US jet engine development without WW2?

Discussion in 'Aviation' started by wiking85, May 29, 2015.

  1. wiking85

    wiking85 Well-Known Member

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    If there was not a WW2, say Hitler dies of a heart attack or something like that pre-1939, how long would it take the US to develop jet engines without British assistance? They were pretty behind compared to the Europeans and needed British developments to jump start their own program in 1943.
     
  2. Shortround6

    Shortround6 Well-Known Member

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    Not as far as you might think.

    The Jump start actually occurred in Feb 1941 with the forming of the Durand committee to look into Jet propulsion and the forming of a group of manufactures and the placing of development contracts.

    Without British assistance and without the threat of WW II as it was causing a rather unnecessary security situation the Army may have actually allowed the different companies to actually talk to each other. For instance GE in Lynn working on the Whittle type jets was not allowed to talk to GE in Schenectady who was working on the TG-100 turbo prop. Even some sharing of knowledge on burner cans and turbines might have been very beneficial even if the compressors were different. That is different divisions of the same company let alone different companies.
     
  3. kool kitty89

    kool kitty89 Well-Known Member

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    The bigger change might have been a lack of cetrifugal turbojet developments in the US, at least initially. (aside from the J31 and J33, it was later turboprop, turboshaft, and small turbojets used for trainers and short life engines for cruise missiles that used such, like the J44)
     
  4. Koopernic

    Koopernic Active Member

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    Nathan Prices work at Lockheed would probably have led to a workable and advanced axial jet.
    Eastman Jacobs advanced aerodynamics for jakes jeep might have used it rather than a motor jet. It's a tragedy that Jacobs was keep out of the loop. The nazis often get accused of mismanagement but the U.S. Seems to have been more restrictive and Byzantine.
     
  5. kool kitty89

    kool kitty89 Well-Known Member

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    #5 kool kitty89, May 30, 2015
    Last edited: May 30, 2015
    Perhaps if he'd been paired with a larger/diversified team that split off to develop more conservative/practical derivatives of his concept it would have proceeded more quickly. (GE or pretty much any engine company probably could have handled that, particularly with the NACA experimental axtial compressor data published and available) Price's earlier centrifugal compressor driven steam turbine engine seemed to develop a lot more smoothly too, so a more direct followon to that design building on a similar compressor and turbine (rather than solely focusing on the incredibly complex, exotic, hybrid reciprocating, axial, intercooled L-1000 engine might have even paralleled Ohain and Whittle's work -in fact, given his paring with Lockheed, the arrangement would be very similar to Ohain's situation with jet engine experimentation at Heinkel in 1937-40 -prior to the Hirth merger in 1941).

    The L-1000 itself, in original concept was a convoluted, overcomplicated mess that took far too long to be trimmed down to something remotely realistic. It wasn't advanced/complex in the sense of Griffith's axial designs at metrovick but just odd and unique in the sense you might expect from a concept design that never progresses far in development even on the drawing board.

    The reciprocating and intercooling really seems odd and unnecessarily complex. I could certainly see combining axial and centrifugal stages given it's inefficient to work with more than 1 (or especially more than 2) centrifugal stages, but adding a single centrifugal stage with one or more axial stages works rather well in concept and (in hindsight) also in practice.

    A turbofan derivative of Price's steam turboprop design might have been compelling as well. (it was also one of the unusual cases of a total loss steam turbine omitting use of a condenser, and applying that concept to a ducted fan that blends bypass air with the combustion chamber exhaust and steam turbine exhaust into a combined hot air/steam stream could have been very interesting, while avoiding using steam alone to power the turbine directly may have sidestepped some of the strength/heat/corrosion resistance needed for an exhaust turbine)
    If they'd ended up using methanol or ethanol as an antifreeze for the water supply, there also might even be enough alcohol in the steam exhaust to merit a sort of afterburning arrangement in the jet/fan exhaust.
     
  6. Koopernic

    Koopernic Active Member

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    By 1941 Prices design had become a 3 section axial compressor with intercooling between stages with multi-stage turbine with reheat between stages. This was Prices's background in steam turbine practice and thermodynamics coming to the fore.

