EP3822539A1 - Dispositif de mélange pour un appareil de chauffage par soufflerie - Google Patents

Dispositif de mélange pour un appareil de chauffage par soufflerie Download PDF

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Publication number
EP3822539A1
EP3822539A1 EP20200059.2A EP20200059A EP3822539A1 EP 3822539 A1 EP3822539 A1 EP 3822539A1 EP 20200059 A EP20200059 A EP 20200059A EP 3822539 A1 EP3822539 A1 EP 3822539A1
Authority
EP
European Patent Office
Prior art keywords
fuel
mixing device
fuel nozzle
flow
tapering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20200059.2A
Other languages
German (de)
English (en)
Inventor
Markus Wacker
Albrecht Schaefer
Patrick Glaser
Steffen Benz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP3822539A1 publication Critical patent/EP3822539A1/fr
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/46—Details, e.g. noise reduction means
    • F23D14/62—Mixing devices; Mixing tubes
    • F23D14/64—Mixing devices; Mixing tubes with injectors

Definitions

  • the invention relates to a mixing device for a fan-operated heater with a burner, to which the mixing device provides a mixture of fuel and combustion air over a larger power range.
  • the mixing device according to the invention with an air path having a constriction through which combustion air can be sucked in, with a fuel nozzle through which fuel can be supplied, and with a body influencing a fluid flow in the flow path of the fuel, is characterized in that the body and / or the Fuel nozzle is equipped with means or are that generate a turbulent flow.
  • the fuel-air mixture can be adjusted through the geometric relationships in the area of the constriction in the airway and through the position of the body in the fuel opening.
  • the power of the heater is then modulated by modulating the speed of the fan that draws in the fuel-air mixture.
  • the mixing ratio of fuel to air remains constant over a modulation range of about 1:10.
  • the modulation range or the power modulation is to be understood as meaning that a heater with a power of a lower power level up to can be operated at an upper level of performance. With a modulation range of 1:10, this corresponds, for example, to a power modulation of 2 kW to 20 kW.
  • the invention is based on the knowledge that at low power the fuel volume flow decreases more sharply than the air volume flow due to boundary layer growth in the area of the fuel nozzle, which results in a fuel-air mixture that is set too lean.
  • the invention starts precisely in this area in which a turbulent fuel flow is created through targeted measures.
  • the modulation range can thus be extended to lower powers and leads to a total range of about 1:14.
  • the means can be implemented simply in that at least one step is formed on the body and / or on the fuel nozzle.
  • the body can preferably have a widening area which is adjoined by a tapering area in the direction of flow.
  • the widening area can be implemented in a simple configuration by means of the step.
  • the fuel nozzle can have a tapering region to which, viewed in the direction of flow, one or the step adjoins.
  • the tapering area of the body and the tapering area of the fuel nozzle are preferably located opposite one another, at least in some areas. In this way, the effects couple.
  • the degree of turbulence generation can be increased if the tapering area of the body has an apex angle enclosing the tapering which is smaller than an apex angle caused by the tapering area of the Fuel nozzle is formed. It is advantageous if the tip angle of the body is 1 ° to 10 ° smaller than the tip angle of the fuel nozzle. An acceleration of the fuel fluid occurs within this range of values, which means that a turbulent flow can be expected. If only a smaller range of values of 2 ° to 5 ° of the apex angles to one another is tolerated, it is ensured that the flow remains turbulent even at low fuel flow velocities.
  • the tip angle of the body is 3 ° smaller than the tip angle of the fuel nozzle.
  • the geometric and thus the hydraulic conditions are optimal and the flow speed of the fuel can be reduced to a minimum, at which turbulence nevertheless occurs in the flow.
  • Turbulence in the flow can be increased if the step formed on the body is arranged within or within a tapering region of the fuel nozzle.
  • the degree of turbulence in the flow can be increased further.
  • the invention also relates to a heater with at least one burner and a fan, the speed of which can be changed for the purpose of power modulation, and with a mixing device according to the invention.
  • a heater 10 is shown schematically, which has a fan 12, a burner 14 and a mixing device 16 for a fuel-air mixture.
  • the mixing device 16 is shown schematically in FIG Figure 2 in which it can be seen that air 20 (shown by an arrow) flowing in in the region of a constriction 18 is supplied with fuel 22 (also shown by an arrow) via an opening 24.
