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Research Papers: Gas Turbines: Turbomachinery

Effect of Temperature on Microparticle Rebound Characteristics at Constant Impact Velocity—Part II

[+] Author and Article Information
J. M. Delimont

Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: jacob.delimont@swri.org

M. K. Murdock

Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: murdockm@vt.edu

W. F. Ng

Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: wng@vt.edu

S. V. Ekkad

Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: sekkad@vt.edu

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received January 21, 2015; final manuscript received March 12, 2015; published online May 12, 2015. Assoc. Editor: Klaus Brun.

J. Eng. Gas Turbines Power 137(11), 112604 (Nov 01, 2015) (8 pages) Paper No: GTP-15-1022; doi: 10.1115/1.4030313 History: Received January 21, 2015; Revised March 12, 2015; Online May 12, 2015

When gas turbine engines operate in environments where the intake air has some concentration of particles, the engine will experience degradation. Very few studies of such microparticles approaching their melting temperatures are available in open literature. The coefficient of restitution (COR), a measure of the particles' impact characteristics, was measured in this study of microparticles using a particle tracking technique. Part II of this study presents data taken using the Virginia Tech Aerothermal Rig and Arizona road dust (ARD) of 20–40 μm size range. Data were taken at temperatures up to and including 1323 K, where significant deposition of the sand particles was observed. The velocity at which the particles impact the surface was held at a constant 70 m/s for all of the temperature cases. The target on which the particles impacted was made of a nickel alloy, Hastelloy X. The particle angle of impact was also varied between 30 deg and 80 deg. Deposition of particles was observed as some particles approach their glass transition point and became molten. Other particles, which do not become molten due to different particle composition, rebounded and maintained a relatively high COR. Images were taken using a microscope to examine the particle deposition that occurs at various angles. A rebound ratio was formulated to give a measure of the number of particles which deposited on the surface. The results show an increase in deposition as the temperature approaches the melting temperature of sand.

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References

Figures

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Fig. 1

Example of sand ingestion in desert conditions

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Fig. 2

Diagram of incoming and rebounding particle trajectories

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Fig. 3

VT Aerothermal Rig

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Fig. 4

Schematic of instrumentation setup

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Fig. 5

Plot of total COR versus angle of impact

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Fig. 6

Plot of normal COR versus angle of impact

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Fig. 7

Plot of tangential COR versus angle of impact

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Fig. 8

Plot of COR versus temperature for different impact angles

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Fig. 9

Averaged rebound ratio of angles

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Fig. 10

Image of sand deposition at 1323 K at 60 deg angle of attack and 200× optical magnification

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Fig. 11

Deposition per mm2 at several angles and at various temperatures

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Fig. 12

Image taken sand particles prior to testing at 200× optical magnification

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Fig. 13

Comparison of amorphous and crystalline particle COR trends at near melting temperatures

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Fig. 14

Hypothesized nonhomogeneous sand particle impact behavior

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