Early British gas turbine development
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red admiral
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Some good information on Griffith's turbofan engine there. You look at the scheme and you've got to be impressed by it's brilliance from a theoretical point of view, but simply unworkable in practice. Each compressor stage being driven by it's own turbine stage and so it can run at it's own theoretical best speed. This then coupled onto a large fan (bypass ratio of 5) for maximum propulsive efficiency at subsonic speeds. The only problem then being in actually engineering the thing and getting it to work.
The CR1 is (or was a few years back) still at RRHT Derby.
There's some additional detail and simplified cross-section of the CR1 Turbofan engine in Gunston's The Development of Jet and Turbine Engines.
The CR1 is (or was a few years back) still at RRHT Derby.
There's some additional detail and simplified cross-section of the CR1 Turbofan engine in Gunston's The Development of Jet and Turbine Engines.
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Donald Eyre was the designer who drew the Griffith perspective above; it was his job to express visually Griffiths's concepts for communication to the rest of the company. As Don once explained over a cup of coffee... one had to remember we were building very complex pieces of machinery anyway... called a V-12 engine.... so the challenges did not seem too great. Some of the engineering RR did at that time was about reorienting thinking of some of the staff away from V12s and to consider the gas turbine and its implications.. RR did, starting with a WR1 built with Whittle's blessing, and 15 years after the CR.1 had built 17,000 RR designed centrifugal engines based on the Whittle concept. I believe Griffith talked to Jakob Ackeret, (famous) Professor of Aerodynamics at ETH in Zurich, at about this time; who persuaded him that matching such a combination of aerofoils was a bit limiting. Further thinking by Griffith led him to think about more conventional and multi spool engines, leading eventually to the Avon and Conway.
While ingenious in some respects, the concept certainly doesn't seem to take advantage of the fact that it is aerodynamically much easier to extract work from the flow than adding work to it. A smaller number of turbine stages is able to drive a larger number of compressor stages, presumably with handsome weight savings for airborne applications. So one can sort of see why the tip driven configuration did not catch on in retrospect - or maybe it has for stationary machinery, anybody know?
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Matching the characteristics of compressor and turbine for each stage over the operating range is quite a challenge too! Can't think of any real-world applications as the sealing issue is a killer ... and all those bearings!
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Although not a turbofan I thought it would be appropriate to show Metrovick's swansong in aircraft gas turbines... the 91st gas turbine they manufactured was the first Sapphire. shown here just after its first run at the 7,000lb rated thrust...17th May 1948. They built other Sapphires then kits of parts for Armstrong Siddeley in order to facilitate the smooth handover of the technology. The plant at Manchester was soon turning out steam turbines for various uses, which is where their expertise really lay. It is interesting that in the USA GE steam division made slow progress in gas turbines with the supercharger division exceeding their capability and creating the aero engine division for the company; just the reverse of Metrovick. It shows how company culture and the competences of the leaders makes a difference.
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US patent 2168726A, submited Feb 27, 1937, has a slightly more detailed diagram of the original ducted fan patent submitted in 1930 in UK(which I cannot locate).
A Canadian patent of 1947, (CA452368A), introduces a front and rear fan concept. The front fan of the engine is like a child's windmill at the outer edge... driven round as work is transferred from the rearward moving air in the intake; the inner row of blades are arranged as a compressor increasing the pressure of the intake air, i. e. work done on outer row is transferred to work done on air in inner row... then the W2/700 type core engine generates an exhaust stream that works on the rear fan in a conventional manner.
A Canadian patent of 1947, (CA452368A), introduces a front and rear fan concept. The front fan of the engine is like a child's windmill at the outer edge... driven round as work is transferred from the rearward moving air in the intake; the inner row of blades are arranged as a compressor increasing the pressure of the intake air, i. e. work done on outer row is transferred to work done on air in inner row... then the W2/700 type core engine generates an exhaust stream that works on the rear fan in a conventional manner.
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A report R&M 2607 covers the aerodynamic and mechanical testing at the RAE, of the Griffiths contra rotating rig constructed by Armstrong Siddeley.
Here is the report summary:
"Summary.--Several methods of constructing contra-flow turbo-compressor wheels have been investigated by
mechanical tests on single-stage wheels. The results have been incorporated in a complete unit which has been designed
and tested at the Royal Aircraft Establishment for research purposes. It was designed to pass 200 lb/min of air at
25,000 It with a compression ratio of 2-7 : 1 and a temperature at inlet to the turbine of 145 deg C.
In designing, the compressor results from aerofoil cascade tests were extrapolated beyond the limits then covered
(1938). Subsequent cascade experiments showed that the compressor efficiency would be low and that the blading
used would be stalled under design conditions. Tests on the unit confirmed this, indicating that a compressor efficiency
of about 70 per cent was the maximum obtainable, whereas the designed efficiency was 83 per cent, a figure which
with present day knowledge is easily obtainable. A slight modification to the compressor-blade heights improved
the efficiency and enabled the range of operation to be extended.
In the contra-flow unit the leakage between the shrouds separating the compressor and turbine annuli is a special
problem. Owing to the departure from design conditions and the intake air boost the leakage observed on the unit
was at times as much as 50 per cent of the entering air. The leakage likely to be obtained in a unit operating under
designed conditions is estimated at 4 per cent.
Most Of the remainder of the running time was devoted to investigation of mechanical problems. These included
the temperature gradients in the wheels, bearing cooling and lubrication, and constructional features. At a gas temperature
of 400 deg C. the constricting section in the wheel disc caused a drop of temperature of 150 deg C. above
the high pressure bearing housing. By increasing the cooling air mass flow this drop was increased to 250 deg C.
The bearings were found to be satisfactory provided their temperature could be maintained at less than 200 deg C.,
but the oil metering supply was unsatisfactory. Some movement of the blades in the rotors was observed and relative
axial expansion of t.he rotors andcasing led to rubbing at the high-pressure end. Trouble was also experienced with
the large gland leakage areas at the shrouds and around the bearing housings.
It was concluded that, in spite of the poor aerodynamic performance, there was no fundamental reason why similar
units should not operate efficiently and why a good mechanical performance should not be obtained."
