Patent Application
20240353101
The invention relates to a mobile heating device with a fuel supply line and a method for operating a mobile heating device.
Burners, in particular evaporator burners, are used in particular in parking and/or auxiliary heaters operated with liquid fuel, in particular for vehicles. In such evaporator burners, liquid fuel is fed into an evaporator via a fuel supply line. Metal fiber fleeces, for example, can be used as the evaporator itself. The evaporator sucks in liquid fuel, in particular via capillary action, and distributes liquid fuel. By means of the heat provided by a glow plug or ignition element, liquid fuel is evaporated and ignited so that combustion of the fuel can take place under supply of air. For this purpose, air supply openings are arranged in a peripheral wall. Such an arrangement is known, for example, from DE 10 2018 111 636 A1.
DE 10 2018 104 517 discloses a combustion air blower, in particular for a side channel blower for a fuel operated vehicle heater, comprising a blower housing, wherein an air flow space through which combustion air to be conveyed can flow is formed in the blower housing and air flowing into the air flow space flows via an inlet region to a conveying region comprising a conveying wheel, wherein at least one hydrocarbon storage element for storing gaseous hydrocarbon present in the air flow space is arranged in the air flow space. The hydrocarbon storage element serves to ensure that hydrocarbon is absorbed when the vehicle heater and a correspondingly deactivated combustion air fan are deactivated and thus does not escape to the outside as unburned fuel.
DE 10 2004 041 202 C5 discloses a method for switching off a motor vehicle heater, by which smoke development and unpleasant smells are to be avoided when the vehicle heater is started.
In this process, a fuel in the fuel line is heated when the dosing pump is switched off and burned off during an early burnout phase. A heating coil provided in the fuel supply line is proposed for heating.
From DE 10 2014 103 815 A1, an evaporator burner for a mobile heater is known. The evaporator has a carrier body made of a non-porous material, which comes into contact with liquid fuel with a side facing the combustion chamber. This side is a fuel preparation surface. The fuel preparation surface has a surface structuring. As a surface structuring, the fuel preparation surface may comprise, for example, elongated grooves and elevations as rib-like protrusions. The fuel preparation surface may be arranged perpendicularly or parallel to a bottom side of the evaporator receptacle.
DE 8403269 U1 discloses inserting a wire-shaped choke in a supply line of a heater having a combustion chamber. Such a choke is formed by a smooth wire and serves in particular to reduce a remaining cross-section of the supply line and thus to increase the flow velocity during operation and to avoid steam bubble formation.
The object of the invention is to provide an improved mobile fuel operated heating device, and to provide a method of operating a mobile heating device. In particular, undefined states during operation and rest phases of the heating device are to be avoided.
The object of the invention is solved with respect to the mobile heating device by the features of claim 1 and with respect to the method by the features of claim 14. Useful embodiments result from the respective subclaims.
The mobile heating device according to the invention comprises a heater assembly with a combustion chamber and a fuel supply line. The fuel supply line is suitable for supplying fuel to the heater assembly, in particular to its combustion chamber. The fuel supply line comprises a supply pipe having an inlet for inputting fuel and an outlet for outputting fuel to the combustion chamber. The fuel supply line further comprises an emptying device for partially or completely emptying the fuel supply line through the outlet. By means of the emptying device, the fuel supply line can be drained in particular at the end of the heating process, when no more fuel is supplied through the inlet. Thus, for a resting state, the fuel supply line is put into a state in which uncontrolled emptying is avoided. Thus, on one hand, an evaporative emission, in particular an evaporative emission of hydrocarbons, is avoided and, on the other hand, a smoke development or unpleasant smell is avoided when the heating device is restarted. The supply pipe can be either a straight pipe or a bent pipe or a pipe with bends. In particular, the emptying device is designed to be non-functional at a typical fuel flow rate during normal operation of the heating device and to develop a function only when a fuel inflow is shut off upstream.
