GB2606376A - Venturi-type mixing nozzle and combustion device with a Venturi-type mixing nozzle - Google Patents

Abstract

A Venturi-type mixing nozzle 100 for mixing a first fluid with a second fluid has a nozzle body 105 that forms a main flow passage 110 that has an inlet end 120 and an outlet end 130. The main flow passage includes a passage constriction 140 between the inlet end and the outlet end for creation of a negative pressure region 125, and at least one bluff body 150, 151 is arranged in the main flow passage at the passage constriction to create a further low pressure zone 240, 241. At least one lateral inlet opening 220, 221 is arranged at the passage constriction and is at least partly formed in the at least one bluff body and permits an inflow of a second fluid into the main flow passage. The bluff body may promote turbulence (310 Fig. 2) in the first fluid and may ensure that the second fluid entering the main flow passage is surrounded by the first fluid. The mixing nozzle can be used in a combustion device for heating of buildings, and the fuel may be hydrogen. The design of the bluff body/mixing nozzle arrangement may prevent flashback.

Description

Description Title

Venturi-type mixing nozzle and combustion device with a Venturi-type mixing nozzle

Background of the Invention

The present invention relates to a Venturi-type mixing nozzle for mixing of a first fluid with a second fluid, comprising a nozzle body that forms a main flow pas-sage having an inlet end and an outlet end, the inlet end being provided to permit inflow of a first fluid in a main fluid flow direction into the main flow passage, wherein the main flow passage comprises a passage constriction between the inlet end and the outlet end for creation of a negative pressure region in the main flow passage, and wherein at least one lateral inlet opening is provided at the passage constriction to permit inflow of a second fluid into the main flow passage.

Moreover, the present invention relates to a combustion device having such a Venturi-type mixing nozzle.

From the state of the art, a Venturi-type mixing nozzle having a nozzle body with a main flow passage that has an inlet end and an outlet end is known. The main flow passage includes a passage constriction between the inlet end and the outlet end for creation of a negative pressure region in the main flow passage. The passage constriction is provided with a plurality of lateral inlet openings. In operation, a first fluid enters the main flow passage via the inlet end and a second fluid enters the main flow passage via the lateral inlet openings for being mixed with the first fluid in the main flow passage.

Summary of the Invention

The present invention relates to a Venturi-type mixing nozzle for mixing of a first fluid with a second fluid, comprising a nozzle body that forms a main flow passage having an inlet end and an outlet end, the inlet end being provided to permit inflow of a first fluid in a main fluid flow direction into the main flow passage. The -1 - -2 -main flow passage comprises a passage constriction between the inlet end and the outlet end for creation of a negative pressure region in the main flow passage. At least one bluff body is arranged in the main flow passage at the passage constriction, the at least one bluff body extending in radial direction of the main flow passage towards a nozzle body central axis or nozzle body central plane for creation of a low pressure zone that extends in the radial direction of the main flow passage along the at least one bluff body and in the main fluid flow direction downstream of the at least one bluff body. At least one lateral inlet opening is provided at the passage constriction to permit inflow of a second fluid into the 1 0 main flow passage, the at least one lateral inlet opening being at least partly formed in the at least one bluff body.

Advantageously, by integrating the at least one lateral inlet opening into the at least one bluff body the second fluid may reliably be injected close to the nozzle body central axis or nozzle body central plane. By injecting the second fluid close to the nozzle body central axis or nozzle body central plane, the second fluid may directly and entirely be surrounded in the negative pressure region by the first fluid for mixing of the first and second fluids. As a result, injection of the second fluid into the main flow passage and, thus, mixing of the first and second fluids is improved and performed over a significantly reduced longitudinal length of the main flow passage inside of the Venturi-type mixing nozzle.

According to one aspect, the low pressure zone is created such that a first fluid flowing in the low pressure zone has a flow velocity in the low pressure zone that is at least reduced compared to a flow velocity that is otherwise attributed to the first fluid flowing in the negative pressure region.

Thus, the first fluid flowing in the negative pressure region may flow along the nozzle body wall in the low pressure zone, thereby improving boundary layer at-tachment, especially when the second fluid has a significantly lower flow density than the first fluid. As a result, a respective surface area or shear layer between the first and second fluids is enlarged, which enhances the mixing of the first and second fluids. Thus, a respective volume of unburned fluid mix in an associated combustion device may advantageously be reduced, thereby reducing the sever-ity of an unintended ignition inside the Venturi-type mixing nozzle. -3 -

According to one aspect, the at least one bluff body creates at least partly in the negative pressure region turbulences of a first fluid flowing around the at least one bluff body.

