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320
5
Pulsejet,
Ramjet,
and
Scramjet
Engines
Fig.
5.3
T-s
AND
P-v
diagrams
for
ideal
Humphrey
cycle
of
pulsejet
engine
1.
Intake
or
diffuser
This
process
occurs
from
state
(a)
to
state
(2)
as
shown
in
Fig.
5.3
.
Air
is
sucked
into
the
combustion
chamber
through
a
bank
of
spring-loaded
check
(one
way)
valve.
State
(a)
is
far
upstream,
while
state
(1)
is
at
the
pulsejet
inlet,
and
state
(2)
is
just
aft
of
the
check
valve
upstream
of
the
combustion
chamber.
Due
to
ram
effect,
both
the
pressure
and
temperature
rise
from
the
ambient
conditions
to
the
values
at
state
(1)
calculated
by
the
relations:
γ
γ
À
c
1
γ
À
1
2
M
2
P
01
¼
P
0
a
¼
P
a
1
þ
c
c
ð
5
:
1
Þ
Here
(
M
)
is
the
flight
Mach
number
and
(
γ
c
)
is
the
specific
heat
ratio
for
cold
air.
If
it
is
assumed
that
the
diffuser
is
an
ideal
one
(isentropic
process),
then
the
total
pressure
and
temperature
at
state
(2)
is
equal
to
those
at
state
(1),
or:
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