This invention relates to a premix burner for operating a heat generator, the burner at least having a swirl generator, a mixing section downstream of the swirl generator and a transition piece for transferring the swirl flow from the swirl generator into the mixing section. The invention further refers to a transition piece for such a premix burner. The transition piece includes an inlet, connected to the swirl generator, an outlet, connected to the mixing tube, and a continuing flow limiting interior contour between said inlet and said outlet, wherein at least in an inlet section said interior contour is curved radially inwards towards the inner diameter of the mixing tube and wherein at the outlet the interior contour is flush with an interior flow limiting contour of the mixing tube.
1. A premix burner for a heat generator, the premix burner, comprising:
a swirl generator, having at least two burner shells which complement one another to form an axially conically widening swirl space and which mutually define, in an axial cone longitudinal direction, tangential slots through which combustion air is introduced into the swirl space, and a fuel feeder to provide a fuel into the combustion air flow arranged at least in sections along the tangential slots;
a mixing tube downstream of the swirl generator for homogeneously mixing fuel and combustion air before introducing the fuel-air-mixture into a combustion chamber, where ignition occurs;
a transition piece between the swirl generator and the mixing tube for transferring the flow of combustion air and fuel from the swirl generator into the mixing tube, wherein
the transition piece comprises an inlet, connected to the swirl generator, an outlet, connected to the mixing tube, and a continuing flow limiting interior contour between said inlet and said outlet, wherein at least in an inlet section said interior contour is curved radially inwards towards the inner diameter of the mixing tube and wherein at the outlet, the interior contour is flush with an interior flow limiting contour of the mixing tube, wherein the radially inwards curved contour has a gradient which declines in a downstream direction, the maximal angle for the gradient being located at the inlet, wherein said radially inwards curved section of interior contour extends from the inlet of the transition piece up to its outlet.
2. The premix burner according to claim 1 , wherein said radially inwards curved interior contour of the transition piece starts at the downstream end of the swirl generator from the leading edge of the slots.
3. The premix burner according to claim 1 , wherein the interior contour at the inlet section of the transition piece is equipped with a concave shape.
4. The premix burner according to claim 1 , wherein the interior contour at the inlet section of the transition piece is equipped with a circular arc profile.
5. The premix burner according to claim 4 , wherein said circular arc profile section includes a central angle (μ) and wherein μ≦90°.
6. The premix burner according to claim 5 , wherein μ≦45°.
7. The premix burner according to claim 1 , wherein the transition piece is an integral part of the swirl generator.
8. A transition piece for a premix burner, the premix burner including a swirl generator, having at least two burner shells which complement one another to form an axially conically widening swirl space and which mutually define, in axial cone longitudinal direction, tangential slots through which combustion air is introduced into the swirl space, and a fuel feeder that provides a fuel into the combustion air flow arranged at least in sections along the tangential slots, said transition piece comprising:
a casing with an inner passage, an inlet, an outlet and a continuing flow limiting interior contour between said inlet and said outlet, wherein at least in the inlet section said interior contour is curved radially inwards, wherein the transition piece is designed to be connected to the outlet of the swirl generator of this premix burner, wherein the radially inwards curved contour has a gradient which declines in a downstream direction, the maximal angle for the gradient is located at the inlet, wherein the radially inwards curved inlet section extends from its inlet up to its outlet.
9. The transition piece according to claim 8 , wherein at least in the inlet section the interior contour is equipped with a concave shape.
10. The transition piece according to claim 8 , wherein at least in the inlet section the interior contour is equipped with a circular arc profile.
11. The transition piece according to claim 10 , wherein said circular arc profile includes a central angle (μ) and wherein μ≦90°.
12. The transition piece according to claim 10 , wherein μ≦45°.