Centrifugal compressors , sometimes called impeller compressors or radial compressors , are a sub-class of dynamic axisymmetric work-absorbing turbomachinery .
127-418: The Rolls-Royce RB.41 Nene is a 1940s British centrifugal compressor turbojet engine. The Nene was a complete redesign, rather than a scaled-up Rolls-Royce Derwent , with a design target of 5,000 lbf (22 kN), making it the most powerful engine of its era. First run in 1944, it was Rolls-Royce 's third jet engine to enter production, and first ran less than 6 months from the start of design. It
254-399: A Distinction in every subject, except mechanical drawing, where he was described as "a very able student. He works hard and has originality. He is suitable for experimental duties." His performance in the course was so exceptional that in 1934 he was permitted, though the scheme for RAF officers had been ended the year before, to take a two-year engineering course as a member of Peterhouse ,
381-459: A First. Without Air Ministry support, he and two retired RAF servicemen formed Power Jets Ltd to build his engine with assistance from the firm of British Thomson-Houston . Despite limited funding, a prototype was created, which first ran in 1937. Official interest was forthcoming following this success, with contracts being placed to develop further engines, but the continuing stress seriously affected Whittle's health, eventually resulting in
508-474: A US patent was made by Power Jets for an "Aircraft propulsion system and power unit" The W.1X engine powered the E.28/39 for taxi testing on 7 April 1941 at Brockworth near the factory in Gloucester, where it took to the air for two or three short hops of several hundred yards at about six feet from the ground. The definitive W.1 of 850 lbf (3.8 kN ) thrust ran on 12 April 1941, and on 15 May
635-427: A centrifugal compressor. Yet, there is one important difference: the need to deal with cavitation in pumps. Centrifugal compressors also look very similar to their turbomachinery counterpart the radial turbine as shown in the figure. While a compressor transfers energy into a flow to raise its pressure, a turbine operates in reverse, by extracting energy from a flow, thus reducing its pressure. In other words, power
762-667: A centrifugal fan are the same as those to design a centrifugal compressor, so they can look very similar. For purposes of generalization and definition, it can be said that centrifugal compressors often have density increases greater than 5 percent. Also, they often experience relative fluid velocities above Mach number 0.3 when the working fluid is air or nitrogen. In contrast, fans or blowers are often considered to have density increases of less than five percent and peak relative fluid velocities below Mach 0.3. Squirrel-cage fans are primarily used for ventilation. The flow field within this type of fan has internal recirculations. In comparison,
889-425: A centrifugal fan is uniform circumferentially. Centrifugal compressors are also similar to centrifugal pumps of the style shown in the adjacent figures. The key difference between such compressors and pumps is that the compressor working fluid is a gas (compressible) and the pump working fluid is liquid (incompressible). Again, the engineering methods used to design a centrifugal pump are the same as those to design
1016-567: A combustor, flow losses can be reduced by directing the flow with stationary turning vanes or individual turning pipes (pipe diffusers). As described in Bernoulli's principle , the reduction in velocity causes the pressure to rise. While illustrating a gas turbine's Brayton cycle, Figure 5.1 includes example plots of pressure-specific volume and temperature-entropy. These types of plots are fundamental to understanding centrifugal compressor performance at one operating point. The two plots show that
1143-531: A compressor with a pressure ratio of 4:1, while the best current supercharger had only half that value. Besides publishing a paper on superchargers, Whittle wrote The Case for the Gas Turbine . According to John Golley, "The paper contained example calculations which showed the big increase in efficiency which could be obtained with the gas turbine at great height due to the beneficial effects of low air temperature. It also contained calculations to demonstrate
1270-435: A considerably greater energy release rate than a flame. The engine was run up to just over 4,000 lbf (18 kN), and a cheer went up around the assembled personnel. However the engine was running hotter than expected and would not reach 5,000 lb, as it was built, without overheating the turbine. Pearson, the performance engineer, insisted that no more running be done without fitting the guide vanes that were available for
1397-596: A day and he suffered from various stress-related ailments such as frequent severe headaches, indigestion, insomnia, anxiety, eczema and heart palpitations, while his weight dropped to nine stone (126 lb / 57 kg). To keep to his 16-hour workdays, he sniffed benzedrine during the day and then took tranquillisers and sleeping pills at night to offset the effects and allow him to sleep. He admitted later he had become addicted to benzedrine. Over this period he became irritable and developed an "explosive" temper. On 30 June 1939, Power Jets could barely afford to keep
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#17327721669371524-527: A few basic concepts in performance can be presented by examining an example test performance map. Pressure ratio and flow are the main parameters needed to match the Figure 5.2 performance map to a simple compressor application. In this case, it can be assumed that the inlet temperature is sea-level standard. This assumption is not acceptable in practice as inlet temperature variations cause significant variations in compressor performance. Figure 5.2 shows: As
1651-545: A large diameter, thin-walled, shaft almost as large as the turbine disc, "necked down" at either end where it connected to the turbine and compressor. In April, the Air Ministry issued contracts for W.2 production lines with a capacity of up to 3,000 engines a month in 1942, asking BTH, Vauxhall and the Rover Company to join. However, the contract was eventually taken up by Rover only. In June, Whittle received
1778-459: A letter from Griffith, who was of the opinion that Whittle's "simple" design could not achieve the sort of efficiencies needed for a practical engine. After pointing out an error in one of Whittle's calculations, Griffith went on to comment that the centrifugal design would be too large for aircraft use and that using the jet directly for power would be rather inefficient. Griffith called the design "impracticable," as current materials could not achieve
1905-645: A letter of support for Whittle and the engine from Henry Tizard (chair of the Engine sub-committee of the Aeronautical Research Committee) in response to Whyte Falk then agreed to finance Whittle. With that the jet engine was finally on its way to becoming a reality. On 27 January 1936, the principals signed the "Four Party Agreement", creating " Power Jets Ltd" which was incorporated in March 1936. The parties were O.T. Falk & Partners,
