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Numerical Quantification of Interaction Effects in a Closely-Coupled Diffuser-Fan System

List, Michael G
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396530464

Abstract Details

2014, PhD, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
Distorted inflow conditions have been a plague for compression system operability and aeromechanics since the dawn of gas turbine engines. This will likely continue to be an issue for all systems, but modern inlet designs, particularly serpentine diffusers, accentuate the existing issues through the production of both total pressure deficits and flow angularity distortion. For the first time, unsteady, full annulus CFD analysis of a coupled diffuser-fan system was pursued to determine coupling effects between the serpentine diffuser and transonic fan stage. Additionally, the harmonic balance method was used for the first time to demonstrate development and transfer of the distortion. These efforts provided a novel demonstration of 3-D analysis using a generated distortion relevant to this class of inlet and fan. Prior distortion analyses have been conducted using prescribed inlet distortion fields typically matching experimental total pressure or bulk swirl profiles. In the present study, an offset serpentine diffuser was used, coupled directly with the fan stage, to generate the distortion pattern. The Star-CCM+ solver was used to complete mixing-plane, harmonic balance, and transient, full annulus simulations of the coupled system. Mixing plane analysis provided a computationally inexpensive way to assess a nominal mass flow rate at which the components were matched, but provided little additional information beyond a flow field initialization for the higher-fidelity methods. The ability of any distortion analysis method to compute the generation of total temperature and swirl distortion through the fan stage is critical. The harmonic balance and full annulus results show appropriate capture of the distortion transfer, generation of intra-stage total temperature distortion, as well as the impact of the turbomachinery upon the incoming flow field. Redistribution of the distorted flow entering the fan was captured reasonably well by the harmonic balance simulation. Entering the rotor region, however, the vortices generated by the diffuser were not fully captured due to an inadequate combination of modes being solved to resolve the vortex structures. This led to an inability of the harmonic balance simulation to match the peak total pressure and total temperature rise generated by the rotor in the distorted regions, though the mass-averaged circumferential distribution and the amplification of distortion per-rev components showed remarkable similarities. A reduction in the total computational requirements was seen using harmonic balance making it of value for detailed design and analysis, though current implementations have limitations prohibiting more rapid turnaround for use in earlier design iterations. Its use in distortion applications, particularly for stage analysis, has been shown to be meaningful and suitable to bridge the gap between reduced order modeling and full annulus simulations. Better understanding of the unsteady aerodynamics will provide a more accurate view of performance in distorted flow and the sources of aerodynamic excitation and damping that dramatically affect the physics in modern fans.
Mark Turner, Sc.D. (Committee Chair)
Steven Puterbaugh, Ph.D. (Committee Member)
Shaaban Abdallah, Ph.D. (Committee Member)
Paul Orkwis, Ph.D. (Committee Member)
396 p.
Aerospace Materials
distortion transfer; inlet-fan interaction; harmonic balance; full annulus; CFD

Recommended Citations

Citations

  • List, M. G. (2014). Numerical Quantification of Interaction Effects in a Closely-Coupled Diffuser-Fan System [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396530464

    APA Style (7th edition)

  • List, Michael. Numerical Quantification of Interaction Effects in a Closely-Coupled Diffuser-Fan System. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396530464.

    MLA Style (8th edition)

  • List, Michael. "Numerical Quantification of Interaction Effects in a Closely-Coupled Diffuser-Fan System." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396530464

    Chicago Manual of Style (17th edition)

ucin1396530464
360
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This open access ETD is published by University of Cincinnati and OhioLINK.