Historical perspective of Gas turbine engines

1. NOTE ON GAS TURBINE ENGINES CHAPTER 5: FUNDAMENTALS OF AVIATION GAS TURBINE ENGINES Prepared By Dr. Semayat Fanta (Assistant Prof.) email: semayat.iitk2016@gmail.com Ethiopian Defence University, College of Engineering Bishoftu, Ethiopia October, 2023

2. INTRODUCTION A gas turbine is a rotary machine, similar in principle to a steam turbine. It consists of three main components-a compressor, a combustion chamber and a turbine. The air after being compressed into the compressor is heated either by directly burning fuel in it or by burning fuel externally in a heat exchange. The heated air with or without products of combustion is expanded in a turbine resulting in work output, a substantial part, about. two-thirds, of which is used to drive the compressor. Rest, about one-third, is available as useful work output

3. A gas turbine is a machine delivering mechanical power or thrust. It does this using a gaseous working fluid. The mechanical power generated can be used by, for example, an industrial device. The outgoing gaseous fluid can be used to generate thrust. In the gas turbine, there is a continuous flow of the working fluid. This working fluid is initially compressed in the compressor. It is then heated in the combustion chamber. Finally, it goes through the turbine. The turbine converts the energy of the gas into mechanical work. Part of this work is used to drive the compressor. The remaining part is known as the net work of the gas turbine. Gas turbines are operated thermodynamically by the Brayton cycle, in which air is compressed isentropically, combustion occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure.

4. EARLY DEVELOPMENT OF GAS TURBINE The concept of turbine prime mover can be traced back to Hero of Alexandria who lived about 2000 years ago. John Barber, an Englishman, was first to develop an important design in 1871. This design used an impulse turbine, a reciprocating compressor, a gas producer and a combustion chamber with water injection. In 1872 Stolze in Berlin and in 1884 John Parsons in England patented their designs but both of them failed. It was Prof. Dr. R. Stodola, the world famous teacher at the Swiss Federal Institute of Technology (from l892 to 1929} who established the scientific and engineering basis for the steam turbine and predicted a bright future for the gas turbine at a very date. Even the first edition of his standard book on steam turbines {1903) contained a chapter on gas turbines, including the general which fa still valid.

5. EARLY DEVELOPMENT OF GAS TURBINE The development of gas turbines was hampered for a long time despite this; general theory because of two basic reasons :- The lack of materials to withstand high temperature The lack of thermodynamic and aerodynamic knowledge of flow mechanism. Early attempts by Stolze in 1904 failed mainly because of the lack of necessary engineering know-how. Some attempts even produced negative power, i.e. power produced by turbine rotor was less than that required by the compressor.

6. RECENT HISTORY OF GAS TURBINES MEDIUM TEXTWe can distinguish two important types of gas turbines. There are industrial gas turbines and jet engine gas turbines. Industrial gas turbines were developed rather slowly. This was because, to use a gas turbine, a high initial compression is necessary. This rather troubled early engineers. Due to this, the first working gas turbine was only made in 1905 by the Frenchman Rateau. The honor of bringing the first industrial gas turbine into practice goes to Adolt Meyer of Brown Boveri when the first 4000 HP set was demonstrated in 1919 on the occasion of Swiss National Exhibition. This was the actual birth of the gas turbine. The use of the gas turbine in military jets brought a great boost in the thermodynamic and aerodynamic knowledge during and after the First World war. So far, all the efforts were concentrated only on open cycle gas turbine and till the end of the war little was known about the closed cycle gas turbine.

7. RECENT HISTORY OF GAS TURBINES The first gas turbine for power generation became operational in 1939 in Switzerland. It was developed by the company Brown Boveri. Gas turbines had a rather low thermal efficiency. But they were still useful. This was because they could start up rather quickly. They were therefore used to provide power at peak loads in the electricity network. In the 1980’s, natural gas made its breakthrough as fuel. Since then, gas turbines have increased in popularity. After world war-II, the gas turbine developed rapidly. New high-temperature materials, new cooling techniques and research in aerodynamics strongly improved the efficiency of the jet engine. It therefore soon became the primary choice for many applications. Currently, there are several companies producing gas turbines. The biggest producer of both industrial gas turbines and jet engines is General Electric (GE) from the USA. Rolls Royce and Pratt & Whitney are also important manufacturers of jet engines.