DE102009026269B4 - Mobile heater with injector - Google Patents

Abstract

Mobile heater, in particular a vehicle heater, which has a catalytic converter (4; 44) and which is designed in such a way that heat can be generated in this heat by catalytic conversion of fuel with combustion air which are supplied to the catalytic converter (4; 44) by an injector (12; 52) for supplying a fuel / combustion air mixture to the catalyst (4; 44), the injector (12; 52) being designed in this way and having a fuel supply (34, 36, 38; 74, 75, 76) and a combustion air supply (16; 56) can be connected in such a way that a fuel propellant jet can be generated from gaseous fuel in the injector (12; 52) and that combustible air for generating the fuel combustion air Mixture is suckable.

Description

The present invention relates to a mobile heater according to the preamble of claim 1.

Heaters for mobile applications (in the following: mobile heaters) are used in particular in the vehicle sector as a stationary or auxiliary heater. Stand heaters (or auxiliary heaters) can be operated both when the vehicle engine is stationary and when the vehicle engine is running, while auxiliary heaters can only be operated when the vehicle engine is running.

In this case, mobile heaters are known in which fuel is converted with combustion air in a flaming combustion to produce heat. For this purpose, such mobile heaters usually have a combustion chamber in which the reaction takes place in a flaming combustion. In some cases, additional catalysts are used for the catalytic aftertreatment of the combustion gases.

DE 27 21 818 A1 describes a burner for burning liquid fuel with a burner head in which the fuel is burned with air. The burner has air supply devices that supply supply air at substantially atmospheric pressure, an air supply line having a diverging diffuser for leading air from the air supply devices to the burner head, and an evaporator for converting liquid fuel into vaporous fuel. The evaporator has a liquid fuel heater.

In addition, mobile heaters are known in which to generate heating heat gaseous fuel with combustion air without flame formation (i.e., without the formation of a visible flame) is reacted on a catalyst. This process is also referred to below as fully catalytic oxidation. The reaction temperature is lower than in a flaming combustion. The catalytic conversion of the fuel-combustion air mixture to the catalyst starts automatically upon reaching a sufficiently high temperature, which is also referred to as catalyst light-off temperature. The advantages of generating thermal heat by a flameless, catalytic conversion compared to a flaming implementation in a combustion chamber include a reduced pollutant emissions and the prevention of combustion noise. Furthermore, the structural complexity is reduced, since no measures for flame retardance and flame monitoring are required.

In mobile heaters in which heat is generated by catalytic conversion of a fuel-combustion air mixture to a catalyst (fully catalytic oxidation), a uniform loading of the catalyst with the fuel-combustion air mixture is an essential criterion. A uniform loading of the catalyst in particular comprises a uniform throughput (or a uniform flow velocity) of the fuel-combustion air mixture over the flow cross-section of the catalyst and a uniform mixture concentration over the flow cross-section of the catalyst. If this is not the case, locally very different temperatures can arise in the catalyst, which are also referred to as hot spots. Such hot spots adversely affect the life of the catalyst. Furthermore, due to an uneven loading of the catalyst with the fuel-combustion air mixture locally only an incomplete implementation of the fuel-combustion air mixture done, which in turn can lead to increased pollutant emissions.

Accordingly, the object of the present invention is to provide a mobile heater, is generated in the heating heat by catalytic conversion of a fuel-combustion air mixture to a catalyst (fully catalytic oxidation) and in the case of a structurally space-saving and simple arrangement, a uniform application of the catalyst can be achieved with the fuel-combustion air mixture.

The object is achieved by a mobile heater according to claim 1. Advantageous developments of the invention are specified in the subclaims.

According to the present invention, a mobile heater, in particular a vehicle heater, is provided, which has a catalyst and which is designed such that in this thermal heat can be generated by catalytic conversion of fuel with combustion air, which are supplied to the catalyst. The mobile heater in this case has an injector for supplying a fuel-combustion air mixture to the catalyst, wherein the injector is designed and connected to a fuel supply and a combustion air supply or connected, that in the injector from a fuel propellant beam can be generated gaseous fuel and that by the fuel propellant jet combustion air for generating the fuel-combustion air mixture is sucked.

