GB2620194A - Fan burner and heater with a fan burner - Google Patents

Abstract

A fan burner 100 in use provides a fuel-air-mixture flow ‘M’ by mixing a fuel flow ‘B’ from a fuel passage 102 and an air flow ‘L’ from an air passage 104. The fuel and air mix in the mixer 106 and flow along a mixed flow passage 108. The fan is of the Tesla turbine/pump design, i.e. it is bladeless and driven by a motor which transfers energy from the motor driven fan rotor 220 to the air flow. The mixer may be a venturi, and the fan burner can be fully or partially premixed. The fan burner can be used in a water heater for space heating and/or hot water supply systems. The fan rotor may have at least two but preferably five discs 224, and the spacing of the discs between each other and/or a fan housing wall 242, 244, is such that flashback is attenuated or prevented. The fan burner is particularly suitable for use with hydrogen fuel.

Description

Description Title

Fan burner and heater with a fan burner State of the art From the prior art, fan burners are known for providing a fuel-air mixture flow by mixing a fuel flow and an air flow as well as for combusting the mixture flow. A fan conveys either the air flow or the mixture flow. Radial fans having impellers are usually used as fans, which have a plurality of circumferentially distributed fan blades. A flame of combustion forms in the flow direction of the mixture flow downstream of a burner mouth and/or a burner surface.

Common fuels are fuel gases or vaporized oil. Among the fuel gases, hydrogen and hydrogen mixtures (for example hydrogen-methane mixtures) are characterized by having a high flame velocity, among other things, which increases a risk of a flashback of the flame in the burner.

US1061142 A discloses a pump according to Nikola Tesla having a fan housing and a fan rotor, wherein the fan rotor comprises a fan shaft and a plurality of mounted, axially spaced apart fan disks having a flat, bladeless surface, further comprising a liquid inlet opening into the fan housing in the area of the shaft and a tangential liquid outlet opening in the outer area of the fan housing.

It is the object of the invention to provide an improved fan burner and heater with a fan burner.

Disclosure of the invention

The invention relates to a fan burner to provide a fuel-air mixture flow by mixing a fuel flow and an air flow as well as to combust the mixture flow, comprising a fuel passage for guiding the fuel flow in a fuel flow direction, an air passage for guiding the air flow in an air flow direction, a mixer for mixing the fuel flow and the air flow, a mixture passage for guiding the mixture flow in a mixture flow direction, and a fan for conveying the air flow or the mixture flow.

It is proposed that the fan be configured in the manner of a Tesla pump, in particular motor-driven, which transfers energy from a fan rotor, in particular motor-driven, to the air flow, in particular a gaseous form, or the mixture flow, in particular a gaseous form.

In this context, a fan burner is to be understood in particular to mean a heat generator for generating heat by means of combustion, in which the air flow or fuel-air mixture flow coming for combustion is conveyed through the burner and into a combustion chamber by means of a fan. The fan burner is in particular a fully premixing burner. Alternatively, the fan burner may also be a partially premixing burner. The fan burner may in particular comprise a control and/or regulator device for controlling and/or regulating the burner, in particular the fan, in particular a fan speed, wherein the fan speed may vary between zero, minimum speed, and/or nominal speed. In particular, a fuel is to be understood herein as a fuel gas, such as hydrogen, natural gas, or liquid gas or mixtures thereof. In particular, a fuel passage is to be understood herein as a fuel conduit for fluid-conducting connection of the burner to a fuel supply, in which the fuel flows to the mixer. In particular, a fuel valve and/or a fuel control valve for influencing the fuel flow can be arranged in the fuel passage. In particular, an air passage is to be understood, in particular, as an air conduit for fluid-conducting connection of the burner to an air inlet opening, in which air flows towards the mixer. The air passage can in particular be part of the mixer and/or be integrated in the mixer. In another embodiment, in particular the air passage may be part of the fan and/or may be integrated in/on the fan. In particular, a mixer is to be understood herein as a device for mixing the fuel flow and the air flow to a fuel-air mixture flow. The mixer may in particular be configured as a venturi mixer. In particular, a mixture passage is to be understood herein to be a mixture conduit for fluidly connecting the mixer to a burner mouth and/or a burner surface in which the fuel-air mixture flows. In particular, a fan is to be understood herein as a fan that transfers energy to the air flow and/or the mixture flow, in particular motor-driven, advantageously electric motor-driven actuator, and thus promotes the air flow or the mixture flow. In particular, the fan comprises a fan housing, for example a helical fan housing, with restrictive housing walls, as well as an inlet opening and outlet opening for the air flow or mixture flow to be conveyed. In particular, the fan may be arranged in a fluid-conducting manner in or at the mixing passage and/or the mixing passage may pass through the fan. In one embodiment, the fan may be an integral part of the mixing passage. In a further embodiment, the mixture passage is configured in the fan, in particular in the fan housing. In a further embodiment, the fan, in particular the fan housing, forms the mixing passage. The fan comprises a fan rotor disposed in the housing. Further, a motor driving the fan rotor, in particular configured as an electric motor, can also be counted as part of the fan. The fan promotes the air flow or mixture flow to a burner mouth and/or a burner surface where the mixture flow is ignited and combusts into an exhaust gas under heat generation, wherein a flame of combustion is stabilized downstream at the burner mouth and/or burner surface in a combustion chamber. The burner mouth and/or the burner surface may be associated with a heat exchanger for transferring the heat of combustion from the exhaust to a heat transfer medium. In particular, a Tesla-pump type fan is to be understood herein to mean a fan having a rotor, wherein the rotor comprises a rotatable fan shaft and a plurality of circular or annular fan disks having a bladeless surface, which are rigidly connected to the fan shaft and axially spaced apart from one another. In particular, the fan disks do not have fan blades distributed on a circumference of an impeller. The fan functions according to the principle of a Tesla turbine inverted to a fluid power machine, and conveys a gaseous medium. A fan disk having a bladeless surface is to be understood herein to mean a fan disk without fan blades, in particular with a smooth surface. A unit of a plurality of axially spaced apart fan disks, in particular arranged parallel to one another, of a fan is also hereinafter referred to as a stack of disks.