Here are a sectional drawing and photos of the rig.. from the report here
Here is the report summary:
"Summary.--Several methods of constructing contra-flow turbo-compressor wheels have been investigated by
mechanical tests on single-stage wheels. The results have been incorporated in a complete unit which has been designed
and tested at the Royal Aircraft Establishment for research purposes. It was designed to pass 200 lb/min of air at
25,000 It with a compression ratio of 2-7 : 1 and a temperature at inlet to the turbine of 145 deg C.
In designing, the compressor results from aerofoil cascade tests were extrapolated beyond the limits then covered
(1938). Subsequent cascade experiments showed that the compressor efficiency would be low and that the blading
used would be stalled under design conditions. Tests on the unit confirmed this, indicating that a compressor efficiency
of about 70 per cent was the maximum obtainable, whereas the designed efficiency was 83 per cent, a figure which
with present day knowledge is easily obtainable. A slight modification to the compressor-blade heights improved
the efficiency and enabled the range of operation to be extended.
In the contra-flow unit the leakage between the shrouds separating the compressor and turbine annuli is a special
problem. Owing to the departure from design conditions and the intake air boost the leakage observed on the unit
was at times as much as 50 per cent of the entering air. The leakage likely to be obtained in a unit operating under
designed conditions is estimated at 4 per cent.
Most Of the remainder of the running time was devoted to investigation of mechanical problems. These included
the temperature gradients in the wheels, bearing cooling and lubrication, and constructional features. At a gas temperature
of 400 deg C. the constricting section in the wheel disc caused a drop of temperature of 150 deg C. above
the high pressure bearing housing. By increasing the cooling air mass flow this drop was increased to 250 deg C.
The bearings were found to be satisfactory provided their temperature could be maintained at less than 200 deg C.,
but the oil metering supply was unsatisfactory. Some movement of the blades in the rotors was observed and relative
axial expansion of t.he rotors andcasing led to rubbing at the high-pressure end. Trouble was also experienced with
the large gland leakage areas at the shrouds and around the bearing housings.
It was concluded that, in spite of the poor aerodynamic performance, there was no fundamental reason why similar
units should not operate efficiently and why a good mechanical performance should not be obtained."
Here are a sectional drawing and photos of the rig.. from the report here
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F.9 became ASM Sapphire because in 1947 MoS was trying to convert much residual munitions industry into the vital Export Drive. HSGroup was willing to build up ASM from its dabbling in turbines and to retain it in Aero, despite its modest stature -Cheetah and not much more. EE had salvaged Napier 23/12/42; its design Consultant, Halford, had moved permanently into DH Engines; those 2 plus Bristol and RR would do nicely, and Aero did not need diversion of the electical powerhouse AEI/BTH/MV. AEI's Chairman was ex-Minister of Production Oliver Lyttleton; a major shareholder (24.8% until 5/53) was (US)GE: both were quite content to exit UK Aero, whose future was blurred.
It is just too complicated to resurrect what then happened. In 1949 English Electric (Napier's owner) bought in the residual shareholding of US Westinghouse. Mergers and insolvency led to today's position where Finmeccanica (the Italian State), BAE (a Company accepted by US and UK Defence Ministers as having no distinctive patrimony - then-MoD Hoon noted that scarcely 51% was UK owned) and RR (10% owned by BMW), own such of these enterprises as still breathe. I think the last owner of the trade name Hawker was Lufthansa.
It is just too complicated to resurrect what then happened. In 1949 English Electric (Napier's owner) bought in the residual shareholding of US Westinghouse. Mergers and insolvency led to today's position where Finmeccanica (the Italian State), BAE (a Company accepted by US and UK Defence Ministers as having no distinctive patrimony - then-MoD Hoon noted that scarcely 51% was UK owned) and RR (10% owned by BMW), own such of these enterprises as still breathe. I think the last owner of the trade name Hawker was Lufthansa.
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Thanks Alertkin... makes sense ... a look at the Metrovick builds reflects the drive for exports and for supporting vital industry at home... Coal Board, Canary Islands, Shell Petroleum, etc., etc.
Incidentally, engine No107, a Sapphire, was shipped in pieces to ASM in April 1950, 3 years to the month after the first run of Sapphire No 91 in the photo above; it was the last Sapphire to be made by the Gas Turbine department. Bench testing of the Metrovick engine at ASM commenced in October, 1948, with official acceptance test being achieved in January 1950.
Incidentally, engine No107, a Sapphire, was shipped in pieces to ASM in April 1950, 3 years to the month after the first run of Sapphire No 91 in the photo above; it was the last Sapphire to be made by the Gas Turbine department. Bench testing of the Metrovick engine at ASM commenced in October, 1948, with official acceptance test being achieved in January 1950.
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alertken said:
A former employer of mine used to have a pair of line drawings that tracked this- one did the actual functioning entities and one the trade names- suffice to say it was all very complicated. One thing I have always been perplexed by is the collapse of DeHavilland (relatively speaking), they seem to have made a bad decision pursuing the Gyron. on the airframe side they had one unfortunate problem (Comet) and one self inflicted one (Venom Nightfighter delay/obsolescence resulting in it being substituted by the F-86 for the NATO all-weather requirement- would have been licence, licence provided in 1950) built by Macchi with Fiat and Alfa Romeo responsible for the Ghost- all funded by US$) but the aero-engine side gets strange. After the Goblin and the Ghost they start on the supersonic Gyron, seemingly without any in-house application and detached from the airframe business pursuing civil aircraft and the Avon powered DH110. There was the brief H3 turboprop project (bench run 1948, 500hp and 130lb of thrust) and an evolved but un-built Ghost (H4) but both seem to have been passed over leaving the turbine business to stumble on with the Gyron (Cancelled F155T- government support for the engine cancelled in 1957 after expenditure of £3.4 million, apparently Dassult looked at it as well) and Gyron Junior (Cancelled SR177, thirsty Bristol 188 and grossly underpowered Buccaneer S1) until finally being acquired by Bristol-Siddeley in November 1961.
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Sir Denning Pearson wrote a paper about the Aero industry in the West since WW2, published in 1962. The paper was an honest attempt to give a clear picture of what was going on in the industry at that time and obviously gives the view as seen from Rolls-Royce's perspective, but was not intended to be biased. I have copied the relevant sections for our perusal and comment.
