Subsonic fuel economy wise no doubt suffers, though should be better than F119 from compression ratio alone. The turbine inlet temperature is not as high as f135 (1900 and 2000 Celsius for takeoff respectively) which decreases takeoff thrust but leaves more room for supersonic heating.
J-20 5th Gen Fighter Thread VIII
- Thread starter Blitzo
- Start date
The F135 chose the lazy path to increasing thrust by jacking up the TIT. Increasing TIT uses up design growth margins. Focusing on compressor efficiency pushes up design growth margins.
Don't want to risk causing troubles if I tell you the origin of my source. The new engine core has 35kg/s equivalent airflow compared to 30kg/s for YWH and f119 matured models. Compression ratio is increased to >28, and they were even envisioning a 20t engine at some point which is definitely possible from the core engine but eventually decreased the thrust for much better lifespan and improved fuel efficiency.
Running a lower theta-break, yeah. Lazy but works. Not like the F-35 is loitering beyond M1 for long anyways...
Idk man, high compression ratios usually means bad news for supersonic performance but I have heard the Chinese have workarounds to that...
It isn't lazy, it's normal. F135 is engine (almost)perfectly matched to the airframe it was developed for(Strike fighter=light bomber). It does exactly what it was meant to, minus electricity/cooling(which aren't its fault).
You can always bleed air somewhere (bonus points if you can use the air for cooling).
The reason that compression ratios are bad news is simply because heat from ram compression, engine compression and burning combines, raises to the point where turbine starts to melt, thus you are forced to turn down the engine. But with the most powerful fighter engine core ever, the burning is much more fuel-lean, you release the same energy but spread across 20% more air which keeps the temperature extremities down.
From an engine technology development standpoint it is lazy, as in it’s the easy low hanging fruit option. PW choosing to do it this way wasn’t a dumb or blind move to be clear. It made sense given the program requirements they were fitting to, especially in terms of risk management and development time. But it does mean the engine is not *as* much of a technical advance from the F119 it shares a base core architecture with as it’s often touted.
Was China lazy when it developed WS-20?
Certainly there are ways to raise efficiency further and avoid drag of huge engine front. All advantages, no disadvantages, global leadership.
Higher bypass is a choice, there's nothing lazy about that. You either aim for higher speed optimization, or you don't. Which is rather sensible on an engine made for aircraft, developed around 2x2000lb bombs and optional STOVL configuration.
J-20A is an air superiority fighter(first). F-35 is not. For range : payload pair, subsonic cruise is just more optimal. And developing a fully separate, even larger low bypass engine(rather than deep evolutioin of F119) just wasn't optimal...
I would say limited variable geometries like VGVs too but yeah cooling is the best one ig if you can bleed them that way somehow...
Ah so that's why the WS-19 is running like a ridiculously high OPR (I can't remember the exact number but it was absurd).