THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 345 E. 47th St., New York, N.Y.10017 97-GT-528 The Society shall not be response* for statements or opinions advancedin papers or clitussion at meetings of the Society or of its Divisions or Sections, or printed In its publications. Discussion is printed only if the paper is published in an ASME Journal. Authorization to photocopy material for Internal or personal use under circumstance not falling within the fair use. provisions of the Copyright Act is granted by ASME to libraries and other users registered with the Copyright Clearance Center (CCC) Transacticcal Reporting Senrice provided that the base fee of $0.30 • per page is paid direcby to the CCC, 27 Congress Street Salem MA 01970. Requests for special pemlission or bulk reproduction shadd be addressed to the ASME Teetotal Pubistting Department Copyright 0 1997 by ASME All Rights Reserved Printed in U.S.A Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78682/V001T01A012/2408878/v001t01a012-97-gt-528.pdf by guest on 23 September 2021 , 111 11111111,11 1)111111111 THE DEVELOPMENT OF THE WHITTLE TURBOJET Cyrus B. Meher-Homji Bechtel Corporation Houston, Texas. ABSTRACT The history of jet propulsion starts with the inventions of Hero of Alexandria (circa AD 60) who developed the first Sir Frank Whittle passed away on August 8, 1996 at the age of reaction type turbine. In 1791 John Barber invented a Watt type 89, in Maryland. His work in developing the turbojet can truly beam engine driven by a primitive gas turbine via reduction be said to represent one of the greatest mechanical engineering gearing. In 1900, Stirling Moss in the U.S, worked on a achievements in the last 70 years. The development of the Doctoral Thesis on gas turbines and upon joining General turbojet demanded that Whittle face almost insurmountable Electric (GE), designed and built one by 1907, albeit with poor technical and institutional challenges. The technical challenges performance. He then turned to his pioneering work on included developing centrifugal compressor pressure ratios of turbochargers for aircraft piston engines. In France, C. Lemale 4:1 from the prevailing technology level of 2.5:1, increasing and R. Armengaud, who worked at the Societe Anonyme des compressor efficiencies from 65 to 80% while designing for Turbomoteurs, designed a crude gas turbine which achieved an combustion intensities that were 10 times the prevailing state of overall efficiency of 3% by 1906. From 1905 through 1940, the the art in boiler technology. He was also responsible for Brown Boveri Corporation of Zurich designed and built several utilizing a vortex turbine design approach. The institutional pioneering gas turbines. In 1919, when the gas turbine was an challenges that he faced included changing a paradigm on established prime mover, the British Air Ministry asked Dr. aircraft propulsion technology and nurturing Power Jets Ltd. to W.I. Stern to report on the prospect for the use of gas turbines produce excellent engine designs with minimal resources in for aircraft propulsion. His study was flawed in its assumptions terms of money, technical manpower and governmental support, and he concluded that the gas turbine was not a feasible It is the object of this paper to document the epic long drawn out propositicml . This report was to have an adverse impact on struggle fought by Sir Frank against entrenched technical Whirde's quest for support years into the future. opinion that ultimately resulted in the turbojet revolution. The Dr. A.A. Griffith, a brilliant scientist working at England's technical aspects of his pioneering work with emphasis on the Royal Aircraft Establishment (RAE) worked in the 1920s on problems he encountered will also be discussed. developing groundbreaking aerodynamic theory where he treated turboznachine blades as airfoils. He built a small, 4 inch diameter, single stage axial compressor driven by an axial 1.0 INTRODUCTION turbine. Griffith played an important part in gas turbine development but, as we will see later, initially rejected 1.1 Historical Antecedents. Whittle's concept, thereby delaying Government assistance at a The turbojet revolution was pioneered by Sir Frank Whittle most critical juncture. in England and Hans von Ohain in Germany, their work being extensively documented by Constant (1980), Schleifer (1950), 1.2 Whittle's Early Work. von Ohain (1979), Scott (1995), and Jones (1989). Both these As a flight cadet attending the Royal Air Force College at pioneers who envisioned flight speeds in excess of 500 mph at Cranwell in 1928, Whittle wrote a thesis titled "Future altitudes of 30,000 feet, had revolutionary ideas as students, and Developments in Aircraft Design." In this thesis he proposed a developed their engines without the help of the traditional propulsion concept that utilized a piston engine driven aeroengine companies. In order to put the development of the compressor to blow air over fuel jets exhausting the high Whittle jet into a historical context, it is necessary to trace the temperature air through a propulsion mule. In October 1929, course of Whittle's thinking as well as the theoretical and practical developments in the field of gas turbines before the Second World War. 