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(I have not yet read tartle's Den). My take on the general demise of DH, not confined to Engine Co.
Sir Geoffrey was co-opted onto Brabazon Committee, 5/43. Various Sir Freds were not. Within 1944 he had won Type II, Airspeed AS.57, Type V, DH.104, and Type IV, DH.106. Military would be of modest business in Victory, so didn't he do well? He reconstructed the firm in 1944 in Aircraft, Engine and Propellor Cos. and recruited the great and good to manage them. His own span of control stretched, and losing a son did not help. By 1949 he had Sir Ralph Sorley (he of 8x.303 in Hurricane/Spitfire) at Props - who took them into his ex-MoS' mates' Guided Projectiles; he had Frank Halford as Engines MD and ex-MoS Sir Aubrey Burke as its Chairman. Halford in 1944 defined the future as H.1 (Goblin), H.2 (Ghost), H.3 small turboprop, H.4 (big Gyron), H.5, a centrifugal turbojet above Ghost, below Gyron...but unsuitable for Aircraft's super-Venom, to be DH.110). Halford later added H.6 (Gyron Jr) and H.7 gas generator.
MoS funded H.4, later H.6; Sir Geoffrey funded nothing PV and sold H.7 to Napier. Halford retired. Props (GW) and Aircraft took up Sir Geoffrey's and everybody's time. (Your choice of cause and effect:) applications for Gyron/Gyron Jr. stumbled. Engine Co. became the poisoned chalice berth, career-wise, just as Special Projects/Weapons Research were to be avoided at Vickers and Avro. Drift, demise, sale to BSEL as Small Engines Division.
Sir Geoffrey was co-opted onto Brabazon Committee, 5/43. Various Sir Freds were not. Within 1944 he had won Type II, Airspeed AS.57, Type V, DH.104, and Type IV, DH.106. Military would be of modest business in Victory, so didn't he do well? He reconstructed the firm in 1944 in Aircraft, Engine and Propellor Cos. and recruited the great and good to manage them. His own span of control stretched, and losing a son did not help. By 1949 he had Sir Ralph Sorley (he of 8x.303 in Hurricane/Spitfire) at Props - who took them into his ex-MoS' mates' Guided Projectiles; he had Frank Halford as Engines MD and ex-MoS Sir Aubrey Burke as its Chairman. Halford in 1944 defined the future as H.1 (Goblin), H.2 (Ghost), H.3 small turboprop, H.4 (big Gyron), H.5, a centrifugal turbojet above Ghost, below Gyron...but unsuitable for Aircraft's super-Venom, to be DH.110). Halford later added H.6 (Gyron Jr) and H.7 gas generator.
MoS funded H.4, later H.6; Sir Geoffrey funded nothing PV and sold H.7 to Napier. Halford retired. Props (GW) and Aircraft took up Sir Geoffrey's and everybody's time. (Your choice of cause and effect:) applications for Gyron/Gyron Jr. stumbled. Engine Co. became the poisoned chalice berth, career-wise, just as Special Projects/Weapons Research were to be avoided at Vickers and Avro. Drift, demise, sale to BSEL as Small Engines Division.
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alertken said:
That is my theory, Halford appears to have been allowed to run and develop a range if military jets with little consideration for the fact that they were not suitable for the military aircraft that airframes were building or for the Civilian aircraft that were becoming the focus.
So for aircraft propulsion gas turbine manufacturing I have:
Armstrong Siddeley: ASX
Metrovick: Eventually became Sapphire
RR: Enough said
DeHavilland: Ghost and Goblin
Bristol: Theseus
Napier: Naiad and Mamba
Am I missing any others?
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The roots of the way post WW2 industry developed started way back...
The building of the aero engine industry in the UK started in 1919.
In February 1919 Lieut Col L. F. R. Fell took over the duties of Assistant Director of Research and Development (Engines) under Brigadier-General Brooke-Popham who was appointed overall Director of Research at about the same time.
As Fell explained at a November 1965 lunch with Frank Nixon, an old colleague and presently the director of Quality at Derby, and myself (earning my meal by making notes of the conversation), "There was very little money to spend on engine development, only a few hundred thousand pounds a year, and production was on so small a scale that it could only be made commercially attractive if the prices were high. There was no time to create new designs. All we could do was to examine what was available, concentrate on the development of the most promising, and reach a production stage at the earliest moment, not only to save time but also to conserve the small amount of money available for development expenditure. For the same reason the industry was restricted to not more than four engine builders. Direct competition between engines of similar types and power could not be supported. the makers and their engines that were chosen for future development were:
Siddely-Deasy Jaguar: Double row 14 cylinder air cooled rated at 350 hp
Cosmos Jupiter: single row 9 cylinder air cooled 350 hp
Napier Lion Broad Arrow 12 cylinder liquid cooled 450 hp
Rolls-Royce Condor 12 cylinder Vee liquid cooled 650 hp
These engines were selected as representing clearly defined lines of development on which each engine builder could specialise. History has shown that this policy was sound taking into account all the difficulties of the time. Napier was on the verge of bankruptcy, Cosmos was in liquidation, When Fell visited Derby to discuss engine development Rolls-Royce had expressed (unknown to Royce) themselves as having no interest in aviation and wished to concentrate on their backlog of car orders. Only Siddeley was able and keen to cooperate immediately.
By the mid-1920's Fairey tried to upset the situation with the licence for the D-12; Napier were complacent with production engineers running the show; Bristol and A-S were busy with radials. Fell tried to get Napier to do a British answer to the D-12, even scheming an engine based on Napier Lion components... they were not interested as they had other ideas.. go back to the Mercedes WW1 construction to help manufacturing!
In desparation Fell asked Royce to do a D-12 killer even though it was out of the agreements on horsepower. Royce had been testing a monobloc aero engine so all the experience was folded into an F.X scheme from which emerged the Kestrel. Napier dwindled and tried to stay in the race with Halford's help... it was actually Brodie who was the person to turn Halford's concepts into things that might work.
When Whittle got into gas turbines BTH... in case I exceed post-size I'll continue separately.
The building of the aero engine industry in the UK started in 1919.
