Reducing agent injection nozzle and reducing agent metering system

Abstract

The invention relates to a reductant injection nozzle and a reductant metering system. The invention relates to a reducing agent injection nozzle (400) for injecting a reducing agent into an exhaust gas flow of an internal combustion engine for selective catalytic reduction, comprising a nozzle body in which a flow channel (6, 7) is formed, the invention relates to a reducing agent injection nozzle having a flow channel through which a reducing agent fed to the reducing agent injection nozzle is conducted from a connecting channel of the reducing agent injection nozzle to a nozzle outlet (1), a vortex chamber (2) being formed upstream of the nozzle outlet (1), the vortex chamber (2) tapering in the direction towards the nozzle outlet (1). The invention also relates to a reducing agent metering system for injecting a reducing agent into an exhaust gas flow of an internal combustion engine for selective catalytic reduction.

Description

[0001] The present invention relates to a reducing agent injection nozzle for injecting a reducing agent into an exhaust flow of an internal combustion engine for performing selective catalytic reduction. The reducing agent injection nozzle comprises a nozzle body, a flow channel formed in the nozzle body, and the reducing agent delivered to the reducing agent injection nozzle is guided from a connecting channel of the reducing agent injection nozzle to a nozzle outlet through the flow channel.

[0002] The invention further relates to a reducing agent metering system for injecting reducing agent into the exhaust gas flow of an internal combustion engine for selective catalytic reduction, the reducing agent metering system comprising at least one metering pump, by means of which the reducing agent is sucked from the tank via an intake line from the reducing agent tank, conveyed via at least one pressure line, and introduced into the exhaust gas flow of the internal combustion engine via at least one nozzle.

[0003] Nozzles and systems of this type are known from the prior art. Valve-controlled nozzles are typically used. These known systems utilize a ring line, a centrifugal pump, and a valve-controlled nozzle to maintain the supply pressure in the line. This results in a closed pressure system from which a corresponding spray pattern of reducing agent can be achieved by opening and closing the valve-controlled nozzle as needed. Overheating of the nozzle and its electronic components is prevented by flushing hot areas with reducing agent and returning it to the ring line. Furthermore, the known nozzles are surrounded by an active cooling jacket, which is cooled by coolant from the internal combustion engine's coolant circuit. All known nozzles and systems are susceptible to a certain proportion of their electronic components, the persistent pressure conditions in the system, and the resulting wear, and are therefore costly.

[0004] Catalysts used for selective catalytic reduction (SCR), also known as SCR catalysts, are used to reduce nitrogen oxide emissions from diesel engines, combustion plants, waste incineration plants, industrial plants, and other sources. To achieve this, a reducing agent is injected into the exhaust system using a metering device. Ammonia, an ammonia solution, or other reducing agents are used as the reducing agent.

[0005] Because the transportation of ammonia in vehicles is crucial for safety, aqueous urea solutions with a typical urea content of 32.5% are used, particularly in accordance with DIN 70070. In the exhaust gas, urea decomposes at temperatures above 150°C into gaseous ammonia and CO2. The parameters governing urea decomposition are primarily time (evaporation time and reaction time), temperature, and the droplet size of the injected urea solution. These SCR catalysts reduce nitrogen oxide emissions by approximately 90% through selective catalytic reduction.

[0006] The terms reducing agent solution or reducing agent include any reducing agent suitable for performing selective catalytic reduction, preferably a urea solution according to DIN 70070. However, the present invention is not limited thereto. The terms reducing agent metering system or metering system are used synonymously within the meaning of the present invention. The terms nozzle and injection nozzle or reducing agent injection nozzle are also used synonymously.

[0007] After the urea-water solution is injected into the exhaust tract, ammonia (NH3) must first be formed to carry out the SCR reaction. Here, reducing ammonia is released by the thermodynamic decomposition (thermal decomposition) of urea and the hydrolysis of the generated isocyanic acid.

[0008] In the first reaction, thermal decomposition, urea is converted into ammonia (NH3) and isocyanic acid (HNCO) due to the influence of temperature. In the second step, hydrolysis is carried out in the presence of water, in which isocyanic acid is also converted into ammonia and carbon dioxide (CO2) is generated.