  • FIG. 1 further assemblies of the heater 10 according to the invention are shown.
  • the fuel 22 is fed to the mixing device 16 via a line 30 via a fuel line 26 and a fuel control valve 28.
  • the fuel regulating valve 28 is constructed in such a way that it regulates the fuel to a value that is proportional to the ambient pressure, to an equal value or to a substantially equal value, regardless of its inlet pressure.
  • the line 30 is shown here as a separate line. However, it can also, in particular when the fuel control valve 28 is connected directly to the mixing device 16, be designed like an internal passage.
  • the fuel 22 is mixed with the inflowing air 20 in an air path 31, sucked in by the fan 12 and fed to the burner 14 via a feed hood 32.
  • a heat exchanger 34 is arranged, to which a flow line 36 and a return line 38 for heating water are connected.
  • the heat exchanger 34 has the hot exhaust gas flowing through it, cools it down and feeds it to an exhaust gas line 40 which opens into an exhaust gas outlet 42.
  • a controller 44 and an expansion vessel 46 are also accommodated in the heater 10.
  • further assemblies such as an additional domestic water heat exchanger or various pumps and mixers, can also be provided.
  • FIG 2 the mode of operation of the heater 10 according to the invention is shown.
  • the fan 12 sucks in a fuel-air mixture via the mixing device 16 according to the invention and conveys it to the burner 14, on the underside of which a flame 50 monitored by a flame monitoring device 48 burns.
  • the mixing device 16 according to the invention has an air path in the form of a Venturi tube, at the inlet 52 of which ambient air is sucked in and accelerated up to the constriction 18.
  • the fuel 22 is provided under a defined pressure in order to then be sucked in through the opening 24 essentially in the direction of flow. This is where the Venturi effect helps, according to which the suction of the fuel is favored by the fast flowing air.
  • the pressure ratios are set so that the ambient pressure of the air 20 supplied and the pressure of the fuel 22 are almost the same and they are brought together in the constriction 18 in the correct mixing ratio.
  • the heating device 10 can be modulated over a power range from a small power to a high power.
  • the speed of the fan 12 is varied from low speeds to higher speeds. Due to the Venturi effect in the area of the constriction 18, the fuel 22 is sucked in directly.
  • the fuel 22 is fed through a fuel nozzle 54 ( Figure 3 ) supplied.
  • the fuel nozzle 54 forms an extension or a termination of the line 30.
  • the opening 24 forms the termination of the fuel nozzle 54.
  • a body 56 is located inside the fuel nozzle 54 in the flow path of the fuel 22 arranged, which influences the fluid flow of the fuel 22.
  • one end 58 of the body 56 protrudes through the opening 24 of the fuel nozzle 54.
  • the body 56 has a shaft 60, via which the body 56 can be fastened in the fuel nozzle 54.
  • the position of the body 56 can be varied and fixed in accordance with the double arrow 62.
  • the end 58 of the body 56 is conical, so that the opening 24 is more or less exposed when it is displaced along the double arrow 62. As a result, more or less fuel 22 can then be mixed into the combustion air 20. Once set, the position should no longer be changed. Changes are only necessary if, for example, the type of fuel is changed or an age-appropriate drift of the system is noticeable.
  • the heater is operated with a high output, a correspondingly high speed of the fan 12 ensures high flow speeds in the mixing device 16 and thus turbulent flow conditions.
  • the mixing device 16 is set to these turbulent flow conditions, and the correct mixing ratio between fuel and combustion air is provided. If a lower output is now demanded from the heater 10, the flow velocities of the combustion air 20 and of the fuel 22 in the area of the mixing device 16 decrease.
  • the invention is based on the knowledge that laminar flow components can develop due to the lower flow velocities. These influence and shift the mixing ratio. According to the invention, it is therefore proposed to equip the body 56 and / or the fuel nozzle 54 with means 64 which generate a turbulent flow. This turbulence should be maintained especially at low flow velocities.
  • a step 66 is formed on the body 56 as one possibility of such a means 64.
  • part of the flowing fuel 22 is blocked by this step 66, on the other hand, there is a tear-off edge 68 at the transition from the step 66 to the elongated shape of the body 56. In this way, nuclei for a turbulent flow are formed in the fuel nozzle 54.
  • the fuel nozzle 54 also has a step 70 in the region of its opening 24, which step is designed in the form of a collar that is smaller than the opening 24. On the one hand, this creates a further tear-off edge, and on the other hand, the narrowing in the area of the opening 24 forces a higher flow velocity. Both means that promote turbulence.
