Some people would have disagreed with you.
"从歼20首飞, 发动机声音判断,绝对是新型的,
大涵道比发动机,它的涵道比, 超过歼10、SU27和F22三种战机"
http://m.huanqiumil.com/news/60838_2.html
"一核多用,WS15是小涵道比歼20用的,WS20是大涵道比运20用的,"
The idea that WS15 has a low bypass ratio, is in comparison, with the huge transporter and airline engines, I believe.
In my opinion, the reason airline jet engines has a bigger thrust is because they have a gigantic fan, and most of the air, bypassed, the core of the engine, and sent to the back of the engine by the huge fan, and so they have a huge bypass ratio. The bypass ratio of the GE9x is
10:1. Most of the power come from the huge Fan. But a huge Fan like that of the GE9x is not suitable for a fighter plane's narrow fuselage, and therefore, not suitable for supersonic speed.
Notice the Huge Gigantic Fan, and the narrow core of the GE9x. A gigantic fan is great for fuel efficiency at subsonic speed, but of course, it stinks at supersonic speed. GE9X has a huge thrust of
450 to 470 kN.
View attachment 415871