GB2566143A

GB2566143A - Venturi nozzle, combustion device incorporating same and building heating system having such a combustion device

Info

Publication number: GB2566143A
Application number: GB1810193.1A
Authority: GB
Inventors: Gregorius Thorsten
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-06-22
Filing date: 2018-06-21
Publication date: 2019-03-06
Also published as: GB201810193D0; DE102017210492A1

Abstract

A venturi nozzle 1 has a main flow passage 2, inlet 3 and outlet 4 ends, an inlet cross-sectional surface 5 and an inlet central axis 6. An air directing element 20 extends along the inlet central axis in the inlet end, and is within an imaginary three-dimensional projection resulting from a projection of the inlet cross-sectional surface in the direction of the inlet central axis. The air directing element is used to calm the flow of fluids through the venturi and reduce noise. The air directing element may screen an outer flow region 10 from an inner flow region 9, and be a hollow cylinder or cone that can be centered relative to the inlet axis. The invention further relates to a combustion device having a venturi nozzle and a building heating system having such a combustion device.

Description

Title

Venturi nozzle, combustion device incorporating same and building heating system having such a combustion device

Prior art

The invention relates to a Venturi nozzle as specified in claim 1, a combustion device incorporating such a Venturi nozzle as specified in claim 11 and a building heating system having such a combustion device as specified in claim 12.

In the prior art, Venturi nozzles are used to mix two fluids with one another. To this end, Venturi nozzles have a main flow passage which has an inlet end and an outlet end. A taper or passage constriction is typically provided between the inlet end and outlet end. The first fluid backs up in the region between the inlet end and the taper. A negative pressure occurs in the region of the passage constriction, i.e. and also just downstream of it, due to the first fluid having been accelerated by the nozzle effect. Since an outlet pipe opens into the main flow passage in this region, a second fluid can be drawn in via the outlet pipe and continually mixed with the first fluid.

The two fluids to be brought together may be liquid or gaseous respectively. In the case of Venturi nozzles operating with a gas/air mixture, air is usually used as the first fluid and a combustible gas as the second fluid.

Venturi nozzles are used in combustion devices, for example. The latter are in turn also used in building heating systems, amongst other things.

A disadvantage of the prior art systems is that due to high flow speeds and the nozzle effect, flow-induced noise occurs at the passage constriction, for example whistling noises. These are annoying and to a certain extent also detrimental to health.

The objective of the invention, therefore, is to propose a simple and, as far as possible, also retrofittable solution by means of which flow-induced noise in Venturi nozzles can be reduced with little effort and expense.

Disclosure of the invention

The main features of the invention are specified in the characterising part of claim 1 and claims 11 and 12. Optional features constitute the subject matter of claims 2 to 10 and the following description.

The invention relates to a Venturi nozzle having a main flow passage which has an inlet end and an outlet end, an inlet cross-sectional surface and an inlet central axis being defined by the inlet end and the section of the main flow passage adjoining it, and an air directing element extending in the direction of the inlet central axis is disposed on the inlet end, the air directing element being disposed within an imaginary three-dimensional projection resulting from a projection of the inlet cross-sectional surface in the direction of the inlet central axis.

Due to the air directing element on the inlet end, the inflowing first fluid is calmed so that flow-induced noise is reduced due to the reduction of turbulence. The air directing element is preferably a separable or separate component. This being the case, it may be used as and when necessary and may also be retrofitted, for example.

A passage constriction is preferably provided in the main flow passage between the inlet end and the outlet end. This enables a negative pressure to be generated in the region of the passage constriction. The inlet end may be regarded as being the region of the main passage up to the passage constriction and the outlet end as being the region after the passage constriction. The internal wall of the main passage is preferably of a smooth-walled design. The passage constriction may be provided as a conical taper, including, for example, two cones directed towards one another which merge with one another at the point of their smallest diameter.