  • the air path 31, the fuel nozzle 24 and the body 56 are arranged rotationally symmetrical and concentric to one another. In other embodiments, however, this can also be deviated from. Structures with an oval or angular cross section are also conceivable.
  • the end 58 of the body 56 is conical.
  • This tapering area 72 of the body 56 directly adjoins the step 66 in the exemplary embodiment. This has the advantage that the tear-off edge 68 is more clearly formed.
  • FIG 4 are the geometric relationships of the first embodiment according to Figure 3 , which influence the path of the fuel 22, shown in more detail.
  • the fuel nozzle 54 with the internal body 56 can be seen in section. It can also be seen that the tapering area 72 of the body 56 lies opposite the tapering area 74 of the fuel nozzle 54 in some areas. This creates an imagination Truncated-cone-almond-shaped flow path 76 directed towards opening 24.
  • the outer boundary of this flow path 76 is formed by the apex angle ⁇ of the tapering region 74 of the fuel nozzle 54.
  • the inner limitation of the flow path 76 is formed by the apex angle ⁇ of the tapering region 72 of the body 56.
  • the tip angle ⁇ of the body 56 is smaller than the tip angle ⁇ of the fuel nozzle 54. This also results in a flow path 76 which becomes narrower in cross section and which further accelerates the flow of the fuel 22.
  • the angle ⁇ of the body 56 is selected to be 3 ° larger than the angle ⁇ of the fuel nozzle 54. This brings about an optimal acceleration of the fuel 22, which is positive over a larger speed range covered by the speed of the fan 12 affects the formation of turbulence.
  • step 20 at the opening 24 is reduced from an outer diameter 78 to an inner diameter 80.
  • the optimal reduction in diameter is 20-30%.
  • the step 66 on the body 56 is created by partially reducing the diameter of the shaft 60 by 40-50% of the shaft diameter 82 to a reduced diameter 84. As a result of this partial reduction in diameter, an enlargement of the cross section of the flow path 76 is achieved in this reduced area 85, which increases in size again with the beginning of the tapering area 74 of the fuel nozzle 54. The flow rate of the fuel 22 is therefore first reduced in this area and then increased again. Only then is the step 66 and the tear-off edge 68 of the body 56 reached. To achieve such a flow profile, the length 86 of the tapered area 72 of the body 56 corresponds to between 50% and 75% of the length 88 of the tapered area 74 of the fuel nozzle 54. Depending on the basic setting, however, the end 58 of the body protrudes from the opening 24 of the fuel nozzle 54 out.
  • the fuel nozzle 54 and the body 56 are made of the same material. They are manufactured with high precision as injection molded parts. However, it is also possible to manufacture these parts from other and also from different materials, for example ceramic and / or steel. It is important to ensure that the materials have the same coefficients of thermal expansion as possible. In this way it can be ensured that the flow conditions are not influenced by temperature fluctuations.
  • the body 56 after Figure 6 has an area 85 that is not excessively reduced and then merges into an enlarged area. As a result, level 66 is less pronounced. Furthermore, the tapering region 72 of the body 56 does not directly adjoin the step 66 of the body 50. In addition, the tapering region 85 is not implemented as a circumferential diameter reduction, but rather as two opposing flattened areas 90.
  • the tapering area 72 of the body 56 is profiled by a helical surface structure 92.
  • the fuel 22 receives a swirl when it emerges from the fuel nozzle 54, which it also transfers into the air path 31 and generates turbulence or keeps it stable.
  • the body 56 after Figure 7 has a helical profile 94 on its surface in the area of the shaft 60. A reduced area 85 is dispensed with here.
  • Figure 8 is a body 56 analogous to body 56 according to Figure 5 shown, wherein the tapered region 72 of the body 56 is provided with spaced apart circular rings 96.
  • the step 70 is attached to the fuel nozzle 54 at a distance from the opening 24 in the tapered region 74 of the fuel nozzle 54.
  • the step 70 can consist of a simple circular ring. However, it can also have further openings in its circular ring structure.
  • the fuel nozzle 54 after Figure 11 corresponds to the fuel nozzle 54 of the exemplary embodiment according to FIGS Figures 3 and 4 . It is shown here again individually so that the step 70 of the fuel nozzle 54 can be seen better.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Gas Burners (AREA)
EP20200059.2A 2019-11-12 2020-10-05 Dispositif de mélange pour un appareil de chauffage par soufflerie Pending EP3822539A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102019217419.1A DE102019217419A1 (de) 2019-11-12 2019-11-12 Mischeinrichtung für ein gebläsebetriebenes Heizgerät

