JPS6021290B2 - Preheating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a preheating device for preheating fuel oil in front of a burner nozzle, which includes a barlet through which an electric current flows and is in thermal conductive contact with a pipe leading fuel oil to the burner nozzle.

Low power oil burners are useful for many applications.

The small burner output Q, which allows even the small demands that exist in the case of floor and room heating to be met with burners of this type, makes the boiler smaller and therefore cheaper and less bulky. The insulation of the boiler is more effective and the temperature of the boiler is controlled during the short start-up process of the burner, resulting in less fouling of the burner and reduced environmental impact. The basic problem in low power oil burners is the small diameter of the nozzle tube.

The small nozzle tube reduces the reproducibility of oil penetration,
The nozzle tube is frequently blocked. It is known to eliminate this defect by heating the fuel oil in front of the nozzle.

The viscosity of the oil is reduced by preheating and complete atomization occurs with relatively little atomization pressure. Due to the decrease in pressure, the amount of oil passing through decreases and the burner output decreases. The low viscosity also reduces the risk of nozzle blockage. The low atomization pressure allows the cross section of the nozzle pipe to be increased if the oil flow rate and therefore the burner output are not to be reduced. In this case, the risk of blockage of the nozzle tube is significantly reduced,
The reliability of burner operation is increased. It is known to use electrical resistance heating to preheat fuel oil.

Electric resistance heating has the disadvantage of requiring a large amount of floor space. A further disadvantage is that the oil is overheated beyond the optimum temperature of, for example, 70-80° C., especially if the burner is stopped or the oil flow rate is low. Overheating causes undesirable decomposition effects on the oil. This drawback of electrical resistance heating is overcome by the device according to German Utility Model No. 7811098.

In this device, a current-carrying barrette (a resistor with a positive temperature coefficient) is used for preheating the fuel oil. The barrettes have the property of self-regulating their heat output in a known manner. This self-regulation allows
Overheating of the twisting oil is prevented without requiring expensive auxiliary control measures. In this known device, the barrette is inserted radially into a thermally conductive metal sleeve that surrounds the pipe leading to the fuel oil.

The efficiency of this preheating device is rather low, since the electrical insulation required between the barrette and the metal sleeve also results in a thermal resistance, and on the other hand, the large surface area of the metal sleeve leads to heat losses. In addition, due to the high heat capacity of the metal sleeve, the self-adjustment of the barrette becomes inactive, which effectively prevents overheating of the fuel oil. Finally, the bulk of the device mounted on the outside of the feed pipe precludes the use of this preheating device without changing the entire burner structure. The object of the invention is to improve a preheating device of the type mentioned above, in which the preheating takes place with high efficiency, the self-adjustment of the barrettes takes place with almost no time delay, the preheating device is not bulky, and the construction of the burner is simplified. The object is to be able to be integrated into the nozzle arrangement of the burner without modification. According to the invention, this problem is solved by the fact that a plate-shaped barlet is inserted into the cross-section of the nozzle arrangement of the burner, and that the pipe leading to the fuel oil is formed as at least one flat conduit in the area of the barlet. , in that at least one flat side of the barlet rests against the wall of the flat conduit in thermal contact therewith.

Other preferred embodiments are described in the respective implementation sections.

In the preheating device of the present invention, the barrettes formed in a plate shape are seated in the cross section of the barrel device, and the fuel oil supply pipe is a conduit that is flatly applied to the entire flat surface of the barrettes. is formed as.

The preheating device can therefore be completely integrated into the nozzle arrangement of the burner, and it is only necessary to lead out the electrical connection line of the barrette from the nozzle arrangement. Therefore, the preheating device
It does not require any modification of the burner structure and can be used without problems with existing burner structures. Direct large surface contact between the barrettes and the fuel oil optimizes preheating efficiency.

Since there are no elements with a heat capacity between the barrette and the fuel oil, the self-adjustment of the barrette takes place with little delay. Therefore, the fuel oil is always kept at the optimum preheating temperature and overheating is accurately prevented. According to safety regulations, the temperature of fuel oil must not exceed 95°C in any case. This requirement is not completely and exactly met in all cases by the self-adjusting properties of the ballet. The reason for this is that the electrical data of the barrettes vary due to production, and the heat capacity and heat transfer of the entire device also vary due to production. According to the invention, therefore, a safety thermostat is used as an aid to the self-regulating action of the barrette, which cuts off the power supply to the barrette as soon as the fuel oil exceeds the maximum permissible temperature. In addition to this, it is preferable to use control thermostats known per se in other types of preheating, such as electrical resistance heating.

A control thermostat wired into the burner control circuit closes electrical contacts when a certain predetermined minimum oil temperature is reached, thereby allowing the oil burner to operate. This prevents the burner from starting when the oil temperature is too low. The control thermostat also opens the electrical contacts to deactivate the burner when the oil temperature falls below the predetermined minimum oil temperature. Therefore, no soot is generated in the boiler when the oil temperature is low. The safety thermostat and the control thermostat are located in direct large surface heat conductive contact with a flat conduit carrying the fuel oil, within which preheating by means of barrettes takes place.

In this way, the safety thermostat and the control thermostat can also be integrated into the cross-section of the nozzle arrangement, without changing the dimensions of the nozzle arrangement, which are advantageous for installation. Because of the large surface thermally conductive contact, the actual oil temperature is determined by the thermostat almost without inertia at the point where the barrettes heat the fuel oil. The safety thermostat thus responds without significant time delay to the maximum temperature effectively achieved by preheating in the oil supply line. A predetermined maximum temperature is thus reliably guaranteed in the entire oil supply system. Other advantages and features of the invention become clear from the following examples of embodiment with the aid of the drawings. 1 to 3 show a fuel oil preheating device according to a first embodiment of the present invention.

The preheating device consists of two metal connecting pieces 10, each of which has a cross-section adapted to the cross-section of the nozzle assembly of the burner.
, 12. The connecting piece 10 has a female threaded portion to which a nozzle rod can be screwed. The connecting piece 12 has an internally threaded portion to which the nozzle of the nozzle assembly can be screwed. The through holes in the connecting pieces 10, 12 are used to guide the fuel oil to the nozzle. Two plate-shaped barrettes 14 (resistors with a positive temperature coefficient) are inserted between the striped pieces 10 and 12. The barrettes 14 are arranged so that their longitudinal axes are coaxial with the connecting pieces 10, 12 and thus with the nozzle assembly, and are abutted against each other in the direction of the sea bream. A passageway consisting of a rectangular cross-section conduit 16, preferably made of brass, abuts the flat sides of the barrette 14. The width of the flat conduit 16 corresponds to the width of the barrette 14, so that the flat conduit 16 is in flat contact with the barrette 14 on all flat surfaces. Conductor layers 18 are attached directly to the opposite planar sides of the barrettes 14, and these conductor layers 18 are used to conduct current and are connected to a current source via connecting conductors.

A thin electrically insulating layer 20 is disposed between the conductor layer 18 and the conduit 16. This insulating layer consists of, for example, thermally injected aluminum oxide and has a low thermal resistance. According to another embodiment, the insulating layer 20 is formed as a layer of synthetic material with high dielectric strength and high temperature resistance.

Villages are preferred because they are easy to manufacture. Polyimide foil (trade name, Kapton) has been found to be particularly preferred. This foil has a dielectric breakdown strength of 280kV/fence and a 180o
o.It can withstand heat of up to 275q0 for a short period of time and has high tear strength. Therefore, if the thickness of the foil is on the 0.1 side, a sufficiently large electrical insulation can be achieved. This small thickness of the foil means that there is little thermal insulation and therefore a desirably good heat conduction. The barrette 14, consisting entirely of its electrical connection leads and conduits 16, is embedded by molding in an insulating synthetic material 22 and held coaxially between the connecting pieces 10, 12 by the synthetic material 22.

A metallic sleeve 24 embedded on the connecting pieces 10, 12 surrounds the synthetic material 22 to the outside and serves as an external mold during the molding of the synthetic material 22. In operation, a current supplied through the conductor layer 18 flows through the barrette 14 and heats it.