2032-663: A more compact engine, but increases the combustor pressure losses which has an adverse effect on engine performance. Less thrust is generated with the same fuel flow. It was during the design of the Nene that Rolls decided to give their engines numbers as well as names, with the Welland and Derwent keeping their original Rover models, B/23 and B/26 . It was later decided that these model designations looked too much like RAF bomber designations (i.e. " English Electric Canberra B.Mk 2 " would often be shortened to " Canberra B.2 "), and "R"
2159-482: A much greater pressure rise in a single stage (e.g. 8 in the Pratt & Whitney Canada PW200 series of helicopter engines) than does an axial stage. The 1940s-era German Heinkel HeS 011 experimental engine was the first aviation turbojet to have a compressor stage with radial flow-turning part-way between none for an axial and 90 degrees for a centrifugal. It is known as a mixed/diagonal-flow compressor. A diagonal stage
2286-463: A nervous breakdown in 1940. In 1944 when Power Jets was nationalised he again suffered a nervous breakdown, and resigned from the board in 1946. In 1948, Whittle retired from the RAF and received a knighthood . He joined BOAC as a technical advisor before working as an engineering specialist with Shell , followed by a position with Bristol Aero Engines . After emigrating to the U.S. in 1976 he accepted
2413-730: A physical training instructor at Halton to build up his physique, only to fail again six months later, when he was told that he could not be given a second chance, despite having added three inches to his height and chest. Undeterred, he applied again under an assumed name and presented himself as a candidate at the No 2 School of Technical Training RAF Cranwell . This time he passed the physical and, in September that year, 364365 Boy Whittle, F, started his three-year training as an aircraft mechanic in No. 1 Squadron of No. 4 Apprentices Wing, RAF Cranwell, because RAF Halton No. 1 School of Technical Training
2540-414: A place on the officer training course at Cranwell . He excelled in his studies and became an accomplished pilot. While writing his thesis he formulated the fundamental concepts that led to the creation of the turbojet engine, taking out a patent on his design in 1930. His performance on an officers' engineering course earned him a place on a further course at Peterhouse , Cambridge , where he graduated with
2667-523: A promotion to wing commander . On 19 July 1940, Power Jets abandoned effort to vaporize fuel, and adopted the controlled atomising burner for the combustion chamber, developed by Isaac Lubbock of Asiatic Petroleum Company (a joint venture of Shell and Royal Dutch) In the words of Whittle, "the introduction of the Shell system may be said to mark the point where combustion ceased to be an obstacle to development." The size of Power Jets also increased with
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#17327721669372794-514: A quick calculation and announced, "We've got a 600-mph [970 km/h] Meteor". Drawings for the 0.855 scale Nene, now known as the Derwent V, were started on 1 January 1945 and on 7 June the engine began a 100-hour test at 2,600 lbf (12 kN), soon reaching 3,500 lbf (16 kN). Weight was 1,250 lb (570 kg). By 1946 thrust had been increased to 4,200 lbf (19 kN) using Nimonic 90 turbine blades. The development of
2921-408: A report noting the limitations his concept. The report said "the internal combustion turbine will not be rendered practical by the revolutionary design of some lucky inventor. The steam turbine engineer and the metallurgist ... are the people with whom the future development of the turbine rests" Whittle recorded that he found the response depressing. Pat Johnson remained convinced of the validity of
3048-479: A scholarship to a secondary school which in due course became Leamington College for Boys , but when his father's business faltered there was not enough money to keep him there. He quickly developed practical engineering skills while helping in his father's workshop, and being an enthusiastic reader spent much of his spare time in the Leamington reference library, reading about astronomy, engineering, turbines, and
3175-547: A shrouded port, an annular duct (see Figure 1.1), a bifurcated duct, stationary guide vanes/airfoils used to straight or swirl flow (see Figure 1.1), movable guide vanes (used to vary pre-swirl adjustably). Compressor inlets often include instrumentation to measure pressure and temperature in order to control compressor performance. Bernoulli's fluid dynamic principle plays an important role in understanding vaneless stationary components like an inlet. In engineering situations assuming adiabatic flow , this equation can be written in
3302-468: A surprise for he had never previously flown a seaplane, but he nevertheless increased his reputation as a pilot by flying some 20 different types of floatplanes, flying boats, and amphibians. While at Felixstowe, Whittle met with the firm of Armstrong Siddeley , and their technical advisor W.S. Farren . The firm rejected Whittle's proposal, doubting material was available to sustain the required very high temperatures. Whittle's turbojet proposal required
3429-478: A version of Power Jet's set-up at Waterloo Mill, associated with their Barnoldswick factory, near Clitheroe . Rover was working on an alternative to Whittle's "reverse-flow" combustion chambers, by developing a "straight-through" combustion chamber and turbine wheel. Rover referred to the engine as the B.26, sanctioned by the Directorate of Engine Development, but kept secret until April 1942, from Power Jets,
3556-492: A well-known independent consulting aeronautical engineer and patent engineer. Bramson was initially sceptical but after studying Whittle's ideas became an enthusiastic supporter. Bramson introduced Whittle and his two associates to the investment bank O.T. Falk & Partners, where discussions took place with Lancelot Law Whyte and occasionally Sir Maurice Bonham-Carter . The firm had an interest in developing speculative projects that conventional banks would not touch. Whyte
3683-492: A wide range of solidities from less than 1 to over 4. Hybrid versions of vaned diffusers include wedge (see Figure 1.3), channel, and pipe diffusers. Some turbochargers have no diffuser. Generally accepted nomenclature might refer to the diffuser's lead edge as station 3 and the trailing edge as station 4. Bernoulli's fluid dynamic principle plays an important role in understanding diffuser performance. In engineering situations assuming adiabatic flow, this equation can be written in
3810-500: A year he was posted to the Central Flying School , then at RAF Wittering , for a flying instructor's course. He became a popular and gifted instructor, and was selected as one of the entrants in a competition to select a team to perform the "crazy flying" routine in the 1930 Royal Air Force Air Display at RAF Hendon . He destroyed two aircraft in accidents during rehearsals but remained unscathed on both occasions. After
3937-399: Is a partial list of centrifugal compressor applications each with a brief description of some of the general characteristics possessed by those compressors. To start this list two of the most well-known centrifugal compressor applications are listed; gas turbines and turbochargers. In the case where flow passes through a straight pipe to enter a centrifugal compressor,