In February 1919 Lieut Col L. F. R. Fell took over the duties of Assistant Director of Research and Development (Engines) under Brigadier-General Brooke-Popham who was appointed overall Director of Research at about the same time.
As Fell explained at a November 1965 lunch with Frank Nixon, an old colleague and presently the director of Quality at Derby, and myself (earning my meal by making notes of the conversation), "There was very little money to spend on engine development, only a few hundred thousand pounds a year, and production was on so small a scale that it could only be made commercially attractive if the prices were high. There was no time to create new designs. All we could do was to examine what was available, concentrate on the development of the most promising, and reach a production stage at the earliest moment, not only to save time but also to conserve the small amount of money available for development expenditure. For the same reason the industry was restricted to not more than four engine builders. Direct competition between engines of similar types and power could not be supported. the makers and their engines that were chosen for future development were:
Siddely-Deasy Jaguar: Double row 14 cylinder air cooled rated at 350 hp
Cosmos Jupiter: single row 9 cylinder air cooled 350 hp
Napier Lion Broad Arrow 12 cylinder liquid cooled 450 hp
Rolls-Royce Condor 12 cylinder Vee liquid cooled 650 hp
These engines were selected as representing clearly defined lines of development on which each engine builder could specialise. History has shown that this policy was sound taking into account all the difficulties of the time. Napier was on the verge of bankruptcy, Cosmos was in liquidation, When Fell visited Derby to discuss engine development Rolls-Royce had expressed (unknown to Royce) themselves as having no interest in aviation and wished to concentrate on their backlog of car orders. Only Siddeley was able and keen to cooperate immediately.
By the mid-1920's Fairey tried to upset the situation with the licence for the D-12; Napier were complacent with production engineers running the show; Bristol and A-S were busy with radials. Fell tried to get Napier to do a British answer to the D-12, even scheming an engine based on Napier Lion components... they were not interested as they had other ideas.. go back to the Mercedes WW1 construction to help manufacturing!
In desparation Fell asked Royce to do a D-12 killer even though it was out of the agreements on horsepower. Royce had been testing a monobloc aero engine so all the experience was folded into an F.X scheme from which emerged the Kestrel. Napier dwindled and tried to stay in the race with Halford's help... it was actually Brodie who was the person to turn Halford's concepts into things that might work.
When Whittle got into gas turbines BTH... in case I exceed post-size I'll continue separately.
Interesting - probably an attempt to overcome the limitations in LPT work extraction and hence fan bypass ratio in aftfans due to the lack of supercharging of the engine core by a conventional LP compressor/fan. Weird though!tartle said:
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Off the top of my head......
Whittle chose BTH to help with development as they were steam turbine (rotating machinery) experts. When Rover were designated the production partner issues developed about who had design authority and who had change authority. Whittle tried to maintain control over design whilst Rover wanted to address the technology to production challenge by ad hoc changes a Barnoldswick. The friction caused slowed things down!Rolls addressed manufacturing challenges of piston engines by ruthlessly pruning production projects... trying only to support Merlin and the bigger Griffon, other projects took second place. When RR was asked/volunteered to help Rover/Power Jets with development they made haste slowly, building 2 centrifugal engines as learning exercises for Stanley Hooker and the team. Then they arranged to swap the manufacture of a tank engine version of the Merlin (done to help get enough power into tanks with WW1 Liberty engine technology). Griffith kept on with axial thinking and by the end of the war was looking at single, two and three spool engines... which led to the AJ65- Avon.
Tizard wanted to widen the expertise being focused on the gas turbine and so as the RAE realised Metrovick had their hands full with the F.2 they turned to ASM who hd built and supported the Griffith rig at Farnborough. ASM were not developing any high priority engines although they were producing many existing designs.. this meant thay could take on turbine work in the experi area. So the ASX based on RAE rig work was born.
Napier were challenged by the Sabre and remained so till the end of the war. At that stage they were entrusted with a gas generator design that turned into the Naiad, then the Eland and Gazelle. I worked on the latter on its transfer to Derby and found assembly a nightmare as well as discovering no sane manufacturing engineer could specify the manufacture and build steps of the compressor. As an apprentice I was given the jobs of rewriting the Napier instructions onto RR headed paper.. an easy job? No, the instructions did not work. A friend was courting a lad who went to Liverpool Uni and met a girl whose dad had recently retired as superintendent of the Speke facilty. We found out that the assembly and balancing of the compressor drum was a 'black art' and that was eventually specified on paper! What a way to win orders for your jet engines... no wonder Napier faded away.
Bristol had lost Fedden and his key engineers (such as Nixon mentioned earlier) and the gas turbine engines they came up with were a nightmare. Hooker fell out with Hives and moved to Bristol... it was he who took turbine development by the scruff of the neck and sorted the Proteus out... the configuration was flawed so he went on to design a new turboprop... the Orion
Fortunately Hooker arrived in time to take the design of the BE 10- the Olympus- into a much less tortured area of the design map and saved the engine division from ignominy. So the company map began to look more like pre war days with ASM, Bristol Napier and Rolls taking a leading role, Metrovick reverting to non-aero and de Havilland enduring by sheer effort and maybe also Napier's lack-lustre performance; this was was not improved by their obsession with the Nomad.. perhaps the diesel division saw it as a good technology platform... certainly its axial compressor should have read across to their early aero gas turbine work. As the direction of dominant gas turbine configurations became cleare and cash got tighter the reversion to a prewar 4 was attractive with a further concentration following as cash got even tighter? The growth of civil aviation was also playing a role as the development monies had to be found even if repaid by royalties. Success in terms of numbers of each engine built was now important as the need for launch money became dependant on previous (economic) performance.... a new world.
Whittle chose BTH to help with development as they were steam turbine (rotating machinery) experts. When Rover were designated the production partner issues developed about who had design authority and who had change authority. Whittle tried to maintain control over design whilst Rover wanted to address the technology to production challenge by ad hoc changes a Barnoldswick. The friction caused slowed things down!Rolls addressed manufacturing challenges of piston engines by ruthlessly pruning production projects... trying only to support Merlin and the bigger Griffon, other projects took second place. When RR was asked/volunteered to help Rover/Power Jets with development they made haste slowly, building 2 centrifugal engines as learning exercises for Stanley Hooker and the team. Then they arranged to swap the manufacture of a tank engine version of the Merlin (done to help get enough power into tanks with WW1 Liberty engine technology). Griffith kept on with axial thinking and by the end of the war was looking at single, two and three spool engines... which led to the AJ65- Avon.