Through the use of an injector complete mixing of gaseous fuel and combustion air in a small space and thus a uniform mixture concentration can be achieved. By using the injector in a heater in which heating heat is generated by fully catalytic oxidation, the benefits of a used fully catalytic oxidation and be further developed in combination with the injector, so that among other things a reduced pollutant emission, a low noise level, a low structural and control engineering effort, a long life of the catalyst, etc., can be achieved. Due to the suction effect generated in the injector due to the fuel propulsion jet for the intake of combustion air, a separate combustion air fan for supplying combustion air is not required. Accordingly, further space, cost and control effort that would be required for the provision and control of a combustion air blower can be saved. Furthermore, the shape of the injector can be selected such that over a wide fuel delivery range, the appropriately aspirated amount of combustion air results in a suitable mixture concentration of the fuel-combustion air mixture. In this case, can be dispensed with a control device, such as a combustion air valve, through which the supply of combustion air to the injector is adjustable.

A "mobile heater" is understood in this context to mean a heater which is designed for use in mobile applications and adapted accordingly. This means in particular that it is transportable (possibly permanently installed in a vehicle or housed only for transport therein) and not exclusively for a permanent, stationary use, as is the case for example when heating a building, is designed. In this case, the mobile heater can also be permanently installed in a vehicle (land vehicle, ship, etc.), in particular in a land vehicle. In particular, it is for heating a vehicle interior, such as a land, water or aircraft, as well as a partially open space, as it is to be found, for example, on ships, especially yachts. The mobile heater can also be used temporarily stationary, such as in large tents, containers (for example, construction containers), etc. According to an advantageous development, the mobile heater as a stationary or auxiliary heater for a land vehicle, such as for a caravan, a Motorhome, a bus, a car, etc., designed.

The principle of fully catalytic oxidation, in which fuel with combustion air (in particular with oxygen contained therein) is flamelessly reacted (oxidized) on a catalyst, is well known and is already used in other technical fields. Therefore, this principle, which is used in the present invention for generating heating heat in the mobile heater, not discussed in detail.

With "injector", which is also referred to as a jet pump, reference is made in particular to a device in which a fluid jet (here fuel propellant jet) can be generated and due to a momentum exchange between the fluid jet and a second medium, in the area the fluid jet is supplied, the second medium (here combustion air) can be sucked and conveyed. In many cases, a nozzle for generating the fluid jet is used in the injector. According to the present invention, a fuel propelling jet of gaseous fuel is generated in the injector. In this case, directly gaseous fuel can be used. Alternatively, however, it is also possible to use liquid fuel which is evaporated before it is fed into the injector.

A "fuel supply" and a "combustion air supply" can be realized, inter alia, by the fact that corresponding connections of the injector are each connected to a sufficiently available quantity of fuel or combustion air (fuel supply or combustion air supply). In this case, the injector can be connected, for example, to a combustion air line, to outside air or to a combustion air tank directly or via further fluid guide elements (valves, pipelines, etc.). Preferably, the injector air, especially outside air supplied. In a corresponding manner, the injector can be connected to a fuel line, to a fuel tank, etc., directly or via further fluid-guiding elements (valves, pipelines, etc.).

According to an advantageous development, the injector has downstream of a section (of the same), in which fuel and combustion air are combined in use, a constriction of the flow cross-section for the fuel-combustion air mixture. Through this constriction, which is also referred to as a catchment nozzle, a mixing chamber is formed through which a uniform mixing of the gaseous fuel and the combustion air is supported.

According to an advantageous development, the injector has downstream of a section (of the same) in which fuel and combustion air are combined in use, in particular downstream of the constriction, a diffuser. By such a diffuser, a slowing down of the flow velocity is achieved with simultaneous pressure build-up of the fuel-combustion air mixture. Such a pressure build-up is particularly advantageous in that in the mobile heater, a sufficiently high pressure for exhaust emissions via the exhaust line, which may comprise, for example, a heat exchanger and corresponding exhaust pipes, is achieved. A pressure build-up within the heater is particularly at high exhaust back pressures, for example, in a long exhaust line occur, required. The pressure build-up can be determined by the dimensions of the diffuser, in particular by the ratio of the flow cross-sections at the inlet and at the outlet of the diffuser. It is further noted that, among other things, by appropriate selection of the dimensions of the injector and the constriction thereof and by selecting the flow rate and flow rate of the fuel propellant jet, a desired fuel-combustion air mixture ratio, a desired fuel-combustion air supply amount, a desired pressure and / or a desired flow rate of the fuel-combustion air mixture can be obtained.

According to an advantageous development of the injector is the only pumping element for conveying combustion air to the catalyst. In the experiment, it has been found that the pumping action generated in the injector is sufficient for the promotion of combustion air and for a desired pressure build-up of the fuel-combustion air mixture. Accordingly, it is possible to dispense with a combustion air blower and corresponding measures for controlling the combustion air blower, so that costs, space and control effort can be saved.