In particular, the heating device may be a heating device with an evaporator burner. In this embodiment, the heater assembly includes an evaporator receiving arrangement for evaporating liquid fuel. The evaporator receiving arrangement includes an evaporator receiving body for receiving an evaporator element for distributing and evaporating liquid fuel.
The heating device may be a vehicle heating device.
For example, an evaporator element may comprise or consist of a metal mesh, a nonwoven fabric made of metal and/or rock fibers, and/or a porous material. Such materials effectively form a large surface area on which liquid fuel can evaporate. The evaporator receiving body has a bottom portion and a peripheral wall with a plurality of air supply openings. In particular, the air supply openings may be arranged in a peripheral wall in one or more rows.
In the evaporator receiving body, a receptacle for a glow plug is expediently provided, by means of which the evaporated fuel can be ignited. This glow plug or the heat release and heat conduction caused by the combustion process also serves as a heat source, which also heats the fuel flowing through the fuel supply line.
The emptying device expediently comprises a nucleating device which comprises at least one rough and/or structured nucleation surface for the formation of boiling bubbles. The rough and/or structured nucleation surface comprises in particular elevations and/or depressions with a height of at least 0.006 mm. The rough and/or structured nucleation surface causes heterogeneous nucleation of gas bubbles from the liquid fuel, in particular from the light-boiling fuel components. This function is only achieved at a reduced flow rate of the fuel compared to a function state of the heating device due to a longer residence time of the fuel at the nucleation surface (at a given temperature). As a result of the longer residence time, the fuel heats up to a higher temperature than during normal operation, so that gas bubbles can be formed. In particular, this can be accomplished by a burnout after upstream shutoff of the fuel flow, in which a combustion air blower of the heater assembly continues to operate and remaining fuel, as well as fuel that is subsequently pushed out, continues to be burned. The gas bubbles also push out liquid portions of the fuel from the fuel supply line, resulting in at least partial emptying of the fuel supply line.
In one embodiment, the nucleating device may be designed as a separate component that is interposed between two sections of the fuel supply line or is designed as an outlet of the fuel supply line. For example, the nucleating device may be a component arranged between two supply pipe sections.
In one embodiment, the nucleation surface is arranged on an inner circumferential surface of the supply pipe and/or on an inner surface of a connecting piece arranged at the inlet of the supply pipe. In particular, the nucleation surface extends over the entire inner circumferential surface of the supply pipe. Alternatively, the nucleation surface can also be arranged only in a partial region of the inner circumferential surface, for example in a region of the supply pipe near the inlet. For this purpose, for example, ribs can also be placed on the inner circumferential surface and/or cross-sectional jumps of the supply pipe can be provided. The nucleation surface expediently extends at least over a length of at least 0.3 cm, in particular at least 0.5 cm, in particular at least 0.8 cm along the flow direction of the fuel. A degree of emptying of the fuel supply line can be controlled via the positioning of the nucleation surface in the fuel supply line, in particular in the supply pipe or connecting piece, since emptying takes place in the region of the nucleation surface and downstream of the nucleation surface by means of the nucleation surface. Expediently, the nucleation surface extends in sections or entirely along the entire circumference of the supply pipe in the circumferential direction. The nucleation surface may be formed as one or more predominantly longitudinally oriented disturbances of an otherwise sufficiently smooth surface or circumferential surface, for example in the form of one or more longitudinal grooves.
The optionally provided connecting piece is provided in particular with a check valve, for example in the form of a pressure relief valve or excess pressure release valve, in order to prevent an unintentional outflow of fuel. Furthermore, a shut-off device and/or back-suction device can be provided in the fuel supply line, preferably upstream of the supply pipe.
The nucleation surface is arranged in particular in a close-up area to the outlet, the close-up area being in particular at a maximum distance of 1.10 m, in particular at a maximum distance of 1 m, in particular at a maximum distance of 0.9 m from the outlet. The outlet itself may be a region in which the fuel supply pipe is fixedly or detachably connected to the actual heating device, in particular to a wall of the combustion chamber or to an evaporator receiving body. A fixed connection is in particular a welded connection. For an alternative detachable connection, a connecting piece, a quickrelease lock or a screw plug can in particular be provided at the outlet of the fuel supply line.