Tizard wanted to widen the expertise being focused on the gas turbine and so as the RAE realised Metrovick had their hands full with the F.2 they turned to ASM who hd built and supported the Griffith rig at Farnborough. ASM were not developing any high priority engines although they were producing many existing designs.. this meant thay could take on turbine work in the experi area. So the ASX based on RAE rig work was born.
Napier were challenged by the Sabre and remained so till the end of the war. At that stage they were entrusted with a gas generator design that turned into the Naiad, then the Eland and Gazelle. I worked on the latter on its transfer to Derby and found assembly a nightmare as well as discovering no sane manufacturing engineer could specify the manufacture and build steps of the compressor. As an apprentice I was given the jobs of rewriting the Napier instructions onto RR headed paper.. an easy job? No, the instructions did not work. A friend was courting a lad who went to Liverpool Uni and met a girl whose dad had recently retired as superintendent of the Speke facilty. We found out that the assembly and balancing of the compressor drum was a 'black art' and that was eventually specified on paper! What a way to win orders for your jet engines... no wonder Napier faded away.
Bristol had lost Fedden and his key engineers (such as Nixon mentioned earlier) and the gas turbine engines they came up with were a nightmare. Hooker fell out with Hives and moved to Bristol... it was he who took turbine development by the scruff of the neck and sorted the Proteus out... the configuration was flawed so he went on to design a new turboprop... the Orion
Fortunately Hooker arrived in time to take the design of the BE 10- the Olympus- into a much less tortured area of the design map and saved the engine division from ignominy. So the company map began to look more like pre war days with ASM, Bristol Napier and Rolls taking a leading role, Metrovick reverting to non-aero and de Havilland enduring by sheer effort and maybe also Napier's lack-lustre performance; this was was not improved by their obsession with the Nomad.. perhaps the diesel division saw it as a good technology platform... certainly its axial compressor should have read across to their early aero gas turbine work. As the direction of dominant gas turbine configurations became cleare and cash got tighter the reversion to a prewar 4 was attractive with a further concentration following as cash got even tighter? The growth of civil aviation was also playing a role as the development monies had to be found even if repaid by royalties. Success in terms of numbers of each engine built was now important as the need for launch money became dependant on previous (economic) performance.... a new world.
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Getting back to the thread ...
Here is a Rolls-Royce layout of the Griffith turbofan shown in post #38. Work on this engine continued until 1944.
Also a link to the Armstrong Siddeley designs inspired by their work on the RAE Griffith contra-rotating rig
Here is a Rolls-Royce layout of the Griffith turbofan shown in post #38. Work on this engine continued until 1944.
Also a link to the Armstrong Siddeley designs inspired by their work on the RAE Griffith contra-rotating rig
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T: thank you.
I now have read den. Tight summary of this industry's history. Shame that he descends into begging. Because moaning about Treasury Sales Levy on products created at (our) expense, is begging. That attitude directly led to RR's demise, in which Denning Pearson was key. (We had) “promised a bit more than we could perform (we) never got cash-flow into our heads.” Sir D.Huddie,RR MD, in P.Pugh,Name/II,P156/i] RR expected MoS to funnel Aimed Research+Launch Aid in the National Interest, to admit PV R&D in prices (it is disingenous of den to claim (£33Mn) vast PV investment: it went straight back into overhead on MoS prices), and to waive the Levy by which Treasury (=you and I) recovered Launch Aid: L’État, c’est moi; what’s good for RR is good for UK. Not so.
I now have read den. Tight summary of this industry's history. Shame that he descends into begging. Because moaning about Treasury Sales Levy on products created at (our) expense, is begging. That attitude directly led to RR's demise, in which Denning Pearson was key. (We had) “promised a bit more than we could perform (we) never got cash-flow into our heads.” Sir D.Huddie,RR MD, in P.Pugh,Name/II,P156/i] RR expected MoS to funnel Aimed Research+Launch Aid in the National Interest, to admit PV R&D in prices (it is disingenous of den to claim (£33Mn) vast PV investment: it went straight back into overhead on MoS prices), and to waive the Levy by which Treasury (=you and I) recovered Launch Aid: L’État, c’est moi; what’s good for RR is good for UK. Not so.
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Alertkin,
They were interesting times...
Post bankruptcy we had to meet a reduced type test on RB211 at an agreed performance increase seemingly each month in order to get paid... we worked like hell to do the reduced Type Test every two weeks so we could have a second go if our DFA drawing driven modifications did not do the job (DFA= Design Fast Action... draw agree run it across road make build test; do it again faster better!).
Yes launch aid is useful and there should be payback; we are all investors in our future, etc..
I also remember den arguing that RR was a better bet for launch aid as it was just about the only engine company to make enough sales to pay it back... so I think the top team actually thought it was a useful source of funds... I suspect the terms of loan were beginning to be too demanding.. even from a taxpayers' point of view! Or maybe looking out gives a distorted view.
They were interesting times...
Post bankruptcy we had to meet a reduced type test on RB211 at an agreed performance increase seemingly each month in order to get paid... we worked like hell to do the reduced Type Test every two weeks so we could have a second go if our DFA drawing driven modifications did not do the job (DFA= Design Fast Action... draw agree run it across road make build test; do it again faster better!).
Yes launch aid is useful and there should be payback; we are all investors in our future, etc..
I also remember den arguing that RR was a better bet for launch aid as it was just about the only engine company to make enough sales to pay it back... so I think the top team actually thought it was a useful source of funds... I suspect the terms of loan were beginning to be too demanding.. even from a taxpayers' point of view! Or maybe looking out gives a distorted view.
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The mathematics of going turbofan were quite persuasive in the mid-1940s. The Germans were actually first to do a turbofan...looking more like a bypass in the RR Conway sense. SNECMA cooperated on a design scheme to put an aft fan on the Rateau turbojet.
These line drawings can be found in Tony Kay's two volume book 'The early History and Development of the Turbojet'.