Rolls-Royce Nene - Misplaced Pages Continue
4064-465: Is credited with co-creating the turbojet engine. A patent was submitted by Maxime Guillaume in 1921 for a similar invention which was technically unfeasible at the time. Whittle's jet engines were developed some years earlier than those of Germany's Hans von Ohain , who designed the first-to-fly turbojet engine as well as Austria’s Anselm Franz . Whittle demonstrated an aptitude for engineering and an interest in flying from an early age. At first he
4191-757: Is implied that mixed-flow turbomachinery lie between axial and radial. Key contributors of technical achievements that pushed the practical application of turbomachinery forward include: Denis Papin , Kernelien Le Demour, Daniel Gabriel Fahrenheit , John Smeaton, Dr. A. C. E. Rateau, John Barber , Alexander Sablukov , Sir Charles Algernon Parsons , Ægidius Elling , Sanford Alexander Moss , Willis Carrier , Adolf Busemann , Hermann Schlichting , Frank Whittle and Hans von Ohain . Centrifugal compressors are similar in many ways to other turbomachinery and are compared and contrasted as follows: Centrifugal compressors are similar to axial compressors in that they are rotating airfoil-based compressors. Both are shown in
4318-429: Is input to compressors and output from turbines. As turbomachinery became more common, standards have been created to guide manufacturers to assure end-users that their products meet minimum safety and performance requirements. Associations formed to codify these standards rely on manufacturers, end-users, and related technical specialists. A partial list of these associations and their standards are listed below: Below,
4445-406: Is kinetic which is converted to increased potential energy/static pressure by slowing the flow through a diffuser. The static pressure rise in the impeller may roughly equal the rise in the diffuser. A simple centrifugal compressor stage has four components (listed in order of throughflow): inlet, impeller/rotor, diffuser, and collector. Figure 1.1 shows each of the components of the flow path, with
4572-425: Is required to understand the compressor performance over its complete operating range. Figure 5.2, a centrifugal compressor performance map (either test or estimated), shows the flow, pressure ratio for each of 4 speed-lines (total of 23 data points). Also included are constant efficiency contours. Centrifugal compressor performance presented in this form provides enough information to match the hardware represented by
4699-415: Is standard practice, Figure 5.2 has a horizontal axis labeled with a flow parameter. While flow measurements use a variety of units, all fit one of 2 categories: Frank Whittle Air Commodore Sir Frank Whittle , OM , KBE , CB , FRS , FRAeS (1 June 1907 – 8 August 1996) was an English engineer, inventor and Royal Air Force (RAF) air officer . He
4826-410: Is today referred to as a motorjet ; an air compressor using a conventional piston engine to provide compressed air to a combustion chamber whose exhaust was used directly for thrust – essentially an afterburner attached to a piston engine driven air compressor. The idea was not new and had been talked about for some time in the industry, but Whittle's aim was to demonstrate that at increased altitudes
4953-423: Is used in the Pratt & Whitney Canada PW600 series of small turbofans. Centrifugal compressors are also similar to centrifugal fans of the style shown in the neighboring figure as they both increase the energy of the flow through the increasing radius. In contrast to centrifugal fans, compressors operate at higher speeds to generate greater pressure rises. In many cases, the engineering methods used to design
5080-426: Is very low." This led to three provisional specifications being filed, as the group sought to develop a jet-propelled aeroplane. The arrangement was that Williams and Tinling would have a quarter share each of the commercial rights but they would not approach any existing company in the aircraft industry. The agreement soon bore fruit, and in 1935, through Tinling's father, Whittle was introduced to Mogens L. Bramson,
5207-561: The Air Ministry enough to fund development with a contract for £5,000 to develop a flyable version. However, it was not until March 1938 that a contract was signed, when Power Jets became subject to the Official Secrets Act , limiting the ability to raise additional funds. In January 1938, BTH invested £2,500. In December 1937, Victor Crompton became Power Jets’ first employee, as an assistant to Whittle. Because of
Rolls-Royce Nene - Misplaced Pages Continue
5334-597: The Gloster Meteor proved so successful with its Derwents that the Air Ministry felt there was no pressing need to improve upon it. Instead a series of much more capable designs using the Rolls-Royce Avon were studied, and the Nene generally languished. A total of twenty-five Nenes were sold to the Soviet Union as a gesture of goodwill - with reservation to not use for military purposes - with
5461-664: The Grumman F9F Panther . Its most widespread use was in the form of the Klimov VK-1 , a reverse-engineered , modified and enlarged version which produced around 6,000 lbf (27 kN) of thrust, and powered the Russian built Mikoyan-Gurevich MiG-15 , a highly successful fighter aircraft which was produced in vast numbers. An uprated version of the Nene was produced as the Rolls-Royce Tay . The Nene
5588-589: The Heinkel He 178 , powered by the Heinkel HeS 3 . There is little doubt that Whittle's efforts would have been at the same level or even more advanced had the Air Ministry taken a greater interest in the design. When war broke out in September 1939, Power Jets had a payroll of only 10 and Griffith's operations at the RAE and Metropolitan-Vickers were similarly small. Whittle's smoking increased to three packs
5715-750: The Hispano-Suiza aircraft factory in Madrid in 1936, but Leret was executed months later by Francoist Moroccan troops after commanding the defence of his seaplane base near Melilla at the onset of the Spanish Civil War . His plans were hidden from the Francoists and secretly handed to the British embassy in Madrid a few years later when his wife, Carlota O'Neill , was released from prison. Despite lengthy delays in their own programme,
5842-693: The Luftwaffe beat the British efforts into the air by nine months. A lack of cobalt for high-temperature steel alloys meant the German designs were always at risk of overheating and damaging their turbines. The low-grade alloy production versions of the Junkers Jumo 004 , designed by Dr. Anselm Franz and which powered the Messerschmitt Me 262 would typically last only 10–25 hours (longer with an experienced pilot) before burning out; if it
5969-442: The aero - thermo domain of turbomachinery. The horizontal axis represents the energy equation derivable from The first law of thermodynamics . The vertical axis, which can be characterized by Mach Number, represents the range of fluid compressibility (or elasticity). The Z-axis, which can be characterized by Reynolds number , represents the range of fluid viscosities (or stickiness). Mathematicians and physicists who established
