[0001] The invention concerns a device for checking the combustion quality obtained through
the checking of the flame light.
[0002] The strict relationship between the colour of the flame and the quality of the combustion
has been known for quite some time. For instance, the presence of a blue flame in
gas combustion guarantees a good combustion, while a white flame indicates that the
combustion is not perfect. Thus, also in the combustion of oils, a good combustion
is obtained when the flame is completely white, while a yellow flame tending to red
shows an imperfect combustion.
[0003] Repeated observations and tests have led to the conclusion that there is a direct
relation between the good quality of the combustion and the low exhaust emission of
fumes containing nitric oxides NO
x which are highly harmful. For this reason it becomes extremely important to obtain
a continuous source of information referring to the quality of the combustion, so
as to minimize the emission of harmful fumes. With reference to what has just been
said, it has been seen that in the gas combustion the blue flame entails a low emission
of fumes of the NO
x groups, while, as the flame turns increasingly whiter, the emission of NO
x becomes increasingly higher. As for the combustion of oils in the burners, when the
flame tends to become yellow-reddish, the NO
x-percentage increases. At the present time there is in all burners a photo resistance
device checking the presence of the flame. This device is of the ON-OFF type, i.e.
it causes the interruption of the fuel inlet into the burner, whenever the flame goes
off for any reason. As a consequence, the air inlet into the burner is also interrupted,
even with a certain delay. Because of the very nature of its function, the photo resistance
ON-OFF device is not able to give off any signal concerning the quality of the flame
seen by the photo resistance. In actuality, there is no way of checking whether the
combustion occurs in a satisfactory fashion with a low emission of NO
x or whether it is necessary to operate a correction of the parameters in the burner.
[0004] The purpose of the present invention is to overcome the previously described limits
and also the inconveniences caused by the impossibility of knowing the quality of
the flame and, therefore, the quality of the combustion occurring in the burner.
[0005] The just mentioned purpose and others which will be better described hereinafter,
are reached by a device for the control of the quality of the flame-light, strictly
in relation with the combustion quality, in a combustion system which is characterized
in that it comprises:
- an electronic circuit, to which a photo resistance is connected having a resistance
which varies in inverse proportion to the intensity of the light hitting said photo
resistance, a tension signal being recorded at the terminals of said photo resistance,
which, after being suitably treated, feeds a control amplifier causing some leds arranged
in a scale to light up, so that the maximum lighting of the leds corresponds with
the maximum tension surveyed at the terminals of the photo resistance and vice-versa.
[0006] Further scope of applicability of the present invention will become apparent from
the detailed description given hereinafter. However, it should be understood that
the detailed description and specific example, while indicating a preferred embodiment
of the electronic circuit constituting the device, are given by way of illustration
only, since various changes and modifications within the spirit and scope of the invention
will become apparent to those skilled in the art from this detailed description and
from the drawings, wherein:
- Fig. 1 represents a block diagram of the device according to the invention;
- Fig. 2 represents in a diagram the development of the NOx emission in relation to the light (LUX) of the flame.
[0007] With reference to Fig. 1 it will be observed that the electronic circuit is supplied
between the terminals A and B by a stabilized direct-current network tension. Said
stabilized tension, which in the example given is of about 15 Volts, supplies the
terminals 12 and 11 of the circuit, between which are inserted the photo resistance
2 and the tension adapter 3. The tension adapter 3 is necessary, since it is important
and basic that there be at the terminals 12 and 11 an insured pre-set tension, in
relation with a light source of a known intensity. Since the photo resistances have
a certain degree of variability, through the tension adapter 3, which presents an
adjustable resistance 4, it is possible to obtain the desired tension, when the photo
resistance 2 is hit by a known source. During lab tests it has been seen that, for
instance, with a source of 3 lux it is possible to intercept a tension signal corresponding
to 1 Volt between the terminals 12 and 11. Since, as is well known, photoresistances
are electrical elements such that the resistance varies in relation with the quantity
of light hitting said photoresistances, when the photo resistance intercepts complete
darkness, the maximum resistance is reached, which means an open circuit between the
terminals 11 and 12. If, on the other hand, the photo resistance is hit by light,
the inherent resistance becomes lower, so that there is a passage of current between
the terminals 11 and 12 and thus the tension between said terminals becomes lower.
In other words, in the presence of complete darkness the maximum tension will be present
between the terminals 11 and 12, while the tension will decrease as the light increases.
This tension variation is intercepted by the terminals 13 and 14 of a section 5 of
the electronic circuit operating as a filter, a limiting device and a delaying device.
The filtering function concerns the filtering of the disturbance tensions induced
by the transformer of the burner. The tension limiting function is just as important
in order to avoid induced excess voltage and the delaying circuit is also necessary
in order for the electronic device to read the intensity of the flame without being
interfered with by the flame pulsations which inevitably occur during the normal working
cycle of the burner. At the limiting outlet of the filter, limiting device and delaying
device, indicated as a whole with 5, a signal 15 is let out, which is sent to the
comparing circuit 6 which amplifies the tension interval let out of section 5 of the
electronic circuit and sends it to the amplifier 7 supplying the leds, which are indicated
with 8. It is easy to understand that when the tension is at its maximum between the
terminals 11 and 12 of the photo resistance 2, which corresponds practically with
darkness and, therefore, with the best combustion conditions, since the flame is blue,
the maximum tension supplying the leds 8 also is let out of amplifier 7. In this case,
then, all the leds are lit up and reach their utmost luminosity. As the tension increasingly
decreases, which means that the luminosity of the flame increases, and as a consequence
the combustion worsens, the intensity of the tension let out by amplifier 7 is also
decreased and the leds 8 go increasingly off.
[0008] Through the leds 8 it is then possible to check the
quality of the combustion , since, when all the leds are lit up the flame is at its best,
since its luminosity is low, while as the leds go increasingly off, the luminosity
of the flame increases and this indicates bad combustion.
[0009] In Fig. 2 it can be observed that the development of the NO
x-emission is practically linear in relation with the flame luminosity.
[0010] The quantity of NO
x present in the exhaust fumes is recorded in the abscissae and the lux of the burner
flame are recorded in the ordinates.
[0011] Obviously, it will be observed that with a low flame luminosity there is a low emission
of NO
x and that the NO
x quantity increases in relation to the luminosity of the flame itself. Therefore,
the purpose of the invention which proposed to obtain a device for visualizing the
quality of the combustion in relation with the luminosity of the flame has been reached,
the quality of the combustion and the luminosity of the flame being in inverse relationship.
1. A device for checking the quality of the flame-light in a combustion system characterized
in that it comprises:
- an electronic circuit, to which a photo resistance is connected having a resistance
which varies in inverse proportion to the intensity of the light hitting said photo
resistance, a tension signal being read at the terminals (11, 12) of said photo resistance,
which feeds a control amplifier (7) causing some leds (8) arranged in a scale to light
up, such that the maximum lighting of the leds corresponds with the maximum tension
surveyed at the terminals of the photo resistance and vice-versa
2. A device according to claim 1, characterized in that the tension signal which is read
at the terminals of the photo resistance, is treated with an electronic circuit (5)
comprising filters for the elimination of disturbance frequencies, a tension limiting
device and a delaying device in order to minimize the effects of the flame pulsations
during the normal working cycle.
