Monty Roberts wrote:

The really interesting thing about Charlie Airesman's
exhaust augmentor design is the venturi effect on the exhaust.
The forward motion of the airplane may actually create a slight
vacuum in the exhaust. I would love to see some pressure measurements
on this set up.

Paul Lamar

Paul,

I plan on using an augmentor. Actually the vacuum is not created by the
forward motion of the aircraft. If the system is designed properly the way
it works is as follows:

1.) A properly designed diffuser slows the incoming cooling air and recovers
the velocity as pressure.

2.) This high pressure air then passes through the radiator, which heats the
air, hopefully enough to raise the pressure so that it cancels the pressure
drop across the radiator or creates a slight pressure rise.

3.) This air is then drawn into the augmentor by the jet pump effect of
directing the hot exhaust into the throat of a venturi (same effect as an
air gun, where a high velocity stream of air draws in surrounding air to
produce more volume)

4.) The air is heated additionally by the exhaust. The high pressure hot air
is then accelerated in a nozzle, trading pressure for velocity. This
produces thrust or at least helps cancel the cooling drag.

If properly designed it should produce some positive thrust. We are doing
the same thing a jet engine does on a much weaker scale. Think of this as a
very weak ram jet. Compress the air, heat it, heat it some more, put it
through a nozzle.

This has several advantages, on the ground the pumping effect of the
augmentor will draw air through the radiator to provide ground cooling. This
is especially true if the airflow path allows the air to rise from inlet to
outlet. In the air it will help reduce cooling drag.

Monty

 
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