6096-583: The 36 Boeing B-17 Flying Fortresses . Earlier, in January, when the company formed, Henry Tizard , the rector of Imperial College London and chairman of the Aeronautical Research Committee (ARC), had prompted the Air Ministry's Director of Scientific Research to ask for a write-up of the design. The report was once again passed on to Griffith for comment, but was not received back until March 1937 by which point Whittle's design
6223-718: The Air Ministry refused to pay it the patent was allowed to lapse. Shortly afterwards, in May, he received mail from Rolf Dudley-Williams , who had been with him at Cranwell in the 1920s and Felixstowe in 1930. Williams arranged a meeting with Whittle, himself, and another by-then-retired RAF serviceman, James Collingwood Tinling . The two proposed a partnership that allowed them to act on Whittle's behalf to gather public financing so that development could go ahead. Whittle thought improvements to his original idea could be patented, noting, "Its virtue lies entirely in its extremely low weight, and that it will work at heights where atmospheric density
6350-452: The Air Ministry, Whittle and, together, Williams and Tinling. Falk was represented on the board of Power Jets by Whyte as chairman and Bonham-Carter as a director (with Bramson acting as alternate ). Whittle, Williams and Tinling retained a 49% share of the company in exchange for Falk and Partners putting in £2,000 with the option of a further £18,000 within 18 months. As Whittle was still a full-time RAF officer and currently at Cambridge, he
6477-402: The F.9/40, but the engine was replaced with the W.2B, having a designed static thrust of 1,800 pounds-force (8,000 N). An experimental version of the W.1, designated W.1X, was used as a mock-up for the E.28 installation. A second E.28 was powered by the W.1A, that incorporated W.2 features such as air cooling of the turbine and a different compressor intake. On 26 March 1940, the jet engine
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#17327721669376604-548: The Model Aircraft Society, where he built working replicas. The quality of these attracted the eye of the Apprentice Wing commanding officer, who noted that Whittle was also a mathematical genius. He was so impressed that in 1926 he recommended Whittle for officer training at RAF College Cranwell. For Whittle, this was the chance of a lifetime, not only to enter the commissioned ranks but also because
6731-421: The Nene combustion chambers found this to be a problem, and the first-run needed to ignite with a flame rather than the spark energy that was considered sufficient at that time. The Nene was subsequently fitted with two torch, or flame, igniters which had a fuel spray next to an igniter. The flame would project into the main combustor fuel spray. Torch igniters were superseded by surface discharge igniter plugs with
6858-521: The Nene under licence as the Hispano-Suiza Nene , with limited production before concentrating on the larger Rolls-Royce Tay/Hispano-Suiza Verdon . Data from Related development Related lists Centrifugal compressor They achieve pressure rise by adding energy to the continuous flow of fluid through the rotor/impeller. The equation in the next section shows this specific energy input. A substantial portion of this energy
6985-554: The Nene was continued with this scaled-down version, the Derwent V having no direct relationship to the earlier Derwent series. On 7 November 1945, the first official air speed record by a jet aircraft was set by a Meteor F.3 of 606 miles per hour (975 km/h) powered by the scaled-down Nene. The Nene doubled the thrust of the earlier generation engines, with early versions providing about 5,000 lbf (22.2 kN), but remained generally similar in most ways. This should have suggested that it would be widely used in various designs, but
7112-481: The Nene were undertaken in an Avro Lancastrian operated by Rolls-Royce from their Hucknall airfield. The two outboard Rolls-Royce Merlins were replaced by the jet engine. The Nene's first flight however was in a modified Lockheed XP-80 Shooting Star . After seeing the Nene running, at an after work drink at the Swan & Royal Hotel , Clitheroe , and hearing the complaints about a lack of any official application for
7239-470: The W.1-powered E.28/39 took off from Cranwell at 7:40 pm, flying for 17 minutes and reaching a maximum speed of around 340 mph (545 km/h). At the end of the flight, Pat Johnson, who had encouraged Whittle for so long said to him, "Frank, it flies." Whittle replied, "Well, that's what it was bloody well designed to do, wasn't it?" Within days the aircraft was reaching 370 mph (600 km/h) at 25,000 feet (7,600 m), exceeding
7366-595: The W.U. and then lend it back to them, injecting cash, and placed an order for a flyable version of the engine, referred to as the Power Jets W.1 and Power Jets W.2 . By then, the Ministry had a tentative contract with the Gloster Aircraft Company for a simple aircraft specifically to flight-test the W.1, the single-engine Gloster E.28/39 . Whittle had already studied the problem of turning
7493-410: The accepted mathematical nomenclature refers to the leading edge of the impeller with subscript 1. Correspondingly, the trailing edge of the impeller is referred to as subscript 2. As working-gas/flow passes through the impeller from stations 1 to 2, the kinetic and potential energy increase. This is identical to an axial compressor with the exception that the gases can reach higher energy levels through
7620-406: The adjacent photograph of an engine with 5 stages of axial compressors and one stage of a centrifugal compressor. The first part of the centrifugal impeller looks very similar to an axial compressor. This first part of the centrifugal impeller is also termed an inducer . Centrifugal compressors differ from axials as they use a significant change in radius from inlet to exit of the impeller to produce
7747-628: The agreement of Stafford Cripps . Rolls-Royce were given permission in September 1946 to sell 10 Nene engines to the USSR, and in March 1947 to sell a further 15. The price was fixed under a commercial contract. A total of 55 jet engines were sold to the Soviets in 1947. Seventeen Soviet engineers trained at the Rolls-Royce factory in Derby in 1947 to maintain and repair the engine. The Soviets reneged on
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#17327721669377874-418: The combustion specialists, and took a wide interest in engine development problems, removed one of the igniters and instead used the flame from an oxy-acetylene torch to ignite the fuel in the combustion chamber. The igniter had to be close enough to the fuel spray to ignite it when starting, but not overheat when subjected to the continuous flame temperature when the engine was running. The larger diameter of
8001-544: The commanding officer of the base. This set in motion a chain of events that almost led to the engines being produced much sooner than actually occurred. Earlier, in July 1926, A. A. Griffith had published a paper on compressors and turbines, which he had been studying at the Royal Aircraft Establishment (RAE). He showed that such designs up to this point had been flying "stalled", and that by giving
