Riello ER Series Installation, Use And Maintenance Instructions page 45

CHAPTER
5.6 Burner setting guidelines
Swirlers configuration
The burner design and configuration, in particular regarding the blades angle on the primary (central) and secondary swirlers, are
usually pre-fixed before the burner delivery, when the burner application is enginered and adapted to the boiler combustion cham-
ber dimensions.
In case of multiple burner application, each burner must be installed according to its pre-defined position on the boiler front wall,
since in such case the burners are manufactured with clockwise or counter-clockwise air swirl, just depending on the whole burners
set and with reference to the right/left beside burner.
Flame register
The function and the effect of the flame register (secondary air swirler) is to get a further tuning on flame shape, but the maximum
effect is anyway limited.
On the full forward position you get the highest air rotation effect, while on the full backward position you get no rotation effect on
the secondary air flow.
In general it is possible to start with a 50% forward positioning; considering your application it could be necessary even to reach
100% in order to get the shortest flame shape.
The flame shape is not depending only from this axial register positioning; in fact it depends from the "swirl index" that is related
to the air rotation effect but also (heavily) to the air mass flowing into the duct.
Since the "total swirl index" is a combination of the "primary swirl number" and of the "secondary swirl number" , each air damper
setting (primary or secondary) will effect directly on its own (primary or secondary) flow, but also as consequence, on the (primary
or secondary) swirl number and finally on the total swirl number.
Since the two air dampers could be freely positioned by their servomotors, it is suggested to fix a "ratio" between primary and
secondary damper positon. Based on the burner basic design , an easy rule to refer, when setting the two air dampers, is to get
the same Delta_P on primary and secondary duct;
Of course in term of total air flow for proper combustion the results from the flue gas analizer must be taken as main priority and
consequently:
– If a total combustion air increase is needed, you shall open primary and secondary air dampers, but preferably keeping
Delta_P1=Delta_P2
(to check this you can connect a digital air pressure gauge on the existing test points on the burner windbox)
– If combustion air must be reduced (in term of total flow), you shall reduce primary and secondary air dampers positon, but
preferably keeping Delta_P1=Delta_P2
– If a variable speed drive is avalaible, then the total air amount will be first changed by the VSD but anyway (Delta_P1-2) shall
be balanced to zero.
5
Preparation for starting up and adjusting the burner
0%
50%
SM2 SM3
M M
100%
D8415
Fig. 24
19