By means of the configuration according to the invention, the fan burner can be operated particularly advantageously. It has been found that by means of a flow form, forming in the fan burner and in particular in the fan, very quiet operation and efficient conveyance of the air flow or mixture flow are carried out and an undesirable return of flames from the burner mouth or burner surface upstream through the mixture passage and/or by the fan is particularly safely attenuated or stopped.

In a preferred configuration of the fan burner, the fan is configured to promote the mixture flow, wherein the fan is disposed in or at the mixture passage in the mixture flow direction downstream of the mixer.

In particular the fact that the fan is disposed in or at the mixing passage should be understood to mean that the mixing passage is passing through the fan, and/or that the fan is an integrated component of the mixing passage, and/or that the mixing passage may be formed in the fan, in particular in the fan housing, and/or that the fan, in particular the fan housing, forms the mixing passage and/or that the fan is arranged fluidly in or at the mixing passage.

In the premixed combustion, the air and fuel are premixed upstream of the burner mouth or burner surface. A quantity ratio of fuel to air in the mixture, or an air quantity equivalent to the fuel-to-air quantity ratio, is often controlled by a pneumatic system, for example by way of aspirating the fuel and mixing it with air in a venturi mixer. In many fan burners, this mixing process occurs at low pressure upstream of the fan, wherein the fan in the mixing passage is disposed downstream of the mixer in the mixture flow direction. This allows a stable control of the ratio of quantities over a very wide modulation range of the mixture amount flowing through the burner (corresponds to a combustion efficiency of the burner upon combustion). A further advantage of this fan arrangement is that the fan accelerates the mixing of air and fuel to a homogeneous mixture with low spatial fluctuations in the quantity. This is advantageous for a clean and complete combustion of the mixture.

In an alternative configuration of the fan burner, the fan is configured to exclusively convey the air flow, wherein the fan is disposed in the air passage in the direction of air flow upstream of the mixer.

In a further preferred configuration of the fan burner, the fan rotor comprises at least two, preferably at least five, fan disks that can be rotated about a fan axis, in particular being arranged parallel to each other and being axially spaced apart from one another. The fan disks each have a perpendicular bisector and/or rotation axis that extends substantially along the fan axis. The fan disks are disposed in a fan housing.

A fan disk has two bladeless, circular or annular surfaces (a surface on a front side of the fan disk) the other surface on a rear side of the fan disk).

The fan axis or the rotation axis of the fan rotor and the fan disk run along the perpendicular bisector and are substantially perpendicular to the circular or annular surface of the fan disk. The surface of the fan disk extends substantially in the radial direction. The perpendicular bisector is perpendicular to a radial extension of the fan disk.

The fan disk is formed very thin and has a large radial extension and a very small axial extension relative to the radial extension. The front side and rear side of the fan disk may be parallel to each other. Deviating from this, the front side and rear side of the fan disk may also have slight deviations from a parallel path, in particular a slight slope to each other.

In one embodiment, a fan disk in a longitudinal section can have two rectangular cutting surfaces (one each above and below the axis of rotation; a rectangular thickness profile). The opposing circular or annular surfaces (front side and rear side of the fan disk) run parallel to each other. This results in interspaces between two fan disks that have a constant width in the radial direction. A longitudinal section is to be understood here as a section through the fan disk along its rotation axis or along the fan axis.

In other embodiments, a fan disk in a longitudinal section may have two trapezoidal cutting surfaces (trapezoidal thickness profile) or two semi-elliptical cutting surfaces (semi-elliptic thickness profile) or two flow-favourably curved cutting surfaces. These cutting surfaces have a narrow, elongated shape and extend substantially in the radial direction. The opposing circular or annular surfaces are not parallel to each other, they may include small angles with each other due to their respective thickness profile. These angles between the front side and the rear side of the fan disk may be in the low angular range, for example in the range of 1°...10°. This results in interspaces between two fan disks, the clear width of which is wider or narrower along the radius.

The circular or annular surfaces of the fan disks may be flat, concave or convex.

The fan disks are used to transfer energy from the fan rotor to the air flow or mixture flow. In particular, the rotating fan disks accelerate the air flow or mixture flow present in the interspace and/or increase a pressure in the air flow or mixture flow so that it flows further to the burner mouth or burner surface.