In a further embodiment, a further element is arranged in the fuel supply line, in particular in the supply pipe, which additionally has the nucleation surface alternatively or as a further nucleation surface. The further element is designed in particular as a displacement wire. Such a displacement wire is basically used to reduce a cross section of the fuel supply line and thus to increase a flow rate of the fuel when the heating device is switched on. Due to the nucleation surface on the displacement wire, at least partial emptying of the fuel supply line can be achieved when the heating process is completed. In particular, the wire may be a flat wire, i.e., flattened round wire, roughened wire, wire with grooves or notches, knurled wire, polygonal wire, profiled wire, chemically or electrochemically treated wire, e.g., etched wire or coated wire.
The nucleation surface is expediently produced by means of mechanical deformation and/or by applying a coating and/or by milling and/or by means of an etching process. It is thus, for example, a mechanically or chemically roughened surface. The nucleation surface can be provided with grooves or notches which have been introduced, in particular, mechanically. The nucleation surface can be produced by direct treatment of the surface to be roughened or indirectly by deformation, in particular of the displacement wire, in which cracks are deliberately produced on a circumferential surface or surface. Furthermore, the wire can be knurled wire as described above or polygonal wire, e.g. star-shaped wire. The structures may be regular or irregular.
In one embodiment with a separate component that is connected into the fuel supply line, the component thus has an inlet that is connected to a first section of the fuel supply line, in particular a first supply pipe. Furthermore, the component has an outlet which is connected to a second section of the fuel supply line, in particular a second supply pipe. The first and second sections of the supply pipe are thus fluidly connected by the component. The component may in particular be a shell-shaped housing, which is preferably cylindrical at least in sections. An inner surface of the component may serve as a nucleation surface. Alternatively or additionally, one or more bodies may be arranged in the component, which are preferably formed of glass or ceramic and/or are in the form of small plates, rods, sleeves, small pipes, beads and/or stones. The nucleation surface may thus comprise the surface or circumferential surface of the bodies. Alternatively or additionally, the bodies may be part of the further element described above.
The emptying device may alternatively or additionally comprise a heat supply element arranged on an outer circumferential surface of the supply pipe and/or on an outer surface of a connecting piece arranged at the inlet of the supply pipe. By supplying heat, the temperature is increased, thus facilitating heterogeneous and homogeneous nucleation of boiling bubbles.
In an alternative, the heat supply element comprises an active heating element, for example in the form of a heating sleeve.
In a further embodiment, the fuel supply line for supplying fuel to the heating device is formed to extend from a fuel source to the heating device and comprises a first zone and a second zone. The fuel supply line in the first zone has a back-suction device comprising a fuel reservoir, the back-suction device being configured to suck fuel from the second zone, in particular completely, back into the first zone by means of a change in volume of the fuel reservoir. The fuel supply pipe of the above embodiments is arranged in particular exclusively in the second zone of the fuel supply line.
The fuel reservoir is expediently formed by at least one cavity and at least one movable piston in such a way that the fuel sucked back from the second zone can be at least partially accommodated in the fuel reservoir. For this purpose, the back-suction device expediently has an actuator, in particular with an actuating motor or binary switching device, for changing the volume of the fuel reservoir.
Alternatively, the fuel reservoir is formed by at least one deformable supply line section, which is preferably arranged in series in the fuel supply line, in such a way that the fuel sucked back from the second zone can be accommodated at least partially in the fuel reservoir. In this regard, the deformable supply line section may comprise a form memory device and/or piezoelectric switching device.
In one embodiment, the back-suction device comprises or is connected to a controller. In particular, the controller is suitable for damping or suppressing a possible overshoot of the system during fuel suck back.
In another or additional alternative, the heat supply element comprises a passive heat conducting element that conducts heat from a heat source to the outer circumferential surface or outer surface. In particular, the passive heat conducting element may comprise or be a hose clamp.