The creation of the turbulences further improves boundary layer attachment, thereby reducing an overall pressure drop of the Venturi-type mixing nozzle. More specifically, if the flow density of the second fluid is significantly lower than the flow density of the first fluid, e.g. if the first fluid is air and the second fluid is hydrogen, then a respective second fluid flow will tend to be laminar, having a lower Reynolds number than a given first fluid flow. As a result, the second fluid flow will be more susceptible to boundary layer separation than the first fluid flow. By creating the turbulences and injecting the second fluid close to the nozzle body central axis or nozzle body central plane, the first fluid flow will be closer to the nozzle body wall than the second fluid flow. Because the denser first fluid flow is more turbulent (higher Reynolds number), it is therefore more resistant to boundary layer separation. Therefore, a respective downstream flow in the diverging part of the main flow passage will have better boundary layer attachment, and therefore a more uniform velocity profile and greater flow deceleration, resulting in a lower overall pressure drop. This lower overall pressure drop may ad-vantageously be used to increase the operating range of the Venturi-type mixing nozzle and/or to reduce a required fan power for creation of the first fluid flow.

According to one aspect, the at least one bluff body is adapted to ensure that a second fluid that enters the main flow passage via the at least one lateral inlet opening is fully surrounded by a first fluid flowing in the main flow passage after having entered the main flow passage through the at least one lateral inlet opening.

Thus, a direct and entire surrounding of the second fluid by the first fluid upon its injection into the main flow passage can easily and reliably be achieved.

Preferably, the at least one bluff body is attached to, or integrally formed with, the nozzle body.

Accordingly, a robust and solid nozzle body may be provided, which may advan-tageously be manufactured using cost-effective processes, such as casting or injection moulding. -4 -

According to one aspect, the at least one bluff body comprises a fluid deflection surface that is oriented toward the nozzle body central axis or nozzle body central plane and an end surface that borders the at least one bluff body in the main fluid flow direction to the low pressure zone, wherein the at least one lateral inlet opening comprises a support channel formed in the at least one bluff body.

Thus, the at least one lateral inlet opening may easily and reliably be connected to an associated fluid supply for the second fluid via the support channel formed in the at least one bluff body.

Preferably, the support channel is formed such that the at least one lateral inlet opening is arranged at the fluid deflection surface.

Accordingly, a second fluid may reliably be injected at a radial position inside the main flow passage that is closer to the nozzle body central axis or nozzle body central plane than to a respective nozzle body inner wall.

Preferably, the support channel is formed such that the at least one lateral inlet opening is arranged at the end surface.

Accordingly, a second fluid may directly be injected into turbulences of a first fluid flowing around the at least one bluff body such that mixing of the first and second fluids may further be improved.

According to a variant, the support channel is formed such that the at least one lateral inlet opening is at least arranged partly at the fluid deflection surface and partly at the end surface.

Thus, the support channel and the at least one lateral inlet opening may easily and reliably be manufactured at the at least one bluff body without a risk of de-creasing the at least one bluff body's mechanical rigidity and stability.

In general, the at least one lateral inlet opening may be punctiform or slot-shaped.

Thus, the at least one lateral inlet opening may be manufactured using a cost-effective process, such as e.g. drilling or milling. -5 -

The at least one bluff body may have the shape of a saw tooth, a rounded unsymmetrical tooth, a pyramidal tooth, a dome, a conical tooth, or a wedge-type fin. Alternatively, the at least one bluff body may be pin-shaped and comprise an arc-shaped surface that faces the inlet end. Still alternatively, the at least one bluff body may be wedge-shaped and comprise an arc-shaped or straight surface that faces the nozzle body central axis or nozzle body central plane.

Thus, the at least one bluff body may be provided with a shape selected out of various different available shapes, which may easily be formed in an efficient and uncomplicated manner.

At least one additional bluff body may be arranged in the main flow passage downstream of the at least one lateral inlet opening in the main fluid flow direction.

Such an additional bluff body may advantageously create swirl or turbulence of a second fluid that enters the main flow passage via the at least one lateral inlet opening, thereby further improving mixing of the first and second fluids.

Furthermore, a hydraulic diameter of the at least one lateral inlet opening may be less than the Maximum Experimental Safety Gap of a second fluid that enters the main flow passage via the at least one lateral inlet opening.

If the second fluid is a combustible gas, this advantageously prevents a flame from being able to travel in operation upstream the Venturi-type mixing nozzle into the associated lateral inlet opening, thereby safely preventing a flame flashback event.

By way of example, the first fluid may be air and the second fluid may be a com-bustible gas.

Thus, the Venturi-type mixing nozzle may advantageously be used with a combustion device that is adapted for combustion of a gas/air mixture, e.g. a hydrogen/air mixture.

Accordingly, the present invention also relates to a combustion device with a Venturi-type mixing nozzle as described above. -6 -

In this case, the at least one bluff body of the Venturi-type mixing nozzle may have a shape that is designed dependent on the size of an associated lateral inlet opening, such that the associated lateral inlet opening has a hydraulic diameter that is smaller than a so-called "Maximum Experimental Safety Gap" of the second fluid. This advantageously prevents a flame from being able to travel in operation of the combustion device upstream the Venturi-type mixing nozzle into the associated lateral inlet opening, thereby safely preventing a flame flashback event.