    There is nothing wrong with intercooling a gas turbine compressor, it is a common practice in gas turbines for power and produces a vastly more efficient gas turbine, it is only avoided when a steam topping cycle is added. It is being investigated for high end turbofans which have a rather massive airflow for cooling. The reheat between turbine stages is rather complex but Prices engine was extremely ambitious in terms of fuel efficiency and power to weight ratio and this is what had to be done within the constraints of available materials. The reheat between stages is perhaps over the top but no doubt someone has tried it and proven that it is possible and workable.

    Secrecy in the US meant that the best aerodynamicists and reaction engine designers did not work together. This is something the Germans did very well.

    Prices focus on fuel efficiency may have seen him come up with a winning engine that dominated the commercial market.
     
  7. pbehn

    pbehn Well-Known Member

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    Without the build up to world war two through the thirties maybe another 20 years to develop but without a war what would you use them in? Post war civilian airliners were modified bombers, without that massive investment there would be no civilian airline industry and without a war jet engines would have taken years to get off the ground (literally). Whittles patents lapsed due to a lack of interest
     
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  8. kool kitty89

    kool kitty89 Well-Known Member

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    #8 kool kitty89, Jun 1, 2015
    Last edited: Jun 1, 2015
    As a long-term research and development project it may have been interesting, but jumping straight into an extremely complex, ambitious design as the primary (and sole) focus is the problem there. Work on the simple, practical problems first and evolve from there. (likewise the L-133 transonic/supersonic fighter project was jumping headlong into an overly ambitious project without intermediate experimental or potential production designs) or Some of the more ambitious, exotic, and theoretically efficient german engine designs like BMW's 002 (or the many more ambitious designs brought over from Junkers with Wagner and Muller -the 5 stage reaction compressor design of the HeS 30 was noted as being the simplest and easiest to work with of Muller's various designs -and indeed, seems simpler than some of the test rigs built at Junkers before the consolidation with the Jumo project)

    I was under the impression that there was still a great deal of secrecy as far as trade secrets, direct competition between firms, and relative lack of cooperation and exchange of information between said firms. Useful information may have been more widely published than in the US (after 1939) but perhaps somewhat worse (or just different?) than the likes of the NACA studies being shared pre-war.

    The British seemed to do it fairly well, at least with the extremely critical combustion chamber problem and the development of the atomizing combustion chambers adopted for the W.I, W.2, Welland, Derwent, Goblin, Nene, J31, J33, and J35 (the J33 and J35 have particularly similar combustion chamber designs), among others.

    Heinkel's Wagner/Muller derived team and Jumo both independently developed flame can type burners, and at least in Jumo's case ended up with the drawing board design working rather well from the start (possibly the most successful paper to reality of the initial jets to run) yet such an arrangement wasn't ever tested or adopted (even in the interim) on BMW's engine when it was suffering combustion problems. (in the end, the production 003's annular combustion chamber was exceptional and far superior to the 004's cans in longevity in spite of being made from mild steel, but that doesn't mean using can type burners wouldn't have allowed less ideal but reasonably serviceable models to enter mass production sooner). In the HeS 8's case, the compressor and turbine arrangement really favors an annular combustor and cans may not have helped much if at all. (they're far more useful when an axial turbine is used, though may also have made sense had Ohain continued to place the combustion section outside of the compressor/turbine discs as on the HeS 3 and 6 -at least allowing easier servicing and possibly more options for cooling air routing both inside and out of the engine more like Whittle's and Halford's designs)

    The L-1000 ended up the J37 and continued development post-war for an extended period and never materialized a production design. The research probably contributed useful data and experience for later projects, but nothing directly came of the J37.

    Aside from that, thermodynamic efficiency is only one facet of overall useful performance from gas turbine aircraft engines. Aerodynamic efficiency (including effective thrust) within given operational conditions (particularly speed ranges) is extremely important. Using jet exhaust for primary propulsion is extremely inefficient for low speeds and still somewhat inefficient at transonic speeds. Price's design may have made sense for a high efficiency supersonic transport, but there's very real practical reasons that A.A. Grifith focused on turboprops and fans so heavily. Griffith's designs at Metrovick managed exceptional fuel efficiency for the time even as pure jets, but the turbofans and open rotor propfans indeed COULD (and probably should) have taken the post-war commercial airline industry by storm ... and encouraged competition with other turbojets being adapted for thrust augmenting bypass fans. (whittle did do that with the modified W.2/700 intended for the M.52's powerplant, but that of course was canceled)
    Using small turbofans on the Vampire and Meteor (and P-8O) would have been extremely useful too, and the large diameter of their respective nacelles would make including fan based designs somewhat more straightforward. (then again, even Grifith's pure turbojets would have been very attractive for those, and the first promising reliable -flame can based- Metrovick F.2/3 was managing 2700 lbf in 1943 and in underwing nacelles likely would have avoided the initial troubles with the Welland/Derwent nacelles -of the war-time Metrovick engines, that would have been the most promising to press into mass production)

