Turbomachinery Research

Design and Optimization of Centrifugal and Axial-centrifugal Compressors

Level of performance:

  • One stage: 10:1 total pressure ratio, isentropic efficiency ~ 0.8 (variable thermal capacity), surge margin ~ 15%;
  • Two stages (mixed-flow (diagonal) impeller of the first stage): > 11.5:1 total pressure ratio;
  • Axial-centrifugal (including High Pressure Compressor for a Turbo-shaft Engine): > 13:1 total pressure ratio, isentropic efficiency ~ 0.8 (variable thermal capacity).

Software:

  • RANS "mixing plane" for CFD design and optimization;
  • URANS to investigate rotor-stator flow physics;
  • ANSYS for structural design.

Method of Investigation:

  • Parameterization of a problem, broad data mining through 3D viscous flow calculations for a wide range of parameters, following data generalization.










Initial vaned diffuser



Optimized vaned diffuser

Main Research and Development Problems Inherent to Centrifugal Wheel (Rotor):

  • One-piece wheel (one disk):
    • Inducer profiling to minimize relative flow Mach number on tip (< 1.4);
    • Blade profiling to control tip clearance leakage and secondary flow;
    • Blade angle at impeller exit: favorable flow outcome;
    • Reduction of wheel axial length ==> reduced weight and inertia moment, improved low-cycle fatigue;
    • Tailoring of rear disk cavity to control flow friction and heating.
  • Split wheel (two pieces - inducer and impeller, two disks ==> reduced weight and inertia moment, improved low-cycle fatigue):
    • Mutual tangential shift of inducer and impeller to control tip clearance leakage and secondary flow.

Main Research and Development Problems Inherent to Vaneless Diffuser:

  • Choice of optimum combination of impeller exit blade height & backsweep angle and vaneless diffuser contraction & radial length to avoid excessive flow angles (reverse flow) wimedium vaneless diffuser.

Main Research and Development Problems Inherent to Vaned Diffuser and Outlet Axial Guide Vane:

  • One-row supersonic vaned diffuser (flow deceleration from Mach number M=1.3 to M=0.4);
  • Tandem (double-row) supersonic vaned diffuser (flow deceleration from M=1.3 to M=0.2);
  • Design of outlet axial guide vane and comparison of static pressure recovery in case of single-row and tandem vaned diffusers.

Unsteady impeller - vaned diffuser interaction (vital to prevent high cycle fatigue):

  • Calculation of unsteady aerodynamic excitation of impeller blade (including diffuser's shock wave impingement);
  • Conditions governing the depth of penetration of the diffuser-generated aerodynamic excitation into impeller passage;
  • Design of vaned diffuser without unsteady flow separation.

Design and Optimization of Axial High Pressure Compressor (HPC)

Level of performance:

  • 8 stages, > 16:1 total pressure ratio, isentropic efficiency ~ 0.85 (variable thermal capacity).

Software:

  • RANS "mixing plane" for CFD design and optimization;
  • URANS to investigate rotor-stator flow physics.

Method of Investigation:

  • Parameterization of a problem, broad data mining through 3D viscous flow calculations for a wide range of parameters, following data generalization.

Investigation and Development of Groups of Stages:

  • Front stages;
  • Middle stages;
  • Exit stages.

Problems:

  • Effectiveness of casing treatment;
  • Shrouded guided vanes (flow with labyrinth seal);
  • Cantilever guided vane (with rotating hub): 3D design of blade to counteract leakage flow;
  • IGV - Rotor1 unsteady flow;
  • Ultra high-pressure front stage.



 

Complex Numerical Investigation of The Multi-Stage Compressor's Unsteady Flow Phenomena

  • Direct URANS numerical simulation of the unsteady 360 degrees circumference flowfield in the multi-stage compressor using the supercomputer;
  • Modelling the compressor surge development;
  • Visualization of the process to understand the phenomenon in detail.
 

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