'Stem based his computations on industrial technology taking for example, 1250 lb. for fuel pumps and drive gears! Presented at the International Gas Turbine & Aeroengine Congress & Exhibition Orlando, Florida — June 2—June 5,1997 he realized that he could increase the blower pressure ratio and 2.0 BRIEF HISTORY OF WHITTLE'S ENGINES replace the piston engine by a turbine. Whittle approached Britain's air ministry with his concept but was told that it was not feasible. This assessment was made by Griffith who was 2.1 Design and Development of the WI) Engine eager to pursue his own complex gas turbine scheme 2 and failed In June 1936, the British Thomson-Houston Co (BTH) of to see the elegant simplicity of Whittle's engine. Rugby was awarded the contract for the detailed design and On January 16, 1930, Whittle filed for Patent No. 347206 for construction of the WU. Operating under severe financial "Improvements in Aircraft Propulsion" (Figure 1). This figure constraints, Whittle recognized he could not afford component Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78682/V001T01A012/2408878/v001t01a012-97-gt-528.pdf by guest on 23 September 2021 depicts a single shaft turbojet with an axial-centrifugal testing and therefore had to boldly take the risk and attempt to compressor, tubular combustor and two stage turbine. Between rim a complete engine'. His initial experiments on combustion 1934 and 1936. he studied for his Tripos at Cambridge and in were run with very envie combustion equipment as illustrated in 1935, allowed his patent to lapse because the Air Ministry Figure 2. As reported by Jones (1989), these experiments would not pay the .£5 renewal fee. Whittle however, doggedly produced deafening noise and thick clouds of fuel vapor and pursued his goal and in March 1936, a company called Power smoke. Reportedly, Power Jet's engineering drawings were Jets Ltt was launched with a nominal capital of t 10,000 with recognizable by the smell of fuel oil with which they became Whittle acting as the Chief Engineer. In May 18, 1935 he filed impregnated. for Patent No 459980 for an experimental turbojet, which would be called the WU. Whittle proceeded to design a double entry compressor with a 19" diameter made of high strength aluminum alloy and having 30 vanes. The compressor was to be driven by a 16.4" turbine operating at 17,750 RPM. The mass flow rate was to be 26 lb/sec and the pressure ratio 4.4:1. Whittle recognized that the area of greatest technical risk was in the combustor where an exceedingly large heat release had to be achieved in a very small volume. After talking to several burner manufacturers, Whittle was able to get the assistance of Laidlaw Drew and Co. to work on a small research contract. tt 15 = u 17 ' ft A.- 15 IMO Mao 6 hi Figure 2. Crude combustion test rig at the BTH factory, This shows the budgetary constraints that Whittle was working with. Deriving a satisfactory combustion chamber was one of the greatest challenges faced by Whittle. (Whittle, 1945) On April 12, 1937, the first few rims of the WU engine were Ut made. These were eventful because in several instances, the turbine accelerated with a rising shriek to 8,000 RPM even with the fuel valve closed. This uncontrolled and noisy acceleration Figure 1. Whittles patent drawing, filed January 16, 1930, caused considerable concern as it was usually accompanied by showing a two stage axial compressor followed by a one stage patches of red heat being visible on the combustor and flames centrifugal compressor. A straight through burner and a two emanating from the jet pipe. Finally, it was determined that fuel stage axial turbine on one disc is shown. pump tests conducted prior to engine light off resulted in an accumulation of fuel in the bottom of the combustion chamber It is interesting to note that the German jet engine which ignited causing the tmoontrolled acceleration. Figure 3 development program was, on the other hand, very well funded. illustrates the assembly of the first model of the experimental In 1938, Helmut Schelp had to pressure German aeroengine engine and the test stand on which it was to be used. The companies into accepting funds for studies on jet engines. The engine had a single large combustor of helical form. Tests German jet engine development program that resulted in the showed that the compressor and turbine efficiencies were below Junkers Jumo 004B, the world's first production jet engine design expectations.