WO2012016817A1

WO2012016817A1 - Burner with steady atomization at low back pressure

Info

Publication number: WO2012016817A1
Application number: PCT/EP2011/062281
Authority: WO
Inventors: Bjoern Damson
Original assignee: Robert Bosch Gmbh
Priority date: 2010-08-04
Filing date: 2011-07-18
Publication date: 2012-02-09
Also published as: US20130133314A1; DE102010038865A1; JP2013538966A; JP5705318B2

Abstract

An apparatus for fuel preparation (100) for a burner (18) for regenerating a particle filter (16) of an exhaust gas aftertreatment system comprising an exhaust gas passage (14) for discharging a hot exhaust gas flow from an internal combustion engine (12), in particular a compression-ignition internal combustion engine, is proposed. The apparatus for fuel preparation (100) has an atomizing device (110) for preparing the fuel, a combustion chamber (116), an ignition device (26) and a combustion air supply (24). The combustion air supply (24) provides a primary air feed line (112) for preparing the fuel and a secondary air feed line (114) for feeding combustion air in order to produce an ignitable fuel/air mixture.

Description

Description title

Burner with stable atomization at low counter pressure state of the art

The tightening legal requirements for the protection of health and the environment, which regulate the emissions of motor vehicles, provide a

Challenge for the development of engines and the

Exhaust gas aftertreatment techniques are of particular importance in this context, the reduction of particulate emissions and, above all, emissions of self-igniting

Internal combustion engines which, among other things, cause cancer. Thus, many methods and devices for exhaust aftertreatment have been developed to eliminate the soot particles present in the exhaust gases. Well known is the use of

Particulate filter systems for retaining particulate pollutants. For particle separation, exhaust gases are passed through a heat-resistant filter medium. The retained by the filter medium particles, which in particular have diameters in the range of 10 to 5000 nm, occupy the filter, which comes to increase the pressure loss across the filter, which makes a continuous or intermittent regeneration of the filter medium necessary. The regeneration is generally carried out by almost residue-free combustion of the deposited soot particles with oxygen. However, ignition temperatures of about 600 ° C are necessary for combustion, which are rarely achieved in the exhaust gas of a self-igniting internal combustion engine even at full load. It is known to provide for this purpose a burner to a

to achieve appropriate increase in the exhaust gas temperature.

From DE 100 24 254 a catalytic burner is known which intervenes

Combustion engine and particulate filter is arranged and increases without the provision of an ignitable fuel mixture, the exhaust gas temperature. The one of the

catalytic burner post-engine injected fuel is attached to one

Oxidizing catalyst reacted with the release of heat of reaction, the Exhaust gas temperature is raised to regeneration temperature. However, it is necessary that the temperature of the exhaust gases must already have reached a certain value in order for the reaction catalyzed by the oxidation catalyst to take place. Below this temperature, the activity of the catalyst is so low that the injected fuel is not sufficiently reacted. Regeneration is not reliably possible in every engine load range. In addition, an additional fuel injection is required, which is only possible with self-igniting internal combustion engines with common rail technology, with a far-reaching intervention in the engine management is necessary. Also known is the use of a combustion device in the filter device to produce the required temperature in the exhaust stream. That's one

Combustion device is known, comprising a combustion chamber and a burner, wherein metered fuel and metered combustion air is mixed to form an ignitable fuel-air mixture. The fuel-air mixture formed in the combustion chamber is ignited by an igniter, the hot fuel gases are mixed with the exhaust gases and raise the exhaust gas temperature so far that the accumulated in the particulate filter

Oxidize soot particles. Generally these are fan burners with a pressure atomizing nozzle. In general, it is needed for sufficient heating of the exhaust stream

Burner power as a function of engine operation, wherein the burner power is adapted to the current operating point of the internal combustion engine. If the entire exhaust gas flow is brought to the required combustion temperature, a high burner output is required, resulting in higher fuel consumption. To achieve an ignitable fuel-air mixture therefore a large amount of air is required, with a large burner is necessary. The air supply, which essentially takes place from a compressed air reservoir or via an electrically operated air pump, thus heavily loads the vehicle electrical system due to the relatively high power consumption of the associated electric motor, which can lead to disruptions, especially at low internal combustion engine speeds.

On the other hand results from the increased amount of air, a correspondingly increasing flow velocity in the air supply line, with a high back pressure is generated. The disadvantage here is that an increased back pressure leads to an increased electrical power consumption. With a low burner output there is also the risk that the treatment of the fuel is insufficient. In case of insufficient preparation or Atomization of the fuel can get unburned fuel into the particulate filter and destroy it.

