Process Gas Centrifugal Compressor

  Radial compressor Copyright: © RWTH Aachen | IST

As part of an ERDF (European Regional Development Fund) grant, which pursued the objective of "Regional Competitiveness and Employment", a new centrifugal compressor test rig was built and put into operation between 2007 and 2013. This is used for the detailed investigation of the complex flow processes that occur in radial process gas compressors with a recirculation stage.


Technical Data

  1. Compressor speed up to 18,750 1/min
  2. Inlet pressure between 0.3 bar and 2 bar
  3. Power drive motor: 1,600 kW



+49 241 80 95514




The test rig is located in the machine hall of the IST and is operated in a closed circuit. In the inlet section, the flow is first directed through a Y-pipe and then fed radially to the compressor stage through two inlets. The inlet temperature is thereby selectively adjusted via a cooler. The inlet pressure can be varied between 0.3 bar and 2 bar. The operating point is adjusted by means of a throttle and a slide valve located downstream of the stage. The mass flow is measured by means of a Venturi tube.

The compressor is driven by an asynchronous machine with a maximum power of 1,600 kW and a speed range of 150 - 1,500 rpm. The power is transmitted to the compressor shaft via a planetary gear. The planetary gearbox has an overall transmission ratio of 1:12.7, allowing a maximum compressor speed of 18,750 1/min, taking into account the gearbox used. The drive speed as well as the torque of the centrifugal compressor are telemetrically recorded by means of a high-speed torque measuring hub, among other things. A flexible steel lamina coupling closes the connection to the shaft of the centrifugal compressor.

The other infrastructure includes an oil supply system with a controlled oil/water cooler and an oil heater. This system ensures lubrication of the planetary gearbox. The compressor stage itself is equipped with a magnetic non-contact bearing in order to be able to determine the absorbed power as accurately as possible. The entire drive system as well as the test rig infrastructure are controlled and monitored by a programmable logic controller (PLC). Based on a high safety standard, this can issue warning messages by monitoring numerous predefined criteria and automatically shut down the compressor in an operationally safe manner.

The flow is fed to the centrifugal compressor stage via two 180° segments and then directed radially inwards. Shortly before the impeller, the flow is deflected back into the axial direction before the impeller subsequently converts the total enthalpy increase. The impeller provides a realistic outflow profile, which is mixed in the subsequent parallel-walled diffuser. The flow then enters the 180° baffle of the recirculation system. In addition to the 180° deflection, the recirculation itself also includes a bladed recirculation passage and a final 90° deflection. This is followed by the axial downstream flow of the stage.


Research Purposes

  • Experimental investigation of the flow in recirculation systems of multistage centrifugal compressors
  • Investigation of different hub ratios
  • Investigation of different Reynolds numbers
  • Investigation of different diffuser diameter ratios