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Research Papers: Gas Turbines: Turbomachinery

Experimental Validation of Numerically Optimized Short Annular Diffusers

[+] Author and Article Information
D. J. Cerantola

Department of Mechanical and
Materials Engineering,
Queen's University,
Kingston, ON K7L 3N6, Canada
e-mail: david.cerantola@queensu.ca

A. M. Birk

Department of Mechanical and
Materials Engineering,
Queen's University,
Kingston, ON K7L 3N6, Canada
e-mail: birk@me.queensu.ca

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 24, 2014; final manuscript received August 27, 2014; published online December 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(5), 052604 (May 01, 2015) (10 pages) Paper No: GTP-14-1437; doi: 10.1115/1.4028679 History: Received July 24, 2014; Revised August 27, 2014; Online December 02, 2014

Short annular diffusers with negative wall angles were evaluated numerically and experimentally with up to 40 deg inlet swirl at an inlet Reynolds number of Ret ≈ 1.4 × 105 and Mach number of Mt ≈ 0.16. The 80% experimental effectiveness of the 1.61 and 1.91 area ratio (AR) diffusers with 0–20 deg inlet swirl were on par with unswirled maximums reported in literature and computational fluid dynamics (CFD) predicted reasonable outlet axial velocity profiles and wall pressure distributions. The AR = 2.73 diffuser's effectiveness without swirl was 13% below the maximum for the given AR and larger discrepancies occurred in the CFD results due to the incorrect prediction of the recirculation zone strength. Preference was given to the realizable k–ε model on coarse grids with wall functions that predicted performance of all cases with at least 20 deg inlet swirl to within 20%.

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References

Figures

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Fig. 1

Annular diffuser cutaway

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Fig. 2

Test section schematic depicting instrumentation locations. Section ⓢ = three-hole probe traverse at annulus outlet (x=1.05Do) and section ⓣ = three-hole probe traverse at annular diffuser inlet (x=0.23Do). Squares along the walls denote pressure taps. At least two instruments were placed at each axial location.

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Fig. 3

Manufactured geometry components (symmetry plane shown)

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Fig. 4

Computational domain and boundary conditions. Cross sections: ⓢ = annulus outlet, ⓣ = annular diffuser inlet (x=0.23Do), ⓔ = diffuser outlet.

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Fig. 5

Config. bb 2D coarse grid mesh. Arrows define mesh driving directions. Fine grids were geometrically similar but with refined boundary layers.

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Fig. 6

No swirl study predicted static pressure contours and streamlines on a symmetry plane. Realizable k–ε coarse grid solutions. (a) Config. aa, (b) Config. bb, (c) Config. cc, and (d) Config. nb.

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Fig. 7

No swirl study wall pressure distributions. CB data (solid symbols) on left axis and OW data (hollow symbols) on right axis. Error bars with symbols denote pressure readings taken by the three-hole probes nearest to the respective wall. CFD nondimensionalized by the experimental 〈qt,exp〉. (a) Config. aa, (b) Config. bb, (c) Config. cc, and (d) Config. nb.

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Fig. 8

No swirl study outlet axial velocity profiles. (a) Config. nb, (b) Config. aa, (c) Config. bb, and (d) Config. cc.

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Fig. 9

Swirl study predicted static pressure contours and streamlines on a symmetry plane. SST S20 swirl solutions. (a) Config. bb and (b) Config. nb.

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Fig. 10

Swirl study Config. bb wall pressure distributions. CB data (solid symbols) on left axis and OW data (hollow symbols) on right axis. CFD nondimensionalized by the experimental 〈qt,exp〉. (a) S10, (b) S20, (c) S40 CB, and (d) S40 OW.

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Fig. 11

Swirl study Config. bb outlet axial velocity profiles. (a) S10, (b) S20, (c) S40, (d) SCV, and (e) S20 Config. nb.

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Fig. 12

Swirl study Config. bb outlet swirl angle profiles. (a) S10, (b) S20, (c) S40, (d) SCV, and (e) S20 Config. nb.

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Fig. 13

Swirl study Configs. bb and nb back pressure versus swirl number. Lines drawn through results using flat-vane swirl and large symbols denote the SCV solutions.

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Fig. 14

Swirl study Configs. bb and nb outlet velocity uniformity versus swirl number

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Fig. 15

Swirl study Configs. bb and nb total pressure loss versus swirl number

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