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Subject: M88, EJ200 and F135 engines compared.
dwightlooi    9/7/2008 2:04:38 PM
Note: All numbers are based on the manufacturer's official specification sheets unless otherwise noted. Figures denoted (est) are estimates based on other known statistics and/or published (non-official) articles. Some of the sources are indicated below:

Mechanical Engineering magazine article - Fahrenheit 3600 (Apr 07)
 
 
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Bluewings12       9/7/2008 3:13:44 PM
Excellent work Dwight :-)
 
With such a small size ,  low weight and small air intakes , the M88 still deliver outstanding performances .
This very good for fuel consumption , IR signature and EM signature .
 It might not be the best engine around but it does its job with Rafale the way we want it .
 
Cheers .

 
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Softwar       9/8/2008 10:17:18 AM

Excellent work Dwight :-)

 

With such a small size ,  low weight and small air intakes , the M88 still deliver outstanding performances .


This very good for fuel consumption , IR signature and EM signature .

 It might not be the best engine around but it does its job with Rafale the way we want it .


 
FYI - a single F135 takes up less room and produces more thrust than 2 M88s.  Of course, we are looking at an early gen 4 design vs current technology but after all - that's what the Rafale is - a 1980s gen 4 design.
 
I wonder what the specs on the F136 will be like?
 
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violentnuke       9/11/2008 7:30:20 PM
Turbine inlet temperature shows how staggering is the advance in the US engine.
 
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doggtag       9/11/2008 8:43:28 PM

Excellent work Dwight :-)

 

With such a small size ,  low weight and small air intakes , the M88 still deliver outstanding performances .


This very good for fuel consumption , IR signature and EM signature .

 It might not be the best engine around but it does its job with Rafale the way we want it .


 

Cheers .






The F135 completely outclasses the other two, so is it even a valid comparison, other than only to show which engine is capable of what?
(might as well compare a CF6/F103 to a Trent or GE90).
 
It'd be a fairer comparison to stick the GE F414 in there, rather than the F135, as the F414 more closely compares to the other two.
 
Swallowing national pride, both France and the Eurofighter partners would've all been better off, performance-wise, in adopting the F414 instead of their homegrown designs.
(anyone else here notice that the Gripen NG uses/will use an F414, and neither the M88 series or EJ200?
And for further, the Rafale could just as easily flown with F404s rated up thru 18,000pounds.)
 
Too bad we don't have an edit feature on this site to correct, adjust, or otherwise add to our previous posts, as you could then add in the F414 to that chart also...
 
Still, points to dwightlooi for laying out the chart together like that.)
 
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dwightlooi       9/11/2008 11:53:19 PM
The F414 is very similar to the other two in many ways, but the idea behind the chart is to compare the engines of the Rafale, Typhoon and F-35. You may want to compare two M88-2s or two EJ200s to one F-135. In that case, the comparison in terms of size, thrust, weight, etc is perfectly valid.
 
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prometheus       9/12/2008 5:54:40 AM
I'm not so sure how much in advance the F414 is over something like the Rolls Royce EJ200 (who had some significant input in both F-135 and F-136 engines, although far more in the latter). Besides, you build the engine to match the aircraft, given teh eurofighter Typhoon's performance, I see no reason why the end users would be unhappy with the EJ200 performance.
 
Besides, simply sticking a bigger engine in an aircraft is no guarentee of improved performance. IIRC the Royal Navy decided to replace the F-4 Phantoms' engines with the far more powerful Rolls royce Spey engines, and simply ended up increasin drag, slowing the aircraft down!
 
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doggtag    in response to last couple posts...   9/12/2008 7:54:54 AM
I was thinking there a bit about that, comparing two of the 2 former (M-88, EJ200) to one of the latter (F135),
and kind of thought along the lines of the F-5/F-20 genesis: a single 16,000+ pounds thrust F404 replacing the earlier two 5000 pounds thrust each J85s.
(The potential of the F135 to power a drive shaft that powers an electric laser could certainly spark interest- excuse the pun- in just such a mod to allow future Typhoons a DEW/laser powered by the F135, akin to how is speculated with a future F-35).
 
