Conventional Combustion Exit Presentation

1

Conventional Combustion Exit Presentation

Megan Karalus Mentor: Robyn Thomas

Technical Adviser: Priyank Saxena Group Manager: Anthony Batakis Functional Manager: Andy Luts

September 7th, 2012

2

Agenda

•  Carbon Formation Investigation and Mitigation

–  Broad Goal: Literature Review, Modeling and Analysis •  Conclusions and Recommendations •  Acknowledgements •  Summer in San Diego

3

Brief History….

•  Current production injector •  No carbon deposition •  Lacks mechanical robustness

Cutback

Carbon deposition

with natural gas

•  New proposed design •  Carbon deposits on the shroud

face.

Fuel

2020 Outer Air Swirler

Inner Air Swirler

Shroud Face

Conventional Dual Fuel Injectors

4

Brief History…

Cutback

2020

Previous Natural Gas Paint Test in Mars 100 Engine

5

Project Outline

•  Broad Goal: develop knowledge base and methodology for troubleshooting carbon buildup on other injector designs. –  Theory and Literature Review –  Chemkin Modeling (equilibrium & detailed chemistry) –  CFD Analysis

6

Carbon Types

Analogy to Snow and Frost Formation “Gas phase nucleation yields snow [carbon black] and

heterogeneous nucleation on a substrate and subsequent growth gives frost [pyrocarbon]” (Bourrat)

Broad Goal: Theory / Chemkin / CFD

Carbon Black / Soot Pyrocarbon

7

Carbon Black

Formation

Fuel

Crucial for Soot -> Pyrene

Controlling Parameters

•  Pressure •  Temperature •  Residence Time •  Higher Hydrocarbons •  Equivalence Ratio


8

Pyrocarbon

Formation and Control

1. More likely than we think? "It is only in very exceptional circumstances that the interaction

of a hydrocarbon with a metal surface does not lead to carbon deposition.” [Bond 1997]

2. Forms at lower temperatures and or pressures than carbon black. “…a pyrocarbon should be formed at a lower T and (or) P than predicted by

classical homogeneous nucleation, which gives rise to the formation of carbon blacks.”

[Delhae 2001]

3. Surface plays a key role. "It has been shown that the substrate plays a role in the first pyrocarbon layers

from a physical (roughness, curvature and surface energy) and a chemical (nucleation sites) point of view.”

[Delhae 2001]


9

Chemkin Outline

1.  Equilibrium 2.  Perfectly Stirred Reactor 3.  Opposed Flow Diffusion Flame


10

1. Equilibrium

Constant mixture temperature and pressure

Temperature and mixing near the shroud are controllable parameters in design of injectors.

What we learn…

•  Temperature threshold for presence of carbon as a function of equivalence ratio.

•  Carbon presence requires rich mixtures


11

2. PSR - Setup

Perfectly Stirred Reactor (PSR) •  Parameter Study Method

–  Hold constant Equivalence Ratio and Pressure.

–  Vary Temperature and Residence Time.

PSR T, P, t

Fuel/Air

Φ

Products

Chemical Mechanism


12

2. PSR - Results

Equivalence Ratio = 2, P=250 psia What we learn… •  Time allowed for reaction

can be important (residence time).

•  Minimum temperature threshold as a function of residence time for carbon.


Mol

e Fr

actio

n P

yren

e

13

3. Opposed Flow Diffusion Flame

•  Transport can be important. •  Pyrene is produced at

higher temperatures but can exist at lower temperatures in rich mixtures.

0

500

1000

1500

2000

2500

3000

3500

0 0.2 0.4 0.6 0.8 1

Distance (cm)

Tem

pera

ture

(F)

-2.0E-12

-1.5E-12

-1.0E-12

-5.0E-13

0.0E+00

5.0E-13

1.0E-12

1.5E-12

2.0E-12

2.5E-12

Rat

e of

Pro

duct

ion

(mol

e/cm

3-s)

Temperature (F) ROP-A4

0

500

1000

1500

2000

2500

3000

3500

0 0.2 0.4 0.6 0.8 1

Distance (cm)

Tem

pera

ture

(F)

0.0E+00

5.0E-11

1.0E-10

1.5E-10

2.0E-10

2.5E-10

3.0E-10

3.5E-10

4.0E-10

4.5E-10

5.0E-10

Mol

e Fr

actio

n A

4

Temperature (F) Mole Fraction A4

What we learn…

Production of Pyrene Location of Pyrene


14


•  Transport can be important. •  Carbon Black is formed

wherever Pyrene is present.

