WO2007096788A1

WO2007096788A1 - Apparatus and method for burning a fuel

Info

Publication number: WO2007096788A1
Application number: PCT/IB2007/050276
Authority: WO
Inventors: Marcel Caminada
Original assignee: Tempratec Ltd.
Priority date: 2006-02-22
Filing date: 2007-01-26
Publication date: 2007-08-30

Abstract

A novel apparatus for burning a liquid or powdery fuel is described, comprising an atomizing nozzle (2) which has a valve arrangement (41) for controlling the feeding of the fuel, a compressed-air connection (4), a mixing chamber (38) for mixing the fuel with compressed air, and a nozzle opening (23) for atomizing a mist of fuel in compressed air. A feed line (28) for the fuel and a preheating device (5) are provided which are attached in a nozzle connection enclosing the nozzle (2). Also provided are air passages in a casing (3) surrounding the preheating device (5) and a fastening sleeve (13) having connecting passages adjoining the air passages, wherein the casing (3) forms with the nozzle connection (12) of the atomizing nozzle (2) an annular gap (21) for the feeding and heating of the compressed air. Starting from the annular gap (21), air feed lines (50) are provided in the nozzle body (20) in such a way that the valve arrangement (41) can be activated by the compressed air.

Description

Apparatus and method for burning a fuel

The present invention relates to the field of combustion technology and relates to an apparatus for burning a liquid or powdered fuel with a spray nozzle, a valve assembly for controlling the supply of fuel, a compressed air connection, a mixing chamber for mixing the fuel with compressed air and a Having nozzle opening for atomizing a mist of fuel in compressed air. There is further provided a means for preheating the fuel to a predetermined temperature, which is mounted in a nozzle stem enclosing the nozzle. The invention further relates to a method for burning a fuel by means of the aforementioned device.

STATE OF THE ART

Such devices are well known in the field of combustion technology and are operated, for example, with a pneumatic oil mist atomizer nozzle known from EP-A-0 566 855 or EP-A-0 731 315. In oil-operated heating systems, the fuel oil to be burned is injected at a pressure of several (about 5 bar) through a compressed air atomizing nozzle into the burner chamber and thereby atomized. In order to prevent the heating oil from dropping due to the high pressure when the burner is switched off, a membrane with a shooting piston pretensioned by a compression spring (EP-A-0 566 855) or a diaphragm clamped between two springs (EP-A-0 566 855) is known in the aforementioned publications. AO 731 315).

These known devices are specially designed for fuel oil, which must comply with special qualities due to environmental regulations. In particular, it is not possible to burn other vegetable oils such as rapeseed oil or fat with such a device. PRESENTATION OF THE INVENTION

It is an object of the present invention to improve such a device for the combustion of liquid fuels so that a combustion of different types of oils and fats is made possible as a heating oil.

This object is achieved by a device having the features of patent claim 1 and by a method having the features of patent claim 6.

The essential finding of the present invention is that, in contrast to the conventional compressed air atomizing nozzles, the compressed air is used as an energy source and control medium for the valve assembly. Thereby, the supply of liquid or powdered fuel can be carried out with a lower pressure and thus a very accurate control of the valve assembly can be achieved. The compressed air used for the control sucks in the liquid or powdery fuel due to the negative pressure, so that even in the mixing chamber is an excellent mixing or atomization of the fuel with the compressed air.

With the device according to the invention different types of fuel and fuel qualities can be burned without having to replace any parts. It is also fuel with an admixture of up to 20% water can be easily burned. When the compressed air is replaced by pure oxygen, part of the mist-entrained water is decomposed and burned, resulting in a higher flame temperature.

Further advantages of the invention will become apparent from the dependent claims and from the following description in which the invention with reference to an embodiment shown in the schematic drawings is explained in more detail. It shows: Fig. 1 shows a combustion device with a spray nozzle, a

Preheater and a compressed air supply,

Fig. 2, the atomizer nozzle of Fig. 1 in more detail, clamped in a nozzle with a sheath, just before opening the

valve,

3 shows the same atomizer nozzle of FIG. 2 with the valve closed, FIG.

FIG. 4 shows the same atomizer nozzle of FIG. 2 with the valve open, FIG.

5 shows the same atomizer nozzle of FIG. 2 after closing the valve, FIG.

6 shows a cross section in the longitudinal direction through a flame tube,

7 shows a cross-section in the transverse direction through the flame tube of Fig. 6,

Fig. 8 is a pneumatic-hydraulic control scheme for the control of

Combustion device, and

9 shows a variant of the atomizer nozzle.

DESCRIPTION OF THE INVENTION

In the figures, the same reference numerals have been used for the same elements and first explanations apply to all figures, unless expressly stated otherwise.

