How have gas turbine engines reduced fuel consumption over past 20 years?
The major improvement to reduced fuel consumption of jet engines was the turbofan engine, where a large fan was added to the front of the engine. This occurred about 50 years ago and reduced fuel consumption by about 1/3. Since then other improvements which came later were higher overall pressure ratios (allowing higher peak cycle Temperature=improved cycle performance), improved aero in the gas path, and tighter blade tip clearances. Regarding the above comments, improved combustion efficiency has added very little as the combustion section has always operated at about 99.9% efficiency. As far as tighter controls on fuel flow go, the fuel control just adds or reduces fuel as direct by the pilot, and does not improve the engine efficiency. Commercial fuel has been the same for the last 40+ years . . .
