixture, and which constituted the first liquid fuel engine.

During the twelve years of collaboration between Barsanti and Matteucci several prototypes of internal combustion engines were realized. It was the first real internal combustion engine, constituted in its simplest realization by a vertical cylinder in which an explosion of a mixture of air and hydrogen or an illuminating gas shot a piston upwards thereby creating a vacuum in the space underneath. When the piston returned to its original position, due to the action of the atmospheric pressure, it turned a toothed rod connected to a sprocket wheel and transmitted movement to the driving shaft.

...
Wikipedia