Page 191 - 48Fundamentals of Compressible Fluid Mechanics

9.7. WORKING CONDITIONS 153
The maximum length in supersonic flow

In Fanno Flow
1.5
1.4
1.3
1.2
4fLmax D 0.9 1
1.1
maximum length, ¾¾ 0.8

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1.2 1.25 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65
Thu Mar 3 16:24:00 2005 spesific heat, k

Fig. 9.5: The maximum length as a function of specific heat,

9.7.1 Variations of the tube length ( ) effects

In part of this analysis of this effect, it should be assumed that that back pressure
is constant and/or low as possibly needed to maintain a choked flow. First, the
treatment of the two branches are separated.

9.7.1.1 Subsonic branch

For converging nozzle feeding, increasing the tube length results in increasing
the exit Mach number (normally denoted herein as N ). Once the Mach num-
ber reaches maximum (N H I ), no further increase of the exit Mach number can
be achieved. In this process, the mass flow rate decrease. It worth noting that
entrance Mach number is reduced (as some might explain it to reduce the flow
rate). The entrance temperature increase as can be seem from Figure 9.7. The
velocity therefor must decrease because the less of the enthalpy (stagnation tem-
and when Pressure is

remains almost constant the the density decreases. Thus, the mass flow rate must
decrease. These results applicable the converging nozzle.

In the case of the converging–diverging feeding nozzle, increase of the
, results in a similar flow pattern as in the converging
perature) is “used.” The density decrease because H
nozzle. Once the flow becomes choked a different flow pattern emerged.
dimensionless friction, WYX(Z [