Comparison of modern fighter turbofans

F119Doctor said:
icyplanetnhc said:
overscan (PaulMM) said:
Unless the 200kg is the weight of the control system.
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I'm not very convinced. The weight difference between the F100-PW-100 and the -220 with the digital electronic engine control (DEEC) is roughly 200 lbs (90 kg); of course, there are also other mechanical differences between the two in order to greatly improve the reliability of the latter, but I doubt that a more modern engine control unit would weigh over twice as much.
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The weight difference between the F100-100 and -220 was primarily due to the durability improvements in the rotating components and a bearing support to increase the depot inspection interval from 1800 TAC cycles to 4000 TAC cycles while maintaining full performance over that interval. The weight change from the original UFC/EEC/ vane type Main Fuel Pump to the DEEC / MFC/AFC/ gear type MFP was minimal.
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The -100 engine had also gained weight before the -220 was produced. The -200 engine for the F-16 incorporated the proximate splitter in the intermediate case aft of the fan (stall / stagnation fix), containment bands around the fan duct (later replaced by thicker LPT cases), the Backup Control (BUC) on the -200, and some of the augmentor nozzle segments and seals had been beefed up for longer life. If I remember correctly, the actual -220 weight gain from the fielded -100 was around 150 lbs, and 125 lbs from the -200.
 
I think it's also interesting to note the architecture of the YF120 (GE37). It has a 2-stage fan, 5-stage compressor, and single stage low pressure and high pressure turbines. For an engine of its class, this appears to have the fewest stages thus far, which makes me curious about the OPR. The EMD F120 would have aimed at producing the same thrust at lower operating temperatures. I believe the EJ200 and the izdeliye 30 has the next fewest stages, with three fan, six five compressor, and single LPT and HPT stages. Interestingly, Piotr Butowski published the stage architecture of the izdeliye 30 as early as 2013.

I would also be curious about the lineage between the YF120 and the current XA100, but it's quite possible that there is very little; not only is there potentially an institutional gap due to a generational difference between most of those working on the respective project, they are also fundamentally different variable/adaptive cycle architectures. According to an Aviation Week article in 2015 describing GE's AETD developments that would eventually lead to the XA100, the adaptive design being tested at the time had a three-stage adaptive fan and a compressor derived from the CFM LEAP's 10-stage compressor. However, I doubt that the current XA100 design, which completed detailed design in 2019, would have that many compressor stages. I believe P&W's adaptive fan design for the XA101 is also three-stage.
 
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icyplanetnhc (Steve) said:
I think it's also interesting to note the architecture of the YF120 (GE37). It has a 2-stage fan, 5-stage compressor, and single stage low pressure and high pressure turbines. For an engine of its class, this appears to have the fewest stages thus far, which makes me curious about the OPR. The EMD F120 would have aimed at producing the same thrust at lower operating temperatures. I believe the EJ200 and the izdeliye 30 has the next fewest stages, with three fan, six compressor, and single LPT and HPT stages. Interestingly, Piotr Butowski published the stage architecture of the izdeliye 30 as early as 2013.

I would also be curious about the lineage between the YF120 and the current XA100, but it's quite possible that there is very little; not only is there potentially an institutional gap due to a generational difference between most of those working on the respective project, they are also fundamentally different variable/adaptive cycle architectures. According to an Aviation Week article in 2015 describing GE's AETD developments that would eventually lead to the XA100, the adaptive design being tested at the time had a three-stage adaptive fan and a compressor derived from the CFM LEAP's 10-stage compressor. However, I doubt that the current XA100 design, which completed detailed design in 2019, would have that many compressor stages. I believe P&W's adaptive fan design for the XA101 is also three-stage.
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The F119 is also 3 stage fan, 6 stage HPC, and single stage high and low turbines.

F135 has the same architecture as F119, except for a larger 3 stage fan and a 2 stage LPT. I’ve heard that the two stage LPT was necessary to extract sufficient power for the lift fan on the F-35B, and is on the other variants only for commonality.

By the way, the EJ200 high compressor is only 5 stages. This data sheet from MTU has a lot of good data on this engine https://www.mtu.de/fileadmin/EN/7_News_Media/2_Media/Brochures/Engines/EJ200.pdf
 
F119Doctor said:
The F119 is also 3 stage fan, 6 stage HPC, and single stage high and low turbines.

F135 has the same architecture as F119, except for a larger 3 stage fan and a 2 stage LPT. I’ve heard that the two stage LPT was necessary to extract sufficient power for the lift fan on the F-35B, and is on the other variants only for commonality.

By the way, the EJ200 high compressor is only 5 stages. This data sheet from MTU has a lot of good data on this engine https://www.mtu.de/fileadmin/EN/7_News_Media/2_Media/Brochures/Engines/EJ200.pdf
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Sorry, I meant to say that both the EJ200 and izdeliye 30 have five compressor stages, that was a brain fart on my part. The F119 and the M88 have six stages.