The fuel supply line, in particular the fuel supply pipe, is connected to the evaporator receiving body, expediently welded to the evaporator receiving body.
The method according to the invention for operating a mobile heating device, in particular for a heating device with an evaporator burner, wherein a complete or partial emptying of a fuel supply line of the heating device takes place, wherein the heating device comprises a supply pipe with an inlet for inputting fuel and an outlet for outputting fuel to a combustion chamber, wherein the method comprises the following steps:
The method is particularly usable with the above heating device.
The method may further comprise, in particular subsequently, the steps of:
The invention is also explained in more detail below with respect to further features and advantages by means of the description of embodiment examples and with reference to the accompanying drawings. It shows in each case in a principle drawing:
The evaporator element 3 can be inserted and fixed in the evaporator receiving body 2 by means of a fixing element 40, as shown in the exploded view in
A recess 42 for a glow plug is further provided in the peripheral wall 8 of the evaporator receiving body 2.
The fuel supply line 4 comprises a supply pipe 5. In this regard, the fuel supply line 4 and the supply pipe 5 may be integrally or materially bonded to each other in one embodiment example. In an alternative embodiment example, fuel supply line 4 and supply pipe 5 may (initially) be separate modules that are joined together (during assembly). For example, supply pipe 5 and fuel supply line 4 may be inserted (plugged) into each other, at least in sections, and sealingly connected. The supply pipe 5 has an inlet 14 and an outlet 16. The inlet 14 is provided with a connecting piece 18 and the outlet 16 of the supply pipe 5 opens centrally into the bottom region 6 of the evaporator receiving body 2. In the embodiment shown, the supply pipe 5 is welded to the evaporator receiving body 2.
The fuel supply line 4, in particular the fuel supply pipe 5, is provided with a nucleating device 20.
The evaporator receiving body 2 follows at the outlet 16 of the supply pipe 5. The evaporator receiving body 2 has a bottom area 6 and a peripheral wall 8. An evaporator element 3 is arranged in the evaporator receiving body 2. Downstream, air supply openings 41 are arranged in the peripheral wall 8, by means of which combustion air is supplied to the combustion chamber 9. The combustion air can, for example, be directed in a region around the supply pipe 5 into an antechamber 43 and then via a further chamber 44 to the air supply openings 41 and further into the combustion chamber 9. Heat exchanger and an exhaust duct are not shown.
The size ratios and pipe lengths shown are not limiting, but can be adapted to actual lengths and size ratios. In particular, the pipes can also have bends, which may be necessary during installation, for example, in a vehicle.
In step b), the fuel supply through the inlet 14 of the supply pipe 5 is terminated. For this purpose, in particular an upstream dosing pump can be switched off or an upstream shut-off valve can be closed. Thus, a flow rate of the fuel is reduced.
After step b), boiling bubbles are formed in the fuel in step c), in particular on a nucleation surface 22, and at least some of the fuel in the fuel supply line is transferred to the combustion chamber 9 by means of the boiling bubbles. Thereby, boiling bubbles are formed homogeneously by a heat supply, for example, via the waste heat of the burner and, if necessary, one or more heat supply elements 28 and/or heterogeneously at the rough or structured nucleation surface 22. This heating of the fuel only has an effect at the lower flow rate of the fuel. The formation of boiling bubbles leads to an increase in volume of the fuel in the fuel supply line 4, in particular the supply pipe 5, so that fuel is forced through the outlet of the supply pipe 5, in particular into an evaporator element. In step d), the transferred part of the fuel is burned in the combustion chamber 9 of the heating device. Thus, the fuel supply line is at least partially emptied.
In
The fuel supply line 4 extends from a fuel source 50 to a heater assembly 1. Thereby, the fuel supply line 4 is formed as a fuel supply of the heater assembly 1 extending from the fuel source 50 to the heater assembly 1 to supply the heating device 100 with fuel B from the fuel source 50.
The heater assembly 1 as well as the fuel supply line 4 is principally as described in the embodiment examples before.
