Jet Engine Efficiency
Discussions center on jet engine design, fuel efficiency tradeoffs, optimization for subsonic cruising speeds versus supersonic performance, and factors like bypass ratios and power-to-weight in aircraft.
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Jet engines achieve higher speeds and efficiencies.
Engine is generally optimised for max efficiency at a cruising speed. A airliner engine is optimised for transonic cruising, you can't just half the plane and double the speed.
When is a more fuel-efficient jet not a good idea?
No, they need a different landing gear to make room for bigger engines. Larger diameter engines are needed for better fuel efficiency. Fly by wire is nice, but fuel economy is more important.
Flying faster uses LOTS more fuel per mile travelled. It's not just the aero but also what engines are optimized for
A lot of the fuel efficiency of modern aircraft comes from having giant turbofans instead of turbojets. By attaching a giant fan the front of your compressor and redirecting most of the air around the engine you can get great efficiency at subsonic speeds. However, the nature of the fan has fundamental limitations when approaching the speed of sound and turbo/ram jets are basically just pouring gas in a tube of precompressed air.
Do electric ‘jet’ engines need ‘bypass’ air for increased efficiency or is just a combustion problem?
Fascinating! Commercial airliners have also optimized their engines enough they don't have the power budget to make up for the difference in lift.
Airplanes have big jet engines. The available power isn't going to be of concern.
How does this happen without jet engines?