    The industry stuck with pure jet engines even up to the first generation of 707s ... and with the sheer level of complexity involved it really does seem quite odd that turbofans hadn't become commonplace on subsonic and transonic turbine powered aircraft. (back during De Havilland's development of the Comet and need for a stopgap powerplant well beyond the Goblin's capabilities, had they modified that engine to include an auxiliary fan stage it may have managed similar or greater thrust to the Ghost at substantially lower fuel consumption and likely somewhat lower weight -a turbofan Ghost derivative might have rivaled the thrust of the later Avon and precluded the need for their use at all)



    And many pre-war bombers were based on airliners, the two are generally interconnected and somewhat interchangeable, but also tend to be more efficient when expressly engineered for the task. As such, airliners likely would have been superior to the bomber derived ones used post-war.

    Whittle's patents had already lapsed pre-war and his work had already inspired some others to make their own attempts (namely Halford with the Goblin). A.A. Grifith had already started his own turboprop developments independently and may have continued along that path without bothering with pure jets initially. (he may have skipped over inefficient turbojets entirely and gone for high speed prop fans when getting into transonic airliner requirements)
     
  9. Shortround6

    Shortround6 Well-Known Member

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    There has always been a a bit of a see-saw between complicated but efficient engines and simple but thirsty engines. The ones in the middle seem to do (sell) best.

    The complicated engines tend to be used for special applications, like the longest range missions/routes. Their fuel economy seldom pays for the increased maintenance and loss of revenue (for commercial flights) due to the extra weight on shorter flights.

    The other problem with complicated engines is that the bar is always moving. A P&W JT-3C turbo jet used about 2/3 the fuel per pound of thrust as a P&W J48 (JT-7 or RR Tay) did. It also weighed about 3/4s as much per pound of thrust.
    A very complicated engine designed to do much better than the Centrifugal turbo jets of the 40s might not show up well against the high pressure ratio (12:1 and higher) axial turbo jets of the 50s. Granted these high pressure ratio Axial engines were anything but simple in their own way. Two spools or variable stators. The heat exchanger idea seems to capture the fancy of idealists looking the best efficiency but it seldom, if ever, worked out in practice.
     
  10. davparlr

    davparlr Well-Known Member

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    A verbose expansion of pbehn’s post.

    A broader question is what would have been the impact on the entire aeronautical development if there was no war threat <1939. In 1938-39, worldwide depression was still going on. Contrary to popular opinion, Roosevelt’s program for recovery was not working well. Unemployment in the US was running 16 – 17% during this period (Wikipedia) and in 1938 the defense budget was 9% of the national budget or 1.7 billion dollars, and in 1939 the defense budget was 10% of the national budget or 1.9 billion dollars. In 1941, with war clouds providing a powerful stimulus, the defense budget went up to 30% of the national budget or 7.2 billion dollars, almost 300% higher than the 1940 budget. Without this huge stimulus, aerospace development was not going to progress quickly, certainly not militarily.

    Since the world’s economy was slowly pulling out of the depression, I do not think the military, due to pathetic funding, would have been the main pusher of advance aircraft design but rather the civilian airliner industry. In my opinion, the most advance aircraft in 1938 (a non-war stimulated economy) was the DC-4, a big, fast aircraft and, with optional pressurization (never used), which also represented the first modern airliner (its basic design was used by the airlines well into the 60’s). Their new, burgeoning business would spur their desire for faster, larger, longer ranged, aircraft. As such I can see a real, although poorly funded, push toward a turboprop engine. U.S. manufacturers were very interested in maintaining their superiority in the passenger aircraft market so I think they would not have been far behind any competitor design.

    In general, I think, due to low funding, turbojet development worldwide would have been delayed at least five years with 1945 jet technology not occurring until 1950, and would have been quite competitive.
     
