 Striae picture of an transonic compressor cascade at M1= 1.25 |
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| View of the test section of the cascade wind tunnel | |
This test facility is used for fundamental analysis of turbomachine profiles and for the study of specific flow phenomenon. Its test section has a variable width of 168 mm x 150-330 mm and allows inflow Mach numbers up to M1 = 1.4 with a very stable operating performance particularly at sonic speed (M1 = 1.0).
The wind tunnel is set up in a closed loop, which allows varying the Reynolds number independently of the Mach number by controlling the total pressure and the total temperature..
The central air supply system of the DLR consists of several centrifugal compressors, which can be connected in parallel or in series. Therefore the wind tunnel is extraordinary flexible
The large suction capacities of the system are unique. They enable controlling the side wall boundary layer in front of the cascade test section, the upper and lower bypass channels as well as operating the transonic upper end wall.
The suction system is also used for controlling the side wall boundary layers within the cascade passage and for suppressing secondary flow.
The great advantages of the analysis of two-dimensional cascades reach from cheap models with relatively large dimensions, easy measurement and optical accessibility, but particularly to the possibility of controlling the aerodynamical and the geometrical parameters independently of each other, which is not possible in real turbomachines.
The test facility is used for the following kind of studies:
- Experimental validation of 2D and 3D numerical flow simulations with very detailed data (reference literature ASME JT July 2002)
- Development and verification of new profile design concepts (reference literature ASME JT July 2000, Part 1, Part 2)
- Fundamental investigation of flow phenomenon in turbomachines, e.g. boundary layer development on the profiles (transition and separation), passive and active separation control, shock boundary layer interaction
- Development and control of secondary flow and corner separation. Analysing the effects of different side wall contouring concepts or profile alignments, as for example sweep or lean.
Further information:
Aerodynamical basics
Technische Daten:
Characteristically parameters:
| Mach number |
M1 = 0.2 - 1.4 |
| Reynolds number |
Re = 1x105 – 3.5x106 |
| Turbulence |
Tu = 1- 4% |
| Total pressure |
pt = 0.1 – 1.8 bar |
| Total temperature |
Tt = 300 –325 K |
| Test facility height |
150 –330mm |
| Profile span width |
168 mm |
| Inflow angle |
80 – 160° |
Air supply system:
- Continuously operating in a closed loop
- Side wall boundary layer suction
- Transonic test facility for M1 = 0.9 – 1.2
- Half symmetric supersonic nozzle
- Silica gel dryer for transonic tests
- Large suction capacity
Flow visualisation system:
- Striation optic
- Oil streak pattern
- Liquid crystals
- Light-section
Testing methods:
- Static pressure distribution
- Three and five hole probes
- Laser two-focus anemometer
Cross-section of the transonic cascade wind tunnel cologne |
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