The axially spaced apart fan disks in the stack of disks have interspaces between each other. Each of two adjacent fan disks defines an interspace. Further interspaces are located between the first fan disk of the stack of disks and the axially adjacent housing wall of the fan housing, as well as between the last fan disk of the stack of disks and the axially adjacent housing wall.

According to the type of Tesla pump, the fan disks do not have fan blades.

In particular, the perpendicular bisector of the fan disk is to be understood as a rotational symmetry axis, which is in particular substantially designed in a rotationally symmetrical fashion. The fan axis is to be understood here, in particular as the rotational symmetry axis of the fan shaft, in particular configured substantially in rotational symmetrical fashion. In particular, the perpendicular bisector and the fan axis coincide.

"In particular, substantially rotationally symmetric" should be understood that the geometry of the fan disk or fan shaft can deviate in details from the rotational symmetry, for example in the spokes or radial through-holes in a hollow shaft sheath surface.

The air flow or mixture flow passes into the fan housing from outside the fan, coming from a portion of the air or mixture passage connected upstream, through an inlet opening in the housing wall in the area of the fan shaft. The air flow or mixture flow is supplied to the interspaces near the fan axis. The transfer of energy from the motor driven rotating fan rotor to the air flow or mixture flow is carried out by means of frictional forces in the fluid dynamic boundary layer contacting the fan disks in the air flow or mixture flow. The air flow or mixture flow is first tangentially carried away by the rotating fan disks, then -accelerated by centrifugal forces radially-flows on spiral tracks through the interspace outward, collects on an inner side of the spiral-shaped housing outer wall and flows to the exit opening, where it exits into a downstream portion of the air or mixture passage.

In order for the air flow or mixture flow to be supplied to all interspaces and to be distributed evenly among the interspaces, the fan disks may each comprise one or more through-holes near the fan shaft. By means of these through-holes, the air flow or mixture flow can flow from one interspace on one side of a fan disk into the next interspace on the opposite side of the fan disk, and so forth, and split up.

Alternatively, in order for the air flow or mixture flow to be supplied to the interspaces, the fan shaft may be embodied as a hollow shaft into which the air flow or mixture flow comes axially from a portion of the air or mixture passage connected upstream. The air flow or mixture flow then flows from the hollow shaft into the interspaces through radially distributed through-holes along the hollow shaft sheath surface. At least one through-hole is provided in the hollow shaft sheath surface for each interspace. Alternatively, two or more through-holes are provided in each interspace, which are circumferentially distributed in the hollow shaft sheath surface.

In another preferred configuration of the fan burner, a measure of a disk spacing between two adjacent, axially spaced apart fan disks and/or between a fan disk and an adjacent, axially spaced apart housing wall is selected less than or equal to a safety spacing distance.

A disk spacing is to be understood here as a clear width, measured particularly in the axial direction, between two adjacent, axially spaced apart fan disks and/or between a fan disk and an adjacent, axially spaced apart housing wall. The disk spacing is in particular equivalent to the clear width of the interstice space between two adjacent fan disks.

This ensures both a quiet and efficient conveyance of the air flow or mixture flow, and an undesirable flashback coming from downstream through the fan is safely attenuated and/or prevented upstream.

It is recommended to choose the disk spacing between a fan disk and an adjacent housing wall smaller than the disk spacing between two fan disks because, due to the stationary housing wall, undesirable reverse flow of the air flow or mixture flow is most likely here.

In another preferred configuration of the fan burner, a measure of a disk spacing between two adjacent, axially spaced apart fan disks and/or between a fan disk and an adjacent, axially spaced apart housing wall is less than or equal to a detonation cell size of the mixture flow under stoichiometric ratios. In particular, for the fuel hydrogen, the disk spacing is selected less than or equal to 15 millimetres.

In another preferred configuration of the fan burner, a measure of a disk spacing between two adjacent, axially spaced apart fan disks and/or between a fan disk and an adjacent, axially spaced apart housing wall is less than or equal to a quenching distance of the mixture flow under stoichiometric ratios. In particular, for the fuel hydrogen, the disk spacing is selected to be less than or equal to 1.0 (± 0.5) millimetres, i.e., less than or equal to 0.5...1.5 millimetres.

In another preferred configuration of the fan burner, a measure of a disk spacing between two adjacent, axially spaced apart fan disks and/or between a fan disk and an adjacent, axially spaced apart housing wall is less than or equal to a maximum experimental safe gap, also called a limit gap width, of the mixture flow under stoichiometric ratios. In particular, for the fuel hydrogen, the disk spacing is selected to be less than or equal to 0.5 (± 0.3) millimetres, i.e., less than or equal to 0.2...0.8 millimetres.

A flame undesirably flashing back from the burner mouth and/or burner surface cannot overcome the selected interspaces with the disk spacing of less than or equal to a threshold value and is extinguished. The physical background of the extinguishment of a flame is based on a balance of energy of the flame, and states that in order to maintain combustion under given boundary conditions such as pressure and air quantity, a burning mixture volume must have a certain minimum temperature. However, the energy required to maintain this minimum temperature is withdrawn from the mixture volume upon contact with the wall, here in particular upon contact with the fan disks.

Among other parameters, the desired fan characteristic may also be set based on the disk spacing, which describes the pressure/volume flow ratio of the fan.