These line drawings can be found in Tony Kay's two volume book 'The early History and Development of the Turbojet'.
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...and why did it take so long to adopt axial compressors? One reason was consistent, high quality manufacture. We discussed the low level of a Parsons compressor above. Here is a couple of pictures of a typical turbine they were turning out in 1895; Rolls-Royce assessed the aerodynamics in terms of what we know today as:
100KW Steam turbine
•Pitch/chord a bit too low.
•Tip thinning on suction side.
•Trailing edge FAR too thick.
•Surface roughness poor.
Compare the photos below with that of #9 above.
Anecdotally... Metrovick were accused of dragging their feet on the F.2, but they did work with High Duty Alloys on pressing techniques in order to turn out blading that was consistent, both blade-to-blade, and engine-to-engine. In the long run Metrovick made rapid manufacture more likely but at the expense of seeming slow to the Ministry.
100KW Steam turbine
•Pitch/chord a bit too low.
•Tip thinning on suction side.
•Trailing edge FAR too thick.
•Surface roughness poor.
Compare the photos below with that of #9 above.
Anecdotally... Metrovick were accused of dragging their feet on the F.2, but they did work with High Duty Alloys on pressing techniques in order to turn out blading that was consistent, both blade-to-blade, and engine-to-engine. In the long run Metrovick made rapid manufacture more likely but at the expense of seeming slow to the Ministry.
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Donald Eyre, who taught me much about advanced project design, worked with Griffith for 21 years translating his sketches into design schemes that had a chance of being practical..a fascinating challenge. He drew a perspective of Griffith's latest idea for a gas turbine which was shown to the King and Qhenn on a tour of Derby works Aug 8th 1940.
Spurred by comment in next post... I have added a pic of RB211-535 for comparison
Spurred by comment in next post... I have added a pic of RB211-535 for comparison
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Johnbr ... I agree it looks almost like the style of the RR Propfan of today... it is based on thinking rather than actuality so it is only when technology (materials, tools, techniques and skills) catch up that they turn into practical reality...
Of the contraflow Griffith's right hand man and translator to something visually discussable had some thoughts...
Don Eyre wrote in his book:
"Returning to the contraflow engine itself, after thorough rig tests of bearings, combustion chambers and burners, etc, the 14-stage high-pressure unit was built for test; the first run being on 3rd March 1942. Alternative schemes of blade cooling were investigated and a specimen twin-blade was cast in Vitallium with a hollow turbine blade. A small hole through the intermediate shroud permitted cooling air to flow from the compressor annulus into the turbine blade. Various schemes of airborne bearings were also devised by Dr. Griffith. Many features of the engine were optimistic relative to the knowledge of gas turbines in those days and the initial tests showed clearly that considerable development would be necessary. The fact that the turbine and compressor blades were indivisible would add to the cost of testing alternatives of either and methods of blade manufacture were in their early stages. Accurate profiling of aerodynamic shapes had not been developed and the blade form in the test engines had been seriously modified to suit avalable milling cutters, thus jeopardising their performance and inducing premature surging. The compressor had a much lower efficiency than Dr. Griffith predicted on the basis of accurate blade profiling and effective interstage sealing and the ARC recommendedthe discontinuance of research.
During the eries of tests, I drew a revised contraflow scheme, designed to eliminate some of the difficulties and to incorporate improvenents which the tests had shown to be desirable. However, by the time accurate blade shapes were attainable, the simpler forms of gas turbine - valuable as a short-term war expedient - had progressed so satisfactorily that the need to return to the contraflow principle did not arise and further work on the engine was suspended although Dr Griffith continued for some time to study various alternative contraflow arrangements. "
A fascinating insight into the challenges faced in developing a new form of prime mover by the designer who had to transform Griffith's ideas into testable hardware.
His book 50 Years with Rolls-royce: My Reminiscences (Rolls Royce Heritage Trust Historical Series)is worth a read if you are interested in a descriptive account of working for Royce himself and his senior engineers over the years.
Of the contraflow Griffith's right hand man and translator to something visually discussable had some thoughts...
Don Eyre wrote in his book:
"Returning to the contraflow engine itself, after thorough rig tests of bearings, combustion chambers and burners, etc, the 14-stage high-pressure unit was built for test; the first run being on 3rd March 1942. Alternative schemes of blade cooling were investigated and a specimen twin-blade was cast in Vitallium with a hollow turbine blade. A small hole through the intermediate shroud permitted cooling air to flow from the compressor annulus into the turbine blade. Various schemes of airborne bearings were also devised by Dr. Griffith. Many features of the engine were optimistic relative to the knowledge of gas turbines in those days and the initial tests showed clearly that considerable development would be necessary. The fact that the turbine and compressor blades were indivisible would add to the cost of testing alternatives of either and methods of blade manufacture were in their early stages. Accurate profiling of aerodynamic shapes had not been developed and the blade form in the test engines had been seriously modified to suit avalable milling cutters, thus jeopardising their performance and inducing premature surging. The compressor had a much lower efficiency than Dr. Griffith predicted on the basis of accurate blade profiling and effective interstage sealing and the ARC recommendedthe discontinuance of research.
During the eries of tests, I drew a revised contraflow scheme, designed to eliminate some of the difficulties and to incorporate improvenents which the tests had shown to be desirable. However, by the time accurate blade shapes were attainable, the simpler forms of gas turbine - valuable as a short-term war expedient - had progressed so satisfactorily that the need to return to the contraflow principle did not arise and further work on the engine was suspended although Dr Griffith continued for some time to study various alternative contraflow arrangements. "
A fascinating insight into the challenges faced in developing a new form of prime mover by the designer who had to transform Griffith's ideas into testable hardware.
His book 50 Years with Rolls-royce: My Reminiscences (Rolls Royce Heritage Trust Historical Series)is worth a read if you are interested in a descriptive account of working for Royce himself and his senior engineers over the years.
