
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 hotair 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 fivestep 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
