BYU Deposition Facility

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BYU Deposition Facility
Previous Turbine Accelerated Deposition Facility
(TADF)

• Design Parameters to match temp, velocity,
  angle, materials, particle size, chemistry, and
  concentration
• Inconel construction allows max jet temperature
  of 1200?C
• Exit velocities up to 300m/s deposition by
  inertial impaction
• Target coupons supplied from industry
• Capability for impingement and film cooling
• Match net particle throughput

8000 hrs ?? 0.1 ppmw 4 hrs ? 200 ppmw
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BYU Coupon Holder
Cooling Air
Coupon w/cooling holes
Thermocouple
Deposit-ladencombustor exhaustat 1183?C
Deposit-ladencombustor exhaustat 1183?C
Coupons generally held at 45? angle to flow
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BYU Previous Testing

• Deposition vs. Temperature
• Deposition increases with gas exit temperature
• Insulated tests conducted up to 1150?C (i.e., no
  cooling)
• No deposition below 950?C
• Deposition vs. Cooling
• Deposition decreases with increasing coupon
  cooling
• backside cooling
• film cooling on surface

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Goal 1Increase gas temperatures to 1400?C

• Why?
• Mimic H class turbine gas temperatures
• Investigate mechanism changes at higher
  temperatures
• Gas temperature affects particle melting
• Surface temperature affects deposit stickiness
  tenacity
• Examine deposition threshold temperatures with
  realistic blowing ratios
• Existing experiments cool surface too much with
  M2
• Distinguish sweeping effect from surface cooling
  effect
• How?
• Build new shell
• Reaction Bonded SiC
• Price 4500
• Modify coupon holder
• New design
• Insulate front face

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Temperature Range
New Range
Previous range of experiments
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BYU Facility Modification
I.D. 2.5 cm

• Redesign For 1400?C
• Cone and Tube
• Reaction bonded SiC (previously Inconel)
• New Max Operating Temp 1500?C
• No problems with thermal shock on startup and
  shutdown

1.2 m
Clamping Ring
SiC Cone
New Cone and Tube
Connection to base
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BYU New Coupon Holder

• Redesign For 1400?C
• Coupon Holder
• Insulating front plate made of SiO2
• Redesigned front side to allow insulation to be
  flush with coupon

SiO2 Face Plate
Inconel Holder
Gas Flow
Test coupon
Test Coupon
Gas Flow
Tube exit
Old Holder
New Holder plus SiO2 faceplate
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Deposits in Tube

• Deposits build up in the tube over successive
  runs
• Less ash impacts the coupon
• Affects capture efficiency
• Some tests were performed after large amounts of
  buildup occurred
• Data points considered outliers
• Solution
• Routine cleaning of tube

Deposits
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Correcting for Ash Deposition in Tube

• Measured mass of deposit in SiC tube
• When accounting for the mass deposited in the
  tube, the capture efficiencies of the new
  facility match those of the old facility

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Recent Results

• Time-Dependent Test Series
• A test series investigating the time-dependent
  nature of deposit growth was performed
• Tests conducted for 20, 30, 40, and 60 minutes
• Tg 1250C
• Capture efficiency, surface roughness (Ra), and
  deposit thickness are measured and calculated
  with respect to time

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Recent Results

• Flyash Characterization
• Two size distributions, with mass mean diameters
  of 13 µm and 4 µm
• Bulk density 0.99 g/cm3
• Apparent Density 1.98 g/cm3

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Recent Results Time-Dependent Deposition at
1250C

• Surface roughness and depositthickness increase
  linearly with time
• Capture efficiency increases exponentially with
  time
• 3 ?m tests show much lower capture efficiency and
  roughness than 13 ?m tests

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Recent Results Time-Dependent Deposition at
1250C

• Sticking Probability
• Particle sticking probability (Ps) as defined by
  Tafti1
• Gives the probability that a particle of certain
  temperature will adhere to a surface upon
  impaction
• µcrit is the viscosity at the ash softening
  temperature and µTp is the viscosity at the ash
  particle temperature, calculated as2
• A and B are dependent upon ash composition
• 1. Tafti, D., 2010, Syngas Particulate Deposition
  and Erosion at the Leading Edge of a Turbine
  Blade with Film Cooling Presented at NETL
  University Turbine Systems Research Workshop.
• 2. Senior, C.L. and Srinivasachar, S., 1995,
  "Viscosity of Ash Particles in Combustion Systems
  for Prediction of Particle Sticking," Energy and
  Fuels, 9pp. 277-283.

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Recent Results Time-Dependent Deposition at
1250C

• Sticking Probability
• The model was used to calculate the sticking
  probability of the particles in the hot gas
  stream
• The model was also applied to the ash particles
  already deposited on the surface of the coupon
• Sticking probability based upon surface ash
  temperature rather than impacting ash temperature

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Surface Temperature MeasurementTg
1250?CUncooled Coupon
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Recent Results Time-Dependent Deposition at
1250C

• Sticking Probability
• Ps in stream 0.185
• Based on Tg 1250?C
• Ps on surface shown in figures
• Based on measured Tsurface

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Recent Results Time-Dependent Deposition at
1250C
Wyoming Powder River Basin Coal Flyash 1250?C
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Began Temperature-Dependent Tests

• Investigate the influence of gas temperature (Tg)
  on deposition
• Vary Tg (1250C - 1400C) while using backside
  cooling to keep the initial surface temperature
  constant
• Only completed a few tests and low end of Tg
  range
• Using flyash samples from bituminous and
  subbituminous coals

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Difference in Coal Ash
(from temperature-dependent series) Tg
1250?C Ts,initial 1071 ?C
Subbituminous
Bituminous
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Conclusions

• Results from the new SiC facility compare well
  with results from the old Inconel facility
• Surface roughness and deposit thickness both
  increase linearly with time at a given gas
  temperature while capture efficiency increases
  non-linearly
• The surface sticking probability increases with
  time, contributing to increase in capture
  efficiency

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Conclusions

• Ash composition affects the manner in which ash
  deposits on the surface
• Bituminous coal ash (higher melting point)
  deposits less evenly and depends more on a
  localized activation point
• Subbituminous coal ash (lower melting point)
  deposits fairly evenly

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Future BYU Work

• Finish current temperature series (varying Tg,
  constant initial Ts)
• Second temperature series (constant Tg, varying
  surface temperature)
• Comparison of the first and second temperature
  series will show whether Tg or Ts has a greater
  impact on deposition
• Study effects of film cooling at Tg up to 1400C
• Study effects of increasing water vapor levels

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