The main flow passage should be provided in the form of a nozzle body. It may have a connector geometry on the inlet end and optionally also on the outlet end for additional pipes. In this respect, connector flanges are preferred. It is preferable to provide a pipe transition without any change in cross-section.

Based on a more specific embodiment, an outlet pipe opens into the main flow passage between the inlet end and outlet end, preferably in the region of the passage constriction. A second fluid can be drawn in via this outlet pipe. Based on a preferred embodiment, an annular internal groove is provided in the main flow passage into which the outlet pipe opens. The second fluid is therefore distributed around the circumference of the main flow passage, in particular before it is entrained by the first fluid.

Based on one optional feature, the air directing element is disposed between the inlet central axis and the imaginary side face of the imaginary three-dimensional projection. In this position, it is able to calm the flow and a laminar flow distribution is obtained. The imaginary side face and the imaginary three-dimensional projection respectively are not a physical constituent part of the Venturi nozzle but are used exclusively as an imaginary aid for defining positions of other components of the Venturi nozzle.

The air directing element preferably screens an inner flow region from an outer flow region, the inner flow region being disposed closer to the inlet central axis than the outer flow region. This primarily prevents fluid migrating outwards from the core of the pipe and vice versa. This contributes to a laminar flow distribution and a reduction in flow-induced noise in the Venturi nozzle.

In one variant, the air directing element is provided in the form of a hollow cylinder or hollow cone. This results in active calming of the flow around the entire pipe circumference and prevents cross-flows. If a hollow cone is used, its conicity should be slight. A cone enables the otherwise decreasing flow speed on the pipe surface to be increased relative to the core speed for example, for which purpose it must be oriented so that it diverges in the flow direction. A more harmonious flow speed then prevails across the cross-section downstream of the air directing element.

Based on one specific embodiment, the external diameter of the air directing element is smaller than the diameter of the inlet cross-sectional surface. As a result, the flowcalmed fluid continues in this manner inside the main flow passage .

Based on a special dimensioning, the external diameter and/or the internal diameter of the air directing element is substantially the same size as the smallest diameter of the main flow passage, preferably the external diameter and/or the internal diameter is in the region of ± 20% of the smallest diameter of the main flow passage, more preferably in the region of ± 10% of the smallest diameter of the main flow passage. This creates order between or calms the core flow and outer flow very effectively relative to one another and little flow-induced noise is generated in the main flow passage.

A high degree of noise prevention is also obtained by an embodiment in which the air directing element is centred relative to, preferably disposed coaxially with, the inlet central axis. It has also proved to be of advantage if the air directing element is centred relative to, preferably disposed coaxially with, the passage constriction.

The air directing element preferably has no moving parts. It is therefore robust and reguires little maintenance.

Based on one particular embodiment, the air directing element is fixed relative to the main flow passage by means of a retaining element. This enables it to be held in the correct position. Such a retaining element should extend parallel with the inlet central axis. It is therefore of a stable design and has a low flow resistance. The retaining element itself therefore becomes an air directing element.

Its function is preferably to prevent swirling flows.

Based on one special embodiment, an inlet pipe with an internal face is connected to the inlet end and the air directing element is disposed at a distance apart from the internal face. This results in particularly good calming of the flow. The optional retaining element may extend between the internal face and the air directing element, for example .

As another option, a passage constriction is provided in the main flow passage between the inlet end and the outlet end and the air directing element is disposed at a distance from the passage constriction. Calming of the flow therefore takes place upstream of the passage constriction already and the acceleration and tapering of the fluid jet in the passage constriction take place harmoniously with little noise generation. The air directing element preferably lies inside a cylindrical pipe section.

Another embodiment is proposed in which the air directing element is disposed at a distance from the inlet end and outside the main flow passage. The air directing element can be mounted in this position at little cost and also in existing systems. For example, intervention in the construction of the main flow passage and hence its production tools is not actually necessary.

