IBN-Halle, Testbed 3 Diffusors

In accordance with the original research tasks, identical centrifugal compressors (dader impellers = 233 mm) are located on both sides of the drive motor, which are, however, equipped with different diffusers.    The stage pressure ratio Π is greater than 3.3 and is achieved at a speed N > 35,800 rpm.  Both compressors can be operated open or in a cooled circuit.     The operating point can be adjusted by means of throttle valves on the suction side and a standardized flow measuring section. A three-phase synchronous motor with an output Pel= 750 kW and infinitely variable speed adjustment up to N max= 1,500 rpm drives the respectively coupled compressor. The drive power is transmitted to the centrifugal compressors via a turbo spur gear and a switchable curved-tooth coupling (both made by Tacke).  The torque is measured by means of a torque measuring shaft (manufactured by Hottinger-Baldwin). On side DF 3-1 of the drive train, a bladeless disk diffuser is installed in order to be able to investigate the subsonic flow in the impeller as far as possible without diffuser feedback.  Meanwhile, a bladed disk diffuser with wedge-shaped blades that can be adjusted during operation is used on side DF 3-2. In addition to conventional measurement techniques (pressure, temperature), the laser-optical L2F method has also been used in the past to resolve the flow phenomena.  Both test rigs are designed in such a way that an easy exchange of the diffusers can be realized.