flow
and to exhaust the cooling flow into the external flow so
as to
result in minimal drag penalty. To adequately perform
the
regulation, the exit must act as both a throttle and a
pump.
Throttling is necessary in cruising flight to
minimize the cooling
drag by
reducing the cooling flow to that sufficient to meet
cooling
requirements.
In ground operation and in
climbing
flight,
the exit must act as a pump to induce sufficient cooling
flow
through the system. Both of these functions can be
performed
by a
hinged flap. The fundamental principle here is
that
for any subsonic flow system, the flow rate through the
system
will always adjust itself so that the static pressure at
the
exit
will match the local external flow static pressure
surrounding
the
exit. The static pressure at the exit is controlled by the
exit
area.
Thus, regulation is obtained by varying this
area.
Opening
the flap beyond the contour of the airframe creates a
low-pressure region that induces additional flow
through the
system.
It became common design practice during World War
II to
serve the exit flap to a coolant temperature sensor to
optimize
the
system operation.
Ed
Anderson
Rv-6A
N494BW Rotary Powered
Matthews,
NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm