Author Topic: I need a jet engine  (Read 78 times)

Offline Rickshaw

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I need a jet engine
« on: Yesterday at 01:15:52 PM »
I need a jet engine.  It must have been comparable with the J79 in service life and about 3/4 the diameter.   Any ideas? 

Offline tankmodeler

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Re: I need a jet engine
« Reply #1 on: Today at 01:01:42 AM »
I need a jet engine.  It must have been comparable with the J79 in service life and about 3/4 the diameter.   Any ideas?
Comparable in what way? Time of service? Cost? Fuel efficiency? Thrust?

If it's thrust, you're pretty much out of luck. Thrust is governed by mass flow and for similar performance you need similar mass flows. Mechanically things that hold the engine together require a certain mount of space at the centreline of the engine and military engines have always pushed the packaging of their engines as tight as possible so the minimum diameters for a given airflow have not changed much over the years. And a more modern turbo fan, while providing more thrust at lower engine mass, usually does so by increasing the diameter to accommodate the low (or high) bypass duct of the engine.

And, because the mechanical gubbins of an engine doesn't really scale well with the airflow, even much lower performance engines don't really get much smaller than the old school turbojets. The 38" diameter of the J79 is really hard to beat unless you're willing to go down to really small jets in the 4-7,000 lb thrust category.

Paul

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Re: I need a jet engine
« Reply #2 on: Today at 03:26:30 AM »
I need a jet engine.  It must have been comparable with the J79 in service life and about 3/4 the diameter.   Any ideas?
Comparable in what way? Time of service? Cost? Fuel efficiency? Thrust?

Yeah.  I assume you are also talking about a 'Western' engine in the same approximate era as the J79.  Given the J79 has a diameter of between 0.973 - 0.992m depending upon version, you are looking at something in the 0.73 - 0.74m diameter range.  A EJ200 (diameter 0.74m) might work, especially given the thrust (13,250 lb dry/20,000lb AB) though not sure how this stacks up for your era.  A Rolls-Royce/MAN Turbo RB.153 (diameter 0.749m) as used in EWR VJ 101D might also work though again depends upon era plus thrust is a lot less (6850 lb dry/11,645 lb AB vs ~10,000lb dry/~18,000lb AB depending upon version).  Finally, some of the RR Vipers are another option (diameter 0.74-0,75m) though again thrust much lower (~4000 lb dry/~5000lb AB).
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Offline Rickshaw

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Re: I need a jet engine
« Reply #3 on: Today at 11:19:42 AM »
OK, just to be a little bit clearer - this engine must be around when the J79 arrives on the scene - that is what I meant by "comparable".  Thrust should be near equal or better, if at all possible.   However that is, upon reflection not going to be likely.  However it needs to be about .75 the diameter of a J79.

Offline Jeffry Fontaine

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Re: I need a jet engine
« Reply #4 on: Today at 11:46:00 AM »
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Offline M.A.D

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Re: I need a jet engine
« Reply #5 on: Today at 01:09:46 PM »
I need a jet engine.  It must have been comparable with the J79 in service life and about 3/4 the diameter.   Any ideas?

Oh, I smell something cooking  :P
Bring it on, I say!!


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