DE 10 2009 051 327 A1 relates to a method for controlling a temperature of a combustion air of an oil burner. The supply of the combustion air to a mixing zone of the burner can be carried out in dependence on an operating mode by a first and / or by a first and a second supply path, wherein heat is supplied to the combustion air in different ways. From DE 38 26 446 A1 also atomizing burners are known for liquid fuels, with heavy oil is fed with a primary air flow in a nozzle tube, which is surrounded by a jacket tube, via which secondary air is supplied.

Presentation of the invention

According to the invention, a device for fuel preparation for a burner for the regeneration of a particulate filter in an exhaust aftertreatment system of

Internal combustion engine proposed with a combustion air supply, wherein the combustion air supply provides a primary air supply line for the treatment of the fuel and comprises a secondary air supply line which supplies combustion air to produce an ignitable fuel-air mixture.

In a particulate filter of an exhaust aftertreatment system, starting from known filter bodies, for example filter channels, filter meshes or filter pockets made of ceramic or sintered metallic material, particles build up over time. The

Particle structures may be so pronounced that the exhaust gas flow through the

Exhaust after-treatment system is limited or even blocked. This leads to an increased back pressure and ultimately to a reduced performance, increased

Exhaust gas temperatures and a deteriorated fuel consumption. The particle filter is therefore regenerated during operation either continuously or periodically with hot air.

In the proposal according to the invention, the temperature required for the regeneration of the particulate filter in the exhaust stream of a combustion device, in particular a burner with a combustion chamber and an atomizer is generated, wherein the combustion air to the burner via a primary and a secondary air supply line is supplied. The fuel preparation at the atomizer is on the primary air supply line, a primary air mass flow available, which can be supplied largely independent of the burner power. With increased

Burner capacity and concomitant increased air demand, the air supply is carried out next to the primary air supply line further via the secondary air supply line, the back pressure at the atomizer can be kept substantially constant at a low level.

Advantages of the invention

According to the invention, a primary air mass flow is fed to the atomizing device via the primary air supply line, which atomizes the injected fuel finely.

Immediately behind a nozzle is obtained by intensive mixing of the fine fuel mist with the combustion air, an aerosol which is ignitable. At a

Increased demand for air is introduced via the secondary air supply line

Secondary air mass flow promoted. The additional air supply line allows a

Setting an appropriate fuel injection ratio may affect the direction of injection and produce a proper size of fuel droplet size. Furthermore, the back pressure can be kept low and thus a

mechanical and electrical power requirements, such as an air pump, in

Essentially kept low.

In a preferred embodiment, the secondary air supply line opens directly into the combustion chamber, wherein the fine aerosol of fuel mist and combustion air generated by the atomizer mixed with the secondary air mass flow. This arrangement can be made very simple, so that the cost of this device can be kept low. Further, in this arrangement, the back pressure remains at a low level because there is no throttle restriction in the secondary air supply line. In an alternative embodiment of the fuel conditioning apparatus for a burner in an exhaust aftertreatment system, that of the secondary

Air supply line supplied secondary air mass flow directly into the

Nebulizer device, so that a support of the atomization of the injected fuel is obtained. Thus, the secondary air mass flow of the atomizer can be supplied in a manner that the atomization of the injected fuel is influenced and substantially improved with regard to the achieved fuel droplet size and the homogenization. In addition, influence can be taken on the flame generated at the burner, for example, by imparting first a twist and optionally secondly a constriction on the forming flame, with a flame stability is achieved even in still different air conditions. By means of the secondary air mass flow, furthermore, the contamination on the atomizing device, in particular on the nozzle, can be kept low, so that even fine nozzles can be used in the atomizing device. So can about the secondary

Air supply line to clean the nozzle and cooled.

The atomizing device may for example have a nozzle tube which is surrounded by a jacket tube. On the jacket tube lateral openings for introducing the secondary air mass flow are provided in the annular space formed. By a certain orientation of the openings can be achieved that the flame through the

Secondary air mass flow a swirl and / or a constriction is impressed, with a stabilization of the flame is achieved. A constriction of the initiated

Air mass flows, generates a high flow velocity. A high

Flow rate of the primary air mass flow or a correspondingly large speed difference to the fuel flow can be used to atomize the fuel. A high speed difference between primary mass flow and

Secondary mass flow promotes aerosol formation, the difference in velocity being particularly great when the two air mass flows are imparted with a twist of different orientation. The metering of the combustion air is generally controlled by a control device. For example, the air supply via a solenoid valve from a compressed air reservoir or by an electrically operated air pump, for example via a vane pump, a claw pump or a rotary lobe pump. In an alternative embodiment of the device according to the invention is in at least one of

Air supply lines arranged a pressure control valve, preferably in the secondary

Air supply line. The pressure control valve in the air supply line may be designed as a simple mechanical pressure valve or be a controllable pressure control valve. Thus, there is a possibility that the combustion air is supplied to the burner from a pressure to be determined in the air supply line via the primary and the secondary air supply line. Thus, the increasing in large amounts of air counter pressure is limited wherein the atomization of the injected fuel can be carried out under optimized conditions and the stability of the flame is achieved in a simple and cost-effective manner.