[0009] The spray pattern of the injected reducing agent has a considerable influence on the quality of the selective catalytic reduction reaction.

[0010] The object of the present invention is therefore to further develop an injection nozzle for a reducing agent metering system so that a good spray pattern of the injected reducing agent is generated with the lowest possible nozzle complexity and high robustness. Furthermore, the nozzle geometry should be designed to prevent nozzle clogging due to drying and crystallization of the reducing agent.

[0011] According to the invention, this object is achieved by an injection nozzle according to claim 1 and a reducing agent metering system according to claim 15. Advantageous developments of the invention are specified in the dependent claims.

[0012] In a reducing agent injection nozzle for injecting reducing agent into the exhaust gas flow of an internal combustion engine for selective catalytic reduction (the reducing agent injection nozzle has a nozzle body, a flow channel is formed in the nozzle body, and the reducing agent supplied to the reducing agent injection nozzle is guided from the connecting channel of the reducing agent injection nozzle to the nozzle outlet through the flow channel), it is particularly advantageous if a swirl chamber is formed upstream of the nozzle outlet, which swirl chamber gradually tapers in the direction of the nozzle outlet.

[0013] By forming a swirl chamber that tapers towards the nozzle outlet, the delivered fluid is accelerated, thereby producing a high-quality spray pattern.

[0014] Preferably, the swirl chamber is designed to be rotationally symmetrical within the nozzle.

[0015] Preferably, the swirl chamber is formed between a conical tip at the bottom of the swirl chamber and a conical recess at the top side of the swirl chamber.

[0016] In particular, such a tapering can be formed by making the cone angle of the cone tip of the bottom of the swirl chamber smaller than the cone angle of the cone recess of the top side of the swirl chamber.

[0017] Preferably, the reducing agent injection nozzle for introducing the reducing agent into the swirl chamber has at least one, in particular two, introduction channels which are arranged offset on the circumference of the swirl chamber and open tangentially into the swirl chamber.

[0018] These inlet channels are designed such that they open tangentially into the conical geometry of the swirl chamber, so that the introduced medium moves in an annular path in a continuously tapering manner towards the outlet opening forming the nozzle outlet.

[0019] Preferably, the diffusion chamber is arranged upstream of the swirl chamber, which is indirectly or directly connected to the connecting channel of the reducing agent injection nozzle, in particular, one or more branch channels (Umleitkanal) leading to the diffusion chamber are arranged starting from the connecting channel of the reducing agent injection nozzle.

[0020] Here, starting from the connecting channel of the reducing agent injection nozzle, the delivered medium is introduced into the diffusion chamber via one or more branch channels, and from the diffusion chamber the medium is further introduced into the downstream swirl chamber via one or more introduction channels.

[0021] Preferably, a diffusion chamber is arranged upstream of the swirl chamber, wherein the diffusion chamber is formed by a rotationally symmetrical annular gap between the inner nozzle body and the outer nozzle body.

[0022] In particular, the nozzle body can thus be composed of an inner nozzle body and an outer nozzle body, wherein the flow channel and the chamber are formed between the inner nozzle body and the outer nozzle body, in particular by correspondingly designed geometries of the inner nozzle body and the outer nozzle body.

[0023] Preferably, the diffusion chamber is arranged upstream of the vortex chamber, wherein the vortex chamber is fluidically connected to the diffusion chamber via at least one inlet channel, in particular via one or more inlet channels opening tangentially into the vortex chamber. connect.

[0024] The swirl chamber preferably opens into a nozzle outlet, wherein the nozzle outlet is formed by a cylindrical bore. The diameter and length of the cylindrical bore determine the spray pattern, i.e., the opening angle and length of the spray cone. Thus, by appropriately designing the nozzle outlet geometry, the spray cone of the nozzle required for a specific application can be produced.

[0025] Furthermore, the arrangement of the guided channels determines the development of the rotational motion in the swirl chamber and thus the characteristics of the spray angle.