The oil led to the nozzle via the conduit 16 is heated by the barrette 14, and due to the action of the barrette 14 which limits the current as the temperature increases, the oil is preheated to a predetermined optimum temperature in a self-limiting manner. In the embodiment of FIGS. 1-3, the conduit 16 itself may be used as the current supply for the barrette 14. To do this, connect the conduit 16 to the barrette 11.
All you have to do is solder it to the flat side of 4. In this case, the current conductor can be soldered to the conduit 16. In this embodiment, the conduit 16 is connected to the metal connecting piece 10.
, 12 or the nozzle shank or nozzle attached thereto, it is of course necessary to avoid electrically conductive contact.

For this purpose, the conduit 16 is coated at both ends with an insulating synthetic material 22 and is threaded through the through holes in the synthetic material 22 into the through holes in the connecting pieces 10, 12. In the embodiments of the present invention described below, parts common to the embodiments in FIGS. 1 to 3 are given the same reference numerals, and the explanations thereof shall also refer to the explanations for FIGS. 1 to 3. do.

In the embodiment shown in FIGS. 4 to 6, the connecting pieces 10, 12
are not penetrated and are closed at the end faces facing each other.

A flat conduit 16 is inserted through these closed end faces of the connecting pieces 10, 12 and, as indicated by reference numeral 26, connects the connecting piece 1.
It is brazed to 0.12. In this example conduit 1
6 is electrically conductively connected to the connecting pieces 10 and 12, so
No current can be supplied to barrette 14 via conduit 16.

The supply of current may take place, for example, via a conductor layer 18 separated from the conduit 16 by an insulating layer 201. 4th ~
In the embodiment of FIG. 6, the connecting pieces 10, 12 are connected and held together by a conduit 16 inserted during manufacture, so that the shaping of the composite material 22 is simplified.

In this embodiment, the push-in sleeve 24 may be eliminated. In the third embodiment shown in FIGS. 7-9, a flat conduit 16
is not used.

A portion of the synthetic material 22 is cut out on both flat sides of the barlet 14 to form a duct 28 . Duct 2
The width of 8 corresponds to the width of the barlet 14. Duct 2
8 is formed during molding of the synthetic material 22. Instead of the flat duct 28, a plurality of through holes may be formed in close proximity to each other so as to cover the entire flat side surface of the barlet 14. The supply of current to the barlet 14 takes place via a conductor layer 18 which is protected from passing oil by an insulating layer 20'.

In this embodiment as well, a push-in sleeve 24 is provided,
This sleeve is basically used for connecting pieces 1 when molding synthetic materials.
Used to keep 0 and 12 fixed.

Although only one barlet 14 is used in FIG. 7, two or more barlets 14 may be disposed in contact with each other, as in each of the embodiments described above.

The number of barlets 14 is basically regulated by the required heating efficiency and therefore essentially by the flow rate. In a fourth embodiment, shown in FIGS. 10-12, a single flat conduit 16 is used, the longitudinal axis of which lies between the connecting pieces 10 and 12.
It is arranged coaxially with.

Similar to the embodiment of FIGS. 4-6, the conduit 16 is connected to the connecting piece 10
, 12. The barlets 14 on either side of the conduit 16 are preferably arranged in series.

This can be done by an electrical conductor embedded in the synthetic material 22, which allows the conduit 16 of the barret 14 to
The side conductor layers are bonded together. The barlets 14 may be electrically connected directly to a flat conduit 16 such that the conduit 16 forms a conductive connection of the cascade of barlets 14.

In this case, of course, the conduit 16 should not be soldered to the connecting pieces 10, 12, but must be insulated therefrom by a synthetic material 22, as explained for the embodiment of FIGS. The embodiments of FIGS. 10-12 are particularly suited to applications where high thermal efficiency is required and the axial length of the device cannot be increased.

Further modifications to the embodiment of FIGS. 10-12 may be made.