The applicable threshold for disk spacing may be based on a theoretically or experimentally determined safety distance, a detonation cell size, a quenching distance, or a maximum experimental safe gap of the mixed flow, in particular under stoichiometric ratios of the selected fuel type.

The exact selection of disk spacing, whether based on the detonation cell size, the quenching distance or the maximum experimental safe gap, depends in particular on the fuel, the constructive design of the fan burner and its operating conditions. With the fuel, hydrogen or hydrogen mixture, stricter requirements for disk spacing will have to be met than with methane. A burner mouth or burner surface can intrinsically be more prone to or more robust against flashback, and so a greater or lesser share of overall safety is assigned to the fan or disk spacing in the fan. Further, flow cross-sections, flow rates, turbulence in the flow, operating pressures, operating temperatures, homogeneity, and/or air amount in the mixture flow may have an impact.

If a flashback were to occur in a burner operation, larger quantities of mixture could combust in a very short period of time. This could cause mechanical and thermal damage, including safety-related damage, to the burner and a connected heater. Thus, a flashback on a burner must be safely dampened (attenuated) and/or prevented, and/or its propagation in the burner must be limited. In particular, a dampening of a flashback is to be understood here as a weakening of its mechanical and acoustic effects.

With the invention, in addition to efficiently conveying air flow or mixture flow, in particular, a flashback barrier or flame breakdown protection is also effectively integrated into the fan. A separate flashback barrier or flame breakdown protection can thus be dispensed with. In particular, the property of radial fans is avoided, which typically lead to deterioration or acceleration of deflagration. A flashback flame would be extinguished in the fan on the fan disks. A pressure wave associated with the flashback could degrade in the fan; an interspace between the fan disks could act as a relaxation device on the pressure wave.

In another preferred configuration of the fan burner, the fan rotor has a fan shaft rotatable about the fan axis, wherein the fan shaft has a shaft axis that runs substantially along the fan axis, wherein the fan disks are connected to each other and/or to the fan shaft by means of at least two spokes.

For example, each fan disk has at least two, preferably at least three radial spokes. The spokes are preferably arranged in a main extension plane of the fan disk and connect, in particular annularly, the fan disk to the fan shaft. In the circumferential direction of the fan disk between the spokes, at least two, preferably at least three, through-holes for supplying the air flow or mixture flow to the interspaces and for distributing it to the interspaces are arranged.

The spokes arranged in a main extension plane of the fan disk may also have a spirally curved shape, deviating from a purely radial path.

For example, the fan disks are configured as annular disks having a concentric recess, in particular having an inner diameter that is significantly larger than the fan shaft diameter. The through-holes form between the fan axis or fan shaft and the inner diameter of the fan disks.

In one embodiment, the fan disks are connected to one another to form a stack of disks unitary in assembly, wherein the stack of disks is connected to the fan shaft as a unit. For example, the fan disks are connected to each other by means of at least two, preferably at least three, axial spokes penetrating the fan disks and holding them at a distance, in particular by means of spacer elements. An axial spoke is to be understood in particular here as an axial connecting rod that is aligned substantially parallel to the axis of rotation of the fan disk or the stack of disks, but is eccentrically offset from the axis of rotation of the fan disk and passes transversely, in particular perpendicularly, through the annular fan disks and connects them.

For example, the concentric recess of a fan disk is identical to its through-hole. In particular, a simple connection device, in particular a shaft-hub connection, in the form of the radial spokes described above, is sufficient for connecting the fan shaft and the stack of disks.

In particular, the shaft axis (also called the shaft longitudinal axis or rotation axis) of the fan shaft coincides with the fan axis.

In a further advantageous configuration of the fan burner, the fan comprises a fan rotor having at least two fan disks, wherein the fan disks have a thickness in the range of 0.8 (± 0.5) millimetres, i.e., in the range of 0.3...1.3 millimetres.

In this context, a thickness is to be understood in particular to mean a measure in the axial direction between a circular or annular front side of the fan disk and a circular or annular rear side of the fan disk.

A fan disk of such thickness represents a targeted compromise between partially contradictory requirements for strength, elasticity, heat capacity, compactness and material savings.

In a further advantageous configuration of the fan burner, the fan comprises a fan rotor having at least two fan disks, wherein the fan disks have a thickness profile having a thickness depending on the radius of the fan disk, in particular variable.

In one exemplary embodiment, a longitudinal section (which is a section through the fan disk along its rotation axis or along the fan axis) through a fan disk having a thickness profile above and below the rotation axis, respectively, may have a rectangular cutting surface. This corresponds to a fan disk having constant thickness (with constant thickness profile) across the radius. In particular, the front side and rear side of the fan disk are parallel to each other.

In a further exemplary embodiment, a longitudinal section through a fan disk having a thickness profile can have a trapezoidal cutting surface above and below the axis of rotation, respectively.

In a further exemplary embodiment, a longitudinal section through a fan disk having a thickness profile can have a semi-elliptical cutting surface above and below the axis of rotation, respectively.

In a further exemplary embodiment, a longitudinal section through a fan disk having a thickness profile can have a flow-favourably curved cutting surface above and below the axis of rotation, respectively.