According to an advantageous development, the mobile heating device has a fuel valve (for example a reducing valve), which is arranged upstream of the injector and by means of which the supply of gaseous fuel to the injector can be set. The heating power provided by the heater scales with the amount of fuel supplied. Accordingly, different heating powers of the mobile heater can be adjusted in this way. In heaters in which heating is provided by a fully catalytic oxidation, the heating power in this way over a wide range is adjustable. As an alternative or in addition to a fuel valve, in the refinement explained below, in which liquid fuel is vaporized in a fuel treatment chamber, the supply of gaseous fuel to the injector can be supplied via a pump via which liquid fuel can be fed to the fuel treatment chamber. be set.

In principle, the amount of combustion air delivered in the injector scales with the amount of fuel supplied via the fuel propulsion jet. In the above-explained development of adjusting the supply of gaseous fuel to the injector while a suitable fuel-combustion air mixture concentration is usually achieved over a wide control range. Nevertheless, in some situations, a targeted adjustment of the supplied combustion air may be desirable. For example, the reaction temperature of the catalyst can be influenced in a targeted manner by the combustion air fraction of the fuel / combustion air mixture. According to an advantageous development, the mobile heater has a combustion air valve which is arranged upstream of the injector and by which the supply of combustion air to the injector is adjustable on. Through such a combustion air valve, throttling can also be carried out as a function of the occurring exhaust gas back pressures in order to adapt the supply of combustion air to changing exhaust gas back pressures. In particular, a compensation of an increasing exhaust backpressure can be achieved by opening the throttle.

As the catalyst of the mobile heater, those materials and structures suitable for performing fully catalytic oxidation can be used. In particular structures are suitable as structures which have a large surface area in relation to their volume. According to an advantageous development of the catalyst is formed in a porous, permeable structure. In this context, a porous structure is understood as meaning a structure which is permeated by a multiplicity of cavities. In particular, in this case structures can be used, which are generally used in catalysts, such as foam-like structures or structures having a plurality of honeycomb, cuboid, etc. cavities. Furthermore, it can be provided that the structure is formed by a carrier material which is coated with a catalyst material. Alternatively, however, it is also possible for the catalyst itself or a carrier material doped with catalyst material to form the structure.

According to an advantageous development, the catalyst is arranged in a chamber which has an inlet for the fuel-combustion air mixture at an upstream end and an outlet for exhaust gases at a downstream end. In this way, apart from the inlet and the outlet, a closed system for carrying out the fully catalytic oxidation is obtained. Preferably, the chamber is filled in a plane perpendicular to the flow direction over the entire flow cross section through the catalyst. In this way, as complete as possible implementation of the fuel-combustion air mixture is achieved with simultaneous uniform application of the catalyst. In this case, the direction of flow is referred to the direction or optionally to the main direction (in the case of a plurality of slightly different directions of flow) along which the gases flow from the inlet to the outlet of the chamber. Furthermore, according to an advantageous development, it is provided that the chamber in the region of the inlet and / or in the region of the outlet has a free space in which the respective gases can flow freely, having. In the region of the inlet, the free space serves, in particular, for the fuel-combustion-air mixture to spread uniformly in the plane transverse to the flow direction, in particular over the entire flow cross-section of the catalytic converter or the chamber. In the region of the outlet, the free space serves, in particular, for the exhaust gases to be able to be discharged uniformly across the plane transversely to the flow direction, in particular over the entire flow cross section of the catalyst or the chamber. In both cases, uniform flow conditions within the catalyst are achieved across the plane perpendicular to the flow direction, thereby promoting uniform catalyst loading and avoiding the formation of hot spots. Preferably, it is provided that the free space on the inlet side and / or the free space on the outlet side extends over the entire flow cross section of the catalyst or the chamber.

According to an advantageous development, a flow distribution element is provided, which is arranged in the free space in the region of the inlet, extends in a plane perpendicular to the flow direction and has a multiplicity of openings. By such a flow distribution element, a uniform distribution of the fuel-combustion air mixture in the plane perpendicular to the flow direction and thus a uniform loading of the catalyst is achieved over the flow cross-section. Furthermore, a temperature barrier between the region of the catalyst and the region of the inlet-side free space can be produced by the flow distribution element. Such a temperature barrier is produced, inter alia, by the heat being taken up by the flow distribution element and possibly dissipated. Furthermore, the flow distribution element has a reduced flow cross-section compared to the inlet-side free space, so that an increased flow rate of the respective gases is obtained in the region of the flow distribution element. By such an increase in the flow rate, a Stromversern the reaction, which is also referred to as a flashback, avoided. Preferably, in the region of the flow distribution element, the flow velocity is greater than the flame propagation velocity. Preferably, in the flow distribution element, the openings in the plane are distributed uniformly perpendicular to the flow direction. For example, the flow distribution element may be formed as a grid, as a sieve, as a perforated plate, etc. Furthermore, it is preferably provided that the flow distribution element extends over the entire flow cross-section of the catalyst or the chamber, so that the catalyst is supplied as uniformly as possible.

