The effect of upstream perturbations on 3D annular diffusers
Abstract/Contents
- Abstract
- This study investigated annular diffuser sensitivity to varying inlet perturbations similar to those found in turbine exhaust diffuser applications. The diffusers had a range of opening angles and contained airfoil shaped struts. The full 3D velocity field was measured using Magnetic Resonance Velocimetry and pressure measurements were acquired with static wall pressure taps. Additionally, the inlet turbulence was characterized using hotwire anemometry. The overall goal was to better understand how to design diffusers which would give high performance without excess sensitivity to highly variable inlet conditions. Three diffusers were investigated which each had a single expanding wall at the outer radius with a high expansion angle for the front half of the diffuser and a lower expansion for the downstream half. The initial expansion angles were 12 deg, 16 deg and 20 deg and the back angle was 6 deg for all three cases. These expansion angles resulted in exit area ratios of 1.21, 1.29 and 1.34, respectively. There was a full annulus model with five struts and a higher resolution one-fifth annular sector with a single strut for each diffuser. Five inlet conditions were investigated; a baseline case with a nominally uniform inlet, thin boundary layers and around 3% turbulence intensity, a high turbulence case that was similar to the baseline case except it had approximately double the turbulence intensity, a hub-strong case with a negative radial velocity gradient, a case with a high velocity wall jet at the outer radius, and a case with swirling inlet flow. The conservative diffuser with the 12 deg initial expansion angle was robust under the inlet conditions investigated. There was little variation in the integral parameters from one inlet condition to another and it had the lowest overall loss coefficient ranging from 0.35 to 0.40. This diffuser did not stall although there were small regions of reverse flow in the corners between the expanding wall and the strut with the swirl inlet. The pressure recovery coefficient for this diffuser ranged from 0.24 to 0.31. The moderate diffuser with the 16 deg initial expansion angle had substantial variation in the integral parameters depending on the inlet condition. The diffuser stalled and had high losses with the uniform inlet while the tip jet case had no reverse flow except in the wake of the strut and had the highest pressure recovery coefficient of all of the cases (0.35). The aggressive diffuser with the 20 deg initial expansion angle was robust in that it always stalled but there was still substantial variation in the integral parameters. The blockage and outlet distortion changed greatly depending on the inlet condition similar to the range of variation for the moderate diffuser. The aggressive diffuser with the hub-strong inlet had the highest loss coefficient and the lowest pressure recovery for all of the cases investigated.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Padilla, Angelina Marianna |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering |
| Primary advisor | Eaton, John K |
| Thesis advisor | Eaton, John K |
| Thesis advisor | Iaccarino, Gianluca |
| Thesis advisor | Santiago, Juan G |
| Advisor | Iaccarino, Gianluca |
| Advisor | Santiago, Juan G |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Angelina Marianna Padilla. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Angelina Marianna Padilla
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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