slide1
Download
Skip this Video
Download Presentation
Autoignition in Turbulent Flows Christos Nicolaos Markides and Epaminondas Mastorakos

Loading in 2 Seconds...

play fullscreen
1 / 1

Autoignition in Turbulent Flows Christos Nicolaos Markides and Epaminondas Mastorakos - PowerPoint PPT Presentation


  • 71 Views
  • Uploaded on

2.0. 20. +2. +1. 1.8. 10. 10. 1.6. 0.4. 15. 1.4. 1.2. 0.3. 1.0. 10. 0.8. 0.2. 0.6. 0.4. 0.1. -3. 0. -1. -2. 5. 10. 10. 10. 10. 0.2. 0. 0. +1.0. -1.0 . -0.5. -1.0 . -0.5. 0. +0.5. 0. +0.5. +1.0. 0. -1.0. -0.5. 0. +1.0. +0.5. Frequency (Hz). +5. +4.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Autoignition in Turbulent Flows Christos Nicolaos Markides and Epaminondas Mastorakos' - whitney-golden


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1
2.0

20

+2

+1

1.8

10

10

1.6

0.4

15

1.4

1.2

0.3

1.0

10

0.8

0.2

0.6

0.4

0.1

-3

0

-1

-2

5

10

10

10

10

0.2

0

0

+1.0

-1.0

-0.5

-1.0

-0.5

0

+0.5

0

+0.5

+1.0

0

-1.0

-0.5

0

+1.0

+0.5

Frequency (Hz)

+5

+4

+3

+2

+1

10

10

10

10

10

Autoignition

Spot

Double flame front spot propagation. Close-up at 40.5 kHz.

L

ign

Quartz Pipe

Insulation

and Sealant

Injection Location

Grid Turbulence

Generator

Fuel Dissociation

Air Mixer

Quartz Sheath

Acetylene ignition spot initiation, double flame front propagation and ‘stabilization’ (no advection). Then,

triple flame structure formation and flashback (upstream advection) to form a flame. Real time at 13.5 kHz.

Injector Alignment

Mechanism

Hot Air from Heaters

Hot Air from Heaters

Fuel/Nitrogen Mixture

at Ambient Conditions

Injector

Earliest Autoignition Length Vs. Jet Velocity

35

NOTHING

Each colour represents data for a particular air velocity and dashed lines are for higher air supply temperatures. Lengths in mm.

30

1.00

o

0.95

o

0.90

o

0.85

o

0.80

o

0.75

o

0.70

STABLE

SPOTTING

REGIME

25

20

-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

o

15

FLASHBACK

1.4

o

1.2

o

1.0

o

0.8

o

0.6

o

0.4

o

0.2

o

0.0

10

5

Injector

0

-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

o

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Kinematic Similarity (Injection to Co-flow) Velocity Ratio

Increasing co-flow air velocity. Each trend-line contains data for various jet velocities but a single air velocity.

Autoignition in Turbulent FlowsChristos Nicolaos Markides and Epaminondas Mastorakos

Goals

  • Aiming to accurately predict and control the occurrence of the phenomenon of autoignition in a turbulent flow field we:
    • Have undertaken an experimental and theoretical investigation in order to understand the fundamental underlying physics of the coupling between turbulent mixing and the chemistry of autoignition down to the smallest relevant length and time scales
    • Are investigating the topological manifestation of autoignition and the dependencies of its genesis
  • We choose a co-flow configuration which:
    • Is a novel approach for the demonstration of autoignition phenomena
    • Is very appropriate for the investigation of mixing effects
    • Allows precise and accurate characterization of the background turbulence (fluid-mechanical character) and mixture fraction

(chemical character) fields

    • Provides direct measurements of autoignition length and associated time, which are quantities that have direct and intuitive

practical meaning and significance

Experimental Configuration

Typical High Speed Sequences

(the relative micro-lengths and micro-times of autoignition)

Typical Results

Cold and Hot Flow Characterization

Acetylene

Fine Scale Turbulence Measurements including

Integral Length Scale Profiles and Power Spectra

Mean Temperature and Velocity Profiles

Many individual snapshots of acetylene autoignition spots (left), are used to define an ‘earliest’ autoignition location. Typical global results for Acetylene are shown on the far right. As far as the location of autoignition is concerned, for a given air velocity and temperature, autoignition is always delayed by an increased jet velocity. This delay may be augmented by decreasing the temperature and/or increasing the velocity of the air. ooooooooo

Mean Velocity and Turbulence Intensity

Profiles at various Re Numbers, Stream-wise

Locations and Injection Velocities

Hydrogen

Many individual snapshots of hydrogen autoignition spots (below left), are used to compile PDFs of the autoignition location (below right). Autoignition lengths can be defined at the earliest location or in terms of the integral (mean) of the PDF and autoignition times by residence calculations based on the fuel jet velocity decay in the centreline of the co-flowing air. Typical Hydrogen results are shown on the far right. The effect of the jet velocity is successfully collapsed for each background air velocity. oo

Mean Mixture Fraction Profiles and

Correlation with corresponding Autoignition PDFs

Injector

ad