Motorjet

A motorjet is a rudimentary type of jet engine which is sometimes referred to as thermojet, a term now commonly used to describe a particular and completely unrelated pulsejet design. At the heart the motorjet is an ordinary piston engine (hence, the term motor), but instead of (or sometimes, as well as) driving a propeller, it drives a compressor. The compressed air is channeled into a combustion chamber, where fuel is injected and ignited. The high temperatures generated by the combustion cause the gases in the chamber to expand and escape at high velocity from the exhaust, creating a thermal reactive force that provides useful thrust. Motorjet engines provide greater thrust than a propeller alone mounted on a piston engine; this has been successfully demonstrated in a number of different aircraft. A jet engine also can provide thrust at higher speeds where a propeller becomes less efficient or even ineffective; in fact, a jet engine gains efficiency as speed rises, while a propeller loses it (outside of a certain design range). This gives better efficiency in either operating range than an aircraft powered by just a propeller or a jet. The same is true of the dual-powerplant aircraft experimented with after the turbojet became practicable, which were equipped with both a piston-driven propeller and a turbojet engine. In 1908 French inventor René Lorin proposed using a piston engine to compress air that would then be mixed with fuel and burned to produce pulses of hot gas that would be expelled through a nozzle to generate a propelling force. In 1917, O. Morize of Chateaudun, France, proposed the Morize ejector scheme in which a reciprocating engine drove a compressor supplying air to a liquid-fueled combustion chamber which discharged into a convergent-divergent tube and ultimately out into the atmosphere. The term "motor jet" was established in a patent filed in Britain by J.H. Harris of Esher, U.K., in 1917. It was next explored by Secondo Campini in the early 1930s, although it was not until 1940 that an aircraft, the Caproni Campini N.