8128-645: The company an emergency loan of £250. On 27 July, Falk's option expired, but they agreed to continue financing Power Jets by loan. Also in July, Whittle's post-graduate stay at Cambridge was over, but then he was placed on the Special Duty List so he could work full-time on the engine. On 1 November, Williams, Tinling and Whittle took control of Power Jets. Whittle was promoted to squadron leader in December. Tizard pronounced it "streaks ahead" of any other advanced engine he had seen, and managed to interest
8255-503: The compressed air for the burner, a turbine could be used to extract some power from the exhaust and drive a compressor, similar as in a turbocharger . The remaining exhaust thrust would power the aircraft. On 27 August 1928, Pilot Officer Whittle joined No. 111 Squadron , Hornchurch, flying Siskin IIIs . His continuing reputation for low flying and aerobatics provoked a public complaint that almost led to his being court-martialled. Within
8382-418: The compressor blades an aerofoil-shaped cross-section their efficiency could be dramatically improved. The paper went on to describe how the increased efficiency of these sorts of compressors and turbines would allow a jet engine to be produced, although he felt the idea was impractical, and instead suggested using the power as a turboprop . At the time most superchargers used a centrifugal compressor , so there
8509-621: The compressor. In some applications, collectors will diffuse flow (converting kinetic energy to static pressure) far less efficiently than a diffuser. Bernoulli's fluid dynamic principle plays an important role in understanding diffuser performance. In engineering situations assuming adiabatic flow, this equation can be written in the form: Equation-1.4 where: Over the past 100 years, applied scientists including Stodola (1903, 1927–1945), Pfleiderer (1952), Hawthorne (1964), Shepherd (1956), Lakshminarayana (1996), and Japikse (many texts including citations), have educated young engineers in
8636-471: The course was that each student had to produce a thesis for graduation: Whittle decided to write his on potential aircraft design developments, notably flight at high altitudes and speeds over 500 mph (800 km/h). In Future Developments in Aircraft Design he showed that incremental improvements in existing propeller engines were unlikely to make such flight routine. Instead he described what
8763-465: The degree to which range would depend on height with turbojet aircraft." Every officer with a permanent commission was expected to take a specialist course, and as a result Whittle attended the Officers School of Engineering at RAF Henlow in 1932. He obtained an aggregate of 98% in all subjects in his entrance exam, which allowed him to complete a shortened one-year course. Whittle received
8890-436: The design target. Hooker, Adrian Lombard , Pearson and Morley designed a new engine, the B.41 later called the Nene, rather than scaling up the Derwent. The double-sided impeller was 28.8 inches (73 cm) in diameter, compared to 20.68 in (52.5 cm) for the Derwent I, to produce an airflow of 80 lb/s (36 kg/s), while the overall diameter of the engine was 49.5 inches (126 cm). A scaled up Derwent of
9017-481: The diffuser discharges into an annular bend the collector may be referred to as a combustor inlet (as used in jet engines or gas turbines) or a return-channel (as used in an online multi-stage compressor). As the name implies, a collector's purpose is to gather the flow from the diffuser discharge annulus and deliver this flow downstream into whatever component the application requires. The collector or discharge pipe may also contain valves and instrumentation to control
9144-434: The durability of the vanes so the first Nene was initially built without them. The Nene was based on the "straight-through" version of the basic Whittle -style layout, with the flow going directly through the engine from front to rear, as opposed to a "reverse-flow" type, which reverses the direction of air flow through the combustor section so that the turbine stage can be mounted within the combustor section; this allows for
9271-454: The effort (they regarded it as long-range research and set up work on an axial flow turbine at the RAE with Hayne Constant in 1937 ), and having no production facilities of its own, Power Jets entered into an agreement with steam turbine specialists British Thomson-Houston (BTH) to build an experimental engine facility at a BTH factory in Rugby, Warwickshire . Work progressed quickly, and by
9398-492: The end of the year 1936 the prototype detail design was finalised and parts for it were well on their way to being completed, all within the original £2,000 budget. However, by 1936, Germany had also started working on jet engines ( Herbert A. Wagner at Junkers and Hans von Ohain at Heinkel ) and, although they too had difficulty overcoming conservatism, the German Ministry of Aviation (Reichsluftfahrtministerium)
9525-432: The engine although intensive development was started on all features of the new combustion chambers. By this point it was clear that Gloster's first airframe would be ready long before Rover could deliver an engine. Unwilling to wait, Whittle cobbled together an engine from spare parts, creating the W.1X ("X" standing for "experimental") which ran for the first time on 14 December 1940. Shortly afterwards an application for
9652-420: The engine, someone - thought to be Whittle - suggested that the Nene be scaled-down to fit a Meteor nacelle. J.P. Herriot or Lombard did the calculation on a tablecloth and announced a thrust of 3,650 lbf (16.2 kN). At this time they were attempting to increase the Derwent's thrust from 2,200 to 2,450 lbf (9.8 to 10.9 kN), and the idea seemed "too good to be true". On hearing this, Hooker did
9779-469: The flow (working gas) entering the centrifugal impeller axially from left to right. This turboshaft (or turboprop) impeller is rotating counter-clockwise when looking downstream into the compressor. The flow will pass through the compressors from left to right. The simplest inlet to a centrifugal compressor is typically a simple pipe. Depending upon its use/application inlets can be very complex. They may include other components such as an inlet throttle valve,
9906-413: The flow is axial, uniform, and has no vorticity, i.e. swirling motion. As the flow passes through the centrifugal impeller, the impeller forces the flow to spin faster as it gets further from the rotational axis. According to a form of Euler 's fluid dynamics equation, known as the pump and turbine equation , the energy input to the fluid is proportional to the flow's local spinning velocity multiplied by
10033-484: The form: Equation-1.1 where: The identifying component of a centrifugal compressor stage is the centrifugal impeller rotor. Impellers are designed in many configurations including "open" (visible blades), "covered or shrouded", "with splitters" (every other inducer removed), and "w/o splitters" (all full blades). Figures 0.1, 1.2.1, and 1.3 show three different open full inducer rotors with alternating full blades/vanes and shorter length splitter blades/vanes. Generally,