  11. pbehn

    pbehn Well-Known Member

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    according to wiki

    The DC-4's tricycle landing gear allowed its fuselage to have a constant cross-section for most of its length, so it could easily be stretched into the later DC-6 and DC-7. 1,163 C-54/R5Ds were built for the United States military between 1942 and January 1946; 79 DC-4s were built postwar.

    Without the war what engines would have gone in it and who would order 1600 to put it into production. Not knocking your post but anything after 1936 in aviation was affected by the war. Many post war airliners were based on the B 29, a civilian airline industry could not take the teething problems with the engines. Post war people were accustomed to the idea that you could fly thousands of miles safely over water.
     
  12. pbehn

    pbehn Well-Known Member

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    The point I was making was how little interest there was until a war appeared. Whittles patents were filed in 1930 by an RAF employee, 10 years later the RAFs front line fighter was a piston engined plane with in many cases a wooden prop, but 4 years after that there were jet powered fighters coming into service.
     
  13. kool kitty89

    kool kitty89 Well-Known Member

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    The problem is Whittle's military position, along with social status and luck/chance. Halford, Griffith, Price, and Ohain were all independent engineered that ended up having their research and development funded as private ventures. (I think Bramo, BMW, Junkers airframe division, and Jumo were developing engines as private ventures pre-war as well, or at least some of them were -I believe Bramo was working on preliminary jet engine development prior to the BMW merger)

    Indeed, the interest would be airliners and experimental aircraft. (and record breaking high speed flights) Heinkel at least was very much interested in funding such ventures.

    In terms of mass production, I agree (even with the war, the mature versions of engines in any country didn't really arrive until 1945 -albeit with a good bit of mismanagement and material shortages), but in terms of experimental design work, it may have gone faster in some areas, slower in others.

    Heinkel's jet experiments like would have been international news rather than secret, though Halford and Whittle's developments likely would not have been shared with the US (aside from licenses purchased later on). Whittle may never have gotten much/any funding from the British government and engine development would be limited to private ventures.

    Fuel hungry, unreliable prototypes would never reach mass production and continued development would likely continue until reliable turboprops and turbofans materialized before being implemented on airliners. (aside from maybe a few high speed airliners using first generation production turbojets) Flight worthy examples would certainly be test flown and used on experimental/record setting aircraft. (and some of those record setters might be the jet powered counterparts to some of the record setting mailplanes and airliners of the 1930s)

    Relevant NACA research would also continue to be published with pre-war level security clearance.



    None of those engines are turbofans, though, and the J48 is more directly comparable to the J35, J47, Orenda, and maybe some models of the Avon. The J48/Tay compares very favorably in fuel consumption to all of those, better than some, only slightly worse in others, and managed more thrust at lower weight than the J35 or J47 without afterburning. (and much lower weight than the Avon) The Metrovik F.2 and Beryl are somewhat smaller but don't appear more complex than the likes of those axial engines. (and the turbofan and propfan derivatives put them closer to the thrust class as well, at even lower fuel consumption)

    The Ghost compares less favorably (as would the Goblin next to the Derwent V or 8 ) in terms of thrust to weight and diameter, though fuel consumption is similar and mechanical complexity is likely the lowest of the lot. (by extension, hypothetical turbofan derivatives of said engines would be the simplest of the lot, and likely also considerably simpler than any of the above axial turbojets as they are without fans)

    Centrifugal engines are also so large in diameter, that little/no increase in maximum diameter would result from rear-fan turbofan implementations, though additional/larger air intakes would be required, obviously.
     
  14. davparlr

    davparlr Well-Known Member

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    I don't think I can agree with this. While it may be true for European countries looking at an aggressive Hitler, isolationist U.S., which really lasted until Dec. 7, 1941, did not seem to reflect any impact to its defense budget. The U.S. Defense budget in 1935 was 1.9 billion dollars, exactly the same as the defense budget in 1939. I have no doubt that the large majority, if not all the DC-4 development cost was supported by the airline industry and Douglas.

    The only airliners I know that was based on the B-29 was the Boeing 377 Stratocruiser and the Tupolev Tu-70.
     
  15. Shortround6

    Shortround6 Well-Known Member

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    This is true but I was referring to complicated engines in General. Like the Lockheed jet engine with heat exchangers. The Post war Napair Nomad being an example of excess complexity in the pursuit of fuel economy.