0

500

1000

1500

2000

2500

3000

3500

0 0.2 0.4 0.6 0.8 1

Distance (cm)

Tem

pera

ture

(F)

0.0E+00

5.0E-11

1.0E-10

1.5E-10

2.0E-10

2.5E-10

3.0E-10

3.5E-10

4.0E-10

4.5E-10

5.0E-10

Mol

e Fr

actio

n A

4

Temperature (F) Mole Fraction A4

0

500

1000

1500

2000

2500

3000

3500

0 0.2 0.4 0.6 0.8 1

Distance (cm)

Tem

pera

ture

(F)

0

2E-16

4E-16

6E-16

8E-16

1E-15

1.2E-15

1.4E-15

1.6E-15

1.8E-15

Rat

e of

Pro

duct

ion

of C

B

(g/c

m3-

s)

Temperature (F) ROP CB

What we learn… Broad Goal: Theory / Detailed Chemistry / CFD

Location of Pyrene Carbon Black Production

15


•  Transport can be important. •  Pyrene is produced at

higher temperatures but can exist at lower temperatures in rich mixtures.

•  Soot is formed wherever Pyrene is present.

•  CO is a good ‘marker’ for the presence of Pyrene and therefore Carbon Black – useful for CFD analysis.

What we learn… Broad Goal: Theory / Detailed Chemistry / CFD

Co-Location of Pyrene and CO

0.0E+00

5.0E-03

1.0E-02

1.5E-02

2.0E-02

2.5E-02

3.0E-02

3.5E-02

4.0E-02

4.5E-02

5.0E-02

0 0.2 0.4 0.6 0.8 1

Distance (cm)

Mol

e Fr

actio

n C

O

0.0E+00

5.0E-11

1.0E-10

1.5E-10

2.0E-10

2.5E-10

3.0E-10

3.5E-10

4.0E-10

4.5E-10

5.0E-10

Mol

e Fr

actio

n A

4

Mole Fraction CO Mole Fraction A4

16

CFD Outline

Assumption #1

Carbon Black (soot formation) is responsible for carbon deposition.

Assumption #2 Pyrocarbon is responsible for carbon deposition

(i.e. the surface participates)


17

CFD: Soot

Assumption #1


Near Shroud

1.  Formed in recirculation zone near shroud (i.e. PSR)?

2.  Formed in flame and transported to shroud?


18

CFD: Soot

"   Formed in recirculation zone near shroud (i.e. PSR)?

2. Formed in flame and transported to shroud?

Assumption #1


Red is all greater than 5% CO Max

2020 Shroud


19

CFD: Soot

"   Formed in recirculation zone near shroud (i.e. PSR)?

"   Formed in flame and transported to shroud?

Broad Goal: Theory / Detailed Chemistry / CFD / Experiments

Assumption #1


Red is all greater than 5% CO Max

2020 Shroud

20

CFD: Pyrocarbon

Assumption #2 Pyrocarbon is responsible for carbon deposition

(i.e. the surface participates)

•  On equilibrium model, plot conditions near shroud determined from CFD and paint tests

Injector Shroud Inner Air Swirler


21

Conclusions and Recommendations

•  Rich mixtures are required for carbon formation (soot or pyrocarbon)

•  Small amounts of higher hydrocarbons in the fuel will increase the likely hood of soot formation

•  Increased pressure allows formation of soot precursors at lower pressures and shorter residence times.

•  The nucleation of soot is not temperature dependent.

•  CO is a good marker species for soot in CFD models.

•  Carbon deposition is most likely due to ‘pyrocarbon’ (the surface participates)

•  Apply equilibrium model in conjunction with CFD as a potential pass/fail design tool for other injectors.

•  Determine if paint application is influencing test results (SI Rig test)

Conclusions Recommendations

22

Acknowledgements

•  Tony Batakis •  Robyn Thomas •  Priyank Saxena •  Ryan Youtsey •  Dan Golden •  Stuart Greenwood •  Mike Lane •  Emily Almaraz •  Jeff Detweiler •  Scott Lindner

•  Paul Cramer •  Barry Raghunathan •  Jack Johnson •  Will Rhodes •  Charmaine Gary •  Denise Rodriguez •  Andy Luts •  Tim Bridgman •  Rotations •  Interns

Documents

Conventional Combustion Exit Presentation