Brief Description of the Drawings

Exemplary embodiments of the present invention are described in detail hereinafter with reference to the attached drawings. In these attached drawings, identical or identically functioning components and elements are labelled with identical ref- erence signs and they are generally only described once in the following descrip-tion.

Fig. 1 shows a sectional view of a Venturi-type mixing nozzle with bluff bodies according to a first embodiment, Fig. 2 shows a schematic view of exemplary flows of first and second fluids in the Venturi-type mixing nozzle of Fig. 1, Fig. 3 shows a further schematic view of the exemplary flows of first and sec-ond fluids in the Venturi-type mixing nozzle of Fig. 1 and Fig. 2, Fig. 4 shows a perspective view of a segment of the Venturi-type mixing nozzle of Fig. 1, Fig. 5 shows a sectional view of the segment of the Venturi-type mixing nozzle of Fig. 4, Fig. 6 shows a sectional view of the Venturi-type mixing nozzle of Fig. 1 with bluff bodies according to a second embodiment, Fig. 7 shows a schematic view of exemplary flows of first and second fluids in the Venturi-type mixing nozzle of Fig. 6, -7 -Fig. 8 shows a perspective view of a segment of the Venturi-type mixing nozzle of Fig. 6, Fig. 9 shows a sectional view of the segment of the Venturi-type mixing nozzle of Fig. 8, Fig. 10 shows a perspective view of a segment of the Venturi-type mixing nozzle of Fig. 1 with a bluff body according to a third embodiment, Fig. 11 shows a sectional view of the segment of the Venturi-type mixing nozzle of Fig. 10, Fig. 12 shows a perspective view of a segment of the Venturi-type mixing nozzle of Fig. 1 with a bluff body according to a fourth embodiment, Fig. 13 shows a sectional view of the segment of the Venturi-type mixing nozzle of Fig. 12, Fig. 14 shows a perspective view of a segment of the Venturi-type mixing noz-zle of Fig. 1 with a bluff body according to a fifth embodiment, Fig. 15 shows a sectional view of the segment of the Venturi-type mixing nozzle of Fig. 14, Fig. 16 shows a perspective view of a segment of the Venturi-type mixing noz-zle of Fig. 1 with a bluff body according to a sixth embodiment, and Fig. 17 shows a sectional view of the segment of the Venturi-type mixing nozzle of Fig. 16.

Detailed Description

Fig. 1 shows an exemplary Venturi-type mixing nozzle 100 with a nozzle body 105 that forms a main flow passage 110. According to one aspect, the Venturi-type mixing nozzle 100 is used for mixing of a combustible gas, e.g. hydrogen, with air in an associated combustion device at a desired concentration or ratio. Such a combustion device may e.g. be used in building heating systems. -8 -

The main flow passage 110 and, more generally, the nozzle body 105 has an inlet end 120 and an outlet end 130. Illustratively, the main flow passage 110 is formed along a longitudinal direction of the nozzle body 105 in an associated main fluid flow direction 190 from the inlet end 120 toward the outlet end 130.

More specifically, the main flow passage 110 in the nozzle body 105 is generally formed as a tubular channel with a smooth inner surface 199.

According to one aspect, the main flow passage 110 has a passage constriction 140 that is arranged between the inlet end 120 and the outlet end 130. The pas-sage constriction 140 is illustratively arranged between the inlet end 120 and the outlet end 130 for creation of a negative pressure region 125 in the main flow passage 110 during operation of the Venturi-type mixing nozzle 100. The negative pressure region 125 in the main flow passage 110 is, only by way of example and for illustration purposes, delimited by means of two dashed lines.

Illustratively, the main flow passage 110 is funnel-shaped between the inlet end 120 and the passage constriction 140 and, thus, having a converging inflow section. Between the passage constriction 140 and the outlet end 130, the main flow passage 110 is illustratively conical and, thus, having a diverging outflow section.

According to one aspect, the passage constriction 140 comprises at least one lateral inlet opening. Preferably, a plurality of lateral inlet openings is provided but, however, only two lateral inlet openings are illustrated and separately labelled with the reference signs 220, 221, for simplicity and clarity of the drawing. In the following description, reference is generally made to one or both of the lateral in-let openings 220, 221, representative for all respectively provided lateral inlet openings.

Furthermore, preferably at least one bluff body is arranged in the main flow pas- sage 110 at the passage constriction 140, i.e. at least partly in the converging in- flow section and partly in the diverging outflow section. Illustratively, a plurality of bluff bodies is provided but, however, due to the sectional view only two bluff bodies are visible and separately labelled with the reference signs 150, 151, for simplicity and clarity of the drawing. In the following description, reference is gen- erally made to one or both of the bluff bodies 150, 151, representative for all re-spectively provided bluff bodies. -9 -

At least one of the bluff bodies 150, 151 may be attached to, or integrally formed with, the nozzle body 105. Alternatively, at least one of the bluff bodies 150, 151 may be attached to, or integrally formed with, a bluff body support that is adapted to be mounted to the nozzle body.

