So, here is my review of the new burner bowl:
The bowl is wider and longer. The pellets burn much better because of less air-speed.
There are no more holes, but slots instead. The advantage is, that no ash or sintered material can block this air- outlets anymore.
Because there is no more secondary air-ring over the burner-bowl, it cleans itself much better from unburned pellets, ash and sinter.
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Below the old type of burner bowl and the secondary air-ring upon it.
The fluegas temp rised about 20 degrees up to 170. I think the flames have more time to burn out now. Before, there was a concentrated gas-stream out of the secondary air-ring. Now the flames burn longer and quieter.
The amount of ash in the horizontal fluegas-channels is reduced very much.
It seems, my boiler is working more efficient now.
Secondary air now is blown right over the glowing pellets through the pipe where the secondary air-ring was mounted.
It is now similar to the ecotec burners, which also have a pipe with secondary air facing to the burner bowl.
All in all: I am very satisfied with the changes thermia made[/img]