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Aerodynamic test stand

Description of the aerodynamic test stand

In order to demonstrate the success of the optimization
work experiments got carried out on a test bench. On this
test stand the hydrodynamic characteristics of the original
and the optimized burner hot-air branch ducts got
compared.

The corresponding test bench is described below.

The test stand works with air as working medium. The
pressure generation is done with two fans. The air duct of
both fans is connected in series.

After the fan follows a pipe (length 2 m) with a measuring
section. The diameter of the pipe is 118 mm. As a transi-
tion from the initial diameter of the fan to this diameter a
confusor was used with a cone angle of 12 °, this ensures
a maximum flow rate coefficient. At the entrance of the
pipe with the measuring section sits a tube kind flow
straightener.

To protect the measuring section from retroactive effects
of the flow in the test objects a pipe section for flow stabili-
zation was installed between them. This pipe section is
provided at the with two tube kind flow straighteners at the
input and output.

The performance of the fan is controlled by a five-step
voltage controller.

The following data were measured before each test series:
t - temperature of working medium, ° C
B – atmospheric pressure, mbar

For each test item are 5 operating regimes by the corres-
ponding switch position on the voltage controller.

One of the operating regimes will carry out approximately
20 measurements in two minutes (= one series of mea-
surements) of the following values:

p
st - Static Pressure, hPa
p
DY differential pressure on flow meter
       (Equivalent to the average flow speed), Pa
P - Power of the fans, W

For each series of measurements the average of the
measured values will be determined.

The results are demonstrated in a dimensionless functional
dependence of the type ζ = f (Re) to ensure a transferability
of the results.

Where:
ζ - coefficient of flow resistance
Re - Reynolds number

The success of the optimization work can be seen by
comparing the coefficient of flow resistance of the
corresponding element before and after optimization for
the same Reynolds number. The percentage ratio of both
quantities provides information about the reduction of the
pressure loss through the optimization work.

With this value and characteristics of the original elements,
the increase of the flow rate or the saving of energy by a
constant flow rate after the optimization work can be
determined.

The following should show that the designed test stand has
quite outstanding results in terms of repeatability of
measurement data.

For this purpose, the coefficient of flow resistance of the
test stand (without test element and transition cone) was
measured on four different days.

The following shows the coefficient of flow resistance for
the test stand on four different days.

Test No. 1

Forkert Technology Services GmbH
Allee der Kosmonauten 28
D-12681 Berlin
Germany
Phone: +49(0)30 / 548 00 450
Fax:     +49(0)30 / 548 01 706
eMail: info@forkert-t-s.com

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Test stand

Volumenstrommessung mit statischer Druckmessung -
Measuring of flow rate and static pressure;
Druckmessung - Measuring of pressure;
Zeitmesser - Chronometer;
Leistungsmessung - Measuring of power consumption
Spannungsregler - Voltage controller

Configuration to test the repeatability of measurement data

Test No. 2

Test No. 3

Test No. 4

To make the tests comparable, they were approximated in
the form of the equation ζ = a.Reb and the coefficients a
and b for each test.

Subsequently, for each test the value ζ at a Reynolds
number of 100.000 was calculated.T

The maximum deviation from the mean has the test No. 4.
But even this value has only a deviation of 1.1%. This
indicates a very good repeatability of the measurement
results and the excellent quality of the test stand.