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Diagram of a typical gas turbine jet engine. Air is compressed by the compressor blades as it enters the engine, and it is mixed and burned with fuel in the combustion section. The hot exhaust gases provide forward thrust and turn the turbines which drive the compressor blades. 1. Intake 2. Low pressure compression 3. High pressure compression ...
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.
Calculating the effective exhaust velocity requires averaging the two mass flows as well as accounting for any atmospheric pressure. [12] For air-breathing jet engines, particularly turbofans, the actual exhaust velocity and the effective exhaust velocity are different by orders of magnitude. This happens for several reasons.
= the mass rate of intake air that flows to the core engine ṁ f = the mass rate of intake air that bypasses the core engine v f = the velocity of the air flow bypassed around the core engine v he = the velocity of the hot exhaust gas from the core engine v o = the velocity of the total air intake = the true airspeed of the aircraft BPR ...
Short velocity stacks on a 302 cu.in. Ford FE engine in the tight confines of a Ford GT-40. A velocity stack, trumpet, or air horn [1] is a typically flared, parallel-sided tubular device fitted individually or in groupings to the entry of an engine's air intake system to smooth high speed airflow, and allow engine intake track tuning to incorporate pressure pulses created by its internal ...
where is the exhaust expulsion velocity [4] and is both the airspeed at the inlet and the flight velocity. For pure jet engines, particularly with afterburner , a small amount of accuracy can be gained by not assuming the intake and exhaust massflow to be equal, since the exhaust gas also contains the added mass of the fuel injected.
[11] [citation needed] [dubious – discuss] However, v e is the effective exhaust velocity. If a turbojet engine has a purely convergent exhaust nozzle and the actual exhaust velocity reaches the speed of sound in air at the exhaust temperature and pressure, the exhaust gas cannot be further accelerated by the nozzle.
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.