Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Fletcher_Thesis_FINAL_VER2.pdf (7.41 MB)

ETD Abstract Container

Abstract Header

Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies

Fletcher, Nathan James
http://orcid.org/0000-0001-6474-7961
http://rave.ohiolink.edu/etdc/view?acc_num=wright1560810428267352

Abstract Details

2019, Master of Science in Mechanical Engineering (MSME), Wright State University, Mechanical Engineering.
A primary source of periodic unsteadiness in low-pressure turbines is the wakes shed from upstream blade rows due to the relative motion between adjacent stators and rotors. These periodic perturbations can affect boundary layer transition, secondary flow, and loss generation. In particular, for high-lift front-loaded blades, the secondary flowfield is characterized by strong three-dimensional vortical structures. It is important to understand how these flow features respond to periodic disturbances. A novel approach was taken to generate periodic unsteadiness which captures some of the physics of turbomachinery wakes. Using stationary pneumatic devices, pulsed jets were used to generate disturbances characterized by velocity deficit, elevated turbulence, and spanwise vorticity. Prior to application in a turbine flow environment, the concept was explored in a small developmental wind tunnel using a single device. The disturbance flowfield for different input settings was measured using hot-film anemometry and Particle Image Velocimetry. Insight was also garnered on how to improve later design iterations. With an array of devices installed upstream of a linear cascade of high-lift front-loaded turbine blades, settings were found which produced similar disturbances at varying frequencies that periodically impinged upon the leading-edge region. These settings were used to conduct an in-passage secondary flow study using high-speed Stereoscopic Particle Image Velocimetry. Results demonstrated the application of the periodic unsteadiness generator but found minor changes to the passage vortex. The vortex rotational strength decreased, and migration increased with increased perturbation frequency. Fourier analyses found the PV to be responsive at the actuation frequency with phase-locked ensemble-averaged data revealing that the disturbance periodically caused the PV to lose rotational strength. However, at the tested discrete frequencies, the vortex did not become locked-in and was defined by an erratic time-character similar to without the disturbances.
Mitch Wolff, Ph.D. (Advisor)
Rolf Sondergaard, Ph.D. (Committee Member)
Christopher Marks, Ph.D. (Committee Member)
139 p.
Aerospace Engineering; Engineering; Experiments; Fluid Dynamics; Mechanical Engineering
aerodynamics; gas turbine engine; low pressure turbine; fluid dynamics; stereoscopic particle image velocimetry; endwall; secondary flow; passage vortex; periodic unsteadiness; turbomachinery; wakes; vortices; linear cascade; wind tunnel; vortex; turbine

Recommended Citations

Citations

  • Fletcher, N. J. (2019). Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies [Master's thesis, Wright State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=wright1560810428267352

    APA Style (7th edition)

  • Fletcher, Nathan. Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies. 2019. Wright State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=wright1560810428267352.

    MLA Style (8th edition)

  • Fletcher, Nathan. "Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies." Master's thesis, Wright State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1560810428267352

    Chicago Manual of Style (17th edition)

wright1560810428267352
216
© 2019, some rights reserved.Creative Commons License Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies by Nathan James Fletcher is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Wright State University and OhioLINK.