    Napier_Nomad.jpg

    People used the Wright Turbo-compound because they had to, it was not well liked. Several other similar engines in concept never made it out of the experimental shops.

    I don't know what the problem was with turbo-fans but it seems to have take until the late 50s for them to catch on.
    Going by Wilkinson's "Aircraft Engines of the World" which means what it announced to the "public" and not what is going on behind closed doors.
    In the 1956 edition only the RR Conway is listed as a turbo fan.
    In the 1958 edition you have the Conway (more models) and The GE CJ -805 aft fan.
    In the 1960-61 edition you have the GE CJ 805 aft fan (more models) and several models of the P W JT-3D for the Americans and the the Bristol Siddely BE 58, The Conway, the the R-R RB 141 and RB 163.
    In the 1962/63 edition you have the CJ-805 aft fan (more models) the GE CF-700 aft fan (J-85 with fan on the back) More JT-3ds, the JT-8D and the start of the TF-30. British have the Bristol Siddeley BS 75, the Bristol Siddeley Pegasus, more Conways, the RR Spey (RB 163) and the French kick in the Turbomeca Aubisque.
    Russian engines are listed in the books but turbofans, if they exist, are not revealed to the west at this time.

    Earlier editions may have mentioned turbo fans or by bypass engines from time to time but most or all the earlier ones were experimental (so were a few of the ones I listed).
    While the idea sounds simple the execution may not have been. I don't know but 10-15 years after the end of WW II for the Turbofan to achieve widespread sales seems like a long time if it was really easy to do. Or maybe the demand wasn't quite strong enough until around 1960. From Wiki on the Boeing 707 "Pan American World Airways began regular 707 service on October 26, 1958" and "The 707-420, a version of the stretched 707 with Rolls-Royce Conway turbofans, debuted in 1960, while Pratt Whitney JT3D turbofans debuted on the 707-120B and 707-320B models in 1961 and 1962, respectively." SO the Turbofans went into production/use just a few years after the most successful early jet airline flew.
     
  16. davparlr

    davparlr Well-Known Member

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    Without digging into, my Kay books, I have a theory on the late fan development. Post WW2 and the cold war era engine development was pushed by military specifications rather than by commercial needs and, during this period, that meant higher and faster. With the advent of aerial refueling, even bombers pushed speed over efficiency. Speed and altitude meant turbojets. In the mid 50s things started to change. With the advent of new engines, J-57, J-79, J-75, with afterburners, the military had the engines capable of pushing warplanes, even bombers to the aerodynamic heating limit of aluminum, a realistic limit for the technology of the day (and today?). With that limit reached, efficiency and range became more important to the military, particularly the B-52, and fans appeared. I do not think the technology was imposing as P&W offered kits that could upgrade the J-57 to the JT3D in overhaul shops (per Kay, I did finally pull it out).

    I was fortunate to fly two aircraft with engines that, unless you were really stupid,could pull you out of problems quickly, the J-85 powered T-38 and the TF33 (JT3D) powered C-141. That TF33 was is a great engine, 10,000 before rebuild, and didn't care what you put into it, JP4,5, avgas, +?. You would have to go to the charts however to see impacts on performance.
     
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  17. kool kitty89

    kool kitty89 Well-Known Member

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    Agreed. Starting at the top with an extremely complex design really doesn't seem like a practical model. Scaling back to the simplest possible form (at last for experimental and proof of concept testing -as whittle and ohan did) and then moving on from there would be most sensible and logical. (and likely would have spurred more serious turbine engine development with other manufacturers in the US early on)

    Honestly, if Price had used his experience with combustion chamber design, centrifugal compressors, and steam turbines (as well as turbochargers), it seems like he could have had a working proof of concept (or possibly even flight worthy) engine ready at Lockheed before WWII even started.

