Turbofan exhaust gases induce additional air into the ejector via an auxiliary air intake, thereby reducing the specific thrust / mean jet velocity of the final exhaust.
22.
If, however, the afterburner is to be hardly used, a low specific thrust ( low fan pressure ratio / high bypass ratio ) cycle will be favored.
23.
At a fixed total applied fuel : air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine.
24.
It's linked to from a wikified table in that article, as an example of a propulsion type which would have very low specific thrust designed to be applied over decades.
25.
When lit, prodigious amounts of fuel are burnt in the afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity / engine specific thrust.
26.
An SST VCE would have to increase the engine airflow substantially at take-off, to reduce the jet velocity at a given thrust ( i . e . a lower specific thrust)
27.
A low ( dry ) specific thrust engine has a low tailpipe temperature, which means that the temperature rise across the afterburner can be high, giving a good thrust boost in afterburning.
28.
The total fuel flow ( main combustor plus afterburner ) is fixed by the temperature rise from air intake to nozzle and, for a given airflow, changes little with dry specific thrust.
29.
Ivchenko Lotarev chose a very low specific thrust ( net thrust / airflow ) cycle for the DV-2, so a single stage fan is sufficient to develop the desired fan pressure ratio.
30.
Military turbofans, however, have a relatively high specific thrust, to maximize the thrust for a given frontal area, jet noise being of less concern in military uses relative to civil uses.