FIG. 1 shows a combustion device 1 with a spray nozzle 2, a jacket 3 with a compressed air connection 4 and an oil preheater 5. The casing 3 substantially surrounds the oil preheater 5, so that the compressed air, which flows through the casing 3, from the same time Preheater 5 is preheated to about the same temperature as the OeI. The Oelvorwärmer 5 consists of a shaft 6 with a wound on this resistance heater 7 and a plastic housing 8 for the connections 9 for the heating coil. A fuel supply pipe 10 is mechanically connected to the shaft 6. On the Oelvorwärmer 5, a connecting sleeve 12 is screwed, which carries on the other side of the atomizing nozzle 2 by means of a screwed fastening sleeve 13. The connection sleeve 12 is provided with a so-called Volustatdrossel 14 with a small flow hole 15, wherein the fuel pressure and the flow rate are reduced. Further, a coarse mesh filter 16 made of sintered metal is mounted in front of the Volustatdrossel 14. With the help of the throttle 14, the pumping pressure of the oil is reduced and at the same time, depending on the power requirement, the desired amount of oil is metered as a function of the pump pressure. The throttle 14 can also be installed in the nozzle directly after the oil pump.

With reference to Figures 2 and 3 further details of the atomizing nozzle 2 are shown and explained. Between the mounting sleeve 13 and the screwed nozzle body 20 of the atomizer nozzle 2, an axially symmetrical receiving space 21 is formed. Seen from this receiving space 21, an axial blind hole 22 is formed in the nozzle body 20, which tapers frustoconically up to a nozzle opening 23 of the nozzle body 20 at its base. In this blind hole 22 of the nozzle body 20, an axially symmetrical insert 24 is screwed. The rear, the nozzle opening 23 facing away from the end of the insert 24 has a front sleeve portion 25 which is inserted into the nozzle sleeve formed as a connecting sleeve 12 and sealed there. The seal is made by an O-ring 26. This O-ring 26 is on the other hand on the inner wall of an axial sliding space 27 of the connecting sleeve 12 into which a feed line 28 for the liquid or powdery fuel flows.

In the receiving space 21 of the mounting sleeve 13 compressed air - shown with arrows 30 - fed. The receiving space 21 then goes through air supply lines or holes 50 - see below - in a substantially cylindrical annular gap 31 formed between the insert 24 and the nozzle body 20, and which in turn because of the frusto-conical taper of the blind bore 22 to the nozzle opening 23 in a substantially frusto-conical gap 32 passes. The cylindrical annular gap 31 is formed by the fact that the diameter of the blind hole 22 is slightly larger than the diameter of the front, the nozzle opening 23 facing sleeve portion 25 of the insert 24. The frusto-conical gap 32 is formed by a corresponding axial offset between the frusto-conical bottom of the blind bore 22 and The bottom of the blind hole 22 is not shown here - approximately tangentially to the nozzle opening 23 extending guide channels occupied, as shown in Figures 2 and 3 of EP-AO 566 855 , The cylindrical annular gap 31 and the frusto-conical gap 32 thus together form an axially symmetrical space between the insert 24 and the nozzle body 20.

Seen from the front sleeve portion 25, a continuous axial bore 36 is formed in a middle part 34 and subsequently in the rear sleeve portion 35 of the insert 24, which is connected to the rear with the sliding space 27 and with the supply line 28 for oil. At its other end, this axial bore 36 tapers, wherein the end of a ring wall 37 is surrounded. The upper edge of the annular wall 37 is located in the same plane as a ring shoulder 42 of the front sleeve portion 25, so that on the other side of the annular wall 37 designed as a mixing chamber annular groove 38 is formed, which via radial bores or radial channels 39 with the cylindrical annular gap 31 in connection stands.

On the upper edge of the annular wall 37 is a disk-shaped membrane 41, which engages over the annular groove 38 and rests with its edge on the annular shoulder 42 of the front sleeve portion 25. On this annular shoulder 42, the membrane 41 is clamped by means of a clamping element 33 at its edge. This Clamping member 33 is pushed into the front sleeve portion 25 with a press-fit and fixed so. In the region of the bottom of the blind bore 22 of the nozzle body 20, this clamping element 33 is frusto-conically shaped toward the nozzle opening 23 to form the frusto-conical gap 32 of the above-mentioned axially symmetric gap.

In the clamping element 33, a blind hole 43 is formed, in which a closing piston 44 is slidably held. This closing piston 44 presses against the membrane 41 by means of a compression spring 45. The compression spring 45 is supported against the funnel-shaped bottom of a blind hole 46 in the closing piston 44 and against a funnel-shaped bottom of the blind hole 43 to the frusto-conical gap 32, which is arranged axially to the opposite nozzle opening 23 of the nozzle body 20.