    With his total loss steam turbine design, the only other possible oddity I could see being practical would be putting a heavy emphasis on water injection for added working mass and turbine cooling on his experimental jet engine designs. (much more realistic than intercooling if nothing else)

    If there's a genuine engineering reason bypass/augmentor fans weren't adopted sooner, I'd certainly like to find out what it is. I suppose it could simply be that the idea didn't occur to many engineers early on in development of turbine engines or testing/implementation of development programs for such devices were overlooked/delayed for various reasons unrelated to technical difficulties. (similar to the American engine industry as a whole starting turbojet/turboprop development en mass a bit late)

    It may also be that neither the M.52 nor Metrovick's engine designs were particularly widely publicized in detail, and it's certainly notable that there were no mass production orders of those engines. (as far as post-war potential sales goes, it seems down more to lack of interest than any faults of the engine -aside from not being a cheap/simple/maintenance friendly as the Derwent, Nene, Goblin, and Ghost -RR engines and the J33 had the added advantage of exceptional resistance to foreign material injestion due to the radial intake vanes and filter screens)

    High speed ducted fans don't seem any more complex or problematic than turboprops (simpler in several respects) so it may have been largely due to turboprops being 'obvious' as well as pure jets being obvious (especially if converted from prototype turbofan developments) while bypass fans/compressors are somewhat in-between conceptually and maybe less obvious. (at least to engineers with solid funding and high enough standing to implement research)

    I know the NACA published research on thrust augmentation in the early 1930s related to jet thrust, and that was attempted on some early turbojets (no fan, just rammed bypass air ducted around the exhaust) but that proved ineffective for the bulk/weight/drag it added. (at least without afterburning)
     
  18. Shortround6

    Shortround6 Well-Known Member

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    Out of my 'collection' of copies of Wilkinson's "Aircraft Engines of the World" some are from public libraries. One was at the British "National Gas Turbine Establishment" at Pyestock (?). At least one from from a US Air Force base and the 1947 edition with illustrations of the Metropolitan-Vickers F3 "turbojetfan" with ducted fan augmenter (including a cut away diagram of the airflow and gas flow) and a photo of the F5 "turbojetfan" with open fan augmentor was in the Rohr Aircraft corp. library.

    Point is that many companies, research establishments had their own libraries and the basics of the M-V turbojetfans were hardly secret. It may have been as simple as lack of demand. The 1947 book claims the ducted fan augmenter, which weighed 625lb was good for raising the thrust of the F2/1 gas generator by 68% and reducing specific fuel consumption by 33% for a 37% increase in weight. A set of numbers are provided for the open fan version.
     
  19. kool kitty89

    kool kitty89 Well-Known Member

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    I suppose the relatively slow progression to jet bombers and airliners (large aircraft in general) and heavy emphasis on progressing towards supersonic fighters would have put some greater emphasis on turbojets with turboprops as more direct replacements for piston engines, and afterburning and water injection ended up seeing greater interest for thrust augmentation. (transonic/supersonic augmented/turbofan arrangements might be compelling too if combined with afterburning, something the M.52 project might have popularized much sooner had it been completed -the arrangement used there seems a bit like a precursor to what was used much later on the SR-71, ram assisted high bypass ducted fan with afterburner)

    The larger diameter and weight increase of ducted fans would seem less attractive on most fighter developments in particular. (with the possible exception of rear-fans added to centrifugal turbojets, where the diameter might not increase, though max diameter might be more tubular and less spheroidal or stubby barrel shaped)

    But with De Havilland's early forray into airliner design AND having their own engine division (and Griffith's efforts being public information) and with Halford's trend in taking engine designs and simplifying/rationalizing them, applying that to augmentor fans in combination with the existing goblin design would seem a fairly logical progression. Though I suppose patent overhead could be an issue too. Halford adapted Whittle's design well after the related patents had lapsed, but this may not have been the case for Griffith's fan developments.
     
  20. kool kitty89

    kool kitty89 Well-Known Member

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    Somehow I missed this before, but the reasoning fits very much with what I said in post 19 above. It does still seem like DeHavilland is the odd one out that should have had more interested in turbofan development.

    Aside from that, the B-49 and even B-36 programs might have made turbofan developments more attractive (particularly developments of the existing J35 or J47), and the only other major area would probably be long range fighters, especially prior to in-flight refueling and especially when still during the first generation of transonic fighters. (or even Bell's XP-83, which might have been designed very differently if targeting some prototype late war turbofan developments -certainly broader implications for post-war fighters in general though, particularly the F-86)

    Anything using the J33, J42, or J48 would have more definite advantages at foreign matter ingestion and hypothetical auxiliary fan stage additions would compromise that. (not a factor for the Goblin or Ghost engines given they all had unfiltered intakes)
     
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