FIELD OF INVENTION
The present invention relates to an apparatus for coal / oil / gas flame detection
by digital signal processing. More particularly, the invention relates to a
microcontroller based flame detection apparatus adaptable to boilers.
BACKGROUND OF THE INVENTION
Boilers are employed world wide by thermal power plants and many other
industries which require steam and / or power for its operation. The boilers are
designed to burn different fuels like coal / oil / gas either separately or in
combination. The fuels are admitted to the boiler furnace through the burners
disposed in different locations in the furnace walls. In some types of boilers, the
burners are located in the four corners of the furnace at different levels (known
as corner fired boiler furnaces). In other type of boilers, the burners are located
in the front wall or rear walls of the furnace at different levels (known as wall
fired boiler furnaces). The flame generated due to firing of the fuel through the
burners, is required to be monitored continuously to avoid accumulation of
unburnt fuel components in the furnace (which may lead to explosion). Suitable
flame detectors are employed to monitor the flame.
In the presently available hardwired electronic (solid state) flame detector
apparatuses, several electronic modules (Electronic cards) are used to perform
the processing and logic control functions.
In such prior art detector apparatuses, several electronic modules are used to
perform the processing and logic control functions. These modules are mounted
in the card rack assemblies. One number card rack assembly is used for
mounting the electronic modules required for monitoring the flame due to one
fuel.
However, such prior art electronic (solid state) flame detector system is bulky
and needs a large number of modules. It is prone for drift, needing frequent
calibrations. The process of frequently adjusting the gain settings for the
intensity and flicker frequency are cumbersome and takes more time.
The processing of the signal from the head electronics is done in analog mode
resulting in errors due to drift. If the flame detector is to be used to monitor the
flame due to two different fuels two separate sets of electronic modules have to
be used. This takes more space. The system has no in-built diagnostic feature,
and further lacks computer connectivity.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a microcontroller - based flame
detection apparatus adaptable to boilers which eliminates the disadvantages of
the prior art.
Another object of the invention is to provide a microcontroller - based flame
detection apparatus adaptable to boilers which is capable of digital setting of
burner flame parameters.
A further object of the invention is to provide a microcontroller - based flame
detection apparatus adaptable to boilers which is capable of efficient processing
of signals.
A still further object of the invention is to provide a microcontroller - based flame
detection apparatus adaptable to boilers which utilizes less number of electronic
modules while maintaining an improved efficiency.
Yet another object of the invention is to provide a microcontroller - based flame
detection apparatus adaptable to boilers which is easy to maintain and provide
user-friendly man-machine interface.
A still another of the invention is to provide a microcontroller - based flame
detection apparatus adaptable to boilers which comprises self - diagnostic
improve reliability.
SUMMARY OF THE INVENTION
In corner fired boiler furnaces, four flame detectors are installed at one level in
the four corners of the furnace. Each flame detector consists of a detector head
with fibre optic cable assembly. The detector head housing contains an
electronics module which converts the light transmitted from the furnace flame
via a fibre optic light guide, to an electric current signal. The electric signal is
further taken to a micro controller based equipment and processed. Input from
each flame detector is divided into two components viz. one corresponding to intensity
and the other one corresponding to flicker frequency. Both signals are processed
digitally in the micro controller based equipment to compute intensity and flicker
frequency parameters of flame. The apparatus also has the facility for digital settings,
indications and processing of other associated state of flame parameters. The apparatus
also determines the required availability of the flame in the respective comers of the
furnace.
Accordingly there is provided an apparatus for boiler furnace flame detection by digital
signal processing for combined and synchronous monitoring of burner flames to avoid
accumulation of unburnt fuel components in the boiler system, the apparatus comprising
atleast four scanner heads , one each disposed at one of the four corners of the furnace
of the boiler system, atleast one detector amplifier having a power supply module, a 2/4
flame detection logic module, and atleast one each microcontroller based digital signal
processing module for the atleast four scanner heads, a signal cable for interconnecting
the scanner heads and the detector amplifier, wherein each detector head is connected
via a signal cable to the atleast one each microcontroller-based digital signal processing
module, the signal processing module processing the electric signal being transmitted
by the detector head, wherein the detector amplifier converting the inputted AC power
supply to DC supply via the power supply module for feeding to the signal processing
modules and 2/4 flame detection logic module, and wherein the 2/4 flame detection
logic module generating signals representative of "flame on" condition based on a
comparison of output signals from the atleast two digital signal processing modules.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - Shows a schematic block diagram of the flame detection apparatus
according to the present invention.
