The Large Scale Rotating Rig (LSRR) is a low speed, open circuit, suck-down type of facility. It is a specially designed experimental rig to carryout basic research and innovation in the field of turbo machinery at low speeds and room temperature. The rig can be used to test a turbine stage or a compressor stage with appropriate hardware changes. The rig incorporates a 12’ diameter circular bell mouth with honeycombs and screens for minimizing flow eddies, followed by an annular model section currently carrying a turbine stage. A dumb diffuser is provided downstream of the model section for pressure recovery. A 200 hp DC motor is mounted inside the dumb diffuser to drive the turbine rotor which can run at various speeds up to a maximum of 950 RPM. This motor also functions as a generator/electrical dynamometer to absorb the power developed by the turbine while the rig is running and regulates the speed of the rotor. At the end of the diffuser a pneumatically operated vortex valve is provided to control the mass flow through the model section.The rig also incorporates a centrifugal blower mounted at the exit of the dumb diffuser to suck air through the model section.The blower is driven by a 600 hp AC motor that can run at a constant speed of 700 RPM. Mechanical instrumentation for measuring aerodynamic quantities are readily available in the rig which includes 5-hole pressure probes, 3-hole cobra probes, static pressure tappings at various locations on the vane / blade surfaces and platforms.One 5-hole probe integrated with a cobra probe is mounted at the vane exit on the casing and another such set is mounted at the blade exit on the rotor disc.The vane exit probe combination is used to measure steady state total pressure, static pressure / flow velocity and flow direction in the circumferential plane at any chosen radial location in the stationary frame.The blade exit probe combination is used to make similar measurements at the rotor blade exit plane in the rotating frame.The rotor casing is instrumented with high response transducers for unsteady pressure measurements.


Stationary Frame Measurements

  • Vane surface pressure distribution measurements using ZOC pressure scanners.
  • External probe traverse system for Vane exit flow measurements


Rotating Frame measurements

  • Internal probe traverse system for Blade exit flow measurements
  • Calibration of Internal Pressure transducers in rotation
  • Blade surface pressure distribution measurements using 48 port Scanivalve mechanical multiplexer.




Capability of the rig


Study of  three dimensional flow over turbine  rotor  blades


Specificatios :


Turbomachinery components


Turbine / Compressor


Test section diameter


1.52m ( 5ft )


Hub / tip  ratio


0.5  to  0.8


Model tested (USA)  


Two rows of airfoils

                   1. First vane

                   2. First blade


Aspect  ratio (span / axial chord)      




Turbine  speed  ( model)


405 rpm (max 890 rpm)


Flow medium air


Incompressible  (close to)


Aerofoil exit mach number




Instrumentation and measurements


Rotating frame of reference




  1. Radial                         : hub to tip
  2. Circumferential  : two blade pitch
  3. Yaw                              :


Traverse probes


Simple Kiel total pressure to combination of five hole and cobra probes


Probe size


Diameter less than 2 percent of the   blade pitch


Stator- rotor gap


Variable from 15 % to 65 % of the axial chord


Blower pressure rise


21 inches of water


Blower motor


600 HP


Data acquisition


On line automatic data acquisition and control system


Communication of rotating frame


Slip ring




System calibrates all transducers in both rotating and stationery frames


LSRR Capabilities:


  • Tip clearance flows
  • Casing treatment flows
  • Inter stage leakage flow effects
  • Effect of inlet distortion
  • Unsteady rotor - stator interaction
  • Secondary flows and wake mixing
  • Active stall control



  • Tip leakage  flows
  • Hot streak migration
  • Gas path, cavity flow interaction / End wall secondary flow
  • Vane/blade platform geometry optimization
  • Unsteady rotor - Stator interaction
  •  Shrouded rotor and vane less contra-rotating turbines



List of Staff:


1. R Senthil Kumaran         -           Senior Scientist

2. Kishor Kumar                   -           Scientist

3. N Poornima                      -           Senior Technical Officer II

4. KS Loganathan               -           Senior Technician II

Last updated on : 27-09-2020 01:31:53pm