The fan can be adjusted in particular based on the thickness profile of the fan disk and/or the disk spacing (radially through-flowable interspaces) and/or the number of fan disks to the particularities of the air flow or mixture flow in the fan operation. These particularities may in particular be a unilaterally axially incoming air flow or mixture flow, and/or a flow to be considered compressible or incompressible, and/or a tendency to flow-separation on the fan disks during fan operation, and/or a desired fan characteristic describing the pressure/flow ratio of the fan.

In a further advantageous configuration of the fan burner, the fan comprises a fan rotor having at least two fan disks, wherein the fan disks comprise a material having a high Young's modulus E, preferably E 6000 MPa.

It has been shown that very useful materials are of Young's modulus, in particular of normal polymers and/or glass fibre-reinforced polymers and/or hard plastics. Other very useful materials are ferrous metals and/or non-ferrous metals.

A fan disk of such elasticity resists its elastic deformation sufficiently and remains dimensionally stable for a long period of time and in changing operating conditions.

In a further preferred configuration of the fan burner, the fan comprises a fan rotor having at least two fan disks, wherein the fan disks comprise a material having a high thermal effusivity of b, preferably b 8000.1.s-°5-m-2.K-2.

A fan disk having such a thermal effusivity cools an adjacent combustion sufficiently quickly, and safely extinguishes the flame.

In another preferred configuration of the fan burner, a diameter of an inlet opening of the fan is substantially as large as a radially outer limitation of the through-hole formed in the fan disk.

In particular, a diameter of an inlet opening of the fan is substantially as large as a diameter of a concentric recess of a annular fan disk.

Such a configuration is characterized by low flow losses of the air flow or mixture flow when entering the fan.

The invention also relates to a heater for heating a heat transfer fluid, in particular a heating water for a space heater and/or a drinking water heating, wherein the heater comprises a fan burner according to any of the above descriptions.

Such a heater has all of the above-mentioned advantages, is very quiet in operation, efficient in energy intake for operation of the fan, and very safe from flashback.

Drawing Further embodiments and advantages arise from the following drawing description. In the drawing, exemplary embodiments of the invention are shown. The drawing, description and claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations. It shows schematically and not to scale: Figure 1 a fan burner Figure 2 a Tesla-pump type fan Figure 3 a first fan rotor having parts of the fan housing Figure 4 a second fan rotor having parts of the fan housing Figure 5 a third fan rotor having parts of the fan housing Figure 6 two fan disks Figure 7 six pairs of fan disks.

Figure 1 shows a fan burner 100.

The fan burner 100 serves to provide a fuel-air-mixture flow M by mixing a fuel flow B and an air flow L, as well as to combust the mixture flow M under the formation of a flame F. For example, the fan burner 100 of a heater (not shown here) serves as a heat generator for heating a heat transfer fluid, in particular a heating water for a space heater and/or drinking water heating. The fan burner 100 comprises a fuel passage 102 for supplying the fuel flow B in a fuel flow direction, an air passage 104 for supplying the air flow L in an airflow direction, a mixer 106 for mixing the fuel flow B and the air flow L, a mixture passage 108 for conveying the mixture flow M in a mixture flow direction and a fan 200 for conveying the mixture flow M. The fan burner 100 further comprises a burner mouth 110 and/or burner surface 110; downstream of the burner mouth 110 and/or burner surface 110, a flame F is ignited from the mixture flow M, and the flame F is stabilized. The fan 200 is formed in the manner of a Tesla pump and transfers energy, in particular from a motor-driven fan rotor 220 to the mixture flow M. The fan 200 is disposed in the mixture passage 108 in the mixture flow direction downstream of the mixer 106, or the mixture passage 108 passes through the fan 200. The fan 200 is configured to convey the mixture flow M. Figure 2 shows a Tesla-pump type fan 200 in a perspective view.

The fan 200 (see in particular Figure 2a) comprises a spiral fan housing 240 having two face-end housing walls 242, 244 (one of which is occluded in the illustration shown herein) and an outer, spirally circumferential housing wall 246. The fan 200, in particular the fan housing 240, may be through-flowed by the air flow L or the mixture flow M. The fan housing 240 has an axially (i.e., substantially along the fan axis 202)-oriented inlet opening 204 in the housing wall 242 in the area of the fan axis 202 in the fan housing 240 and a tangentially-oriented exit opening 206 in the housing wall 246 in the outer housing area out of the fan housing 240.

The fan 200 further comprises a fan rotor 220 disposed in the fan housing 240, having a fan shaft 222 and a plurality of circular or annular fan disks 224 (see in particular Figure 2b for details of the fan disks 224 forming a stack of disks). On the fan shaft 222, the axially spaced apart fan disks 224 are disposed and rigidly connected to the fan shaft 222. The fan axis 202 coincides with the rotation axis of the fan rotor 220, with the rotation axis of the fan shaft 222, and with the rotation axis of the fan disks 224. The circular or annular surfaces of the fan disks 224 are configured bladeless. The fan disks 224 each have a perpendicular bisector 226 that run along the fan axis 202. The fan disks 224 are disposed in the fan housing 240 and configured to transfer energy from the fan rotor 220 to the air flow L or mixture flow M during the fan operation.

The fan rotor 220 in Figure 2b comprises eight fan disks 224 rotatable about a fan axis 202, axially spaced apart from one another, having a bladeless surface 225. In particular, the fan 200 may comprise about five to thirty fan disks 224, for example 16 fan disks 224.

