Analysis, design and manufacturing of solarised gas turbine compressor

Schommarz, Timmo Marc (2019-04)

Thesis (MEng)--Stellenbosch University


ENGLISH ABSTRACT: An existing three-dimensional fluid mechanical design of a compressor is reviewed and compared to mean-line simulation results obtained using the Comp- Aero® compressor design code. Mean-line simulation results give a compressor total-to-static pressure ratio of 3.2. The three-dimensional CFD analysis performed using ANSYS CFX® calculates a total-to-static pressure ratio of 3.4. This is an increase of 31% from the pressure ratio of the currently installed compressor (2.6). ANSYS Mechanical® is used to perform finite element analyses for deformation, stress and vibrational behaviour. The maximum calculated axial deflection is 0.24 mm. The calculated maximum equivalent stress is 218 MPa. All vibration modes occur at frequencies higher than the operating speed of the compressor. The first damped frequency occurs at 837 Hz which represents and over-speed condition of 9.24%. Over-speed simulations to 110% operating speed calculate a maximum stress in the impeller of 264 MPa. This is 1.8 times less than the yield strength of Aluminium 7075 which was used to manufacture the part. Axial forces due to the increased outlet pressure of the compressor are calculated. The total load on the angular contact bearing increased from 376 N, as experienced with the old compressor, to 955 N when using the new compressor. The new impeller and diffuser are designed using the Autodesk Inventor® CAD program. The components are machined using five- and three-axis computer-aided milling.

AFRIKAANSE OPSOMMING: n Vorige drie-dimensionele, vloei-meganiese ontwerp word hersien en met eendimensionele berekeninge vergelyk. Een-dimensionele berekeninge is met die CompAero® sagteware pakket gedoen en voorspel ’n totaal-tot-statiese drukverhouding van 3.2. Die drie-dimensionele berekenig is met ANSYS CFX® gedoen en voorspel ’n totaal-tot-statiese drukverhouding van 3.4. Die drukverhouding word met 31% verbeter vanaf die van die kompressor wat huidiglik gebruik word (2.6). ANSYS Mechanical® is gebruik om strukturele analises vir vervorming, spanning en vibrasie uit te voer. Die grootste aksiale vervorming is 0.24 mm. Die grootste spanning word bereken as 218 MPa. Alle modes van vibrasie is hoër as die ontwerpspoed van die kompressorrotor. Die eerste gedempte mode verskyn by 837 Hz wat gelyk is aan ’n oor-spoed toestand van 9.24%. Oor-spoed berekeninge tot en met 110% ontwerpsspoed bereken ’n maksimum spanning van 264 MPa. Hierdie spanning is 1.8 keer kleiner as die swik-krag van Aluminium 7075. Die totale las op die aksiale laër verhoog van 376 N, soos bereken met die ou kompressor, na 955 N as gevolg van die styging in druk. Die nuwe rotor and stator is in Autodesk Inventor® ontwerp en vervaardig met vyf- en drie-as rekenaar-ondersteunde masjienering.

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