Individual burner air/fuel ratio control optical adaptive feedback control system
Author(s)
Beér, James Miklós; Jacques, M. T.; Teare, J. Derek
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Conventional combustion control systems for multiburner installations
which rely on monitoring the average C02 and/or 02 content of the gases
have a number of inherent limitations on their ability to maintain efficient plant operation. Air infiltration'into the flue or sampling lines
has the same effect as an instrumental error in causing the control
system to adjust the stoichiometry to an incorrect level. Even' when the
overall stoichiometry of the furnace is correctly and accurately controlled
it is still extremely difficult to ensure that no individual burners are
operating inefficiently due to local maldistributions of air or fuel, or
to poor nozzle spray characteristics. The potential for fuel savings and
for'improved limitation of pollutant emissions has provided strong incentive for the development of individual burner fuel/air ratio control
systems which would eliminate the shortcomings associated with the global
control method.
The present report first reviews past attempts to identify some unique
property of an individual flame which can be reliably interpreted as an
indicator of the flame behavior over a wide range of operating conditions..
Information potentially usable in this manner could be contained in the
acoustic characteristics of the flame, in the local distribution of key
chemical species, or in the electromagnetic radiation or absorption
behavior of regions of the flame. For many reasons the previous studies
have tended to concentrate on the optical portion of the electromagnetic
spectrum, with particular emphasis on emission from flames over much of
the ultraviolet (u.v.), visible and infrared (i.r.) wavelength regions. A
brief review is given of the pioneering work of Penzias and his associates, and of the later work carried out at Sheffield University by Smith which
led to the development of the LandTM control system. All of these studies
dealt with the infrared emission from flames, wilth particular emphasis on
the CO2 barnd at 4.3 pm, and on the H0/CO2 binds near 2.8 m.
The report then addresses the experimental work carried out at M.I.T
under the sponsorship of five utility companies supporting the M.I.T.
Energy Laboratory Electric Power Program. This focused initially on
attempts to use a Land control system in the Combustion Research Facility
(CRF), with limited success in terms of achieving stability and adequacy
of control when operating conditions were varied over a moderate range.
The experiments in the CRF also yielded very useful data on the intensities
and sources of u.v. emission from No. 6 fuel oil flames over a wide range
of fuel equivalence ratio. One other set of experiments carried out in the
CRF made use of equipment and personnel supplied by the Foxboro Company,
and results of this work are discussed.
Also included in the report is a summary of measurements carried
out on a small methane-fueled burner which add appreciably to the
available information on the dependence of the infrared emission on viewing
location relative to the flame front and on fuel equivalence ratio.
The overall results obtained under this program do not leave the
prospect of individual fuel/air ratio controllers within immediate grasp,
but they substantially advance the state of knowledge required for attainment of such control. They give a strong indication that satisfactory
control could be obtained over a wide range of furnace operating conditions
if both i.r. and u.v. signals were monitored and used in the control
system.
Description
On cover : Combustion Research Facility.
Date issued
1982-01Publisher
MIT Energy Laboratory
Other identifiers
10647693
Series/Report no.
MIT-EL82-001
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