here in this presentation we will be knowing about Propulsive efficiency and specific fuel consumption of air-craft, propeller propulsive efficiency, turbo jet efficiency, rocket and ramjet propulsive efficiency, fuel consumption calculations,

1. Aerospace propulsion and combustion
Propulsive efficiency and specific fuel
consumption of aircraft

2. Introduction
Propulsive efficiency, but it is an indicator as to how much engine
power is being converted into propulsive power (thrust × airspeed).
Thus, a particular propeller may be 0.80 efficient at a specific
condition. This means that 80% of the engine power (BHP) is being
converted into propulsive power.
Specific fuel consumption is the amount of fuel consumed by a
vehicle for each unit of power output. A vehicle's specific fuel
consumption is more or less independent from its nitrogen oxide
emissions per kilometer. The specific fuel consumption of an engine
is the rate of fuel burnt to produce a unit of thrust.
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3. Propeller propulsive efficiency
The propeller is the most
efficient propulsive method
at low speeds, while the jet
engine achieves best
efficiency only at relatively
high flight speeds. The very
high exhaust velocities of
the rocket make its
propulsive efficiency high
only at very high flight
speeds.
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4. Turbo jet propulsive efficiency
Thus for a jet engine with a
constant relative exit
velocity (a close
approximation of
a turbojet) the propulsive
efficiency increases with
aircraft velocity. The
reduction in exhaust
velocity also reduces the
exhaust noise, but has the
disadvantage that the thrust
reduces more markedly
with speed than for
a turbojet.
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5. Rocket propulsive efficiency
In aircraft and rocket
design, overall propulsive
efficiency is the efficiency
with which the energy
contained in a vehicle's
propellant is converted into
kinetic energy of the
vehicle, to accelerate it, or
to replace losses due to
aerodynamic drag or
gravity.
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6. Ramjet propulsive efficiency
efficiency with which the
energy contained in a
vehicle's propellant is
converted into kinetic
energy of the vehicle, to
accelerate it, or to replace
losses due to aerodynamic
drag or gravity.Overall
propulsive efficiency is
greatly dependent on air
density and airspeed.
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7. Specific fuel consumption
The value of TSFC for a given engine will vary with speed and
altitude, because the efficiency of the engine changes with
atmospheric conditions. Fuel flow rate = 3000 pounds per hour. Fuel
flow rate = 4500 pounds per hour.
 How to calculate SFC
number of crankshaft rotations for a complete engine cycle, nr = 2.
number of cylinders, nc = 4.
cylinder bore, B = 82 mm.
piston stroke, S = 90 mm.
mean effective pressure, pme = 5.16 bar.
engine speed, Ne = 2500 rpm.
fuel mass flow rate, mf = 1.51 g/s.
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