In a starting phase of the burner, in which only a small amount of air is needed, the prevailing pressure is below the opening pressure of the arranged in at least one air supply line pressure control valve. The amount of air is provided only via an air supply line of the preparation of the fuel. With increasing performance of

Internal combustion engine, the power requirement of the burner increases, so the needed

Air volume increases, the back pressure increases and after exceeding the

Opening pressure of the at least one pressure control valve, the amount of air is supplied via the primary and the secondary air supply line.

The switching of the air supply via one or two air supply lines is arbitrarily adjustable, both the conditions at low burner power and at high

Burner performance can be accommodated.

In a further embodiment of the device for fuel preparation for a burner is provided that the fuel to be injected with the air, in particular the primary air mass flow supplied via the primary air supply line, before the

Atomizer is mixed and this mixture is supplied to the combustion chamber. For example, the fuel and the air mass flow at a junction of the lines, for example in the form of a tee, merged. The combustible fuel-air mixture thus produced enters the atomizer premixed. Furthermore, a reliable ignition of the fuel-air mixture is ensured, since the mixture is not generated in the combustion chamber, but outside of it, wherein an ignitable mixture can be adjusted with a certain air ratio. Furthermore, in this embodiment, a plurality of necessary components, for example metering valves, check valves and / or pressure control valves, can be combined to form one component. Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it:

Figure 1 shows an exhaust gas treatment system according to the prior art; Figure 2 shows an embodiment of a device according to the invention for

Fuel preparation for a burner with a secondary air inlet into a combustion chamber;

Figure 3 shows an embodiment of a device according to the invention for

Fuel treatment with a secondary air inlet into a mixing zone;

Figure 4 shows an alternative embodiment of the inventive device for

Fuel preparation for a burner. FIG. 1 shows, in a highly schematic illustration, an exhaust aftertreatment system 10 according to the prior art.

From an internal combustion engine 12 exhaust gases pass through an exhaust pipe 14 into a particle filter 16 via an interposed burner 18, wherein the burner 18 and the particulate filter 16 in a housing 20 in the flow direction of the exhaust gases

arranged one behind the other. Soot particles, which are discharged with the exhaust gas, accumulate in the particulate filter 16. Depending on the selected mode of operation, the fuel-air mixture generated by the supply of fuel 22 and air 24 is ignited via an ignition device 26 on the burner 18. The emerging from the burner 18 hot gases mix in an anteroom 28 of the particulate filter 16 while raising the

Exhaust gas temperature with the exhaust gases such that the accumulated particulate filter 16 soot particles oxidize. The regeneration of the particulate filter 16 is usually carried out during operation of the internal combustion engine 12, wherein the residual oxygen in the exhaust gases for the operation of the burner 18 can be used. The combustion air is supplied via an electrically operated air pump 30, which is driven by an electric motor, not shown. The electric motor is connected to an onboard battery that is charged by the alternator (not shown). variants

In Figure 2 is an embodiment of a device according to the invention for

Fuel processing 100 for a burner 18 shown.

The device for fuel treatment 100 comprises an atomizer 1 10, is processed with the injected fuel in a suitable manner, in particular atomized. The atomizer 1 10 fuel is supplied via the supply 22, wherein, for example, for metering the fuel, a solenoid valve or a

Fuel pump is provided, which is driven by a controllable electric motor (not shown). The fuel can be removed via a suction line a fuel tank of the internal combustion engine 12, wherein the flow rate can be varied by varying the rotational speed of the electric motor. Combustion air is the burner 18 according to the invention via a primary air supply line 1 12 and a secondary

Air supply line 1 14 supplied. The metering of the air supply takes place, for example, via a solenoid valve or via an electrically operated air pump (not shown). At the atomizer 1 10, which is designed for example as a swirl burner with a tangential fuel and / or air supply, the supplied fuel is finely atomized, forming an ignitable fuel-air mixture. The atomizing device 110 of the burner 18 can be constructed, for example, as an annular nozzle, at whose annular atomizing tongue the fuel passes along and is finely atomized by a rotating air flow. The aerosol generated entering a combustion chamber 1 16 is ignited in the usual way by an ignition device 26. The use of ignition electrodes, glow plugs or an incandescent body is known. In addition to the primary air mass flow through the primary air supply line 1 12 supplied combustion air required additional amount of combustion air with increased burner power is passed according to the invention via the secondary air supply line 1 14 according to the embodiment shown in Figure 2 directly into the combustion chamber 1 16. In the secondary air supply line 1 14, a pressure regulating valve 1 18 is arranged. This pressure control valve 1 18 may be formed as a simple mechanical pressure control valve, which releases the secondary air supply line at a certain opening pressure. Alternatively, the pressure regulating valve 1 18 may be formed as a controllable pressure control valve, in which the opening pressure can be varied, for example via a control device. Thus, a modulatable device is available to the burner 18 with Supply combustion air. Especially in a start phase of

