As speed and altitude increases the efficiency of fan blades decreases dramatically. The air is too thin and too fast for the fan to generate significant thrust. Better to compress and burn it in the engine core.
Chinese Engine Development
- Thread starter jackbh
- Start date
Tbh there are other ways around it other than shrinking the BPR.
Not if you also want to reduce compressor stages because weight requirements!
Originally they designed a BPR 0.25 engine that had a 160KN max thrust. Fuel efficiency suffered so the new redesigned engine should be BPR 0.37 and max thrust 180KN I've heard.
I would really like to know what its overall pressure ratio and HPC pressure ratio are haha.
Dunno, I'm not exactly an expert on this. But if you do a linear extrapolation of F119: 168KN and BPR 0.3, F135: 191KN and BPR 0.57, it seems that the new WS15 specs of BPR 0.37 and thrust 180KN is pretty impressive.
IMO, we don't actually know what the current spec for WS-15 is considering they threw out the old spec back in 2018. If they could get a TIT higher than the F-135 with more efficient compressor, turbine and fan design, they could probably get an engine with 180kN thrust with a BPR similar to the F-119.
Well no, it's impossible to just make an engine turbine core "bigger", as the extra centrifugal forces of the spinning parts, especially the high pressure turbines will be unbearable. What you can do is make a larger fan and fan casing, deriving more thrust from bypass air. The low pressure spool and the fan spins at lower velocities so the centrifugal force is possible to manage. Clean thrust, the power obtained from the engine core cannot easily be improved upon, and is an excellent indicator of the supersonic performance of military jet engines. Engine weight associated with TWR ratios used to be the gold standard, but as engines improved the fuel became a lot heavier than the engine making improvements in weight less useful. Fuel efficiency became more important as a result. For modern day low BPR engines, a combination of core thrust and fuel efficiency is the measuring stick for technological advance.