According to an advantageous development, it is provided that the flow cross-section of the catalyst increases along the flow direction. In this way, a thermal expansion of the gases when flowing through the catalyst can take place without or with only a slight pressure increase. Accordingly, the effect of a thermal constriction of the gases when passing through the catalyst, which can lead to pressure losses and thus a complicated exhaust emissions via the exhaust system, prevented or reduced. Preferably, it is provided that the flow cross-section of the chamber increases in a corresponding manner, so that the catalyst fills the chamber over its extension region along the flow direction in a plane transverse to the flow direction. Furthermore, it is preferably provided that along the flow direction and the individual pores of the catalyst, in particular the individual, z. B. honeycomb or cuboid channels of the catalyst, increase in cross-section to allow thermal expansion of the gases. In order to further increase the catalytic effect, it may further be provided that with increasing broadening of the flow cross-section of the catalyst further (eg honeycomb or cuboid) channels are inserted into the catalyst, or that individual channels of the catalyst along the flow direction in each case split into two or more channels.

According to an advantageous development, the mobile heater has a heatable fuel treatment chamber, which can be connected via a pump to a fuel supply of liquid fuel and which is connected to the injector such that vaporized fuel from the fuel processing chamber can be supplied to the injector , In this way, liquid fuel can also be used in the mobile heater.

In this embodiment, the amount of fuel supplied via the injector can be adjusted inter alia by the pressure that is built up by the pump. The vaporized fuel discharged from the fuel processing chamber is then preferably passed through a nozzle in the injector to produce the fuel propellant jet. Preferably, the fuel in the fuel conditioning chamber is heated so that superheated fuel vapor, which is then supplied to the injector, is obtained. As a result of the overheating, the formation of condensation nuclei can be prevented in the region of the injector and downstream thereof, in particular in the region of the constriction and / or the diffuser of the injector. With "fuel supply" is doing on a sufficiently available amount of fuel, as is the case for example with a fuel tank or a fuel line. The connection to such a fuel supply can take place directly or via further fluid-guiding elements (valves, pipelines, etc.).

According to an advantageous development, the mobile heating device has an electrical heating element, by means of which the catalyst and / or the fuel treatment chamber can be heated. During a starting phase, heating of the catalyst is required to achieve the required temperature for the catalytic conversion of fuel with combustion air. If sufficient heat is released by the catalytic conversion, the heating of the catalyst can be stopped by the electric heating element. Heat which is released during the catalytic conversion of fuel with combustion air onto the catalyst is also preferably used for the heating of the fuel treatment chamber after the starting phase. The control of the electric heating element is preferably carried out by a control of the mobile heater, in particular depending on the temperature in the region of the catalyst and / or the temperature in the region of the fuel processing chamber. For the heating of the catalyst and the fuel processing chamber, one and the same electrical heating element, such as a glow plug, is preferably used, so that the number of components and the required control thereof can be reduced. Such a glow plug can be used after the starting phase in a known manner for monitoring the temperature within the catalyst. Alternatively, however, it is also possible to provide in each case a separate electrical heating element for the catalytic converter and the fuel treatment chamber. Furthermore, only one electric heating element can be provided for heating the catalyst, in particular when gaseous fuel is used.

In operation, to facilitate heating of the fuel processing chamber by heat released in the catalyst, the fuel processing chamber is preferably arranged to be in thermal contact with the chamber within which the catalyst is disposed. According to an advantageous development, the fuel processing chamber is disposed within the chamber in which the catalyst is accommodated. In this way, heat released in the catalytic conversion of fuel with combustion air to the catalyst can be used for heating the fuel processing chamber. An effective heating of the fuel treatment chamber by this released heat can be carried out in particular when the fuel processing chamber is completely or at least partially surrounded by the catalyst. Furthermore, an effective use of this heat for heating the fuel processing chamber is also achieved if the fuel processing chamber is arranged wholly or partly in the outlet-side space of the chamber, which is flowed through by the hot exhaust gases and in the correspondingly high temperatures in use to rule. Preferably, in the latter case, the fuel treatment chamber is simultaneously arranged such that it can be heated by an electric heating element which is used for heating the catalyst. This can be achieved, for example, by extending the fuel treatment chamber at least partially into the region of the catalytic converter in which the electrical heating element is also disposed.