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Stanley Hooker, Adrian Lombard and co, up in Barnoldswick had a good working relationship with Frank Whittle and took notice of his efforts to create both a fan engine and a turboprop. engines were investigated whilst they put a gearbox on a Derwent and produced the Trent engine. The RB 39 was schemed out by Hooker's team to be used either as a fan or prop engine. It was decided to proceed and the turboprop seemed the first version to be of use.. there were suitable aircraft being investigated. Aimed to deliver 3,000 shp the RB 39, to be known as the Clyde was stared in 1944. Anyone who has studied the wartime developement of the Merlin will know how adept Hooker was at suggesting adding a bit of this and a bit of that to quickly get a prototype (put a Vulture supercharger in front of the Merlin supercharger yields a twin stage supercharger for the Merlin). Having looked at scaling the Merlin 2-stage supercharger as the basis of the turboprop, Hooker opted for a two-spool engine, giving a PR= 6.0, consisting of an lp turbine driving a gearbox that had shaft outputs for the propeller and the 9-stage axial l-p compressor- which was in fact David Smith's seventh design iteration of the Metrovick F.2 engine, being downrated to 6,000 maximum speed (PR=2.65); co-axially was a single-sided hp centrifugal compressor of 2.35 PR, a scaled up Merlin 46 supercharger, driven by a single hp turbine. The engine ran on 1st Aug. 1945 giving 2,000 shp... sorting out the mismatch between the compressors soon yielded its design power and by the time the ninth engine was built horsepower had reached 4,200 shp. (in 1949). It was a great engine in the Wyvern but for various reasons Hives never let it go into production, one reason being his belief in the Avon as the next Merlin. The Clyde behaved well during its development programme but the fan version was never built
The section drawing and a photo of the Clyde on test are below:
The section drawing and a photo of the Clyde on test are below:
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So let me get this straight, The Clyde axial LP compressor was
driven via the propeller reduction gearbox, and not directly via
the LP turbine.......
"Though it looked like two engines joined together"
cheers,
Robin.
driven via the propeller reduction gearbox, and not directly via
the LP turbine.......
No wonder the Great Gunston said of this engine in 'World Encyclopaedia of Aero Engines' :-
"Though it looked like two engines joined together"
cheers,
Robin.
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I think there was a better relationship between RR B'wick and Whittle..as a friend of Sir Frank reminded me the other day... it was Rover's top management that he couldn't abide... apparently.
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Renamed topic as it is increasing wide-ranging.
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tartle said:
Sounds like the perfect split to me; nicely takes into account the primary wartime developments.
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So was the Clyde compressor geared up or down from the LP turbine speed?
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When I have got some spare time I will, unless a gear expert out there wants to, calculate the gear ratios; but assuming the MV turbine ran optimally and as the Clyde is derated to a lower pressure ratio my guess is compressor runs slower.. but my guesses can be hopeless so I'll do more digging! aha! lp turbine is 12720 rpm and lp compressor is 6,000 rpm, hp is 10,800 rpm.. both ends!!
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We must not forget the impact of Whittle on early gas turbine development in Britain. There is an interesting family tree of Rolls-Royce RB centrifugals that grew as RR took an interest in the activity at Barnoldswick and began to help Whittle to keep development on track.
RR's centrifugal branch starts with the WR.1, a learning engine done at Derby, and then gets into full swing with the W.2/23 soon to be RB.23 Welland; Lombard straightened out the /23 to create the /26 which annoyed Whittle but when inherited by RR became the RB.26 which was the technology demonstrator for the RB.37 Derwent, followed by the RB.41 Nene and RB.44 Tay ... the latter having a better life abroad as Hives switched efforts to axials...
So we'll start with the WR.1............
Rolls-Royce got involved with the Whittle's development team at Power Jets quite early on in the development of a practical flight engine that Rover aimed to put into production. In August 1940 Hooker took Hives to Lutterworth to see the W1 engine running .. at the time it delivered 800 lb thrust (for powering the Gloster E28/39) and Hives thought it must be a very 'small' engine. Hooker calculated that the Merlin in a Spitfire flying at 300 mph delivered 840 lb thrust which changed Hives' view immediately. Whittle meanwhile was working on a larger a larger engine for the Meteor. It turned out that there were no facilities for running the larger impeller so Whittle was working in the dark as to how good his design was; during a war the more you can find out before you commit designs to manufacture will shorten development cycles and time.
In spite of the difficulties between Rover and Power Jets over what design authority Rover had over PJ designs (maybe benzedrine played a part in all that) Whittle did not feel that way about Rolls-Royce and when Hives offered help to get the W2 moving he took up the offer immediately. In spite of the huge committment to developing and producing the Merlin plus supporting Ford's factory in Manchesterand Packard's in the USA RR were able to supply some of the critical parts that were delaying the testing and improvement of the W2. Realising that Whittle's PJ team were having to estimate compressor performance and modifications and then test them on a real engine as there was no test rig in the country powerful enough to drive the compressor. RR suggested a better way was to build on their supercharger experience... Stanley Hooker and Geoff Wilde immediately proposed a rig design that could be quickly built at Derby. The rig was a Vulture 2,000 hp engine driving a 6:1 step up gear increasing the Vulture's 3,000 rpm to 18,000 rpm of the W2. The step up gear was simply constructed by taking two Merlin reduction gears, mounting them in series and then driving them backwards! The individual reduction gear ratio was 0.42:1 so backwards it provided about 2.5:1; so two in series easily gave the 6:1 requirement. Using the rig enabled Whittle to cut and try various fixes to the surge problem and eventually the surge characteristic was made tame enough for service operation
All this support work... compressor testing, turbine blade manufacture in the experi machine shop, etc made Rolls-Royce realise that they needed to get some design and testing experience of their own. The WR1 was designed by Stanley Hooker's Derby design team together with J.P.Herriot as the development engineer. The brief was to follow the conservative initial design phase as used in piston engine development allowing for uprating as experience built up.
The Ministry funded the manufacture of six engine sets of parts so the project went ahead.....
RR's centrifugal branch starts with the WR.1, a learning engine done at Derby, and then gets into full swing with the W.2/23 soon to be RB.23 Welland; Lombard straightened out the /23 to create the /26 which annoyed Whittle but when inherited by RR became the RB.26 which was the technology demonstrator for the RB.37 Derwent, followed by the RB.41 Nene and RB.44 Tay ... the latter having a better life abroad as Hives switched efforts to axials...
So we'll start with the WR.1............