The bluff bodies 150, 151 protrude illustratively from the smooth inner surface 199 of the main flow passage 110 and are preferably attached to, or integrally formed with, the nozzle body 105. In other words, the bluff bodies 150, 151 are formed as bumps or dents on the otherwise smooth inner surface 199 inside of the main flow passage 110 and, thereby, form additional constrictions of the main flow passage 110.

More specifically, the bluff bodies 150, 151 preferably extend in radial direction 107 of the main flow passage 110 towards a nozzle body central axis or nozzle body central plane 290 for creation of associated low pressure zones that extend in the radial direction 107 of the main flow passage 110 along the bluff bodies 150, 151 and in the main fluid flow direction 190 downstream of the bluff bodies 150, 151. A respective low pressure zone that is associated with the bluff body 150 is illustratively labelled with the reference sign 240, and a respective low pressure zone that is associated with the bluff body 151 is illustratively labelled with the reference sign 241. Each one of the associated low pressure zones 240, 241 extends along the respectively associated bluff body 150, 151 and in the radial direction 107 of the main flow passage 110. The low pressure zones 240, 241 in the main flow passage 110 are, only by way of example and for illustration purposes, delimited by means of associated dashed lines.

According to one aspect, the bluff bodies 150, 151 are provided with the lateral inlet openings 220, 221. Illustratively, the bluff body 150 is provided with the lateral inlet opening 220 and the bluff body 150 is provided with the lateral inlet opening 221. Preferably, one bluff body is provided for each lateral inlet opening.

However, at least one bluff body may alternatively also be provided for two or more lateral inlet openings. In other words, it is possible to provide a single bluff body for all lateral inlet openings.

Preferably, the lateral inlet opening 220 is at least partly formed in the bluff body 150. Similarly, the lateral inlet opening 221 is preferably at least partly formed in the bluff body 151. In other words, each one of the lateral inlet openings may be formed at least partly in a respectively associated bluff body.

-10 -According to one aspect, the Venturi-type mixing nozzle 100 is embodied for mixing of a first fluid 210 with a second fluid 230. Therefore, the inlet end 120 is configured to permit inflow of the first fluid 210 in the main fluid flow direction 190 into the main flow passage 110 and the lateral inlet openings 220, 221 are provided at the passage constriction 140 to permit inflow of the second fluid 230 into the main flow passage 110. The first and second fluids 210, 230 are respectively represented by arrows to illustrate associated flow directions thereof 1 0 In an exemplary operation of the Venturi-type mixing nozzle 100, the first fluid 210 enters the main flow passage 110 via the inlet end 120 and the second fluid 230 enters the main flow passage 110 via the lateral inlet openings 220, 221 for being mixed with the first fluid 210 in the main flow passage 110. By way of example, the first fluid 210 is air and the second fluid 230 is a combustible gas, e.g. hydrogen. More specifically, the first fluid 210 that enters the main flow passage via the inlet end 120 backs up in the converging section 140 between the inlet end 120 and the passage constriction 140 such that the negative pressure region 125 is created due to an acceleration of the first fluid 210 by means of the nozzle effect. Since the lateral inlet openings 220, 221 open into the passage constriction 140 at the bluff bodies 150, 151, the second fluid 230 is drawn into the main flow passage 110, where the second fluid 230 is mixed with the first fluid 210.

Illustratively, the second fluid 230 is guided to the lateral inlet openings 220, 221 via associated support channels 227, 229 in the nozzle body 105, which are pro-longated by associated support channels 277, 279 in the bluff bodies 150, 151, all of which are exemplarily arranged at an angle of 90° relative to the nozzle body central axis or nozzle body central plane 290. Thus, the second fluid 230 is guided through the associated support channels 227, 229 via the lateral inlet openings 220, 221 toward the nozzle body central axis or nozzle body central plane 290 until entering the main flow passage 110.

As described above, the bluff bodies 150, 151 are provided for creation of the low pressure zones 240, 241 in the negative pressure region 125 such that the first fluid 210 has a flow velocity in the low pressure zones 240, 241 that is at least re-duced compared to a flow velocity that is otherwise attributed to the first fluid 210 in the negative pressure region 125. More particularly, the bluff bodies 150, 151 are preferably adapted to ensure that the second fluid 230 is fully surrounded by the first fluid 210 after having entered the main flow passage 110 through the lateral inlet openings 220, 221.

