A Mechanical Freelancing Hub

We are developing a compact gas turbine system with a compressor comprising two centrifugal stages on a common shaft, each housed in individual scroll casings (sequential turbo configuration). 

The system targets a combined pressure ratio of ~10:1, with stage-to-stage flow routed via an external crossover. 

Design Conditions & Constraints

• Stage 1 (S1)
  • Mass Flow: ~0.15 kg/s
  • Inlet: 1 atm, 25°C → Exit Target: 3.3 atm, 150°C
  • Operating Speed: 60,000–100,000 RPM
  • Inducer Eye Diameter: Ø62 mm
  • Exit Tip Diameter: Ø95 mm (housing constrained)
  • Axial Envelope: ≤22 mm 
• Stage 2 (S2)
  • Mass Flow: ~0.15 kg/s
  • Inlet: 3.3 atm, 50°C (intercooled) / 150°C (test)
  • Exit Target: ~11 atm, 280–350°C
  • Operating Speed: 60,000–100,000 RPM
  • Inducer Eye Diameter: Ø48 mm
  • Exit Tip Diameter: Ø78 mm (fixed)
  • Axial Envelope: ≤20 mm 
• Both impellers share a Ø16 mm tie-bolt bore and operate as a matched aerodynamic set, with S1 discharge feeding S2 inlet. 

Material & Manufacturing Constraints

• Material: Inconel 625 
• Manufacturing: FFF metal printing (Markforged Metal X process) 
• Minimum feature size: ~2.8 mm → design with ≥3.0 mm margin 
• Configuration: Open (unshrouded) impellers 
• Tip clearance: 1.0 mm (housing-controlled)