10160-497: The form: Equation-1.2 (see Figures 1.2.2 and 1.2.3 illustrating impeller velocity triangles) where: The next component, downstream of the impeller within a simple centrifugal compressor may the diffuser. The diffuser converts the flow's kinetic energy (high velocity) into increased potential energy (static pressure) by gradually slowing (diffusing) the gas velocity. Diffusers can be vaneless, vaned, or an alternating combination. High-efficiency vaned diffusers are also designed over
10287-424: The form: Equation-1.3 where: The collector of a centrifugal compressor can take many shapes and forms. When the diffuser discharges into a large empty circumferentially (constant area) chamber, the collector may be termed a Plenum . When the diffuser discharges into a device that looks somewhat like a snail shell, bull's horn, or a French horn, the collector is likely to be termed a volute or scroll . When
10414-453: The foundations of this aero-thermo domain include: Isaac Newton , Daniel Bernoulli , Leonhard Euler , Claude-Louis Navier , George Stokes , Ernst Mach , Nikolay Yegorovich Zhukovsky , Martin Kutta , Ludwig Prandtl , Theodore von Kármán , Paul Richard Heinrich Blasius , and Henri Coandă . Figure 2.2 (shown right) represents the physical or mechanical domain of turbomachinery. Again,
10541-739: The fundamentals of turbomachinery. These understandings apply to all dynamic, continuous-flow, axisymmetric pumps, fans, blowers, and compressors in axial, mixed-flow and radial/centrifugal configurations. This relationship is the reason advances in turbines and axial compressors often find their way into other turbomachinery including centrifugal compressors. Figures 2.1 and 2.2 illustrate the domain of turbomachinery with labels showing centrifugal compressors. Improvements in centrifugal compressors have not been achieved through large discoveries. Rather, improvements have been achieved through understanding and applying incremental pieces of knowledge discovered by many individuals. Figure 2.1 (shown right) represents
10668-523: The future must produce 2,000 hp with one moving part: a spinning turbine and compressor.' However O.T. Falk & Partners specified they would only invest in Whittle's engine if they had independent verification that it was feasible. They financed an independent engineering review from Bramson (the historic "Bramson Report" ), which was issued in November 1935. It was favourable and together with
10795-543: The hazardous nature of the work being carried out, development was moved largely from Rugby to BTH's lightly used Ladywood foundry at nearby Lutterworth in Leicestershire in 1938. Tests with a reconstructed W.U. engine commenced on 16 April 1938, and proceeded until a catastrophic failure of the turbine on 6 May. Yet, the engine ran for 1 hour and 45 minutes, and generated a thrust of 480 pounds-force (2,100 N) at 13,000 rpm . Another W.U. engine reconstruction
10922-481: The high temperatures. Griffith did say "the internal combustion turbine will almost certainly be developed into a successful engine, but before this can be done the performance of both compressors and turbines will have to be greatly improved. However it has been of real interest to investigate your scheme and I can assure you that any suggestion submitted by people in the Service is always welcome." Whittle received
11049-415: The horizontal axis represents the energy equation with turbines generating power to the left and compressors absorbing power to the right. Within the physical domain the vertical axis differentiates between high speeds and low speeds depending upon the turbomachinery application. The Z-axis differentiates between axial-flow geometry and radial-flow geometry within the physical domain of turbomachinery. It
11176-417: The idea, and had Whittle patent the idea in January 1930. Since the RAF was not interested in the concept they did not declare it secret, meaning that Whittle was able to retain the rights to the idea, which would have otherwise been their property. Johnson arranged a meeting with British Thomson-Houston (BTH), whose chief turbine engineer seemed to agree with the basic idea. However, BTH did not want to spend
11303-479: The impeller intake. Upon Hooker's arrival next morning, and informed that the inlet vanes had been fitted during the night, Hooker was overjoyed to see the thrust gauge needle registering 5,000 lbf (22 kN) at the same temperature that had only given 4,000 lb the previous night, making the B.41 the highest thrust jet engine in the world. Weight was around 1,600 lb (730 kg). Inlet guide vanes had been in use in Whittle engines for some time. They improve
11430-440: The impeller's increasing radius. In many modern high-efficiency centrifugal compressors the gas exiting the impeller is traveling near the speed of sound. Most modern high-efficiency impellers use "backsweep" in the blade shape. A derivation of the general Euler equations (fluid dynamics) is Euler's pump and turbine equation , which plays an important role in understanding impeller performance. This equation can be written in
11557-457: The lights on when yet another visit was made by Air Ministry personnel. This time Whittle was able to run the third reconstructed W.U. at 16,000 rpm for 20 minutes without any difficulty. One of the members of the team was the Director of Scientific Research, David Randall Pye , who walked out of the demonstration utterly convinced of the importance of the project. The Ministry agreed to buy
11684-433: The local impeller tangential velocity . In many cases, the flow leaving the centrifugal impeller is traveling near the speed of sound . It then flows through a stationary compressor causing it to decelerate. The stationary compressor is ducting with increasing flow-area where energy transformation takes place. If the flow has to be turned in a rearward direction to enter the next part of the machine, e.g. another impeller or
11811-762: The low air density would greatly reduce resistance in proportion to speed." Of the few apprentices accepted into the Royal Air Force College, Whittle graduated in 1928 at the age of 21 and was commissioned as a pilot officer in July. He ranked second in his class in academics, won the Andy Fellowes Memorial Prize for Aeronautical Sciences for his thesis, and was described as an "exceptional to above average" pilot. However, his flight logbook also showed numerous red ink warnings about showboating and overconfidence, and because of dangerous flying in an Armstrong Whitworth Siskin he
11938-437: The lower outside air density would increase the design's efficiency. For long-range flight, using an Atlantic-crossing mailplane as his example, the engine would spend most of its time at high altitude and thus could outperform a conventional powerplant. According to Whittle, "...I came to the general conclusion that if very high speeds were to be combined with long range, it would be necessary to fly at very great height, where
12065-541: The map to a simple set of end-user requirements. Compared to estimating performance which is very cost effective (thus useful in design), testing, while costly, is still the most precise method. Further, testing centrifugal compressor performance is very complex. Professional societies such as ASME (i.e. PTC–10, Fluid Meters Handbook, PTC-19.x), ASHRAE ( ASHRAE Handbook ) and API (ANSI/API 617–2002, 672–2007) have established standards for detailed experimental methods and analysis of test results. Despite this complexity,