Fig. 2 shows a section of the main flow passage 110 with the smooth inner sur-face 199 that is formed by the nozzle body 105 of the Venturi-type mixing nozzle of Fig. 1. Illustratively, the bluff body 150 protrudes from the smooth inner surface 199 of the main flow passage 110 as described above at Fig. 1. The bluff body 150 is preferably attached to, or integrally formed with, the nozzle body 105.

1 0 Fig. 2 further illustrates operation of the Venturi-type mixing nozzle 100 as de- scribed above at Fig. 1, wherein the first fluid 210 flows in the main fluid flow direction 190 in the main flow passage 110 toward, along and at least partly around the bluff body 150. Thereby, the bluff body 150 creates at least partly turbulences 310 of the first fluid 210 flowing around the bluff body 150. Preferably, the turbu- lences 310 are at least created in the negative pressure region 125 of Fig. 1. Fur-thermore, the second fluid 230 is drawn through the support channel 277 and the lateral inlet opening 220 provided in the bluff body 150 into the main flow passage 110 such that the first fluid 210 flows along the smooth inner surface 199 and directly surrounds the second fluid 230 downstream of the bluff body 150. By creating the turbulences 310 of the first fluid 210 around the second fluid 230, mixing of the first and second fluids 210, 230 is significantly improved.

Fig. 3 shows the section of the main flow passage 110 with the smooth inner surface 199 that is formed by the nozzle body 105 of the Venturi-type mixing nozzle 100 of Fig. 1 for further illustrating mixing of the first and second fluids 210, 230.

As described above at Fig. 2, in operation the first fluid 210 flows in the main fluid flow direction 190 in the main flow passage 110 toward, along and at least partly around the bluff body 150. More specifically, the first fluid 210 flows essentially at least partly around the bluff body 150 in the low pressure zone 240 associated with the bluff body 150. The second fluid 230 flows through the support channel 277 and the lateral inlet opening 220 of the bluff body 150 into the main flow passage 110 and is illustratively at least partly deviated by a part of the first fluid 210 that flows along the bluff body 150 into the low pressure zone 240, thereby improving mixing of the first and second fluids 210, 230.

Fig. 4 shows a segment of the Venturi-type mixing nozzle 100 of Fig. 1 that is illustratively only provided with a single bluff body, i.e. the bluff body 150, which is -12 -provided with the lateral inlet opening 220 and configured to form the low pressure zone 240. As described above, the Venturi-type mixing nozzle 100 has the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199.

Fig. 4 further illustrates the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. Illustratively, the support channel 277 is formed as a prolongation of the support channel 227 inside the bluff body 150 up to the lateral inlet opening 220 of the bluff body 150 According to one aspect, the bluff body 150 comprises a fluid deflection surface 420 and an end surface 415. Preferably, the fluid deflection surface 420 is oriented toward the nozzle body central axis or nozzle body central plane 290 of Fig. 1, i.e. on a side of the bluff body 150 that-in Fig. 4 -points away from the nozzle body 105. The end surface 415 illustratively points away from the inlet end and, thus, borders the at least one bluff body 150 in the main fluid flow direction 190 of Fig. 1 to the low pressure zone 240. According to one aspect, the support channel 277 is formed such that the lateral inlet opening 220 is arranged at the fluid deflection surface 420.

Fig. 5 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 4 with the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199. The Venturi-type mixing nozzle 100 illustratively further comprises the bluff body 150, which is provided with the lateral inlet open-ing 220 and configured to form the low pressure zone 240, as well as the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. The bluff body 150 has the fluid deflection surface 420 and the end surface 415 Fig. 5 further illustrates the prolongation of the support channel 227 formed in the nozzle body 105 by means of the support channel 277 inside the bluff body 150, as well as arrangement of the lateral inlet opening 220 on the fluid detection surface 420 of the bluff body 150. Furthermore, the support channel 277 is shown having a hydraulic diameter D that is preferably smaller than a so-called "Maxi-mum Experimental Safety Gap" of the second fluid (230 of Fig. 1 to Fig. 3).

More specifically, the bluff body 150 may have a maximum height -measured in the radial direction 107 of Fig. 1 -, e.g. the height of the end surface 415, that -13 -amounts at least to half of the hydraulic diameter D of the lateral inlet opening 220, and at most to a radial distance between the nozzle body 105 and the nozzle body central axis or nozzle body central plane (290 of Fig. 1) at the lateral inlet opening 220. Furthermore, the bluff body 150 may have a width -measured in circumferential direction of the Venturi-type mixing nozzle 100-that amounts at least to half of the hydraulic diameter D of the lateral inlet opening 220, and at most to twice the hydraulic diameter D. Fig. 6 shows the Venturi-type mixing nozzle 100 of Fig. 1 with the nozzle body 105 that forms the nozzle body central axis or nozzle body central plane 290 and the main flow passage 110 having the smooth inner surface 199. The main flow passage 110 and, more generally, the nozzle body 105 has the inlet end 120 and the outlet end 130, as well as the passage constriction 140. The Venturi-type mixing nozzle 100 further comprises the bluff bodies 150, 151, which are pro- vided with the lateral inlet openings 220, 221 and configured to form the low pres- sure zones 240, 241, as well as the support channels 227, 229 formed in the nozzle body 105 and the support channels 277, 279 formed in the bluff bodies 150, 151. The lateral inlet openings 220, 221 are provided to permit inflow of the second fluid 230 into the main flow passage 110 and the inlet end 120 is pro-vided to permit inflow of the first fluid 210 into the main flow passage 110.

