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How to detect radiant surface area?

C

Chris Carlen

Jan 1, 1970
0
Greetings:

I have a scientist who needs to determine the area of the emitting
surface of a radiant soot cloud in the combustion chamber of an
optically accessible internal combustion engine. The measurement needs
to be done at a rate of at least 4kHz, preferrably 15kHz, with a
resolution of at least 1 part in 256, preferrably 1024 or so.

We have considered a high frame rate low resolution camera, but these
are somewhat expensive, and we would like to investigate cheaper
alternatives before attempting to justify the purchase of such a camera.

We plan to image the soot cloud onto some suitable detector or camera.
The individual pixel data would be compared against a threshold in
post-processing, to reveal the area of the image.

What other methods might be able to return the same information?

Thanks for input.

Good day!


--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
[email protected] -- NOTE: Remove "BOGUS" from email address to reply.
 
R

R.Legg

Jan 1, 1970
0
Chris Carlen said:
Greetings:

I have a scientist who needs to determine the area of the emitting
surface of a radiant soot cloud in the combustion chamber of an
optically accessible internal combustion engine. The measurement needs
to be done at a rate of at least 4kHz, preferrably 15kHz, with a
resolution of at least 1 part in 256, preferrably 1024 or so.

Sounds like a sampling problem. Does he really need sequential images
of 4000 clouds?

I would have thought that unstable conditions in an engine, designed
to do things repeatedly and reliably, should show up just as easily
looking at periodic images. The same with dynamic conditions, if
properly synchronized.

As an alternative - why not slice the image, looking at adjacent scan
lines of a slow-scan camera? (~4Hz total scan with single-line images
from 1000 clouds). It might tell you as much as you want to know, when
compared to known references of single cloud events.

RL
 
I

Ian Stirling

Jan 1, 1970
0
In sci.electronics.design Chris Carlen said:
Greetings:

I have a scientist who needs to determine the area of the emitting
surface of a radiant soot cloud in the combustion chamber of an
optically accessible internal combustion engine. The measurement needs
to be done at a rate of at least 4kHz, preferrably 15kHz, with a
resolution of at least 1 part in 256, preferrably 1024 or so.

Hmm.
At some wavelengths, the soot should emit as a black body (assuming for
the moment that it's isothermal).
If you can take a spectrum of the emission, you may be able to isolate this
black body emission, and simply measuring a grain of soots emissivity will
get you the rest.
 
C

Chris Carlen

Jan 1, 1970
0
R.Legg said:
Sounds like a sampling problem. Does he really need sequential images
of 4000 clouds?

Actually, what is needed is only 10 images (or more if possible), but
only 250us or less apart.
I would have thought that unstable conditions in an engine, designed
to do things repeatedly and reliably, should show up just as easily
looking at periodic images. The same with dynamic conditions, if
properly synchronized.

Things aren't quite so ideal. What is being attempted is a measure of
the effective soot temperature, or "bulk" soot temp. This must be
determined at several crank angles per cycle, then over several other
parameter variations.

This requires determining the radiant surface area so as to be able to
normalize an intensity reading, which will be factored in with two color
intensity measures to fit to an emission curve to get temp.
Unfortunately, the soot doesn't behave as a black body, so additional
info is needed than just two colors. Hence the desire to make an
absolute intensity per area determination.

Now what I am unsure about, is if it would be possible to simply
characterize the average soot radiant surface area at a given crank
position, for a given set of conditions. This could be done once, then
the desired experiments performed using that data to make sense of the
two color data on the fly.

But I don't think this will work. The scientist has spend considerable
time on this, and he is refining still more efforts on the part of many
others as reported in literature. I don't think there is such an easy
way out that has been overlooked. I think the reason has to do with the
fact that the soot radiant surface area is just not consistent enough
from cycle to cycle at any given crank position to be able to make such
a one time characterization. But I am guessing a bit here since I am
not the scientist, just helping the fellow to find out what techniques
might be available that he may not be aware of.

As an alternative - why not slice the image, looking at adjacent scan
lines of a slow-scan camera? (~4Hz total scan with single-line images
from 1000 clouds). It might tell you as much as you want to know, when
compared to known references of single cloud events.

Hmm. I really think 2D spatial resolution is needed.

Thanks for the input!

Good day.
 