DETAILED DESCRIPTION OF A PREFFERED EMBODIMENT OF
THE INVENTION
As shown if figure 1, the flame detection apparatus has three means. The first
means constitute a scanner head (1). Each scanner head consists of a lens barrel
(2), fiber optic cable (3) and head electronics (4). One scanner head is provided
to monitor the flame due to each burner.
The second means comprise a detector amplifier (5). Each detector amplifier
consists of a card rack (6), containing a plurality of electronic modules - micro
controller based digital signal processing module (7), a power supply module (8)
and a 2/4 flame detection logic module (9). The third means constitute a signal
cable (10) for interconnecting the flame detector head (1) and the detector
amplifier (5). The detector amplifier is normally located inside a cabinet.
In the case of a corner fired boiler furnace, atleast four numbers of detector
heads (1) are used to monitor the flame in the four corners of the furnace at one
level. The electrical signal from each detector head (1) is connected to the digital
signal processing module (7) through the signal cable (10). One number digital
signal - processing module (7) is provided with LEDs, display selection push
button, dip switches and digital display. The output from 4 numbers of digital
signal processing modules (7) pertaining to one level of burners is connected to
a 2/4 flame detect logic module (9). Based on the availability of the output from
atleast two number of digital signal processing modules (7), "flame ON"
condition is generated by the 2/4 flame detection logic module (9). The detector
amplifier (5) is provided with either 110 V or 240 V AC power supply. This is
converted into DC supply at required voltage by the power supply module (8) for
feeding to the other electronic modules. Provision is made in the 2/4 flame
detection electronic module (8), to transmit the various information through
serial communication Ports (Rs 232c) to other electronic means like distributed
control system etc,.
In case of wall fired boiler furnaces, the 2/4 flame detection logic module is not
applicable, as the flame due to each burner is monitored independently. The
device is capable for separate gain adjustments for different types of useable
fuels.
We Claim:-
1. An apparatus for boiler furnace flame detection by digital signal processing for
combined and synchronous monitoring of burner flames to avoid accumulation of
unburnt fuel components in the boiler system, the apparatus comprising:
- atleast four scanner heads (1), one each disposed at one of the four
corners of the furnace of the boiler system;
- atleast one detector amplifier (5) having a power supply module
(8), a 2/4 flame detection logic module (9), and atleast one each
microcontroller based digital signal processing module (7) for the
atleast four scanner heads (1);
- a signal cable (10) for interconnecting the scanner heads (1) and
the detector amplifier (5), wherein:
- each detector head (1) is connected via a signal cable (10) to the
atleast one each microcontroller-based digital signal processing
module(7), the signal processing module (7) processing the electric
signal being transmitted by the detector head (1), wherein
- the detector amplifier (5) converting the inputted AC power supply
to DC supply via the power supply module (8) for feeding to the
signal processing modules (7) and 2/4 flame detection logic module
(9), and wherein
- the 2/4 flame detection logic module (9) generating signals
representative of "flame on" condition based on a comparison of
output signals from the atleast two digital signal processing
modules(7).
2. The apparatus as claimed in claim 1, wherein each digital signal processing
module (7) comprises atleast one Light emitting diode (LED), a display selection
push button, atleast one dip switch, and a digital display.
3. The apparatus as claimed in claim 1, wherein the detection amplifier (5)
comprises a card rack (6) which accommodates the microcontroller-based digital
signal processing module (7), the power supply module (8), and the 2/4 flame
detection logic module (9).
4. The apparatus as claimed in any of the preceding claims wherein the scanner
heads (1) each comprises a lens barrel (2), a fibre optic cable (3), and atleast
one electronic head (4).
5. An apparatus for boiler furnace flame detection by digital signal processing as
herein substantially described and illustrated with reference to the accompanying
drawing.

A microcontroller-based flame detection apparatus adaptable to a boiler system for combined and synchronous monitoring of burner flames to avoid accumulation of unburnt fuel components in the boiler system is disclosed. The apparatus comprises atleast four scanner heads (1), atleast one detector amplifier (5) having a power supply module (8), a 2/4 flame detection logic module (9), and atleast one each microcontroller based digital signal processing module (7) for the atleast four scanner heads (1). Each detector head (1) is connected via a signal cable (10) to each microcontroller-based digital signal processing module (9). The detector amplifier (5) converts the inputted AC power supply to DC supply via the power supply module (8) for feeding to the signal processing modules (7) and the 2/4 flame detection logic module (9). The 2/4 flame detection logic module (9) generates signals representative of "flame on" condition based on a comparison of output signals from the atleast two digital signal processing modules (7).