[0026] Preferably, the flow cross section of the connecting channel of the reducing agent injection nozzle is larger than or equal to the flow cross section of the diffusion chamber downstream of the connecting channel.

[0027] Preferably, the diffusion chamber is arranged upstream of the swirl chamber, wherein the flow cross section at the outlet of the diffusion chamber is greater than or equal to the flow cross section at the inlet of the swirl chamber.

[0028] Preferably, the flow cross section at the outlet of the swirl chamber is greater than or equal to the flow cross section of the nozzle outlet.

[0029] Therefore, the nozzle is preferably designed so that the flow cross section decreases along each section forming the flow channel in the nozzle, starting from the nozzle connecting channel to the nozzle outlet, thereby accelerating the flow. By accelerating the flow, the flow velocity distribution over the flow cross section becomes more uniform. Preferably, each transition area between the flow channel and the chamber in the nozzle is designed to avoid dead volume.

[0030] Preferably, the nozzle body is accommodated by the cooling body; in particular, an air gap can be formed between the nozzle body and the cooling body.

[0031] If an air gap is formed between the nozzle body and the cooling body, the air gap serves as an air gap insulation. Alternatively, the cooling body can accommodate the nozzle body without an air gap. In this case, heat is conducted from the nozzle body to the cooling body.

[0032] Preferably, the nozzle body is accommodated by a cooling body, wherein the cooling body has at least one inlet connection piece and at least one outlet connection piece for the coolant, via which the cooling body can be connected to a coolant circuit.

[0033] Reductant injection nozzles are used to inject reductant into the exhaust gas flow of an internal combustion engine for selective catalytic reduction. Such internal combustion engines usually have a cooling circuit, in which case the cooling body can be connected to the cooling circuit via a coolant inlet and outlet connection.

[0034] The nozzle body is preferably accommodated by a cooling body, wherein the cooling body has a flange on its outer side, by means of which flange it can be mounted, in particular gas-tightly mounted, on an exhaust duct of an internal combustion engine.

[0035] The flange thus serves to mount the reducing agent injection nozzle and the cooling body accommodating the nozzle in a gas-tight manner on the exhaust gas line.

[0036] The nozzle body preferably has a fastening surface via which thermal energy from the exhaust gas flow of the internal combustion engine can be introduced into the nozzle body.

[0037] In a reducing agent metering system for injecting reducing agent into the exhaust gas flow of an internal combustion engine for selective catalytic reduction, the reducing agent metering system has at least one metering pump, with the help of which the reducing agent in the reducing agent tank is sucked from the tank via a suction line, conveyed via at least one pressure line, and introduced into the exhaust gas flow of the internal combustion engine via at least one nozzle. It is particularly advantageous if the at least one nozzle is formed by the reducing agent injection nozzle according to the present invention.

[0038] Preferably, the metering pump is a piston pump. Preferably, the pressure line between the metering pump and the reducing agent injection nozzle is formed by a pressure-stable line.

[0039] Furthermore, the reducing agent metering system can have a control device or be connected to a control device, by means of which the metering pump is controlled, in particular in a closed-loop control circuit, in which the metering pump is regulated as a function of operating parameters (e.g., exhaust gas mass flow and / or exhaust gas temperature). In particular, the metering pump can be controlled by means of the control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The embodiments of the present invention are shown in the accompanying drawings, and the embodiments of the present invention will be described below. In the accompanying drawings:

[0041] Figure 1 shows a schematic diagram of a reducing agent metering system;

[0042] Figure 2a An idealized sequence of pressure pulses starting downstream of a piston metering pump is shown;

[0043] Figure 2b The actual course of the pressure pulse train starting from the downstream of the piston metering pump is shown;

[0044] Figure 3 shows a cross section of a nozzle consisting of an inner nozzle body and an outer nozzle body;

[0045] Figure 4 The inner nozzle body is shown;

[0046] Figure 5 shows a cross section of a nozzle consisting of an inner nozzle body and an outer nozzle body;

[0047] Figure 6 shows a simulation of the flow in the nozzle body in the nozzle outlet region;

[0048] Figure 7a shows a cross section of a cooling body for cooling the nozzle;

[0049] Figure 7b A cross section of the nozzle is shown;

[0050] Figure 8shows a section through a cooling body in an installed state with a nozzle accommodated therein;

[0051] Figure 9 The physical effects of drying are shown.

