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The type of jet engine used to explain the conversion of fuel into thrust is the ramjet.It is simpler than the turbojet which is, in turn, simpler than the turbofan.It is valid to use the ramjet example because the ramjet, turbojet and turbofan core all use the same principle to produce thrust which is to accelerate the air passing through them.
Jet airliners became 70% more fuel efficient between 1967 and 2007, [49] 40% due to improvements in engine efficiency and 30% from airframes. [50] Efficiency gains were larger early in the jet age than later, with a 55-67% gain from 1960 to 1980 and a 20-26% gain from 1980 to 2000. [45]
Aircraft engine performance refers to factors including thrust or shaft power for fuel consumed, weight, cost, outside dimensions and life. It includes meeting regulated environmental limits which apply to emissions of noise and chemical pollutants, and regulated safety aspects which require a design that can safely tolerate environmental hazards such as birds, rain, hail and icing conditions.
For example, Concorde cruised at 1354 mph, or 7.15 million feet per hour, with its engines giving an SFC of 1.195 lb/(lbf·h) (see below); this means the engines transferred 5.98 million foot pounds per pound of fuel (17.9 MJ/kg), equivalent to an SFC of 0.50 lb/(lbf·h) for a subsonic aircraft flying at 570 mph, which would be better than even ...
A corollary of this is that, particularly in air breathing engines, it is more energy efficient to accelerate a large amount of air by a small amount, than it is to accelerate a small amount of air by a large amount, even though the thrust is the same. This is why turbofan engines are more efficient than simple jet engines at subsonic speeds.
The Aircraft Engine Historical Society; Jet Engine Specification Database; Aircraft Engine Efficiency: Comparison of Counter-rotating and Axial Aircraft LP Turbines; The History of Aircraft Power Plants Briefly Reviewed : From the " 7 lb. per h.p" Days to the " 1 lb. per h.p" of To-day "The Quest for Power" a 1954 Flight article by Bill Gunston
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In February 2012, GE announced studies on a more efficient derivative of the GE90, calling it the GE9X, to power both the -8 and -9 variants of the new Boeing 777X.It was to feature the same 128 in (325 cm) fan diameter as the GE90-115B with thrust decreased by 15,800 lbf (70 kN) to a new rating of 99,500 lbf (443 kN) per engine. [1]