__Section 5__

**A Note on Isentropic Flow
‘Perpetual Motion’**

** **__Introduction__

Since isentropic flow is so efficient – that is to say it can be
made almost 100% ‘loss free” -
it naturally invites speculation
as to the possibility of a ‘perpetual motion’
or ‘quasi-perpetual motion’ flow model. However, the long standing
prohibition against heat engine or thermodynamic perpetual motion as a
violation of the second law of thermodynamics, naturally creates a well founded caution – or even resistance
to- such possibility in other areas of
physics.

However, one other example of quasi -perpetual motion occurs in outer space, where loss-free
motion of a space satellite through a frictionless space in the absence of any
substantial gravitational or other force field,
results in quasi-perpetual orbital motion under

It seems well worthwhile, therefore, to examine the motion of
isentropic gas flows in a bit more
detail from this standpoint.

__ Frictionless Isentropic Flow__

Ideal isentropic flow is
frictionless, so that its accelerations and decelerations are ideally lossless.
In practice isentropic *accelerations* are nearly ideal with very
small pressure- head losses due to
friction, turbulence or viscous effects ;
however, low loss *decelerations* are more difficult to achieve [12,3].

__Invention No. 1 in a
Perpetual Motion Mode.__

In Section 2 an isentropic air motor is described with an
extremely large amplification of flow power in a De Laval converging nozzle.The resulting available power is so
many times greater than the necessary mass flow air power from a conventional
low efficiency vacuum pump that perpetual
motion from a feed back of amplified flow power is obvious as a self-
sustaining motion. However, if flow losses are considered, the operation
becomes one of a decline in power
towards an eventual cessation of the
flow. This is best seen from an analysis of mass flow rate rather than from that of flow power.

For example, let us take a vacuum source sustaining a mass flow
rate of 0.074 kg/s for a power input of 1690 watts. This flow rate corresponds
to an air flow power of flow of only about 100 watts (or a vacuum
source efficiency of 100/1690 = 5.9%).

If we pass this mass flow through a De Laval Nozzle ( Fig. 1) of throat diameter of 1.98 cm the
flow will then be sonic at the nozzle
throat. The throat power will be P= ˝ x 0.074 x 313^{2} = 3625
watts.

Since it only requires 100 watts of flow power to sustain 0.074
kg/s inflow to the nozzle, we then, by inserting a bypass feed-back duct
connecting the throat to the system flow exit,
bleed off this amount of power from the throat, and ( Figure 2) we can then shut down the
inefficient vacuum source which requires 1690 watts to deliver 100 watts of
flow power and the system will be self sustaining - __if there are no frictional
or other losses. Under this assumption the motion would be
self-sustaining indefinitely.__

If losses are present, the mass flow will have to decrease. This mass
flow decrease is usually observed as a
pressure rise or a flow velocity decrease. For frictional losses, the pressure
is related to the velocity squared so that the observed velocity will drop
rapidly at first and then much more slowly. Low losses will therefore
exhibit a long slow decline in any
self-sustaining flow velocity.

__Conclusion__

__ __In the absence of any flow losses perpetual flow motion is
possible. The practical limits and usefulness of the possibility remain to be
fully investigated.

__References__

1. Munson, Bruce, R.,
Donald F. Young, and Theodore H. Okiishi, *Fundamentals
of Fluid Mechanics, * Wiley and Sons,
New York, 1990.

2. Shapiro, Ascher, H., *The
Dynamics and Thermodynamics of Compressible Fluid Flow, * 2 Vols.,
John Wiley & Sons, New York.1954.

3. R. Courant and K.O.
Friedrichs, *Supersonic Flow and Shock Waves. *Interscience,

**Copyright
Bernard A. Power , May 2011**

**Section Links:**

**Section 1: Linear ( streamline) Flow and Flow Power
Amplification**

**Section 2 : Invention
No.1: A New Isentropic Air Motor and
Clean Energy Source**

**Section 3 To be posted in near future**

** **