However, in contrast to Fig. 1 where the support channels 277, 279 formed in the bluff bodies 150, 151 are straight and arranged at an angle of 90° relative to the nozzle body central axis or nozzle body central plane 290 according to a first em-bodiment of the bluff bodies 150, 151, they are now kinked relative to the support channels 227, 229 formed in the nozzle body 105, according to a second embodiment of the bluff bodies 150, 151. More specifically, according to the second embodiment the support channels 277, 279 are now angled such that the lateral inlet openings 220, 221 are opened toward the low pressure zones 240, 241.

Fig. 7 shows a section of the main flow passage 110 with the smooth inner surface 199 that is formed by the nozzle body 105 of the Venturi-type mixing nozzle 100 of Fig. 6. Illustratively, the bluff body 150 protrudes from the smooth inner surface 199 of the main flow passage 110 and is preferably attached to, or inte-grally formed with, the nozzle body 105.

-14 -Fig. 7 further illustrates flow of the first fluid 210 in the main flow passage 110, as well as flow of the second fluid 230 through the support channel 277 and the lateral inlet opening 220 into the main flow passage 110. As the lateral inlet opening 220 is opened toward the low pressure zone 240, the second fluid 230 is directly injected into the low pressure zone 240.

Fig. 8 shows a segment of the Venturi-type mixing nozzle 100 of Fig. 6 that is illustratively only provided with a single bluff body, i.e. the bluff body 150, which is provided with the lateral inlet opening 220 and configured to form the low pres-sure zone 240. As described above, the Venturi-type mixing nozzle 100 has the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199.

Fig. 8 further illustrates the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. Illustratively, the sup-port channel 277 is formed as a prolongation of the support channel 227 inside the bluff body 150 up to the lateral inlet opening 220 of the bluff body 150.

According to one aspect, the bluff body 150 comprises the fluid deflection surface 420 and the end surface 415 similar to the bluff body 150 of Fig. 4 and Fig. 5.

However, according to the second embodiment the support channel 277 is formed in contrast to Fig. 4 and Fig. 5 such that the lateral inlet opening 220 is arranged at the end surface 415.

Fig. 9 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 8 with the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199. The Venturi-type mixing nozzle 100 illustratively further comprises the bluff body 150 according to the second embodiment, which is provided with the lateral inlet opening 220 and configured to form the low pres-sure zone 240, as well as the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. The bluff body 150 has the fluid deflection surface 420 and the end surface 415.

Fig. 9 further illustrates the prolongation of the support channel 227 formed in the nozzle body 105 by means of the support channel 277 inside the bluff body 150, as well as arrangement of the lateral inlet opening 220 on the end surface 415 of the bluff body 150. By way of example, the support channel 277 is straight such that the second fluid 230 of Fig. 6 and Fig. 7 is injected out of the lateral inlet -15 -opening 220 in a direction pointing away from the smooth inner surface 199 and out of the low pressure zone 240. However, the support channel 277 as such may also be angled such that the injection is e.g. directed into the low pressure zone 240 in a direction that is more or less parallel to the smooth inner surface 199, for instance.

Fig. 10 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 8 with the bluff body 150, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240. As described above, the Venturi-type mixing nozzle 100 has the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199.

Fig. 10 further illustrates the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. Illustratively, the sup-port channel 277 is formed as a prolongation of the support channel 227 inside the bluff body 150 up to the lateral inlet opening 220 of the bluff body 150. The bluff body 150 comprises the fluid deflection surface 420 and the end surface 415 However, in contrast to Fig. 8 where the end surface 415 is at least approxi-mately perpendicular to the smooth inner surface 199 in the region of the support channel 227 formed in the nozzle body 105 according to the second embodiment of the bluff body 150, the end surface 415 is now angled by a predetermined angle 1000 relative to the smooth inner surface 199 in the region of the support channel 227 formed in the nozzle body 105, according to a third embodiment of the bluff body 150. Illustratively, the predetermined angle 1000 amounts to approximately 60°. Preferably, the predetermined angle 1000 is comprised in the range of 40° to 80°.

