Basic mechanics for JET ENGIN

INTRODUCTION
1. The development of the gas turbine engine as an aircraft power plant has been so rapid that it is difficult to appreciate that prior to the 1950s very few people had heard of this method of aircraft propulsion. The possibility of using a reaction jet had interested aircraft designers for a long time, but initially the low speeds of early aircraft and the unsuitably of a piston engine for producing the large high velocity airflow necessary for the ‘jet’ presented many obstacles.

2. A French engineer, René Lorin, patented a jet propulsion engine (fig. 1-1) in 1913, but this was an athodyd (para. 11) and was at that period impossible to manufacture or use, since suitable heat resisting materials had not then been developed and, in the second place, jet propulsion would have been extremely inefficient at the low speeds of the aircraft of those days. However, today the modern ram jet is very similar to Lorin’s conception.

3. In 1930 Frank Whittle was granted his first patent for using a gas turbine to produce a propulsive jet, but it was eleven years before his engine completed its first flight. The Whittle engine formed the basis of the modern gas turbine engine, and from it was developed the Rolls-Royce Welland, Derwent, Nene and Dart engines. The Derwent and Nene turbo-jet engines had world-wide military applications; the Dart turbo-propeller engine became world famous as the power plant for the Vickers Viscount aircraft. Although other aircraft may be fitted; with later engines termed twin-spool, triple-spool, by-pass, ducted fan, unducted fan and propfan, these are inevitable developments of Whittle’s early engine.



4. The jet engine (fig. 1-2), although appearing so different from the piston engine-propeller combination, applies the same basic principles to effect propulsion. As shown in fig. 1-3, both propel their aircraft solely by thrusting a large weight of air backwards.

5. Although today jet propulsion is popularly linked with the gas turbine engine, there are other types of jet propelled engines, such as the ram jet, the pulse jet, the rocket, the turbo/ram jet, and the turborocket.