In general, the fuel processing chamber may be wholly or partly disposed in the chamber in which the catalyst is arranged, and in front of, wholly or partly within or after the catalyst. Furthermore, it can also be arranged on the outside of the chamber in which the catalyst is arranged, and in front of, behind or in the region of the catalyst. The arrangement preferably depends on the specific conditions, the desired reaction temperature in the catalyst and the required temperatures in the fuel treatment chamber.

According to an advantageous development, the heating heat provided by the heater is generated predominantly by a flameless, catalytic conversion of fuel with combustion air to the catalyst. Preferably, the heating heat provided by the heater is generated solely by a flameless, catalytic conversion of fuel with combustion air to the catalyst. This means in particular that the heater has no combustion chamber and no measures for flame retardancy and / or flame stabilization are provided.

Further advantages and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. From the figures show:

1 FIG. 2 is a schematic cross-sectional view of a mobile heater according to a first embodiment of the present invention; FIG. and

2 FIG. 4 is a schematic cross-sectional view of a mobile heater according to a second embodiment of the present invention. FIG.

1 is a schematic representation of a mobile heater 2 in the form of a stationary heater, which is fixedly installed in a land vehicle (not shown), such as an RV, for heating an interior thereof. The mobile heater 2 has a catalyst 4 on that inside a chamber 6 is arranged. In the mobile heater 2 is thermal heat by fully catalytic oxidation of gaseous fuel with combustion air to the catalyst 4 mountable. In particular, takes place in the mobile heater 2 no flammable conversion of fuel with combustion air instead, as is the case for example in mobile heaters, which have a combustion chamber.

The chamber 6 has an inlet 8th on, over the catalyst 4 a gaseous fuel-combustion air mixture can be fed. Further, the chamber has 6 an outlet 10 on, on the exhaust gases that are produced in the implementation of fuel with combustion air, can be derived. Apart from the inlet 8th and the outlet 10 forms the chamber 6 a closed system. The pressure of the gases inside the chamber 6 is for discharging the exhaust gases via a (not shown) exhaust line of the mobile heater 2 used.

For the supply of gaseous fuel-combustion air mixture is an injector 12 used, the outlet side with the inlet 8th the chamber 6 connected is. In the injector 12 is a nozzle 14 provided, via the gaseous, pressurized fuel can be supplied and through which a fuel propellant jet of gaseous fuel can be generated. The injector 12 is also with a combustion air supply 16 connected in such a way that in use by the fuel propulsion jet combustion air via the combustion air supply 16 is sucked. For example, the injector 12 To be connected via a (not shown) line system to outside air, so that outside air can be sucked by the fuel propellant jet. The injector 12 forms the only pumping element of the mobile heater 2 , which is used to promote combustion air to the catalyst 4 is used.

The aspirated combustion air is then mixed with the gaseous fuel of the fuel propulsion jet. Good mixing is particularly assisted by the fact that downstream of a portion of the injector 12 , in which fuel and combustion air are combined in use, a constriction 18 is provided so that in the area before the constriction 18 a mixing chamber 20 , in which a mixing of the gases takes place in use, is formed. Downstream of the narrowing 18 turn is a diffuser 22 arranged so that the flow cross-section for the fuel-combustion air mixture from the constriction 18 to the inlet 8th the chamber 6 is enlarged. As explained above, thereby the flow rate of the fuel-combustion air mixture is lowered and the pressure thereof is increased.

In the illustrated embodiment, the inlet opens 8th centrally in the chamber 6 with respect to their flow cross-section. The fuel-combustion air mixture reaches after passing through the inlet 8th not directly the catalyst 4 , Rather, the chamber points 6 in the area of the inlet 8th first a free space 24 on, which is in a plane perpendicular to the flow direction 26 (the gases inside the chamber 6 ) over the entire flow cross-section of the chamber 6 extends and in which the gases can flow freely. As explained above, by the provision of the free space 24 a uniform supply of the fuel-combustion air mixture over the entire flow cross-section of the catalyst 4 and thus a uniform loading of the catalyst 4 supported.

In the inlet-side free space 24 is adjacent to the catalyst 4 a flow distribution element 28 arranged in the plane perpendicular to the flow direction 26 extends over the entire flow cross-section. In the illustrated embodiment, the flow distribution element 28 formed by a, in a plane extending grid. As explained above, through the flow distribution element 28 a uniform admission of the catalyst 4 supported with the fuel-combustion air mixture and a temperature barrier between the catalyst 4 (Higher temperature range) and the free space 24 (Lower temperature range) formed.

