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The metric formula is: = ... The thrust-to-weight ratio of an engine is greater than that of the complete launch vehicle, ... 1.8 Pratt & Whitney J58 jet engine
The meaning of jet engine performance has been phrased as 'the end product that a jet engine company sells' [1] and, as such, criteria include thrust and fuel consumption, life, weight, emissions, diameter and cost. Performance criteria reflect the level of technology used in the design of an engine and the technology has been advancing ...
Specific thrust is the thrust per unit air mass flowrate of a jet engine (e.g. turbojet, turbofan, etc.) and can be calculated by the ratio of net thrust/total intake airflow. [1] Low specific thrust engines tend to be more efficient of propellant (at subsonic speeds), but also have a lower effective exhaust velocity and lower maximum airspeed.
The thrust-to-weight ratio of jet engines with similar configurations varies with scale, but is mostly a function of engine construction technology. For a given engine, the lighter the engine, the better the thrust-to-weight is, the less fuel is used to compensate for drag due to the lift needed to carry the engine weight, or to accelerate the ...
If a jet aircraft is at full throttle but attached to a static test stand, then the jet engine produces no propulsive power, however thrust is still produced. The combination piston engine –propeller also has a propulsive power with exactly the same formula, and it will also be zero at zero speed – but that is for the engine–propeller set.
The familiar study of jet aircraft treats jet thrust with a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and ...
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 ...
Currently, F1 engines rev up to about 13,000rpm, while the combustion efficiency has risen to about 40 bar BMEP and beyond, using lean and rapid burn techniques enabling λ<1 (average air/fuel ratio much leaner than 14.7:1 by mass) [14] and very high mechanical and effective compression ratios.