On 1/1/2011 8:30 PM, dpb wrote:
The Daring Dufas wrote:
...

I think I understand about the pulverized coal. Ultrasonic transducers
are used to measure the flow of material through the pipes because a
paddle wheel would quickly disintegrate? Rereading what you wrote it
seems that you were listening for a specific resonance or you were
trying to separate the sound of the airflow from the noise of the flow
of the pulverized coal mixed with it. Is that what all the processing
power is required for? It kind of reminds me of what modern military
sonar systems do. ...

Anything like a paddle wheel wouldn't make it 5 minutes.

In an early stage of the work, I tried a hardened steel drill rod as a
sounding rod in one small-scale test facility. The test duration was
only for a couple of days and it came out oval in cross-section in even
that short a time frame with a good third of the frontal surface gone.
The utilities are very reluctant to insert stuff into the coal pipes
that could fail and either block the flow in a pipe w/ a resultant high
pressure event back at the pulverizer or block a burner nozzle in the
furnace and cause an event there. The air:fuel mixture is right at the
limits and so it's a real danger of fire or explosion if something goes
wrong outside the boiler or in a coal pipe. Needless to say, an open 14"
pipe w/ a burn out isn't a desirable event... In at least few cases
where they have happened the flame has actually melted the side of a
boiler containment and ended up w/ an entire boiler open. That wreaks
havoc in a plant _very_ quickly.

As far as more explanation of exactly what the computations are,
unfortunately, the actual technique is proprietary but it does not look
at the signal in a conventional sense at all; it is not, as I've stated,
based on frequency components per se, but on the fact that turbulent
flow is chaotic, not random. It doesn't repeat exactly, but there are
certain patterns and we have identified some 30 scale-invariant measures
that can be calculated from the broadband ultrasonic signal as picked up
by a passive accelerometer as minute vibrations transmitted through the
pipe wall. We do not introduce any additional energy into the pipe at
all as does a classic ultrasonic detector.

There were some other research teams looking at other techniques such as
microwave and/or more approximating conventional ultrasonics but our
technique was/is unique.

--



In other words your sensors were passive listening devices not active
like the ultrasonic flow sensors I'm familiar with? I'm guessing you
were looking for a semblance of a pattern in the white noise of the
chaos. Am I getting warmer? :-)

TDD