Internal combustion engine 12, the secondary air supply line 1 14 are kept closed, via the primary air supply line 1 12 a primary air mass flow of the atomization of the fuel is available. Accordingly, the atomization of the fuel with respect to the amount of air provided and the formation of the atomizer 1 10 can be optimized.

FIG. 3 shows an alternative embodiment of the fuel processing device 100 of a burner 18. In this case, the secondary air supply line does not open directly in the combustion chamber 1 16, but in the atomizer 1 10. The atomizer 1 10 has, for example, a central nozzle tube, in the fuel and a

Primary air mass flow flows. Furthermore, the central nozzle tube surrounds a jacket tube which has openings through which the secondary mass flow is supplied. The orientation of the openings can be such that a swirl is impressed. The generated flame is thereby stabilized and their direction determined. With this

Atomizer 1 10 can be maintained even if an air flow for cleaning and cooling the nozzle when the fuel and primary air supply is interrupted. The service life of such an atomizer 1 10 increases. FIG. 4 shows a further exemplary embodiment of the device for fuel preparation 100 of a burner 18. The supply of fuel 22 flows into the primary

Air supply line 1 12, wherein via a suitable means fuel in the primary air supply line 1 12 is introduced. Thus, the supply of the fuel 22 in a suction line of the air pump can open, for example, a vane pump. The fuel is intimately mixed with the air and the generated aerosol is fed through a feed line 120 of the atomizer 1 10. If necessary, further combustion air can be supplied via the secondary air supply line 1 14 via a pressure regulating valve 1 18, which is mixed with the aerosol generated and ignited as an ignitable fuel-air mixture in the combustion chamber. In Figure 4 is further shown that the fuel is metered, for example by means of a controllable fuel pump or by means of a Kraftstoffdosierventils 122. In the primary air supply line 1 12 is a

Check valve 124 is provided. According to the invention, the multiple valves, pressure control valve, metering valve, check valve can be combined in one component.

Claims

claims

1 . A fuel conditioning apparatus (100) for a burner (18) for regenerating a particulate filter (16) of an exhaust aftertreatment system having an exhaust passage (14) for exhausting a hot exhaust stream from an internal combustion engine (12), particularly a self-igniting internal combustion engine, the fuel conditioning apparatus (16). 100) an atomizing device (1 10) for the treatment of fuel, a combustion chamber (1 16), a

Combustion air supply (24) and an ignition device (26), characterized in that the combustion air supply (24) has a primary

Air supply line (1 12) provides for the treatment of the fuel and a secondary air supply line (1 14) for supplying combustion air to produce an ignitable fuel-air mixture.

2. Device for fuel treatment (100) according to claim 1, characterized

characterized in that at least one of the primary and secondary

Air supply lines (1 12, 1 14) a pressure control valve (1 18) is arranged.

3. A device for fuel preparation (100) according to claim 2, characterized

characterized in that the pressure regulating valve (1 18) is a mechanical pressure regulating valve.

4. An apparatus for fuel preparation (100) according to claim 2, characterized

characterized in that the pressure regulating valve (1 18) is a control valve.

5. A device for fuel preparation (100) according to claim 2, characterized

characterized in that when the pressure regulating valve (1 18) is open

Combustion air supply (24) via the primary and the secondary

Air supply line (1 12, 1 14) takes place.

6. A device for fuel preparation (100) according to claim 5, characterized

characterized in that the primary air supply line (1 12) in the Atomizer (1 10) and the secondary air supply line (1 14) in the combustion chamber (1 16) opens.

Means for fuel treatment (100) according to claim 5, characterized

characterized in that the primary air supply line (1 12) and the secondary

Air supply line (1 14) in the atomizer (1 10) opens.

Fuel conditioning device according to one of claims 1 to 7, characterized in that fuel is injected into at least one of the primary or secondary air supply line (1 12, 1 14) and the generated fuel-air mixture of the atomizer (1 10) is supplied.

Means for fuel treatment (100) according to one of claims 1 to 8, characterized in that the combustion air supply (24) comprises a metering valve and the fuel is metered by means of a Kraftstoffdosierventils (124), wherein in a valve block a plurality of valves (1 18, 122 , 124) are summarized.