Fig. 11 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 10 with the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199. The Venturi-type mixing nozzle 100 illustratively further comprises the bluff body 150 according to the third embodiment, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240, as well as the support channel 227 formed in the nozzle body and the support channel 277 formed in the bluff body 150. The bluff body 150 has the fluid deflection surface 420 and the end surface 415. Fig. 11 further illustrates the predetermined angle 1000 between the end surface 415 and the -16 -smooth inner surface 199 in the region of the support channel 227 formed in the nozzle body 105 according to the third embodiment of the bluff body 150.

Fig. 12 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 4 with the bluff body 150, which is provided with the lateral inlet opening 220 and config-ured to form the low pressure zone 240. As described above, the Venturi-type mixing nozzle 100 has the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199.

Fig. 12 further illustrates the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. Illustratively, the support channel 277 is formed as a prolongation of the support channel 227 up to the lateral inlet opening 220 of the bluff body 150. The bluff body 150 comprises the fluid deflection surface 420 and the end surface 415.

However, in contrast to Fig. 4 where the support channel 277 is formed in the main flow passage 110 entirely inside the bluff body 150 according to the first embodiment of the bluff body 150, the support channel 277 is now at least partly integrated into the end surface 415, according to a fourth embodiment of the bluff body 150. Accordingly, the support channel 277 is formed inside the main flow passage 110 similar to a half-pipe instead of being formed as a closed tube. Thus, in the fourth embodiment the support channel 277 is formed such that the lateral inlet opening 220 is at least arranged partly at the fluid deflection surface 420 and partly at the end surface 415.

It should be noted that the expression "similar to a half-pipe" is merely used to illustrate a possible shaping and configuration of the support channel 277 according to the fourth embodiment. However, this expression should not be construed to limit a respective opening angle of the support channel 277 according to the fourth embodiment to a particular angle. Instead, various different opening angles are equally considered.

Fig. 13 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 12 with the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199. The Venturi-type mixing nozzle 100 illustra-tively further comprises the bluff body 150 according to the fourth embodiment, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240, as well as the support channel 227 formed in the nozzle body and the support channel 277. The bluff body 150 has the fluid deflection surface 420 and the end surface 415. Fig. 13 further illustrates the support channel 277 which is formed similar to a half-pipe according to the fourth embodiment of the bluff body 150.

Fig. 14 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 12 with the bluff body 150, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240. As described above, the Venturi-type mixing nozzle 100 has the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199.

Fig. 14 further illustrates the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. Illustratively, the support channel 277 is formed as a prolongation of the support channel 227 up to the lateral inlet opening 220 of the bluff body 150. The bluff body 150 comprises the fluid deflection surface 420 and the end surface 415.

However, in contrast to Fig. 12 where the support channel 277 is formed inside the main flow passage 110 similar to a half-pipe according to the fourth embodi-ment of the bluff body 150, the support channel 277 is now partly formed in the main flow passage 110 inside the bluff body 150, according to a fifth embodiment of the bluff body 150. Illustratively, in the fifth embodiment a step 1400 is provided such that the support channel 277 forms in the main flow passage 110 a closed tube close to the smooth inner surface 199. The step 1400 may be at- tached to, or integrally formed with, the bluff body 150 according to the fifth em-bodiment.

Fig. 15 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 14 with the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199. The Venturi-type mixing nozzle 100 illustra- tively further comprises the bluff body 150 according to the fifth embodiment, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240, as well as the support channel 227 formed in the nozzle body 105 and the support channel 277. The bluff body 150 has the fluid deflection sur-face 420 and the end surface 415. Fig. 15 further illustrates the support channel 277 which is formed partly similar to a half-pipe and partly similar to a closed tube by means of the step 1400, according to the fifth embodiment of the bluff body 150.

-1 8 -Fig. 16 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 8 with the bluff body 150, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240. As described above, the Venturi-type mixing nozzle 100 has the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199.

Fig. 16 further illustrates the support channel 227 formed in the nozzle body 105 and the support channel 277 formed in the bluff body 150. Illustratively, the sup- 1 0 port channel 277 is formed as a prolongation of the support channel 227 up to the lateral inlet opening 220 of the bluff body 150. The bluff body 150 comprises the fluid deflection surface 420 and the end surface 415.

However, in contrast to Fig. 8 the step 1400 of Fig. 14 is now provided at the end surface 415, according to a sixth embodiment of the bluff body 150. The step 1400 may be attached to, or integrally formed with, the bluff body 150 according to the sixth embodiment.

Fig. 17 shows the segment of the Venturi-type mixing nozzle 100 of Fig. 16 with the nozzle body 105 that forms the main flow passage 110 with the inlet end 120 and the smooth inner surface 199. The Venturi-type mixing nozzle 100 illustratively further comprises the bluff body 150 according to the sixth embodiment, which is provided with the lateral inlet opening 220 and configured to form the low pressure zone 240, as well as the support channel 227 formed in the nozzle body 105 and the support channel 277. The bluff body 150 has the fluid deflection sur-face 420 and the end surface 415. Fig. 17 further illustrates the bluff body 150 that is provided according to the sixth embodiment with the step 1400.