By way of example, a further flat conduit 16 can be arranged on the flat outer surface of the barlet 14 in order to increase the oil flow cross-section. The basic configuration of the embodiment shown in FIG. 13 corresponds to the embodiments shown in FIGS. 4 to 6.

In addition, however, a safety thermostat 29 is fitted onto the outer surface (the upper surface in the figure) of the flat conduit 16 opposite the barlet 14. Safety thermostats of known types, which may be e.g. bimetallic thermostats29
are brushed flat on the flat side of the conduit 16 to ensure good heat transfer between the conduit 16 and the safety thermostat 29. A safety thermostat 29 is connected in series in the electrical circuit of the barlet 14 and
4 interrupts this electrical circuit as soon as it reaches a certain predetermined maximum temperature.

This predetermined maximum temperature is a value slightly lower than the maximum oil temperature allowed for fuel oil preheating, and this oil temperature is set at 95 qo according to safety specifications. Maximum allowable oil temperature (e.g. 95oo) and safety thermostat29
This difference from the response temperature of the safety thermostat 29 to the temperature of the barlet 14 takes into account the time delay due to heat capacity and heat conduction. On the outer surface (the lower surface in the figure) of the other flat conduit 16, a control thermostat 30 is likewise arranged in flat contact.

Control thermostat 30 may also be of known type. A control thermostat 30 is connected in the control circuit of the burner and is activated so that the burner can be ignited when a predetermined temperature, for example 60 qo, is reached. When the temperature drops again below a predetermined value, for example 40qo, the control thermostat 30
deactivates the burner. This prevents uneconomical ignition of the burner when the oil temperature is too low and the formation of soot on the burner when the oil temperature is too low during burner operation.
The safety thermostat 29 and the control thermostat 30 are adapted to the cross-sectional shape of the connecting pieces 10, 12 and thus to the cross-sectional shape of the nozzle assembly.

In addition, the thermostat 29, the amount of insulating synthetic material 22
It may also be embedded by molding. What is common to the preheating devices according to all the embodiments described above is that the cross-section and therefore the circumferential shape of the preheating device corresponds to the cross-section and circumferential shape of the nozzle assembly, so that the geometry and dimensions of the nozzle assembly and the burner are - The preheating device can be inserted axially into the nozzle assembly without changing the method. A further common feature is that the oil passes through the barlet contact point with a large heat exchange surface, so that a low inertia and an optimum effect during preheating of the twisting oil are achieved. Despite the large heat exchange surface, the oil does not come into direct contact with the barret, so the oil cannot chemically act on the barret material. Furthermore, the preheating device according to all the embodiments described above can be produced in a simple manner in terms of manufacturing and assembly techniques and from a small number of simply constructed components.

[Brief explanation of the drawing]

FIG. 1 is a sectional view in the vertical direction of a preheating device according to a first embodiment of the present invention, FIG. 2 is a left side view of the preheating device shown in FIG. 1, and FIG.
The figure is a sectional view taken along the line A-A in FIG. 1, FIG. 4 is a cross-sectional view in all axial directions of a preheating device according to a second embodiment of the present invention, and FIG. 5 is a left side view of the preheating device shown in FIG. 4. , FIG. 6 is a sectional view taken along the line B-B in FIG. 4, FIG. 7 is a sectional view in the vertical direction of the preheating device according to the third embodiment of the present invention, and FIG. 8 is a left side view of the preheating device in FIG. 7. 9 is a sectional view taken along line C--C in FIG. 7, FIG. 10 is an axial sectional view of the preheating device according to the fourth embodiment of the present invention, and FIG.
The figure is a left side view of the preheating device in Figure 10, and Figure 12 is a left side view of the preheating device in Figure 10.
FIG. 13 is a cross-sectional view taken along the line D--D in FIG. 0, and FIG. 13 is a cross-sectional view in all axial directions of a preheating device according to a modification of the embodiment shown in FIG. 14... Barlet, 16... Conduit (conduit) with a rectangular cross section, 28... Duct (conduit). FIG. TFIG. 2 FIG・muFIG. 5 FIG. 6 FIG. 7 FIG. 3 FIG. 8 F! 6.9 FIG. 10 FIG. 11 FIG”2 FIG. '3

