CT-2C facility is here!
After several years of brainstorming and some month of detailed design and commissioning, the von Karman Institute for Fluid Dynamics is proud to announce that the CT-2C wind tunnel is finally up and running, providing new engine-like testing capabilities for compressors linear cascades!
The CT-2C facility can be considered as an upgrade of the historical CT-2 light weight isentropic compression tube Facility of VKI (Figure 1). Designed in 1975 by Richards  for heat transfer research only, CT-2 was soon converted into a fully featured turbomachinery linear cascade wind tunnel .
CT-2 tube and test section, around 1990
Simplified cutview of the CT-2 original configuration
CT-2 is a short duration wind tunnel able to operate in engine similarity in terms of Mach number and Reynolds number. The flow-to-wall temperature ratio can also be adjusted up to a value of about 1.8. As shown in Figure 2, pressurised air is injected from the right-hand side of the compression tube. The piston, under the effect of the injection, accelerates quickly towards left, compressing the column of air enclosed in the cylinder. When the desired conditions are met (i.e. compression final pressure and temperature), the fast shutter valve opens, releasing the inlet flow into the test section and eventually in the dump tank.
Following the validation test-cases requested by the CFD community and thanks to the support of Safran, CT-2 was re-engineered to provide compressors linear cascade testing capabilities in engine-like conditions. CT-2 in compressor testing configuration (CT-2C), features a 100 mm x 250 mm wide test section, hosting up to 9 prismatic profiles. The outlet boards are fully adjustable for proper periodicity tuning and they discharge in an outlet plenum that ensures 60+ chords of axial development downstream the trailing edge plane. The plenum is then connected to the dump tank through an adjustable sonic throat.
Figure 3: the new CT-2C configuration. From left to right: a) plenum and sonic throat; b) test section (in red) with traversing system installed; c) compression tube.
The CT-2C configuration (Figure 3) was fully commissioned for high subsonic inlet Mach numbers and for a Reynolds number range spanning from 140 K up to 800 K (considering a chord of 0.03 m).
Still, plans for CT-2C don’t end here. The focus of the VKI Compressors Research Group is moving more and more towards high speed transonic axial compressors, forcing the CT-2C facility and the R4 closed loop high speed axial compressor rig of VKI to evolve accordingly.
In the end, we would like to re-assure all the turbine fans: the modification is fully reversible and CT-2 can be brought back to the turbine linear cascade configuration (CT-2T) in a few hours’ time!
We will keep you posted!
Assistant Professor Turbomachinery and Propulsion Dept. “Jacques Chauvin”
Laboratory von Karman Institute for Fluid Dynamics
 Richards, B. E. "Isentropic Light Piston Facilities for Simulation of Hot Flows Through Turbines." VKI LS 78 (1978).
 Consigny, H., Richards, B.E., 1982, ‘Short duration measurements of heat transfer rate to a gas turbine rotor blade’, Journal of Engineering for Power 104.3: 542-551
 Arts, Tony, and M. Lambert de Rouvroit. "Aero-thermal performance of a two-dimensional highly loaded transonic turbine nozzle guide vane: A test case for inviscid and viscous flow computations." Journal of Turbomachinery 114.1 (1992): 147-154.