It should be noted that the embodiments described above are merely intended to illustrate preferred realisations of the inventive Venturi-type mixing nozzle without restricting the present invention thereto. Instead, various modifications are contemplated and may be envisaged as long as a respectively provided bluff body is adapted to ensure that a second fluid that enters the main flow passage of the Venturi-type mixing nozzle via an associated lateral inlet opening is fully sur- rounded by a first fluid flowing in the main flow passage of the Venturi-type mix-ing nozzle after having entered the main flow passage through the associated lateral inlet opening.

-19 -Furthermore, various different shapes and geometries of the bluff body may be realised in any of the embodiments described above. For instance, each bluff body may have the shape of a saw tooth, a rounded unsymmetrical tooth, a pyramidal tooth, a dome, a conical tooth, or a wedge-type fin. Alternatively, each bluff body may be pin-shaped and comprise an arc-shaped surface that faces a respective inlet end. Still alternatively, each bluff body may be wedge-shaped and comprise an arc-shaped or straight surface that faces the nozzle body central axis or nozzle body central plane, and so on.

1.0 Furthermore, one or more lateral inlet openings may be punctiform or slot-shaped. Moreover, one or more additional bluff bodies may be arranged in the main flow passage of a given Venturi-type mixing nozzle downstream of one or more lateral inlet openings in the main fluid flow direction, and so on. -20-

Claims (3)

1. Claims 1. Venturi-type mixing nozzle (100) for mixing of a first fluid (210) with a second fluid (230), comprising a nozzle body (105) that forms a main flow passage (110) having an inlet end (120) and an outlet end (130), the inlet end (120) being provided to permit inflow of a first fluid (210) in a main fluid flow direc-tion (190) into the main flow passage (110), wherein the main flow passage (110) comprises a passage constriction (140) between the inlet end (120) and the outlet end (130) for creation of a negative pressure region (125) in the main flow passage (110), wherein at least one bluff body (150, 151) is arranged in the main flow passage (110) at the passage constriction (140), the at least one bluff body (150, 151) extending in radial direction (107) of the main flow passage (110) towards a nozzle body central axis or nozzle body central plane (290) for creation of a low pressure zone (240, 241) that extends in the radial direction (107) of the main flow passage (110) along the at least one bluff body (150, 151) and in the main fluid flow direction (190) downstream of the at least one bluff body (150, 151), and wherein at least one lateral inlet opening (220, 221) is provided at the passage constriction (140) to permit inflow of a second fluid (230) into the main flow passage (110), the at least one lateral inlet opening (220, 221) being at least partly formed in the at least one bluff body (150, 151).
2. 2 Venturi-type mixing nozzle of claim 1, wherein the low pressure zone (240, 241) is created such that a first fluid (210) flowing in the low pressure zone (240, 241) has a flow velocity in the low pressure zone (240, 241) that is at least reduced compared to a flow velocity that is otherwise attributed to the first fluid (210) flowing in the negative pressure region (125).
3. 3. Venturi-type mixing nozzle of claim 1 or 2, wherein the at least one bluff body (150, 151) creates at least partly in the negative pressure region (125) turbu-lences (310) of a first fluid (210) flowing around the at least one bluff body (150, 151). -21 -4. 5. 6. 7. 8. 9. 10.Venturi-type mixing nozzle of any one of the preceding claims, wherein the at least one bluff body (150, 151) is adapted to ensure that a second fluid (230) that enters the main flow passage (110) via the at least one lateral inlet opening (220, 221) is fully surrounded by a first fluid (210) flowing in the main flow passage (110) after having entered the main flow passage (110) through the at least one lateral inlet opening (220, 221).Venturi-type mixing nozzle of any one of the preceding claims, wherein the at least one bluff body (150, 151) is attached to, or integrally formed with, the nozzle body (105).Venturi-type mixing nozzle of any one of the preceding claims, wherein the at least one bluff body (150) comprises a fluid deflection surface (420) that is oriented toward the nozzle body central axis or nozzle body central plane (290) and an end surface (415) that borders the at least one bluff body (150) in the main fluid flow direction (190) to the low pressure zone (240), and wherein the at least one lateral inlet opening (220) comprises a support channel (277) formed in the at least one bluff body (150).Venturi-type mixing nozzle of claim 6, wherein the support channel (277) is formed such that the at least one lateral inlet opening (220) is arranged at the fluid deflection surface (420).Venturi-type mixing nozzle of claim 6, wherein the support channel (277) is formed such that the at least one lateral inlet opening (220) is arranged at the end surface (415).Venturi-type mixing nozzle of claim 6, wherein the support channel (277) is formed such that the at least one lateral inlet opening (220) is at least arranged partly at the fluid deflection surface (420) and partly at the end surface (415).Combustion device with a Venturi-type mixing nozzle (100) according to any one of the preceding claims.