The invention further relates to a combustion device having a Venturi nozzle of the type described above and below, and an inlet pipe for a first fluid is connected to the inlet end and an outlet pipe for a second fluid opens into the main flow passage between the inlet end and the outlet end.

Such a Venturi nozzle enables the first and second fluid to be continually mixed, in particular before being ignited.

Based on one special variant, the first fluid is a fluid containing oxygen. The first fluid is preferably gaseous. The first fluid may be air, for example. The second fluid is preferably a fluid containing fuel. The second fluid may be a gaseous fluid in particular. In this manner, a wellmixed and cleanly combusting mixture may be provided which in particular can be also be produced continually until just before ignition but still outside of a combustion chamber .

At the intake end, the inlet pipe is preferably connected to a fluid storage means or a fluid source containing the first fluid. This enables the first fluid to be directed to the main passage. At the intake end, the outlet pipe is preferably connected to a storage means or pipe containing the second fluid. This enables the second fluid to be directed via the outlet pipe to the main passage.

Based on one embodiment, the outlet end of the main flow passage is fluidically connected to a combustion chamber. A combustion chamber prevents uncontrolled changes in the mixture to be combusted and enables the heat to be selectively directed to heat receiving means.

The invention further relates to a building heating system having a combustion device as described above and below and a storage means or a pipe with a heat transfer medium, preferably water, which can be heated by means of the combustion device. Due to the quiet Venturi nozzle, the building heating system proposed by the invention can also be used in areas that are sensitive to noise. In particular, this applies not only to closed plant rooms but also to water heaters in the living area, for example.

Other features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of an exemplary embodiment given with reference to the drawing.

Fig. 1 illustrates a longitudinal section through a Venturi nozzle having an air directing element.

Fig. 1 illustrates a longitudinal section through a Venturi nozzle 1 having an air directing element 20. The Venturi nozzle 1 comprises a nozzle body 15 with a main flow passage 2 extending from an inlet end 3 to an outlet end 4. The nozzle body 3 has a first connector geometry 16 on the inlet end and a second connector geometry 17 on the outlet end 4 for additional pipes. The connector geometries 16, 17 are respectively provided in the form of a connector flange .

Between the inlet end 3 and the outlet end 4, the nozzle body 15 forms a passage constriction 13 in the main flow passage 2. An outlet pipe 14 opens into the main flow passage 2 between the inlet end 3 and outlet end 4, in particular in the region of the passage constriction 13.

The passage constriction 13 has a tapered ramp, a virtually cylindrical middle section and a pressure-reducing ramp.

The tapered ramp is steeper than the pressure-reducing ramp .

In the passage constriction 13, an annular internal groove is provided in the main flow passage 2 into which the outlet pipe 14 opens. It lies in the middle section of the passage constriction 13 in particular. The internal groove 18 is slit-shaped, i.e. deeper than it is wide. The second fluid is therefore distributed around the circumference of the main flow passage 2, in particular before it is entrained by the first fluid flowing through the main flow passage 2.

An inlet cross-sectional surface 5 and an inlet central axis 6 are defined by the inlet end 3 and the section of the main flow passage 2 adjoining it. An air directing element 20 extending in the direction of the inlet central axis 6 is disposed on this inlet end 3. The air directing element 20 is disposed within an imaginary threedimensional projection 7 resulting from a projection of the inlet cross-sectional surface 5 in the direction of the inlet central axis 6. As may be seen, the air directing element 20 is disposed between the inlet central axis 6 and the imaginary side face 8 of the imaginary threedimensional projection 7. In particular, the external diameter of the air directing element 20 is smaller than the diameter of the inlet cross-sectional surface 5. The air directing element 20 screens an inner flow region 9 from an outer flow region 10, the inner flow region 9 being disposed closer to the inlet central axis 6 than the outer flow region 10.

The air directing element 20 in this instance is provided in the form of a hollow cylinder and has no moving parts.