12192-438: The massive W.U. into a flyable design, with what he described as very optimistic targets, to power a little aeroplane weighing 2,000 lb with a static thrust of 1,389 lb. The designed maximum thrust for the W.1 was 1,240 pounds-force (5,500 N), while that for the W.2, was 1,600 pounds-force (7,100 N) The W.2 was to be flown in the twin-engine Gloster Meteor fighter, at the time known by its Air Ministry specification as
12319-534: The oldest college of Cambridge University , graduating in 1936 with a First in the Mechanical Sciences Tripos . The Ministry gave him permission to spend a further year after graduation working with the aerodynamicist Melvill Jones . On 1 February 1934, he was promoted to the rank of flight lieutenant . Still at Cambridge, Whittle could ill afford the £5 renewal fee for his jet engine patent when it became due in January 1935, and because
12446-419: The overall performance of the engine significantly by "helping the air round the corner". However they were made from thin sheet metal and often broke damaging the engine. For Hooker they were a worrying mechanical problem which he did not want so they were not fitted when the Derwent entered service, although the turbine had to run 90 degC hotter to give the take-off thrust of 2,000 lb. He was still concerned with
12573-602: The performance of the contemporary Supermarine Spitfire fighters. Success of the design was now evident, and in 1941, Rolls-Royce , Hawker Siddeley , the Bristol Aeroplane Company , and de Havilland became interested in gas turbine aircraft propulsion. Under Harold Roxbee Cox , the Gas Turbine Collaboration Committee was created to give a forum for all the companies for exchange of information. The stress on Whittle
12700-682: The position of NAVAIR Research Professor at the United States Naval Academy from 1977 to 1979. In August 1996, Whittle died of lung cancer at his home in Columbia, Maryland. In 2002, Whittle was ranked number 42 in the BBC poll of the 100 Greatest Britons . Whittle was born in a terraced house in Newcombe Road, Earlsdon , Coventry, England, on 1 June 1907, the eldest son of Moses Whittle and Sara Alice Garlick. When he
12827-459: The pressure rises between the compressor inlet (station 1) and compressor exit (station 2). At the same time, the specific volume decreases while the density increases. The temperature-entropy plot shows that the temperature increases with increasing entropy (loss). Assuming dry air, and the ideal gas equation of state and an isentropic process, there is enough information to define the pressure ratio and efficiency for this one point. The compressor map
12954-482: The promise to not use it for military purposes, and reverse engineered the Nene to develop the Klimov RD-45 , and a larger version, the Klimov VK-1 , which soon appeared in various Soviet fighters including Mikoyan-Gurevich MiG-15 . Pratt & Whitney acquired a licence to produce the Nene as the Pratt & Whitney J42 , and it powered the Grumman F9F Panther which first flew in November 1947. The Nene
13081-441: The same thrust would have had a 60-inch (150 cm) diameter. The compressor casing was based on Whittle's Type 16 W.2/500 compressor case which was more aerodynamically efficient than that on the Derwent but also eliminated cracking. Other design advances included nine new low pressure-drop/high efficiency combustion chambers developed by Lucas and a small impeller for rear bearing and turbine disc cooling. The first engine start
13208-401: The second incident an enraged Flight Lieutenant Harold W. Raeburn said furiously, "Why don't you take all my bloody aeroplanes, make a heap of them in the middle of the aerodrome and set fire to them – it's quicker!" Whittle showed his engine concept around the base, where it attracted the attention of Flying Officer Pat Johnson, formerly a patent examiner. Johnson, in turn, took the concept to
13335-501: The team pressed ahead, and the Power Jets WU (Whittle Unit, or W.U.) engine began test runs on 12 April 1937. Initially, the W.U. showed an alarming tendency to race out of control, due to issues with the fuel injection, before stable speeds were reached. However, by August, Whittle acknowledged a major reconstruction effort was needed to solve the combustion problem and compressor efficiency. On 9 July, Falk & Partners gave
13462-568: The theory of flight. At the age of 15, determined to be a pilot, Whittle applied to join the RAF . In January 1923, having passed the RAF entrance examination with a high mark, Whittle reported to RAF Halton in Buckinghamshire as an Aircraft Apprentice . He lasted only two days: just five feet tall and with a small chest measurement, he failed the medical. He then put himself through a vigorous training programme and special diet devised by
13589-581: The training included flying lessons on the Avro 504 . While at Cranwell he lodged in a bungalow at Dorrington . Being an ex-apprentice amongst a majority of ex- public schoolboys , life as an officer cadet was not easy for him, but he nevertheless excelled in the courses and went solo in 1927 after only 13.5 hours’ instruction, quickly progressing to the Bristol Fighter and gaining a reputation for daredevil low flying and aerobatics. A requirement of
13716-435: The war effort, increasing from 25 employees in January 1940 to 70 in September 1940. Meanwhile, work continued with the W.U., which eventually went through nine rebuilds in an attempt to solve the combustion problems that had dominated the testing. On 9 October the W.U. ran once again, this time equipped with Lubbock or "Shell" atomising-burner combustion chambers. Combustion problems ceased to be an obstacle to development of
13843-609: The £60,000 it would cost to develop it, and this potential brush with early success went no further. In January 1930, Whittle was promoted to flying officer . In Coventry, on 24 May 1930, Whittle married his fiancée, Dorothy Mary Lee, with whom he later had two sons, David and Ian. Then, in 1931, he was posted to the Marine Aircraft Experimental Establishment at Felixstowe as an armament officer and test pilot of seaplanes, where he continued to publicise his idea. This posting came as
13970-475: Was accelerated too quickly, the compressor would stall and power was immediately lost, and sometimes it exploded on their first startup. Over 200 German pilots were killed during training. Nevertheless, the Me 262 could fly far faster than allied planes and had very effective firepower. Although Me 262s were introduced late in the war they shot down 542 or more allied planes and in one allied bombing raid downed 32 of
14097-627: Was added to the front, the "R" signifying "Rolls" and the original Rover "B" signifying Barnoldswick . This RB designation scheme continued into the late 20th Century, with turbofan designs such as the RB.199 , RB.203 and RB.211 ; the most recent family of Rolls-Royce turbofans (a development of the RB.211) goes under the simple designation " Rolls-Royce Trent ", with variants given their own designator number or letter series (i.e. Trent 500 , Trent 900 , Trent 1000 , Trent XWB , etc.). Early airborne tests of