The catalyst 4 , in the fuel-combustion air mixture after passing through the free space 24 enters, extends with respect to a plane perpendicular to the flow direction 26 over the entire flow cross section of the (cylindrically shaped) chamber 6 , The catalyst 6 is formed in a porous, permeable structure. In the present embodiment, the catalyst 6 a variety of honeycomb channels 30 on, extending parallel to each other along the flow direction 26 extend.

After passing through the catalyst 4 At first the gases (exhaust gases) reach a free space 32 which is in a plane perpendicular to the flow direction 26 (the gases inside the chamber 6 ) over the entire flow cross-section of the chamber 6 extends and within which the exhaust gases can flow freely. As explained above, this results in a, over the entire flow cross-section of the catalyst 4 uniform discharge of the exhaust gases and thus the occurrence of hot spots avoided within the catalyst. The outlet 10 is with respect to the flow cross-section of the (cylindrically shaped) chamber 6 centrally located in the present embodiment.

In the mobile heater 2 liquid fuel is used. This must be before feeding to the injector 12 treated in such a way, in particular evaporated, that the injector 12 gaseous fuel is supplied and that when passing through the injector 12 (especially in the area of narrowing 18 and the diffuser 22 ) And downstream of the same as possible condensation nuclei of the fuel are formed. The treatment (evaporation) of the fuel should preferably be such that the fuel reaches the catalyst completely gaseous, since otherwise the conversion of fuel with combustion air to the catalyst is impaired. For this purpose, the mobile heater 2 a heatable fuel treatment chamber 34 on that inside the chamber 6 is trained. The fuel processing chamber 34 is via appropriate lines 36 and a pump 38 connected to a fuel tank (not shown) containing liquid fuel. From a section of the fuel processing chamber located at the top of the unit 34 leads a line 39 to the nozzle 14 of the injector 12 , About the pump 38 can the pressure within the fuel processing chamber 34 and with it over the nozzle 14 supplied amount of fuel can be adjusted.

The fuel processing chamber 34 is so inside the chamber 6 arranged that they are from the catalyst 4 is surrounded. Part of the heat generated in the catalytic conversion of fuel with combustion air in the range of the catalyst 4 Accordingly, it can be used to heat the fuel processing chamber 34 and thus used to vaporize liquid fuel. In addition, an electric glow plug 40 provided, both for heating the fuel processing chamber 34 as well as for heating the catalyst 4 is used. For effective heat transfer from the glow plug 40 on the fuel processing chamber 34 and the catalyst 4 to enable is the electric glow plug 40 arranged such that it at least partially through the catalyst 4 as well as through the fuel processing chamber 34 extends. The glow plug 40 is by a (not shown) control of the mobile heater 2 controlled such that through this during a starting phase of the mobile heater 2 the catalyst 4 and the fuel processing chamber 34 be heated. After a start-up phase, that is, as soon as in the area of the catalyst 4 a sufficiently high temperature (for the catalytic conversion and for heating the fuel treatment chamber 34 ), the heating operation of the glow plug becomes 40 set. Subsequently, the glow plug 40 in a known manner for temperature monitoring of the catalyst 4 be used.

The following is with reference to 2 A second embodiment of the present invention is explained. In this case, the differences compared to the first embodiment will be considered.

2 is again a schematic representation of a mobile heater 42 in the form of a parking heater. Again, the mobile heater features 42 a catalyst 44 on that inside a chamber 46 is arranged. The chamber 46 has an inlet 48 and an outlet 50 on, each central to the chamber 46 lead. For supplying the gaseous fuel-combustion air mixture is again an injector 52 used, which according to the first embodiment, a nozzle 54 and with a combustion air supply 56 connected is. Downstream of a section of the injector 52 , in which fuel and combustion air are brought together, the injector points 52 a narrowing 58 on, so before the constriction 58 a mixing chamber 60 is formed. Downstream of the narrowing 58 turn is a diffuser 62 arranged. The injector 52 forms the only pumping element of the mobile heater 42 , which is used to promote combustion air to the catalyst 44 is used.

As in the first embodiment, the chamber 46 each on the inlet side and on the outlet side a free space 64 and 72 extending in a plane perpendicular to the flow direction or main flow direction 66 (the gases inside the chamber 46 ) each over the entire flow cross-section of the chamber 46 extend and in which the respective gases can flow freely. In the inlet-side free space 64 is adjacent to the catalyst 44 again a flow distribution element 68 arranged in the plane perpendicular to the flow direction 66 over the entire flow cross-section of the chamber 46 extends.