Figure 3 shows a first fan rotor 220. Figure 4 shows a second fan rotor 220. Figure 5 shows a third fan rotor 220. Figures 3a, 4a, 5a each depict a sectional view of the fan rotor 220 with parts of the fan housing 240 above the fan axis 202 (symmetry axis) in the longitudinal section. Figures 3b, 4b, 5b, each show a top plan view of a fan disk 224 rotated by 90° against the representation from Figures 3a, 4a, 5a, respectively,.

A longitudinal section through the fan 200 is to be understood herein to mean a section through the fan rotor 220 and/or fan housing 240 along its axis of rotation, or along the fan axis 202.

The fan housing 240 comprises two face-end housing walls 242, 244 and an outer, spirally circumferential housing wall 246. The air flow L or mixture flow M to be conveyed passes through the here axially oriented inlet opening 204 in the end-faced housing wall 242 in the area of the fan axis 202 into the fan housing 240. The air flow L or mixture flow M to be conveyed passes through a tangentially oriented outlet opening 206 (not shown here, outward direction perpendicular to the sign plane) in the housing wall 246 in the outer housing area out of the fan housing 240. The stationary fan housing 240 is sealed against the rotating fan shaft 222 by means of a common seal 248 to prevent leakage.

The fan rotor 220 comprises five bladeless fan disks 224 disposed in the fan housing 240 and rotatable about the fan axis 202. The fan disks 224 are axially spaced apart from one another and have a flat surface 225. The fan disks 224 each have a perpendicular bisector 226 that runs along the fan axis 202. An air flow L or a mixture flow M passes through the fan housing 240, driven by the rotating fan rotor 220, wherein the fan rotor 220 is in turn in particular motor-driven. The fan disks 224 are configured to transfer energy from the fan rotor 220 to the air flow L or mixture flow M. The axially spaced apart fan disks 224 form a disk stack. Adjacent fan disks 224 have throughflowable interspaces 228 between each other. Further through-flowable interspaces 228 are located between the first fan disk 224 of the disk stack and the adjacent axially spaced apart face-end housing wall 242 of the fan housing 240, as well as between the last fan disk 224 of the disk stack and the adjacent axially spaced apart face-end housing wall 244.

The air flow L or mixture flow M to be conveyed is fed, from the inlet opening 204, to the interspaces 228 between the rotating fan disks 224, as well as between rotating fan disk 224 and adjacent housing wall 242, 244, and is distributed throughout the interspaces 228. In the interspaces 228, the air flow L or mixture flow M is accelerated and pushed radially outwards due to frictional forces between the fan disk 224 and air flow L or mixture flow M. The air flow L or mixture flow M collects in the radially outer region of the fan housing 240 and flows towards the exit hole 206 (not shown in Figures 3, 4, 5, but compare Figure 2).

A disk spacing A, i.e., a clear width of the interspace 228 between two adjacent, axially spaced apart fan disks 224 and/or between a fan disk 224 and an adjacent, axially spaced apart housing wall 242, 244 is less than or equal to a safety distance, so the fan burner 100 can be operated particularly efficiently and safely. In particular, conveying the air flow L or the fan flow M is very quiet and efficient while a flashback is safely attenuated or prevented by the fan 200.

In one embodiment, the disk spacing A is less than or equal to a detonation cell size of the mixture flow M under stoichiometric ratios.

If the fan burner 100 is in particular designed to combust the fuel of hydrogen, the disk spacing A is in particular chosen to be less than or equal to 15 millimetres.

In another embodiment, the disk spacing A is less than or equal to a quenching distance of the mixture flow M under stoichiometric ratios.

If the fan burner 100 is in particular designed for the combustion of the fuel hydrogen, the disk spacing A is in particular selected less than or equal to 1.0 (± 0.5) millimetres, i.e., less than or equal to 0.5...1.5 millimetres.

In a further embodiment, the disk spacing A is less than or equal to a maximum experimental safe gap of the mixture flow M under stoichiometric ratios.

If the fan burner 100 is in particular designed for the combustion of the fuel hydrogen, the disk spacing A is in particular selected to be less than or equal to 0.5 (± 0.3) millimetres, i.e., less than or equal to 0.2...0.8 millimetres.

The fan rotor 220 has a fan shaft 222 rotatable about the fan axis 202, wherein the fan shaft 222 has a shaft axis that runs along the fan axis 202.

Each fan disk 224 in Figure 3 is connected to the fan shaft 222 using radial spokes 230 (see the top view in Figure 3b). The spokes 230 are disposed in the plane of the fan disk 224. Between the spokes 230, there are through-holes 232 in the fan disk 224 for passage of air flow L or mixture flow M from one side of the fan disk 224 to the other side of the fan disk 224.

In the fan rotor 220 in Figure 4, the annular fan disks 224 are connected to a disk stack by means of axial spokes 234 (axial link bars 234). The axial spokes 234 are eccentrically offset and in particular parallel to the fan axis 202 through the fan disks 224 and fix them to one another with axial distances A. The disk stack is connected to the fan shaft 222 only via the last fan disk 224 -for example, as in the example above (Figure 3) by means of radial spokes 230. Thus, larger through-holes 232 may be realized to supply the air flow L or mixture flow M to the interspaces 228.

