Construction of an 1.5-stage Air-Axial-Turbine Test Rig „MIGH“

 

The test rigs main component is formed by the 1.5-stage axial turbine.

Due to its two-parts design, the turbine may be opened by pushing the anterior part outwards. Consequentely, the effort to change sealing configurations or to vary the axial gap between the blade rows using spacer rings remains low. The outside casing may be rotated in all instrumented areas, thus enabling measurements over a wide circumferential range. To enforce a symetrical flow in circumferential direcation, a honeycomb rectifier is mounted downstream of the inlet housing, at the inlet of the main flow channel. As a result, reproducibility of all measurements should not be influenced by circumferential asymmetries. A clutch connects the shaft at the turbine outlet with an eddy current brake, which serves the purpose of controlling the turbines speed and power.

Compressed air is supplied by the institutes 6-stage radial high pressure compressor. A screw compressor supplies the turbine with the necessary sealing air.

 

Applications

  • Investigation of hot gas penetration in rotor-stator cavities
  • Investigation of sealing effectiveness using different sealing geometries and sealing mass flow
  • Investigation of hot gas and sealing gas interaction
 

Measurement Technology

  • > 115 stationary pressure measurements for balancing the flow field and for radial and circumferential recording of the pressure field in the wheel side space
  • Dynamic wall pressure sensors (500 kHz) at 8 measuring points for resolving transient flow phenomena in the wheel side space
  • Temperature measurement technology (thermocouples and resistance thermometers)
  • Fully automatic multisensor (fast-response) CO2 concentration measurement at up to 96 measuring points to determine seal effectiveness as a function of radius and circumferential position in the wheel side space
  • Capacitive distance measurement for detection of real gap dimensions
  • Speed and power measurement

 

Technical design data of the air turbine (current design)

Inlet pressure [bar]

5

Pressure ratio [-]

2.2

Inlet temperature [°C]

75

Mach number [-]

0.7

Reynolds number axial (according to guide vane series 1) [-]

2.1 * 106

Reynolds number circumferential [-] 5.9 * 106

Speed [1/min]

13,000

Mass flow [kg/s] 8.7
Maximum sealing gas mass flow per wheel side chamber [kg/s] 0.15
 

Duration and Project Partners

Construction of the test turbine is scheduled to end in October 2021.

The project is financially supported by the Research Association for Combustion Engines (Forschungsvereinigung Verbrennungskraftmaschinen). MTU Aero Engines is the chairman of the associated project committee.