T

Tim Shoppa

Jan 1, 1970
0
Chris Carlen said:
Things aren't quite so ideal. What is being attempted is a measure of
the effective soot temperature, or "bulk" soot temp. This must be
determined at several crank angles per cycle, then over several other
parameter variations.

This requires determining the radiant surface area so as to be able to
normalize an intensity reading, which will be factored in with two color
intensity measures to fit to an emission curve to get temp.
Unfortunately, the soot doesn't behave as a black body, so additional
info is needed than just two colors. Hence the desire to make an
absolute intensity per area determination.

My gut feeling is that measuring at many more than 2 wavelengths will
give you a better handle on the temperature than just at 2 wavelengths.
Probably good enough that you won't have to know radiant surface area
at all.

Nothing is a perfect black body, but if you look at a restricted part
of the spectrum (away from emission lines/absorption lines) it will
probably be good enough. Lots of people make their livings by looking
at spectra and turning them into temperature/density measurements.

Tim.
 
J

Jim Meyer

Jan 1, 1970
0
Chris Carlen said:
Greetings:

I have a scientist who needs to determine the area of the emitting
surface of a radiant soot cloud in the combustion chamber of an
optically accessible internal combustion engine.

The area of a cloud is a particularly ill defined quantity.

Could it be that he wants to measure the total amount of soot and
that he assumes that if he measures the total emission from the soot
cloud that he can derive the total soot from that?

Or is he more concerned with the shape of the cloud?

Jim
 
J

Jim Meyer

Jan 1, 1970
0
Chris Carlen said:
Greetings:

I have a scientist who needs to determine the area of the emitting
surface of a radiant soot cloud in the combustion chamber of an
optically accessible internal combustion engine. The measurement needs
to be done at a rate of at least 4kHz, preferrably 15kHz, with a
resolution of at least 1 part in 256, preferrably 1024 or so.
Does this paper describe what you want to do?

http://www.osti.gov/fcvt/1999-01-2246.pdf

Jim
 
C

Chris Carlen

Jan 1, 1970
0
Jim said:
Does this paper describe what you want to do?

http://www.osti.gov/fcvt/1999-01-2246.pdf

Jim


This is a paper from my department, and the "Sandia Cummins heavy Duty
Engine" is the experiment that this post is about.

The paper is a bit old. The lab changed hands since then. I'll try to
persuade the scientist to join the discussion, as some of the questions
folks are responding with might better be considered by him.

Thanks for the input.

Good day!



--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
[email protected] -- NOTE: Remove "BOGUS" from email address to reply.
 
T

Tim Jackson

Jan 1, 1970
0
Chris Carlen said:
Things aren't quite so ideal. What is being attempted is a measure of
the effective soot temperature, or "bulk" soot temp. This must be
determined at several crank angles per cycle, then over several other
parameter variations.

This requires determining the radiant surface area so as to be able to
normalize an intensity reading, which will be factored in with two color
intensity measures to fit to an emission curve to get temp.
Unfortunately, the soot doesn't behave as a black body, so additional
info is needed than just two colors. Hence the desire to make an
absolute intensity per area determination.

Now what I am unsure about, is if it would be possible to simply
characterize the average soot radiant surface area at a given crank
position, for a given set of conditions. This could be done once, then
the desired experiments performed using that data to make sense of the
two color data on the fly.

But I don't think this will work. The scientist has spend considerable
time on this, and he is refining still more efforts on the part of many
others as reported in literature. I don't think there is such an easy
way out that has been overlooked. I think the reason has to do with the
fact that the soot radiant surface area is just not consistent enough
from cycle to cycle at any given crank position to be able to make such
a one time characterization. But I am guessing a bit here since I am
not the scientist, just helping the fellow to find out what techniques
might be available that he may not be aware of.
If what you really want is emission per unit area then just measure emission
from "one unit" of area: mask off a known small area of the cloud, say 5mm
square, and measure the radiation characteristics of that.

As the radiation is presumably not uniform then knowing the total area and
total emission won't allow you to normalise the intensity anyway, you.would
need to map your measurements and integrate over the visible area.

You can get plenty of time resolution with a photocell (or two) and an
oscilloscope on one point. If you need a spatial map then you can move your
mask mechanically (step and repeat) from cycle to cycle to progressively map
the whole chamber. You can take several traces at each point to determine
the relevance of instabilities and get an average temperature for each
region

If you really -have- to do it in parallel and in one cycle then what you are
doing is to all intents and purposes building a high speed camera

Tim Jackson
 
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