The diameter of the inlet opening 204 of the fan 200 is substantially as large as a radially outer boundary of the through-holes 232 formed in the fan disk 224. For example, an inner diameter of a annular fan disk is approximately as large as the diameter of the inlet opening 204 of the fan 200.

In the fan rotor 220 in Figure 5, the fan disks 224 are directly connected to the fan shaft 222, particularly without spokes. The fan shaft 222 is configured as a hollow shaft through which the incoming air flow L or mixture flow M enters the fan 200. By means of radial through-holes 232 distributed along the hollow shaft sheath surface, the air flow L or mixture flow M flows out of the hollow shaft 222 through the interspaces 228. Each interspace 228 is provided with at least one through-hole 232 in the hollow shaft sheath surface. Alternatively (not shown here), two or more through-holes 232 are provided per interspace 228, circumferentially distributed in the hollow shaft sheath surface.

The radial spokes 230, or rather the fan disks 224 may be particularly adhered, shrunk, welded, soldered, bolted, riveted to the fan shaft 222, or integrally formed with the fan shaft 222.

The fan disks 224 are formed very thin based on their outer diameter. For example, a thickness/diameter-ratio is in the range of 0.002...0.01. For an exemplary diameter of approximately 130 mm, the thickness D of a fan disk 224 would be advantageously in the range of 0.3...1.3 mm.

Figure 6 shows two fan disks 224 having radial spokes 230 for connecting the fan disk 224 to the fan shaft 222 in a top view.

The embodiment in Figure 6a shows an annular fan disk 224 having four, for example rod-shaped radial spokes 230, between which the through-holes 232 form.

The embodiment in Figure 6b shows an annular fan disk 224 having four circular through-holes 232 between which the curved radial spokes 230 form.

The radial spokes 230 support and are connected to the fan shaft 222 (not shown here). The fan shaft 222 may be disposed in the central recess of the fan disk 224.

The diameter of an inlet opening 204 of the fan 200 (see also Figure 3) is advantageously chosen to be substantially as large as the radially outer boundary of the through-hole 232 formed in the fan disk 224.

Figure 7 shows six pairs of differently profiled fan disks 224 in a longitudinal section. A longitudinal section is herein to be understood to mean a section through the fan disk 224 along its axis of rotation, or along the fan axis 202. Only the half of the fan disk 224 located above the rotation axis or the fan axis 202 (symmetry axis) is depicted. The six pairs of differently profiled fan disks 224 show details and alternatives to the fan disks 224 shown in Figures 3, 4, 5. Between each of the two fan disks 224 of a pair of fan disks 224, the forming interspace 228 can be seen.

A fan 200 of a fan burner 100 comprises at least two, preferably at least five fan disks 224 having bladeless surface 225, rotatable around the fan axis 202 and axially spaced apart from one another.

The fan disks 224 have a thickness profile D(R) with a thickness D, particularly variable, depending on the radius R of the fan disk 224. The available volume of the air flow L or mixture flow M in the intermediate space 228 between two fan disks 224 along the radius R of the fan disk 224 can be adjusted by selecting disk spacing A and thickness profile D(R). Depending on the thickness profile D(R) selected, in particular for predetermined operating conditions, such as a fan speed, a flow rate and/or pressure in the air flow L or mixture flow M can also be adjusted in the interspace 228 along the disk radius R and at the exit opening 206 (not shown in Figure 7). Volume, flow rate and/or pressure may thus remain constant, increase or decrease along the radius R. A fan characteristic can be set.

The expression D(R) means that the thickness D can be represented as a function of the radius R. Figure 7a shows a longitudinal section through two adjacent fan disks 224 having rectangular thickness profile D(R). This corresponds to fan disks 224 having constant thickness D across the radius R. The two annular surfaces 225 (front side and rear side) of a fan disk 224 are configured parallel to each other and flat. The interspace 228 between two adjacent fan disks 224 maintains a constant width across the radius.

Figure 7b shows a longitudinal section through two adjacent fan disks 224 having trapezoidal thickness profile D(R). The long base sides of the trapezoid face the rotation axis 202. The two annular surfaces 225 of a fan disk 224 are slightly inclined towards each other and are flat. The interspace 228 between the fan disks 224 widens as the radius R increases.

Figure 7c shows a longitudinal section through two adjacent fan disks 224 having trapezoidal thickness profile D(R). The short base sides of the trapezoid face the rotation axis 202. The two annular surfaces 225 of a fan disk 224 are slightly inclined towards each other and are flat. The interspace 228 between the fan disks 224 tapers as the radius R increases.

Figure 7d shows a longitudinal section through two fan disks 224 having a half-elliptical thickness profile D(R). The minor axes of the half ellipses face the rotation axis 202. The two annular surfaces 225 of a fan disk 224 are slightly inclined towards each other and are convexly formed. The interspace 228 between the fan disks 224 widens as the radius R increases.

Figure 7e shows a longitudinal section through two fan disks 224 having a half-elliptical thickness profile D(R). The minor axes of the half ellipses are facing away from the rotation axis 202. The two annular surfaces 225 of a fan disk 224 are slightly inclined towards each other and are convexly formed. The interspace 228 between the fan disks 224 tapers as the radius R increases.

