The test rig is used for basic aerodynamic analyses of turbomachinery profiles and for detailed investigations of individual flow phenomena in the compressor.
The main advantages of testing on flat grids are very good metrological and optical accessibility and the ability to analyse aerodynamic and geometric parameters independently of each other, which is not possible on the real machine. The wind tunnel has a test section with variable duct height and allows inflow coefficients up to Ma1 = 1.4 with very stable operating behaviour, especially with acoustic inflow (Ma1 = 1.0). The facility is operated in a closed-loop mode, allowing the Reynolds number to be varied independently of the Mach number, with total pressure and total temperature independently adjustable. This versatility is made possible by DLR's centralised air supply, which gives the wind tunnel exceptional performance. As a result, investigations can be carried out under conditions similar to Mach and Reynolds numbers, which is particularly important for turbomachinery experiments.
An outstanding feature of the system is its impressive extraction capacity. These allow efficient extraction of the sidewall boundary layers ahead of the measurement section, the upper and lower bypass ducts and the operation of the transonic upper end wall. The suction system is also used to control the sidewall boundary layers within the blade channels and to suppress secondary flow in the edge regions. The inflow turbulence of the duct is extremely low at only 0.6-0.8%, but can be gradually increased to over 4% by the selective use of different turbulence grids.
The transonic lattice wind tunnel at the Institute for Propulsion Technology in Cologne