The fuel source 50 comprises a fuel tank 51 and a dosing pump 52.
The fuel tank 51 is filled or fillable with fuel B. This fuel B can be supplied from the fuel tank 51 to the fuel supply line 4 by the dosing pump 52, to be conveyed to the heater assembly 1 via the fuel supply line 4.
In this embodiment example, the fuel supply line 4 has a first zone 4a and a second zone 4b. In
In the first zone 4a of the fuel supply line, the fuel back-suction device 60 is arranged, which comprises a fuel reservoir ΔV.
The back-suction device 60 is designed to suck back fuel B from the second zone 4b, into the first zone 4a—in particular at least largely into the fuel reservoir ΔV—by means of a change in volume or an increase in volume of the fuel reservoir ΔV, in order to empty the second zone 4b essentially completely (of fuel B).
In the embodiment example according to
For example, the cavity 61 and the piston 62 form a device substantially similar to the principle of a syringe.
Via a change in volume or an increase in volume of the fuel reservoir ΔV by moving the piston 62, the fuel B can be sucked out of the second zone 4b to substantially completely empty the second zone 4b.
To move the piston 62 or to change the volume of the fuel reservoir ΔV, the fuel back-suction device 60 may comprise at least one (electric) actuator—for example an actuating motor.
Alternatively or additionally, the fuel back-suction device 60 may comprise an (electrical) binary switching device—for example a magnetic switch—for moving the piston 62 or for changing the volume of the fuel reservoir ΔV.
By means of an opposite volume change or volume reduction of the fuel reservoir ΔV via a corresponding movement of the piston 62, the fuel B can be pushed out of the fuel reservoir ΔV back into the fuel supply line 4 and into the second zone 4b (towards the heater assembly 1).
The change in volume of the fuel reservoir ΔV can optionally be specifically controlled, for example by means of a control device, in such a way that an oscillating system is thereby avoided and it can be ensured that substantially all of the fuel is sucked out of (or introduced into) the second zone 4b in a controlled and defined manner and/or that no bubbles can form in the fuel B when fuel B is sucked back or pushed out. For this purpose, according to the embodiment example, the pushing out and/or the sucking back of fuel B takes place in a time window of at least 0.3 s, preferably at least 0.5 s, further preferably of at least 1 s.
Depending on the used fuel B, an inner diameter of the fuel supply line 4 may vary. For example, an inner diameter of the fuel supply lines 4 may range from 0.5 mm to 4 mm, preferably from 1 mm to 4 mm, more preferably from 1 mm to 3 mm.
A distance or a line length between the back-suction device 60 and the heater assembly 1 is at most 1 m, preferably at most 0.8 m, further preferably at most 0.6 m, in the embodiment example shown. Furthermore, preferably the second zone 4b of the fuel supply line 4 has a smaller line volume than the first zone 4a.
Overall, in this embodiment example, this results in a maximum volume change of the fuel reservoir ΔV of the back-suction device 60 of at least 6 ml, preferably at least 8 ml, further preferably at least 10 ml.
In any case, the maximum volume change of the fuel reservoir ΔV is dimensioned such that it holds at least the line volume of the second zone 4b.
In the embodiment example shown, the fuel back-suction device 60 is connected to the fuel supply line 4, for example, via a single T-connector, such that the fuel reservoir ΔV forms a sub-volume of the fuel supply line 4.
In an alternative embodiment example, the fuel back-suction device 60 may be integrally formed to the fuel supply line 4.
By reducing the volume of the fuel reservoir ΔV, the fuel B can be pushed-out back into the second section 4b of the fuel supply line 4 to start a heating process with the heater assembly 1.
In an alternative embodiment example, the fuel back-suction device 60 may be arranged in the vicinity of a connection to the fuel source 50, in particular in the vicinity of the dosing pump 52. In this manner, the second zone 4b of the fuel supply line 4 is formed by an entire line section between the heater assembly 1 and the dosing pump 52. In this way, an entire line section between heater assembly 1 and dosing pump 52 can be substantially completely drained by means of the fuel return suction device 60.