Rolls-Royce got involved with the Whittle's development team at Power Jets quite early on in the development of a practical flight engine that Rover aimed to put into production. In August 1940 Hooker took Hives to Lutterworth to see the W1 engine running .. at the time it delivered 800 lb thrust (for powering the Gloster E28/39) and Hives thought it must be a very 'small' engine. Hooker calculated that the Merlin in a Spitfire flying at 300 mph delivered 840 lb thrust which changed Hives' view immediately. Whittle meanwhile was working on a larger a larger engine for the Meteor. It turned out that there were no facilities for running the larger impeller so Whittle was working in the dark as to how good his design was; during a war the more you can find out before you commit designs to manufacture will shorten development cycles and time.
In spite of the difficulties between Rover and Power Jets over what design authority Rover had over PJ designs (maybe benzedrine played a part in all that) Whittle did not feel that way about Rolls-Royce and when Hives offered help to get the W2 moving he took up the offer immediately. In spite of the huge committment to developing and producing the Merlin plus supporting Ford's factory in Manchesterand Packard's in the USA RR were able to supply some of the critical parts that were delaying the testing and improvement of the W2. Realising that Whittle's PJ team were having to estimate compressor performance and modifications and then test them on a real engine as there was no test rig in the country powerful enough to drive the compressor. RR suggested a better way was to build on their supercharger experience... Stanley Hooker and Geoff Wilde immediately proposed a rig design that could be quickly built at Derby. The rig was a Vulture 2,000 hp engine driving a 6:1 step up gear increasing the Vulture's 3,000 rpm to 18,000 rpm of the W2. The step up gear was simply constructed by taking two Merlin reduction gears, mounting them in series and then driving them backwards! The individual reduction gear ratio was 0.42:1 so backwards it provided about 2.5:1; so two in series easily gave the 6:1 requirement. Using the rig enabled Whittle to cut and try various fixes to the surge problem and eventually the surge characteristic was made tame enough for service operation
All this support work... compressor testing, turbine blade manufacture in the experi machine shop, etc made Rolls-Royce realise that they needed to get some design and testing experience of their own. The WR1 was designed by Stanley Hooker's Derby design team together with J.P.Herriot as the development engineer. The brief was to follow the conservative initial design phase as used in piston engine development allowing for uprating as experience built up.
The Ministry funded the manufacture of six engine sets of parts so the project went ahead.....
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The catalyst for Rolls-Royce to move from making parts for the W2B was the first flight of the Gloster E28/39 15 May 1941.
Given the other (Merlin, Griffon) priorities at Derby, it was December 1942 before the WR1 was first run
The basic data and comparison to other engines of the time shows how cautious Derby was in entering a new field of technology
(all figures from RR data sheets 1945)
Basic data CR1 B23 W2/500 W2/700
design mass flow lb/sec 46 31 32.2 40
max thrust lb 2,000 1600 1700 2,000
sfc lb/lb/hr 1.27 1.12 1.1 1.08
max temp deg K 1,000 1,060 1,000 1,000
max rpm 10,000 17,100 16,750 16,750
compression ratio 2.67 3.9 4.0 4.0
compressor dia in. 27.5 20.68 20.0 20.68
No combustion chambers 10 10 10 10
turbine mean blade speed ft/sec 938 1040 n/a n/a
weight lb 1,200 850 850 875
length to end exhaust cone in 78 71 61 61
max dia in 51.5 40 40 42
-----------------------------------------------------------------------------------------------------------
Taking the W2B as the starter, RR designed their own impellor based on Merlin experience. of design AND manufacture. The mechanical design also differed from the W2B series as RR explored ways of overcoming the deficiencies of the PJ design. It was an experimental rig... not designed to fly and so was comparitively big for its given thrust. The first engine ran for some 35 hours during which the combustion equipment gave trouble so an extensive programme of experimental work started on combustion chambers and turbines was initiated.
The advent of impellers giving 4:1 compression ration and other technology advances rendered the engine concept obsolete and the WR2 improved version never got beyond the project idea stage. The engine introduced Stanley Hooker to the challenges of turbine engine design and also J.P.Herriot who was on loan from the AID at MAP since 1940 (to Rover and RR) gained valuable experience as the development engineer on the project.
I have attached a diagrammatic x-section of the WR1 and B23 for comparison (Note fullscap doesn't fit A4 scanner- will get them redone) and a photo of the prototype.
Given the other (Merlin, Griffon) priorities at Derby, it was December 1942 before the WR1 was first run
The basic data and comparison to other engines of the time shows how cautious Derby was in entering a new field of technology
(all figures from RR data sheets 1945)
Basic data CR1 B23 W2/500 W2/700
design mass flow lb/sec 46 31 32.2 40
max thrust lb 2,000 1600 1700 2,000
sfc lb/lb/hr 1.27 1.12 1.1 1.08
max temp deg K 1,000 1,060 1,000 1,000
max rpm 10,000 17,100 16,750 16,750
compression ratio 2.67 3.9 4.0 4.0
compressor dia in. 27.5 20.68 20.0 20.68
No combustion chambers 10 10 10 10
turbine mean blade speed ft/sec 938 1040 n/a n/a
weight lb 1,200 850 850 875
length to end exhaust cone in 78 71 61 61
max dia in 51.5 40 40 42
-----------------------------------------------------------------------------------------------------------
Taking the W2B as the starter, RR designed their own impellor based on Merlin experience. of design AND manufacture. The mechanical design also differed from the W2B series as RR explored ways of overcoming the deficiencies of the PJ design. It was an experimental rig... not designed to fly and so was comparitively big for its given thrust. The first engine ran for some 35 hours during which the combustion equipment gave trouble so an extensive programme of experimental work started on combustion chambers and turbines was initiated.
The advent of impellers giving 4:1 compression ration and other technology advances rendered the engine concept obsolete and the WR2 improved version never got beyond the project idea stage. The engine introduced Stanley Hooker to the challenges of turbine engine design and also J.P.Herriot who was on loan from the AID at MAP since 1940 (to Rover and RR) gained valuable experience as the development engineer on the project.
I have attached a diagrammatic x-section of the WR1 and B23 for comparison (Note fullscap doesn't fit A4 scanner- will get them redone) and a photo of the prototype.
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The U.K. develops the gas turbine significantly quicker
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