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10.7 Example of FGR factor and FGR Maps Factor on the burner regulation.
We consider to set the AUX3 for FGR with the "temp.contr." Mode
The curve is as per the below table.
Point
Load %
AUX3 FGR Curve
FGR temperature
LMV52.400 will calculate a "Zero Curve" referred to flue gas 0°C temperature.
The "Zero Curve" is calculated in reference to the effect of the temperature on the smoke density.
If "FGR factor" is set at 100% LMV will not make any additional correction.
Point
Pos. FGR con T = 0 °C zero
curve
If "FGR factor" is set at lower value than 100% LMV will apply an additional correction to calculate the "Zero Curve".
If "FGR factor" is 50%, the new "zero Curve" will be
Point
Pos. FGR con T = 0 °C zero
curve
If the temperature value of the smoke during the operation of the burner is higher than the temperature value during the commissioning, the AUX3
position will be bigger than the set values.
To avoid a wide opening of the FGR butterfly valve it could be necessary to limit the automatic correction LMV52.400.
This could be necessary if the AUX3 opening become bigger than 90°, if a flame instability happen, or the flue gas recirculation is too big...
To limit the correction due to a higher temperature value, it become necessary to set the parameter "FGR MaxPOS Factor".
Point
Pos. FGR
90
80
70
60
50
40
30
20
10
0
30
1
2
3
37,5 %
62,5 %
75 %
19,3 °
25,0 °
28,5 °
72 °C
105 °C
121 °C
1
2
3
15 °C
18 °C
19,7 °C
1
2
3
7,6°
9,0°
9,8°
1
2
3
21,2°
27,5°
31,4°
50
70
Burner load [%]
4
Note
100 %
37,0 °
The flue gas value increase from low to high flame.
150 °C
The temperature is with burner in operative condition.
4
Note
23,8 °C
FGR Factor set on 100%
4
Note
FGR Factor set on 50%
The above example shows that – with the zero curve – a flue gas
11,9°
recirculation (FGR) factor of 50% leads to a 50% reduction of the damper
positions.
4
Note
FGR MaxPOS Factor set on 10%
40,7°
I valori sono il 10% in più rispetto ai corrispondenti settati inizialmente.
The LMV52.4... performs a linear interpolation of the damper
positions between the setting values and the zero curve,
depending on the current flue gas temperature.
When the flue gas temperatures lie above the setting values, the
calculated damper positions are higher than the setting values.
90
35
AUX3 FGR Curve
on commissioning
Zero Curve
FGR Factor 50%
Zero Curve
FGR Factor 100%
AUX3 FGR Curve
FGR MaxPOS Factor
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