It’s rather interesting to note that the M88 has a lower published OPR, BPR, but higher TIT than the EJ200, despite the latter being considered a more optimized for supersonic performance. The M88’s lower OPR and BPR is a bit puzzling, considering that they’re both of roughly the same vintage, and I don’t think supersonic performance was as large of a design driver as the EJ200.
 
M88 needed more stages than EJ200 for slightly less OPR as it is a bit less modern in design. M88-2 is somewhere between F404 and EJ200 at least in earlier models. Thrust to weight is 8.52:1 where EJ200 is 9:1+.

The initial M88-1 demonstrator TET was 1700K and M88-2 is 1850K. 1800K was given earlier for EJ200, but recently no value is generally given so not sure if that's still correct. Other EJ200 figures are approximate ("thrust class") not exact so I'd say they are likely very close.

Bypass ratio of the M88-2 is 0.3. EJ200 settled on 0.4. Not vastly different. F404 is 0.34.

The EJ200 was designed to have built in 15% thrust growth capability margin that hasn't been used to my knowledge - with priority given to increased reliability instead.
 
SFC figures show slight dry thrust SFC advantage to EJ200 (consistent with higher BPR) with parity in afterburner.

M88-2 - 0.782/1.663
EJ200 - 0.74/1.66
 
EJ200 cycle was optimised for lower fuel consumption in afterburner for better supersonic performance, not supercruise in particular.

Tornado F3's RB.199 SFC was 2.5 with afterburning. EJ200's 1.66 was a dramatic improvement.
 
SNECMA stuck waaay too long with Atar 9. Early atempts to get out of it in the 50's were crushed or didn't worked - Vulcain, Super Atar... and then they missed the turbofan train, hanged out with Pratt for a decade and ultimately beat them at their own TF30 game - the 306E was a fine engine. For nothing, just like the M45.
From these two come the M53 which suffered a bit the comparison with contemporary engines of the 70's.
The CFM56 smart trick granted them access to a F101 core on a civilian disguise and it helped too.
The M88 was the one engine where they really caught up with RR and the Americans.
 
icyplanetnhc (Steve) said:
I think it's also interesting to note the architecture of the YF120 (GE37). It has a 2-stage fan, 5-stage compressor, and single stage low pressure and high pressure turbines. For an engine of its class, this appears to have the fewest stages thus far, which makes me curious about the OPR. The EMD F120 would have aimed at producing the same thrust at lower operating temperatures. I believe the EJ200 and the izdeliye 30 has the next fewest stages, with three fan, six five compressor, and single LPT and HPT stages. Interestingly, Piotr Butowski published the stage architecture of the izdeliye 30 as early as 2013.

I would also be curious about the lineage between the YF120 and the current XA100, but it's quite possible that there is very little; not only is there potentially an institutional gap due to a generational difference between most of those working on the respective project, they are also fundamentally different variable/adaptive cycle architectures. According to an Aviation Week article in 2015 describing GE's AETD developments that would eventually lead to the XA100, the adaptive design being tested at the time had a three-stage adaptive fan and a compressor derived from the CFM LEAP's 10-stage compressor. However, I doubt that the current XA100 design, which completed detailed design in 2019, would have that many compressor stages. I believe P&W's adaptive fan design for the XA101 is also three-stage.
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YF120 had an unusual architecture related to its variable design. It had a 3 stage fan, but the first two were on the low rotor, and the 3rd stage was at the front end of the high rotor. The true high compressor was only 4 stages. When in high bypass mode, part of the second and part of the third stage discharged into the fan duct. In low bypass, the 2nd stage bypass was closed off and only the 3rd stage bypassed into the fan flow.

The low stage count resulted in the low OPR, but that gives a lower compressor discharge temperature which lets them push more fuel into the combustor before reaching turbine temperature limits. Good for supersonic thrust, but it was definitely a thirstier engine than the YF119.
 
F119Doctor said:
YF120 had an unusual architecture related to its variable design. It had a 3 stage fan, but the first two were on the low rotor, and the 3rd stage was at the front end of the high rotor. The true high compressor was only 4 stages. When in high bypass mode, part of the second and part of the third stage discharged into the fan duct. In low bypass, the 2nd stage bypass was closed off and only the 3rd stage bypassed into the fan flow.
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True, and I do recall seeing a diagram of the F120’s VABI architecture from Aronstein’s ATF book; it showed two bypass channels, one in front of and one behind the third core-driven fan stage. The variable bypass was pressure driven for simplicity and reliability, although according to YF-23 test pilot Paul Metz, the YF120 exhibited noticeable throttle input lag. During aerial refueling, they would set one engine at a constant throttle setting and use the other to control speed.

I do think that the F120 would have been slightly larger in at least one of the cardinal dimensions than the F119; if you compare the EMD F-23A schematics, DP-232 with the F120 has a slight notch/serration in the fuselage trailing edge geometry while DP-231 with the F119 did not, which I presume is because of the former’s larger dimensions. DP-232 also has slightly longer overall length. DP-232 probably wouldn’t represent a production F-23/F120, as I would imagine that they would eliminate that notch when refining the design when going into CDR, but it’s interesting to see that the airframe designs were slightly different due to the engines.
 
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