Claims (1)

[Scope of Claims] 1. A preheating device for preheating twisting oil in front of a burner nozzle, comprising a barlet through which an electric current flows and is in thermal conductive contact with a pipe that leads twisting oil to a burner nozzle. A plate-like barlet 14 is fitted in the cross-sectional area of the nozzle arrangement, and the piping for conducting the twisting oil is provided in the area of the barlet 14 with at least one flat conduit 16, 2.
8 and that at least one flat surface of the barlet 14 rests in thermal contact with the wall of the flat conduit 16, 28. . 2. The preheating device according to claim 1, characterized in that it has a barlet 14 with flat conduits 16, 28 in contact with the flat surfaces of both sides. 3. Preheating device according to claim 1, characterized in that it has a flat conduit (16) with barlets (14) in contact with both flat surfaces, the barlets (14) being preferably connected in parallel. 4. The preheating device according to claim 3, characterized in that one separate flat conduit is brought into contact with each of both flat surfaces of the barlet 14. 5. The preheating device according to claim 1, characterized in that the barlet 14 and the flat conduits 16, 28 are embedded in an insulating synthetic material 22. 6 Each flat conduit is a metal conduit 1 with a rectangular cross section.
6, characterized in that they are electrically conductively coupled to each barlet 14 to form its current-carrying portion, and that the conduit 16 is electrically insulated from the metallic nozzle arrangement by a synthetic material 22. A preheating device according to claim 5. 7 Each flat conduit is a metal conduit with a rectangular cross section 1
6, which are connected to a metal nozzle device, in particular by brazing, and conductive layers 18 are provided on the flat sides of each barlet 14 as its current-carrying part, and these conductive layers are The conduit 1 is separated by an electrically insulating layer 20 of low resistance.
6. The preheating device according to claim 1, wherein the preheating device is separated from the preheating device 6. 8 that each barlet 14 is completely embedded in the synthetic material 22 and that each flat conduit is a duct 28 formed by cutting or perforating the synthetic material, which forms a current-carrying section; 6. The preheating device according to claim 5, wherein the preheating device is separated from the conductor layer 28 of the barlet 14 by an electrically insulating layer 20 having low thermal resistance. 9. Preheating device according to claim 7 or 8, characterized in that the electrically insulating layer 20 with low thermal resistance is made of thermally injected aluminum oxide. 10. Claim 7 or 8, characterized in that the electrically insulating layer 20 with low thermal resistance is a layer of a synthetic material with high dielectric breakdown strength and high heat resistance, in particular a synthetic material foil, in particular a polyimide foil. Preheating device as described in section. 11. The preheating device according to claim 1, characterized in that the one or more barlets 14 are replaced by two or more barlets that abut each other in the axial direction. 12 Each barlet 14 and flat conduit 16, 28
is arranged in the axial direction between two metal connecting pieces 10, 12, and these connecting pieces are particularly provided with a threaded part so that they can be inserted in the axial direction into the nozzle device. A preheating device according to claim 1. 13. An insulating synthetic material 22 is molded between the connecting pieces 10, 12, and the connecting pieces 10, 12 are held in place by a metallic sleeve 24 which is fitted onto the connecting pieces 10, 12 for molding of the synthetic material 22. A preheating device according to claim 5 or 12. 14. Claim 1 characterized in that a safety thermostat 29 connected in series with each barlet 14 is arranged in thermally conductive contact with the wall of the flat conduit 16.
Preheating device as described in section. 15. Preheating device according to claim 1, characterized in that a control thermostat (30) connected in the control circuit of the burner is arranged in heat transfer contact with the wall of the flat conduit (16). 16 Safety thermostat 29 and control thermostat 3
16. The preheating device according to any one of claims 2, 14, and 15, characterized in that the preheating device is positioned so as to be in contact with the outer surface of the flat conduit 16. 17 Safety thermostat 29 and control thermostat 3
17. The preheating device according to claim 5 or 16, characterized in that the barlet 14 and the flat conduit 16 are embedded in an insulating synthetic material 22.