14224-422: Was attempted on 27 October 1944. A number of snags delayed the run until nearly midnight, when with almost the entire day and night shift staff watching, an attempt was made to start the engine. To the frustration of everyone with a vested interest in it starting the engine refused to light - positioning the igniter was a trial-and-error affair at the time. On a subsequent attempt, Denis Drew, who had come from Lucas,
14351-495: Was designed as a result of a June 1944 visit to the US by Stanley Hooker . He discovered that General Electric already had two engine types running, an axial and a centrifugal, of 4,000 lbf (18 kN) thrust. He was determined to produce a higher thrust engine and subsequently obtained a Ministry of Aircraft Production contract for an engine of 4,200 lbf (19 kN) thrust with the understanding that 5,000 lbf (22 kN) would be
14478-409: Was disqualified from the end-of-term flying contest. Whittle continued working on the motorjet principle after his thesis work but eventually abandoned it when further calculations showed it would weigh as much as a conventional engine of the same thrust. Pondering the problem he thought: "Why not substitute a turbine for the piston engine?" Instead of using a piston engine driven compressor to provide
14605-597: Was expressed in a 27 May 1941 letter to Henry Tizard : The responsibility that rests on my shoulders is very heavy indeed. We are faced with two alternatives – either we place a powerful weapon in the hands of the Royal Air Force or, if we fail to get our results in time, we may have falsely raised hopes and caused action to be taken which may deprive the Royal Air Force of hundreds of aeroplanes that it badly needs. In mid-1941, relations between Power Jets and Rover had continued to deteriorate. Rover had established
14732-435: Was given the title "Honorary Chief Engineer and Technical Consultant". Needing special permission to work outside the RAF, he was placed on the Special Duty List and allowed to work on the design as long as it was for no more than six hours a week. However he was allowed to continue at Cambridge for a year doing post-graduate work which gave him time to work on the turbojet. The Air Ministry still saw little immediate value in
14859-481: Was impressed by the 28-year-old Whittle and his design when they met on 11 September 1935: The impression he made was overwhelming, I have never been so quickly convinced, or so happy to find one's highest standards met... This was genius, not talent. Whittle expressed his idea with superb conciseness: 'Reciprocating engines are exhausted. They have hundreds of parts jerking to and fro, and they cannot be made more powerful without becoming too complicated. The engine of
14986-416: Was limited interest in the paper. Encouraged by his commanding officer, in late 1929 Whittle sent his concept to the Air Ministry to see if it would be of any interest to them. Whittle was invited to the Ministry and met an officer of the Ministry's Department of Scientific and Industrial Research (DSIR) and Griffith (at the time a member of the Aeronautical Research Committee). Afterwards, Whittle received
15113-404: Was listed as a potential war winner by Air Marshal Tedder , and given the associated priority. Power Jets also spent some time in May 1940 drawing up the W.2Y, a similar design with a "straight-through" airflow that resulted in a longer engine and, more critically, a longer driveshaft but having a somewhat simpler layout. To reduce the weight of the driveshaft as much as possible, the W.2Y used
15240-417: Was more supportive than their British counterpart. Von Ohain applied for a patent for a turbojet engine in 1935 but having earlier reviewed and critiqued Whittle's patents, had to narrow the scope of his own filing. In Spain, air-force pilot and engineer Virgilio Leret Ruiz had been granted a patent for a jet engine in March 1935, and Republican president Manuel Azaña arranged for initial construction at
15367-675: Was named after the River Nene in keeping with the company's tradition of naming its jet engines after rivers. The design saw relatively little use in British aircraft designs, being passed over in favour of the axial-flow Avon that followed it. Its only widespread use in the UK was in the Hawker Sea Hawk and the Supermarine Attacker . In the US it was built under licence as the Pratt & Whitney J42 , and it powered
15494-552: Was nine years old, the family moved to the nearby town of Royal Leamington Spa where his father, a highly inventive practical engineer and mechanic, purchased the Leamington Valve and Piston Ring Company, which comprised a few lathes and other tools and a single-cylinder gas engine , on which Whittle became an expert. Whittle developed a rebellious and adventurous streak, together with an early interest in aviation. After two years attending Milverton School, Whittle won
15621-435: Was started on 30 May 1938, but using ten combustion chambers to match the ten compressor discharge ducts. Avoiding a single large combustion chamber made the engine lighter and more compact. Tests commenced with this third W.U. on 26 October 1938. These delays and the lack of funding slowed the project. In Germany, Hans von Ohain had filed for a patent in 1935, which in 1939, led to the world's first flyable jet aircraft ,
15748-399: Was turned down by the RAF but, determined to join the force, he overcame his physical limitations and was accepted and sent to No. 2 School of Technical Training to join No 1 Squadron of Cranwell Aircraft Apprentices. He was taught the theory of aircraft engines and gained practical experience in the engineering workshops. His academic and practical abilities as an Aircraft Apprentice earned him
15875-489: Was unable to accommodate all the aircraft apprentices at that time. Whittle hated the strict discipline imposed on apprentices and, convinced there was no hope of ever becoming a pilot, he at one time seriously considered deserting. However, throughout his early days as an aircraft apprentice (and at the Royal Air Force College Cranwell ), he maintained his interest in model aircraft and joined
16002-687: Was used to power the first civil jet aircraft, the Nene Viking, a modified Vickers Viking , the single example of which first flew on 6 April 1948 from Wisley Airfield . It was briefly made under licence in Australia for use in the RAAF de Havilland Vampire fighters. It was also built by Orenda in Canada for use in 656 Canadair CT-133 Silver Star aircraft from 1952. Hispano-Suiza in France built
16129-531: Was well along. Griffith had already started construction of his own turbine engine design and, perhaps to avoid tainting his own efforts, he returned a somewhat more positive review. However, he remained highly critical of some features, notably the use of jet thrust. The Engine Sub-Committee of ARC studied Griffith's report, and decided to fund Griffith's effort instead. Given this astonishing display of official indifference, Falk and Partners gave notice that they could not provide funding beyond £5,000. Nevertheless,
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