Further, in the middle part 34 of the insert 24 formed as air supply lines bores 50 are provided which lead from the receiving space 21 to the annular groove 38. These holes 50 connect the receiving space 21 with the annular groove 38, so that the compressed air 30 is directed directly to the membrane 41.

In FIGS. 4 and 5, the atomizing nozzle 2 with the valve or the membrane 41 is shown in the open state or in the closed state.

A specific flame tube 55 is shown in FIGS. 6 and 7, which is fastened in the threaded bores 56 by means of screws on a conventional fastening tube (not shown here). The combustion device shown in Figure 1 has on the front of a conventional - not shown here - mixing system with ignition electrodes and is mounted with the sputtering nozzle 2 at the beginning of the flame tube 55. As can now be seen from FIGS. 6 and 7, the flame tube 55 is largely tapered in the entry region 57 and screwed to the attachment tube only at the bulges 58 which correspond to the inner diameter of the attachment tube, so that the heat is absorbed Flame tube is limited to the mounting tube is transferred. The flame tube 55 is preferably made of a ceramic material. By the so-called recirculation gap between the flame tube 55 and the mounting tube now hot exhaust gases of the flame are supplied again. These exhaust gases are sucked back from the outside of the flame tube 55 through the recirculation gap. The gases sucked in achieve better exhaust gas values.

The flame tube 55 may also be made of metal and lined internally with a felt of refractory ceramic fibers or with an inner tube vacuum-pressed or drawn from ceramic fibers. Preferably, the sheath 3 (see Fig. 1) is coated on the flame side with such a felt. This lining or felt prevents the spray in the cold

Condition condensed on the relatively cold surface of the flame tube 55. Further, the felt isolates the flame tube 55 and the jacket 3 from the hot one

Flame, so there is less material aging.

FIG. 8 shows a pneumatic-hydraulic control scheme for the combustion device 1 according to the invention. In the holder of the compressed air atomizing nozzle 1, a control electronics 60 with a heater 61, a sensing element 62 and a thermostat 63 is provided. The thermostat 63 is connected to a timing relay 64. By means of a motor M on the one hand a double diaphragm compressor 66 and on the other hand an oil pump 67 is driven. In the compressed air supply line 68, a solenoid valve 69 and an air pressure monitor 70 and an air pressure regulation 71 is provided. In the oil supply line 72, a solenoid valve 73 is provided.

FIG. 9 shows a variant of the atomizer nozzle 2. The same elements are identified by the same reference numerals, and not further explained here. In the blind hole 22 'of the nozzle body 20', an axially symmetrical clamping element 33 'is fixed, which with the bottom of the blind hole 22' a frusto-conical gap 32 'with tangential to the nozzle opening 23' forms running guide channels. The closing piston 44 'is now formed with a circumferential annular groove 82, in which an O-ring 83 is inserted, which completely seals the gap between closing piston 44' and clamping element 33 '. Instead of the diaphragm 41 of the embodiment of FIG. 1, a sealing disc 84 made of rubber is now inserted in a keisscheibe-shaped recess 85, which forms the valve. In the middle part 34 'of the insert 24' are now formed as air supply lines, parallel to the axial bore 36 'arranged holes 50' are provided, which lead to the annular groove 38 '. This annular groove 38 'is towards the center in a frusto-conical annular groove 86 which is sealed by the sealing disc 84. This sealing disc 84 simultaneously seals the axial bore 36 ', which serves to supply oil.

The operation of the combustion device 1 can now be explained with reference to the figures as follows:

When the burner receives a pulse to start the combustion process, first fuel in the nozzle with the oil preheater is warmed up to a maximum temperature of 80 ° C, to prevent the oil from coking. After release by the thermostat 63, the time relay 64 is activated with an adjustable residence time. For highly flammable oils such as mineral oil, the residence time can be set to zero so that the burner starts immediately. For flame retardant fuels such as vegetable oils, the residence time can be set to several minutes, so that the generated heat can propagate through the Volustatdrossel 14 to the nozzle 2. After the set time has elapsed, the burner is started.