Publications (1)

Publication Number Publication Date
EP3822539A1 true EP3822539A1 (fr) 2021-05-19

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP20200059.2A Pending EP3822539A1 (fr) 2019-11-12 2020-10-05 Dispositif de mélange pour un appareil de chauffage par soufflerie

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EP (1) EP3822539A1 (fr)
DE (1) DE102019217419A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH209029A (de) * 1939-03-09 1940-03-15 Zuberbuehler Albert Gasluftmischer für Leuchtgasbrenner.
CH212284A (de) * 1938-10-28 1940-11-15 Zuberbuehler Albert Verfahren zum Mischen von spezifisch schweren Brenngasen mit Luft und Vorrichtung zur Durchführung des Verfahrens.
US5716203A (en) * 1994-03-01 1998-02-10 Sirand; Joseph Injection apparatus for an atmospheric burner in a gas heating apparatus, especially of the infrared type, and heating apparatus provided with such an injection device
EP2863125A1 (fr) * 2013-10-16 2015-04-22 Robert Bosch Gmbh Appareil de chauffage doté d'un brûleur assisté d'un ventilateur
EP3203151A1 (fr) 2016-02-03 2017-08-09 Robert Bosch Gmbh Dispositif de mélange d'air/gaz de combustion pour un appareil de chauffage
EP3462088A1 (fr) * 2017-09-27 2019-04-03 Robert Bosch GmbH Dispositif de mélange d'air/gaz de combustion et appareil de chauffage

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB375569A (en) * 1931-07-14 1932-06-30 Angelo Paganini Improvements in spray nozzles for oil burners
DE102010046956B4 (de) * 2010-09-29 2012-08-30 Robert Bosch Gmbh Ölvormischbrenner
TR201517546A2 (tr) * 2015-12-30 2017-07-21 Bosch Termoteknik Isitma ve Klima Sanayi Ticaret Anonim Sirketi Hava ve/veya yakıt için bir açıklığa sahip olan brülör ve bu tip bir brülöre sahip olan bir ısıtma cihazı.

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH212284A (de) * 1938-10-28 1940-11-15 Zuberbuehler Albert Verfahren zum Mischen von spezifisch schweren Brenngasen mit Luft und Vorrichtung zur Durchführung des Verfahrens.
CH209029A (de) * 1939-03-09 1940-03-15 Zuberbuehler Albert Gasluftmischer für Leuchtgasbrenner.
US5716203A (en) * 1994-03-01 1998-02-10 Sirand; Joseph Injection apparatus for an atmospheric burner in a gas heating apparatus, especially of the infrared type, and heating apparatus provided with such an injection device
EP2863125A1 (fr) * 2013-10-16 2015-04-22 Robert Bosch Gmbh Appareil de chauffage doté d'un brûleur assisté d'un ventilateur
EP3203151A1 (fr) 2016-02-03 2017-08-09 Robert Bosch Gmbh Dispositif de mélange d'air/gaz de combustion pour un appareil de chauffage
EP3462088A1 (fr) * 2017-09-27 2019-04-03 Robert Bosch GmbH Dispositif de mélange d'air/gaz de combustion et appareil de chauffage

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