Earlier post I made on the underlying issue:
By the way, to find a relevant info suggesting the single Word "engine" in search bar for this topic makes me laugh. This is not how SEO works. You could always add more parameters to the query and narrow your search results. We're not running raw SQL commands on forum database here. It's a...
defencehub.live
Especially this part:
His implying ~1:1 bypass ratio for TF-6000 illustrates the MIUS basically will balance supersonic capability with payload/range/endurance curves as best as theoretically possible. Since going above this will make supersonic impossible and going well below it (and having lower bypass realm) will reduce the mass and payload efficiency of the platform.
and this earlier one:
Military turbofans that go supersonic also have to follow this constraint and are essentially fan augmented turbojets. There is more design expectation for such aircraft to perform in the subsonic realm (compared to say a concorde) so having/balancing as much as bypass as possible is a good advantage since you have more effective range/time that way.
But generally cannot go much above a bypass ratio of 1:1 if you want to have supersonic capability (you start to invest too much in the fan side of things and impose penalties on the core relative to the mission/design profile of the aircraft). i.e To better provide for supersonic capability at larger engine thrusts, simply the bypass ratio is often kept in 0.5 - 0.8 design range so as to not impose on having larger afterburner or having complex intake systems for the engine itself.
Essentially (variable cycle) allows engines of much higher bypass than 1:1 to go supersonic by the (flow management, ducting etc during specific regimes) summary that yasar gave a few posts above.
For commercial turbofans large scale market economics, supersonic is just not important at all compared to total thrust...so high bypass engines are name of the game (and they are impossible to go supersonic as result, given they gear towards moving large amount of air more slowly to develop their total thrust, whereas supersonic needs the bulk of the air to be supersonic i.e more core-based).
Where you have tradeoff is for aircraft that will have to operate in all regimes (subsonic, transonic, supersonic) and obviously fighter aircraft are in this realm.
More bypass is advantageous for efficiency at subsonic travel which the fighter aircraft overall spends most of its mission time life on (amount of time you can spend in air with same fuel onboard as more thrust is simply from the fan rather than core, which essentially "gears" the thrust more optimally), just like a higher gear setting available for car (say Overdrive or 5th compared to having just 4th and the lower gears).
Many other matters are also improved (engine cooling, long term performance and health and so on) by higher bypass thrust compared to something closer to a turbojet...given the problems of making large turbojets (as the Soviets especially would find out but were stuck with).
i.e The engine onboard a fighter plane starts to dip into all the advantages high bypass engines in commercial sector enjoy etc....but retains (more turbojet like) supersonic capability at same time.
The historic comparison of note here would be the US approach of developing essentially a related concept of variable cycle for the Blackbird (in that the turbojet was able to switch to something closer to a ramjet at higher speed regime) and compare that with the approach the Soviets took with the Mig-25 (just making a turbojet bigger).
The latter was "easier" route development wise but was baked in with serious problems as well...showing the dividends of having variable cycle even back then.
There are however a myriad of design challenges with variable cycle (it remains a frontier RnD area) compared to traditional "fixed cycle" gas turbines.
It is still early days in addressing them more optimally with the research we have progressed into in the last few decades.
That's why they are only likely to be somewhat mature for introduction in 6th Gen warplanes/drones onwards.