During the pre-purging of the burner, the compressed air is built up with the double-diaphragm compressor 66 and then stops at the solenoid valve 69. When the controller of the burner gives the start release, the solenoid valve 69 is opened. The pressurized air then flows in the direction of nozzle 2. So that the compressed air does not cool the fuel to be atomized, it is guided on the oil preheater 5 in the casing 3. The preheated air is at the valve or on the membrane 41 of the nozzle 2 at. As soon as the pressure of the compressed air is greater than the counterpressure exerted by the firing piston 44 and the compression spring 45 on the membrane 41, the valve or membrane 41 is opened and flows the oil into the annular groove 38 formed as a mixing chamber, so that air and oil are mixed and the oil is taken away by the outflowing air. The negative pressure generated at the nozzle opening 23 also acts on the firing piston 44 and thus on the membrane 41. The fuel flowing out of the valve is entrained by the passing air and by tangential channels just before the nozzle exit (as shown in FIGS. 2 and 3 of EP -AO 566 855 known) brought to rotation. As a result of this rotation and the forward flow of the fuel-air mixture, an extremely fine fuel mist, which is similar to a gas, is produced on leaving the nozzle opening 23. This fine misting or gasification has made the flame-retardant mixture more flammable. The ignited mixture burns all the better because the flame is not only supplied with air from the outside, but the compressed air, which is used for atomization, now also reacts from the flame center to the outside, which significantly accelerates the combustion. The combustion preferably takes place in a flame tube 55, which advantageously consists of a ceramic. The exiting from the flame tube 55 exhaust gases have no unburned residues and thus require no afterburning.

It is understood by those skilled in the art that the operation of the atomizer nozzle according to FIG. 9 is similar. Again, the shooting piston 44 'is moved by the overpressure to the nozzle opening 23' out and thus opened the valve.

The flame tube 55 can be adjusted with an adjustable recirculation gap on the mounting tube, whereby the combustion can be additionally optimized.

Claims

claims

1. A device for burning a liquid or powdery fuel with a spray nozzle (2) having a valve assembly (41) for controlling the supply of the fuel, a compressed air connection (4), a

Mixing chamber (38) for the mixing of the fuel with compressed air and a nozzle opening (23) for atomizing a mist of fuel in compressed air, with a supply line (28) for the fuel and with a device (5) for preheating the fuel to a predetermined Temperature, which is provided in the nozzle (2) enclosing nozzle, characterized in that air ducts in a preheating device (5) surrounding sheath (3) and a fastening sleeve (13) are provided with connecting to the air ducts connecting channels, wherein the sheath (3) with the nozzle assembly (12) of the atomizer nozzle (2) forms an annular gap (21) for the supply and heating of the compressed air, and in that the annular gap (21) outgoing air supply lines (50) are provided in the nozzle body (20), the valve arrangement (41) can be activated by the compressed air.

2. Device according to claim 1, characterized in that the valve arrangement of a clamped membrane (41) or of a

Thrust washer (84) is formed and the nozzle (2) has an axial, sealed by the membrane fuel passage (36), and the air supply lines (50) radially surround the fuel passage and push on the diaphragm or the pressure plate.

3. Apparatus according to claim 2, characterized in that at least two air supply lines (50) are provided, which are arranged at an equal distance opposite to the fuel channel.

4. Apparatus according to claim 2 or 3, characterized in that the mixing chamber of a fuel channel (36) surrounding the annular groove (38) is formed, in which the air supply lines (50) open.

5. Device according to one of claims 1 to 4, characterized in that the nozzle is formed by a connecting sleeve (12) with a throttle (14) for reducing the flow rate and the fuel pressure.

6. The device according to claim 5, characterized in that the connecting sleeve (12) fixed liquid-tight with the transition sleeve (13) and the transition sleeve (13) is fixed liquid-tight with the nozzle body (2).

7. Apparatus according to claim 6, characterized in that the connecting sleeve (12) by means of a screw connection with the transition sleeve

(13) and the transition sleeve (13) is fastened by means of a screw connection with the nozzle body (20).

8. Device according to one of claims 1 to 7, characterized in that the output of the atomizing nozzle (2) a flame tube (55) is preferably made of a ceramic or internally with a lining of ceramic fibers, which at the rear of the atomizing nozzle (2 ) facing end is substantially tapered, so that between a mounting tube and the flame tube (55) a recirculation gap is formed.

9. Device according to one of claims 1 to 8, characterized in that in front of the compressed air connection (4) a solenoid valve (73) is provided, which is switched by means of a time delay relay (64) via a burner control to the fuel for a predetermined time heat up and after this time to open the valve assembly (41) and start the burning process.

10. A method for burning a fuel with a device according to one of claims 1 to 9, characterized in that a liquid or powdered fuel in a supply line (28) by means of a preheater (5) preheated and fed to a valve assembly (41), that compressed air in the immediate vicinity of the preheating device (5) is preheated and is supplied via air supply lines (50) in the nozzle body (20) on the valve assembly (41), such that the compressed air controls the valve assembly (41).

11. The method according to claim 10, characterized in that the compressed air after a time delay, the valve assembly (41) opens to preheat the fuel for a predetermined time by means of the preheater (5) and to start the firing after this predetermined time.