Instead of a back-suction device 60 with a cavity 61 and pistons 62 movable therein, the fuel supply line 4 according to this embodiment example has a back-suction device 60 formed by a (reversibly) deformable supply line section 63 in the fuel supply line 4.
For the principle operation and further features of the fuel supply line, explicit reference is made to the embodiment example previously described in
The deformable supply line section 63 has a form memory device, such as a form memory alloy, on a corresponding jacket section of the fuel supply line 4. Alternatively, the corresponding jacket section of the fuel supply line 4 may (directly) comprise or be formed from the form memory device.
Alternatively or additionally, the deformable supply line section 63 has at least one piezoelectric switching device for changing the volume of the fuel reservoir ΔV.
Generally, the deformable supply line section 63 is configured to change its shape (based on a received electrical signal) and thus its volume.
In particular, the deformable supply line section 63 can thus form or enlarge or reduce a fuel reservoir ΔV (serially in the fuel supply line 4).
In the embodiment example according to
By changing the volume or enlarging the deformable supply line section 63 or its fuel reservoir ΔV, fuel B can be sucked back from the second zone 4b of the fuel supply line 4 into the first zone 4a (in particular largely into the fuel reservoir ΔV).
In this way, the fuel supply line 4 with a back-suction device 60 can be formed as a single unbranched fluid line.
In
In this way, all of the fuel B from the second zone 4b of the fuel supply line 4 is sucked back into the first zone 4a. The significant portion of the back-sucked fuel B is thereby received in the fuel reservoir ΔV of the back-suction device 60. By a significant portion of the back-sucked fuel B is meant at least 80%, preferably at least 90%, further preferably at least 95% of the conduit volume of the second section 4b.
By reducing the volume of the fuel reservoir ΔV, the fuel B can be pushed-out back into the second section 4b of the fuel supply line 4 to start a heating process with the heater assembly 1.
The system may, for example, be part of a (motor) vehicle.
The heating device 100 as well as the system has a high temperature region HT and a low temperature region NT. Whereby the high temperature area HT is characterized in that in this high temperature area are arranged those devices or apparatuses that produce waste heat. In particular, such that a temperature in the high temperature region HT is above a boiling point of the used fuel B. For example, the heater assembly 1 is arranged in the high temperature region HT. In addition, the high temperature region HT may include other heat radiating devices 70, 80 such as a vehicle engine.
The low temperature zone NT is characterized in that a predominant temperature therein is below a boiling point boiling range of the used fuel B.
Thus, the second zone 4b of the fuel supply line 4 has such a length that a boiling point or boiling range of the fuel B used can be reached at least temporarily during an operation of the heater assembly 1. The first zone 4a has such a distance from the heater assembly 1 and possibly further heat sources that a temperature predominantly prevailing therein is below a boiling point or boiling range of the used fuel B. The fuel supply line 4 includes a back-suction device 60 in the first zone 4a.
The back-suction device 60 is designed to suck fuel B from the second zone 4b back into the first zone 4a—in particular at least for the most part into the fuel reservoir ΔV—by means of a change in volume or an increase in volume of the fuel reservoir ΔV, in order to empty the second zone 4b substantially completely (of fuel B).
In this way, the back-suction device 60 can suck back the fuel B from a high-temperature zone HT to a low-temperature zone NT.
This makes it possible to avoid evaporation of fuel B remaining in the fuel supply line 4 (for example, after a heating process has ended).
Although in
At this point, it should be noted that all of the above-described parts are claimed to be essential to the invention when considered alone and in any combination, especially of the details shown in the drawings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 112 550.2 | May 2021 | DE | national |
This application is a 35 U.S.C. § 371 National Stage Entry of International Application No. PCT/EP2022/063102 filed May 13, 2022, which claims the priority benefit of German Patent Application Serial Number DE 10 2021 112 550.2 filed May 14, 2021, all of which are incorporated herein by reference in their entirety for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/063102 | 5/13/2022 | WO |