Figure 7f shows a longitudinal section through two fan disks 224 having flow-favourably curved thickness profile D(R). A section of the fan disk 224 facing the rotation axis 202 and the inlet opening 204 of the air flow L or mixture flow M into the fan 200 (compare Figures 3, 4, 5) is formed asymmetrically with respect to radial extension of the fan disk 224 and shaped rounded at the edges. A single-sided axially incoming air flow L or mixture flow M (coming from the right here) may flow into the interspace 228 with low loss without any flow break.

Claims (1)

1. Claims 1. A fan burner (100) for providing a fuel-air-mixture flow (M) by mixing a fuel flow (B) and an air flow (L), as well as for combusting the mixture flow (M), comprising a fuel passage (102) for guiding the fuel flow (B) in a fuel flow direction, an air passage (104) for guiding the air flow (L) in an air flow direction, a mixer (106) for mixing the fuel flow (B) and the air flow (L), a mixture passage (108) for guiding the mixture flow (Ml in a mixture flow direction, and a fan (200) for conveying the air flow (L) or the mixture flow (M), characterized in that the fan (200) is configured in the manner of a Tesla pump and transfers energy in particular from a motor-driven fan rotor (220) to the air flow (L) or mixture flow (m) 2 The fan burner (100) according to claim 1, characterized in that the fan (200) is configured to convey the mixture flow (M), wherein the fan (200) is disposed in/at the mixture passage (108) in the mixture flow direction downstream of the mixer (106).3. The fan burner (100) according to any one of the preceding claims, characterized in that the fan rotor (220) comprises at least two, preferably at least five fan disks (224) having a bladeless, in particular smoother surface, rotatable about a fan axis (202) and axially spaced apart from one another, wherein the fan disks (224) each have a perpendicular bisector (226), which runs substantially along the fan axis (202), wherein the fan disks (224) are disposed in a fan housing (240), wherein the fan disks (224) are configured to transfer energy from the fan rotor (220) to the air flow (L) or mixture flow (M).4 The fan burner (100) according to claim 3, characterized in that a disk spacing (A) between two adjacent, axially spaced apart fan disks (224) and/or between a fan disk (224) and an adjacent, axially spaced apart housing wall (242, 244) is less than or equal to a safety distance so that a flashback by the fan (200) is safely attenuated or prevented.5. The fan burner (100) according to claim 3 or 4, characterized in that a disk spacing (A) between two adjacent, axially spaced apart fan disks (224) and/or between a fan disk (224) and an adjacent, axially spaced apart housing wall (242, 244) is less than or equal to a detonation cell size of the mixture flow (M) under stoichiometric ratios, in particular less than or equal to 15 millimetres.6. The fan burner (100) according to claim 3 or 4, characterized in that a disk spacing (A) between two adjacent, axially spaced apart fan disks (224) and/or between a fan disk (224) and an adjacent, axially spaced apart housing wall (242, 244) is less than or equal to a quenching distance of the mixture flow (M) under stoichiometric ratios, in particular less than or equal to 1.0 (± 0.5) millimetres.7 The fan burner (100) according to claim 3 or 4, characterized in that a disk spacing (A) between two adjacent, axially spaced apart fan disks (224) and/or between a fan disk (224) and an adjacent, axially spaced apart housing wall (242, 244) is less than or equal to a maximum experimental safe gap of the mixture flow (M) under stoichiometric ratios, in particular less than or equal to 0.5 (± 0.3) millimetres.8 The fan burner (100) according to any one of claims 3 to 6, characterized in that the fan rotor (220) comprises a fan shaft (222) rotatable about the fan axis (202), wherein the fan shaft (222) has a shaft axis that extends substantially along the fan axis (202), wherein the fan disks (224) are connected to each other and/or to the fan shaft (222) by means of at least two spokes (230, 234).9. The fan burner (100) according to any one of the preceding claims, characterized in that the fan (200) comprises a fan rotor (220) having at least two fan disks (224), wherein the fan disks (224) have a thickness (D) in the range of 0.8 (± 0.5) millimetres.10. The fan burner (100) according to any one of the preceding claims, characterized in that the fan (200) comprises a fan rotor (220) having at least two fan disks (224), wherein the fan disks (224) have a thickness profile (D(R)) having a thickness (D) in particular variable, depending on the radius (R) of the fan disk (224).11. The fan burner (100) according to any one of the preceding claims, characterized in that the fan (200) comprises a fan rotor (220) having at least two fan disks (224), wherein the fan disks (224) have a material having a high Young's modulus E, preferably E 6 000 MPa.12. The fan burner (100) according to any one of the preceding claims, characterized in that the fan (200) comprises a fan rotor (220) having at least two fan disks (224), wherein the fan disks (224) have a material having high thermal effusivity of b, preferably b 8 000 J*s-°5.m-2.K-1, particularly preferably b > 10 000 J*s-°5*171-2*Ci 13. The fan burner (100) according to any one of the preceding claims, characterized in that a diameter of an inlet opening (204) of the fan (200) is substantially as large as a radially outer boundary of the through-hole (232) formed in the fan disk (224).14. Heater for heating a heat transfer fluid, in particular a heating water for a space heater and/or a drinking water heating, with a fan burner (100) according to any one of the preceding claims.