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Next: Nozzle Flow With External Up: Normal Shock in Variable Previous: Nozzle efficiency Index
The efficiency of the diffuser is defined as the ratio of the
enthalpy change that occurred between the entrance to exit stagnation
pressure to the kinetic energy.

The condition at
is summarized in following table
The nozzle area can be calculated by
In this case, is constant (constant mass flow). First the stagnation behind the shock will be

Solution
This is a case of completely and suddenly
open valve with the shock velocity,
temperature and pressure ``upstream'' known.
In this case PottoGDC provides the following table
Then calculate the by using PottoGDC or utilize the Tables. For example PottoGDC (this code was produce by the program)
Finally utilizing the equation to calculate the following

Solution
This is an open valve case in which the pressure ratio is given.
For this pressure ratio of
the following table
can be obtained or by using PottoGDC
The temperature ratio and the Mach numbers for the velocity of the air (and the piston) can be calculated. The temperature at ``downstream'' (close to the piston) is
The velocity of the piston is then

Solution
This is the case of a close valve in which mass flow rate
with the area given.
Thus, the ``upstream'' Mach is given.
Thus the static Mach number, is
With this value for the Mach number PottoGDC provides
This table was obtained by using the procedure described in this book. The iteration of the procedure are