My question is: I understand that the F-35 is built with the idea of using circulating fuel as some form of heat pump to keep temps down,
but still,
wouldn't that considerably larger heat index the F-135 generates make it a far more attractive target to IR-type systems?
(especially if it's expected to radiate some of that heat away thru the fuel, and eventually the airframe surface...)
 
At ~3600° F (love to know what alloys they're using in there), that's a heckuva lot of heat to dissipate into the fuel (and surrounding airframe?).
Anyone know then, with such temperatures, if they'll need a different formula of jet fuel altogether, specifically tailored for the several hundred degrees extra in temperature in the newest US engines?
(what's the flash point of current fuel? Will it stand up to absorbing that much extra heat without igniting or detonating in the wrong places inside the airframe?)
 
...perhaps in light of this, it's then no small wonder that the F-35 will certainly cost more than either the Rafale or Typhoon: stealth aside, the aircraft obviously has considerably more technical complexities going on inside the aircraft than in the Rafale and Typhoon (despite all the hype about those supposed holographic bragg cells or whatever that provides the HAL-9000-like brainpower to Rafale!).
 
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VelocityVector    dogtag   9/12/2008 3:13:19 PM
Only a fraction of the heat is transferred to fuel.  Most gets ejected through the nozzle.  Another fraction mixes with the bypass air.  All this heat is hidden from sensors by the tail design until it dissipates through the airstream.  The fuel boils at roughly twice water, which gives an intuitive feel for how much more heat hydrocarbons can soak up.  The fuel circulates over broad internal volume distributing the heat.  The heat eventually makes its way through the a/c skin, which occupies large surface area compared to the engine, thus its contribution to allaspect IR signature is small.  Jet fuel flashpoint is ~140F, so the fuel management system attempts to keep the fuel temp as low as possible.  The fuel won't ignite under a/c operating conditions unless it's in the presence of atmosphere, so the a/c generates nitrogen, which is inert, and pressurizes the fuel tanks with this so no atmosphere can enter.  No worries, except as fuel depletes the system capability diminishes and unspent fuel could get hot enough to start breaking down, producing gunk and corrosion over time that needs to be dealt with. 0.02
 
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dwightlooi       9/12/2008 9:04:51 PM
A few things...
 
(1) The EJ200 is actually more advanced than the F414 in certain ways. For instance, it has a 5-stage compressor and has the fewest 1st stage fan blades of any fighter engine, whereas the F414 has a 7-stage compressor and a greater number of blades. However, the F414 makes a bit more thrust. The EJ200 is a clean sheet engine, the F414 is an evolution of the F404.
 
(2) The turbine inlet temperature does not reflect the engine case temperature or even the exhaust plume temperature. It simply means that the gases entering the turbine is at a higher energy state and the engine will yield more gross energy per drop of fuel or air entering the combustor(s). That energy however is extracted to do work -- first by the high pressure turbine, then by the low pressure turbine before going out the tail pipe at a given velocity. The final temperature depends on how much energy is extracted to drive the compressors and the fan, and how much bypass air is mixed into the exhaust. The F-35 has twice as many low pressure turbine stages which in theory will extract more energy. It also has a bigger and higher pressure ratio fan which adds energy to the exhaust as well as introduce relatively cold air into the mix. The exhaust plume temperature and engine case temperature can never be derived from the turbine inlet temperature alone.
 
(3) IR sensors do not see total calorific values, they see temperature gradients. In otherwords, huge swats of airframe surfaces being 1 degree warmer is much less detectable than a 100 degree hotspot or two may only be a few tens of square centimeters. Also, huge swats of slightly warm surfaces also cools down in that -50 degree airstream a lot faster than small swats of very hot metal simply because there is a heck of a lot more dissipation area.
 
 
 
 

 
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Shooter2K       9/22/2008 10:18:43 PM
I find several mistakes or estimates that are obviously off, far off!
The SFCs are obviously not on! The -135 has a SFC of 1.47, Vs 1.7( wrong!) and 1.74 almost right! and your estimate of 1.9? RIGHT! PRs are also not supported by the links you post. The M88/Rafale has a demonstraited SFC of all most 1.92 in NORMAL flight opps! How did you get 1.7?
 
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