It doesn't necessarily mean that the intake area will be increased, but that it's likely for it to be increased. To achieve thrust increases with only temperature increases is extremely difficult, first, and we know the WS-10 and AL-31 are banded within the J-20 engine compartment to account for the diameter difference between the WS-15 and interim engines.Switching from WS-10 to WS-15 does not necessarily mean the intake area has to be drastically increased, or increased at all.
Yes, the thrust of WS-15 is much higher than WS-10, but that does not mean that WS-15's intaking air volume per unit time must be increased in the same percentage as thrust increase. Thrust increase is achieved by two main means. One is increasing intaking air volume as F-135 does with bigger fan. The other way is by increasing the temperature in the turbine, so the same amount of fuel and air can create more thrust. The limit to the second approach is the materials' ability to withstand the temperature. And we know that WS-15 (F119 as well) works on higher temperature than earlier generation engines. There is still a big room to increase the thrust without increasing air-flow so long as the material can improve until theoretical efficiency limitation of turbo jet takes over. In another words, new engines are improving their thermal efficiencies rather than wastefully sucking more air and burning more fuel.
The bigger question is whether the J-20 can achieve the WS-15's required airflow with just DSI mods, or whether the intakes would need to be adjusted and the entire airframe readjusted for the airflow.
And what's wrong with an entirely different aircraft that shares certain commonalities with its predecessor? This is basically what happened with the F/A-18E Super Hornet compared to the F/A-18 Hornet, but it meant that the Super Hornet had drastically improved development times compared to an old-growth variant.Well I don't think a strike variant J-20 makes much sense, that's why I said that if there wasn't a JH-XX, that buying more H-20s and J-20s would be a fine solution.
The idea of a strike variant J-20 would require the aircraft to have some rather significant modifications to make such a variant worthwhile to begin with, that it would end up basically being an entirely different aircraft.
Likewise, consider the Su-35 vs the Su-27. There's been tremendous weight growth, and the Su-35 is probably terrible on wing loading compared to the Su-27, and the structural airframe has changed tremendously with use of composites and internally enlarged fuel tanks. But the increased thrust with new engines should make the Su-35 either the equal or better of the Su-27.
Basically, when you think of a strike J-20, the trade-offs are:
-A strike J-20 can likely dogfight as well or almost as well as a J-20A / J-20B.
-A strike J-20 will likely have a more limited maximum speed compared to a J-20A / J-20B, as with all strike aircraft, slightly weakening its interception ability.
-A strike J-20 can carry a significantly better air to air missile payload as well as an air-to-ground missile payload, possibly making a strike J-20 better than a J-20A / J-20B in the interception role due to its better missile loadings and better in the air-to-air role simply by carrying more air-to-air missiles.
We've mostly identified that the J-20 is anemic in terms of air-to-air missile load-out, the PL-15 will need to be modified just so the J-20 can carry 6 of them, and the modified PL-15 will be less capable.
A strike J-20 will likely be as capable or more capable than the current J-20A / J-20B in almost every way, just as the Su-30MK and F-15E outshone their "air superiority-only" variants.
Basically, if the J-20 is redesigned to carry a Kinzhal-class missile, you'll have effectively double the air to air payload, or 150% if part of the payload is used for internal fuel tanks to further extend range. If you treat the rumors of the J-20 as around 100 million USD, and assume the F-35 drops to the equivalent of 50 million USD, you have a platform that's fully competitive with the F-35 in terms of strike capability for cost, as well as granting in further improved range if it's on a pure air superiority mission.
The weapons bay payload is the greatest weakness of the J-20; it's way better than the F-22 and better than that of the Su-57, but it can't compete with the F-35 for cost.
A redesigned "strike" J-20 would basically knock off the tailfins and move the engines to where the tailfin is right now, and if TVC is sufficiently mature there shouldn't be a significant loss in maneuvering ability and possibly even a gain with drag reduction from removal of tailfins and ventral fins. Likewise, the loss of 2-4 planes of planform alignment would further increase its stealth.
This would have the further advantage that Western commentators would immediately mistake it for a light bomber like the FB-22 or FB-23, instead of a strike platform using next-gen aerodynamics.