The catalyst 44 in the fuel-combustion air mixture after passing through the inlet-side clearance 64 enters, extends with respect to a plane perpendicular to the flow direction 66 over the entire flow cross-section of the chamber 46 , In contrast to the first embodiment, the flow cross-section of the catalyst increases 44 and in a corresponding manner, the flow cross-section of the chamber 46 along the flow direction 66 to. In particular, the catalyst 44 and the chamber 46 in the 2 illustrated cross-section (along a plane parallel to the flow direction 66 through the central axis of the chamber 46 leads) formed frusto-conical. As explained above, by such an increase in the flow cross-section pressure losses that may occur due to the thermal expansion of the gases can be reduced or even avoided. The catalyst 44 itself is again formed in a porous, permeable structure. In the present embodiment, the catalyst 44 a variety of honeycomb channels 70 on, which are essentially parallel to the flow direction 66 extend. As in 2 is shown, the individual channels fan out 70 however, according to the increase of the flow area of the catalyst 44 and the chamber 46 along the flow direction 66 on. This will be along the flow direction 66 the cross section of the individual channels 70 increased. Furthermore, the individual channels extend 70 not exactly parallel to the drawn flow direction 66 but the extension direction of the individual channels is with increasing distance of the channels 70 from the central axis of the chamber 46 increasingly outward from the flow direction 66 angled. The flow directions within the individual channels also run in the corresponding direction 70 , so with the flow direction 66 is essentially referred to a main or an average flow direction.

In order to achieve the highest possible catalytic effect, it may further be provided that the individual channels 70 along the flow direction 66 branched into two or more channels, so that the largest possible catalyst surface is provided. This is in 2 schematically through the additional lines 71 im (in 2 ) lower portion of the catalyst 44 shown.

In addition to the above-explained avoidance of pressure losses during the passage of gases through the chamber 46 Another advantage of this arrangement is that the catalyst 44 has a reduced inlet flow cross-section and thus the input side, a uniform distribution of the fuel-combustion air mixture over the flow cross-section of the catalyst 44 is relieved.

In the mobile heater 42 According to the second embodiment, gaseous fuel is used. Accordingly, a fuel processing chamber as provided in the first embodiment is not required. As in 2 is shown, is the nozzle 54 of the injector 52 via a fuel valve 74 and a corresponding fuel line 75 at a fuel tank 76 connected. In the fuel tank 76 gaseous, pressurized fuel is stored. The fuel valve 74 is about a controller 78 of the mobile heater 42 controllable, so that in this way the amount of fuel supplied adjustable and thus a heating power of the mobile heater 42 is controllable.

The injector 52 is also via a combustion air line 80 and a combustion air valve 82 connected to outside air. The combustion air valve 82 is about the controller 78 of the heater 42 can be controlled, so that in addition to the control of the amount of fuel supplied and the supplied amount of combustion air is adjustable. As explained above, this control of the amount of combustion air supplied is not absolutely necessary, but may be advantageous in certain situations or operating conditions.

Furthermore, the mobile heater 42 an electric glow plug 84 on, in contrast to the first embodiment exclusively for heating the catalyst 44 during a starting phase of the mobile heater 42 is used. The glow plug 84 is in turn from the controller 78 controllable. Preferably, it is provided that the glow plug in dependence on a temperature in the region of the catalyst 44 from the controller 78 is controlled, in particular that the heating operation of the glow plug 84 upon reaching a predetermined temperature in the range of the catalyst 44 is stopped. The electric glow plug 84 extends into the catalyst 44 into it, so that an effective heat transfer is achieved. The glow plug 84 may also, if it is not used for heating, in a known manner for temperature monitoring of the catalyst 44 be used.

The control lines 86 that from the controller 78 to the combustion air valve 82 , the fuel valve 74 and the electric glow plug 84 lead, are in 2 each shown in dashed lines.

The present invention is not limited to the embodiments shown in the figures. In particular, it is not absolutely necessary for the injector to have a constriction and a diffuser downstream of a section in which fuel and combustion air are combined in use. As explained above, however, this constriction and the diffuser are advantageous in terms of good mixing of the gases and pressure build-up.

Furthermore, it is not absolutely necessary that the inlet and the outlet are each arranged centrally with respect to the flow cross-section of the chamber. Rather, these can also be arranged laterally. Preferably, however, the arrangement should be tuned so that as uniform as possible loading of the catalyst with the fuel-combustion air mixture is achieved.

For reasons of clarity, the figures did not show the type of heat dissipation of the heating power provided by the mobile heater. This can be done, inter alia, in a known manner, such as via a heat exchanger.