However, a hollow cone would be conceivable, preferably with a slight conicity. The diameter of such a cone should become smaller in the flow direction of the first fluid.

Hollow cones include both variants in which the internal surface and the external surface are of a cone-shaped design and variants in which one of the two surfaces is cylindrical and the other one is conical.

The cylindrical air directing element 20 is of a very thinwalled design so that its external diameter and internal diameter are substantially the same size as the smallest diameter of the main flow passage 2. As may be seen, the external diameter and the internal diameter differ from the smallest diameter of the main flow passage by no more than ± 20 %. A maximum variance of ± 10 % from the smallest diameter of the main flow passage 2 is preferred.

As may also be seen, the air directing element 20 is centred and is disposed coaxially with the inlet central axis 6. To this end, the air directing element 20 is held fixed relative to the main flow passage 2 by means of a retaining element 21. The retaining element 21 extends parallel with the inlet central axis 6.

An inlet pipe 11 with an internal surface 12 is connected to the inlet end 3. An inner pipe transition without a change in cross-section is provided between the inlet pipe and the main flow passage. The air directing element 20 is spaced at a distance apart from the internal surface 12 of the inlet pipe 11. The air directing element 20 also lies in a cylindrical pipe section and is spaced back from the passage constriction 13. In particular, the air directing element 20 is disposed at a distance apart from the inlet end 3 and outside the main flow passage 2.

The invention is not restricted to one of the embodiments described above but may be adapted in numerous ways.

All of the features and advantages found in the claims, description and drawing, including structural details, spatial layouts and method steps, may be construed as essential to the invention both individually and in a range of different combinations.

Claims

1. Venturi nozzle (1) having a main flow passage (2) which has an inlet end (3) and an outlet end (4), an inlet cross-sectional surface (5) and an inlet central axis (6) being defined by the inlet end (3) and the section of the main flow passage (2) adjoining it, characterised in that an air directing element (20) extending in the direction of the inlet central axis (6) is disposed on the inlet end (3), the air directing element (20) being disposed within an imaginary three-dimensional projection (7) resulting from a projection of the inlet cross-sectional surface (5) in the direction of the inlet central axis (6).

2. Venturi nozzle (1) as claimed in claim 1, characterised in that the air directing element (20) is disposed between the inlet central axis (6) and the imaginary side face (8) of the imaginary threedimensional projection (7).

3. Venturi nozzle (1) as claimed in one of claims 1 or 2, characterised in that the air directing element (20) screens an inner flow region (9) from an outer flow region (10), the inner flow region (9) being disposed closer to the inlet central axis (6) than the outer flow region (10).

4. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that the air directing element (20) is provided in the form of a hollow cylinder or hollow cone.

5. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that the external diameter of the air directing element (20) is smaller than the diameter of the inlet cross-sectional surface (5).

6. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that the external diameter and/or the internal diameter of the air directing element (20) is substantially the same size as the smallest diameter of the main flow passage (2).

7. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that the air directing element (20) is centred relative to the inlet central axis (6).

8. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that an inlet pipe (11) with an internal surface (12) is connected to the inlet end (3) and the air directing element (20) is disposed at a distance apart from the internal face (12).

9. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that a passage constriction (13) is provided in the main flow passage (2) between the inlet end (3) and the outlet end (4) and the air directing element (20) is disposed at a distance apart from the passage constriction (13).

10. Venturi nozzle (1) as claimed in one of the preceding claims, characterised in that the air directing element (20) is disposed at a distance apart from the inlet end (3) and outside the main flow passage (2).

11. Combustion device having a Venturi nozzle (1) as claimed in one of the preceding claims, wherein an inlet pipe (11) for a first fluid is connected to the inlet end (3) and an outlet pipe (14) for a second fluid opens into the main flow passage (2) between the inlet end (3) and the outlet end (4).

12. Building heating system having a combustion device as claimed in claim 11 and a storage means or a pipe with a heat transfer medium which can be heated by the combustion device.