13-15 Sep 2004 [PDF] - Orbiter Space Flight Simulator - UCL

Air-breathing engines: scramjet (2)
F
m
= 1+
D v − v
Specific thrust is given by ( )
e ∞
where
D
= m f
/ m
a
D
a
is the fuel-to-air ratio.
The amount of fuel burned in the combustion
chamber must be adjusted so that the burner
temperature limit is not exceeded. This leads
to the following expression for D:
Tb
−Td
=
Q / c −T
where Q is a fuel-specific heating value and
c p
is the specific heat at constant pressure,
given by c p
= γR/(γ-1).
The exhaust velocity
the energy balance
v e
p
b
can be obtained from
Thrust vs. Mach number:
N ]
[k
F
180
160
140
120
100
80
60
40
20
Engine thrus t
0
0 1 2 3 4 5 6 7 8 9
Mach number
TSFC vs. Mach number:
k J]
g / [k
C
T SF
0.8
0.7
0.6
0.5
0.4
0.3
0.2
Thrus t-s pecific fuel cons umption
c T = c T + v
p
b
p
e
2
e
/ 2
0.1
0
0 1 2 3 4 5 6 7 8 9
Mach number