Claims (15)

Mobile heater, in particular vehicle heater, having a catalytic converter ( 4 ; 44 ) and which is designed such that in this thermal heat by catalytic conversion of fuel with combustion air, the catalyst ( 4 ; 44 ) can be generated, characterized by an injector ( 12 ; 52 ) for supplying a fuel-combustion air mixture to the catalyst ( 4 ; 44 ), the injector ( 12 ; 52 ) and configured with a fuel supply ( 34 . 36 . 38 ; 74 . 75 . 76 ) and a combustion air supply ( 16 ; 56 ) is connectable in that in the injector ( 12 ; 52 ) A fuel propellant jet of gaseous fuel can be generated and that by the fuel propulsion jet combustion air for generating the fuel-combustion air mixture is sucked. Mobile heater according to claim 1, characterized in that the injector ( 12 ; 52 ) downstream of a section in which fuel and combustion air are combined in use, a constriction ( 18 ; 58 ) has the flow cross-section for the fuel-combustion air mixture. Mobile heater according to claim 1 or 2, characterized in that the injector ( 12 ; 52 ) downstream of a section in which fuel and combustion air are combined in use, in particular downstream of the constriction ( 18 ; 58 ), a diffuser ( 22 ; 62 ) having. Mobile heater according to one of the preceding claims, characterized in that the injector ( 12 ; 52 ) the only pumping element for conveying combustion air to the catalyst ( 4 ; 44 ). Mobile heater according to one of the preceding claims, characterized by a fuel valve ( 74 ), upstream of the injector ( 12 ; 52 ) and by which the supply of gaseous fuel to the injector ( 12 ; 52 ) is adjustable. Mobile heater according to one of the preceding claims, characterized by a combustion air valve ( 82 ), upstream of the injector ( 12 ; 52 ) and by which the supply of combustion air to the injector ( 12 ; 52 ) is adjustable. Mobile heater according to one of the preceding claims, characterized in that the catalyst ( 4 ; 44 ) is formed in a porous, flow-through structure. Mobile heater according to one of the preceding claims, characterized in that the catalyst ( 4 ; 44 ) in a chamber ( 6 ; 46 ), which at an upstream end has an inlet ( 8th ; 48 ) for the fuel-combustion air mixture and at an downstream end an outlet ( 10 ; 50 ) is arranged for exhaust gases, and that the chamber ( 6 ; 46 ) in a plane perpendicular to the flow direction ( 26 ; 66 ) over the entire flow cross section through the catalyst ( 4 ; 44 ) is filled out. Mobile heater according to one of the preceding claims, characterized in that the catalyst ( 4 ; 44 ) in a chamber ( 6 ; 46 ), which at an upstream end has an inlet ( 8th ; 48 ) for the fuel-combustion air mixture and at an downstream end an outlet ( 10 ; 50 ) is arranged for exhaust gases, and that the chamber ( 6 ; 46 ) in the area of the inlet ( 8th ; 48 ) and / or in the area of the outlet ( 10 ; 50 ) a free space ( 24 . 32 ; 64 ; 72 ), in which the respective gases can flow freely. Mobile heater according to claim 9, characterized by at least one flow distribution element ( 28 ; 68 ) in the open space ( 24 ; 64 ) in the area of the inlet ( 8th ; 48 ) is arranged in a plane perpendicular to the flow direction ( 26 ; 66 ) and having a plurality of openings. Mobile heater according to one of the preceding claims, characterized in that the flow cross-section of the catalyst ( 4 ; 44 ) along the flow direction ( 26 ; 66 ) increases. Mobile heating appliance according to one of the preceding claims, characterized by a heatable fuel processing chamber ( 34 ) via a pump ( 38 ) is connectable to a fuel supply of liquid fuel and with the injector ( 12 ) is connected such that vaporized fuel from the fuel processing chamber ( 34 ) the injector ( 12 ) can be fed. Mobile heating appliance according to one of the preceding claims, characterized by an electric heating element ( 40 ; 84 ), by which the catalyst ( 4 ; 44 ) and / or the fuel processing chamber ( 34 ) is heated. Mobile heater according to claim 12 or 13, characterized in that the fuel processing chamber ( 34 ) within the chamber ( 6 ; 46 ) in which the catalyst ( 4 ; 44 ) is arranged, in particular that the fuel processing chamber ( 34 ) at least partially from the catalyst ( 4 ; 44 ) is surrounded. Mobile heating appliance according to one of the preceding claims, characterized in that the heating heat provided by the heater predominantly, in particular exclusively, by a flame-free, catalytic conversion of fuel with combustion air to the catalyst ( 4 ; 44 ) is produced.

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