[0052] Figure 1 A schematic diagram of a reducing agent metering system is shown, wherein reducing agent is delivered from a tank 100 by means of a metering pump 200 via a pressure-stabilized line 300 to a reducing agent injection nozzle 400. The pressure-stabilized line 300 is connected to the nozzle 400. The nozzle 400 can be connected to the vehicle's exhaust system in a vehicle. The reducing agent injection nozzle 400 is used to inject reducing agent into the exhaust gas flow of an internal combustion engine to perform selective catalytic reduction.

[0053] In the illustrated embodiment, the metering pump 200 is a piston metering pump that draws the required mass from the tank 100 and discharges it in pulses into the supply line 300 to the nozzle 400. A pressure pulse is generated in the supply line 300 to the nozzle 400 and propagates to the nozzle outlet. This pressure pulse ensures a spray pulse of a certain length at the nozzle outlet. In order not to weaken or reduce the generated pressure pulse (the mass per piston stroke of the metering pump 200), all dead volume and sharp-edged or undercut transition areas at the entry and connection points must be eliminated so that the pressure pulse can reach the nozzle outlet as unimpeded as possible.

[0054] Figure 2a shows an ideal pressure pulse sequence starting from the piston metering pump downstream to the nozzle 400, and Figure 2b The actual change process of the pressure pulse sequence from the downstream of the piston metering pump to the nozzle 400 is shown. The ideal pressure pulse sequence p( Figure 2a ) or actual pressure pulse train p( Figure 2b ), time t corresponds to the journey from the pump outlet along the supply line 300 to the nozzle 400.

[0055] The metering is carried out by a piston metering pump 200 controlled by the control device, which intermittently draws the reducing agent mass required by the control device from the tank 100 and discharges the reducing agent mass in a pulsed manner into the pressure-stabilized supply line 300 to the injection nozzle 400 via the piston stroke.

[0056] Here, a pressure pulse is generated in the supply line 300 to the nozzle 400 and continues to the nozzle outlet. Due to various influencing factors, this pressure pulse is compressed on the way to the nozzle. This creates a pressure cushion (dynamic head). This pressure cushion ensures a certain length of the spray pulse at the nozzle outlet.

[0057] The pressure pulses from the pressure-stabilized supply line 300 are absorbed by the nozzle 400, the structure of which will be described below based on the Figures 3 to 5 Provide explanation.

[0058] Figure 3 A cross section of a nozzle 400 is shown, which consists of an inner nozzle body 410 and an outer nozzle body 420. The surfaces of the inner nozzle body 410 and the outer nozzle body 420 are designed such that a chamber and a flow channel are formed between the inner nozzle body 410 and the outer nozzle body 420.

[0059] Figure 4 A perspective view of the inner nozzle body 410 is shown, and Figure 5 Another cross section of a nozzle 400 consisting of an inner nozzle body 410 and an outer nozzle body 420 is shown.

[0060] Dosing medium is centrally introduced into the connecting channel 7 of the reducing agent injection nozzle 400 via the supply line 300 and diverted into the diffusion chamber 4 by means of two branch channels 6. The connecting channel 7 and the branch channels 6 are introduced into the inner nozzle body 410. The diffusion chamber 4 is formed between the inner nozzle body 410 and the outer nozzle body 420. The diffusion chamber 4 is used to balance pressure pulses.

[0061] Starting from the diffusion chamber 4, there are two inlet channels 3, which are circumferentially offset by approximately 80° relative to the branch channel 6 and open into the swirl chamber 2. This means that the dosing medium is guided from the diffusion chamber 4 into the swirl chamber 2 via these inlet channels 3. The circumferential offset of the inlet channels 3 relative to the branch channel 6 has the function of keeping the dosing medium in motion, so that there is no stagnant medium, which could lead to overheating of the reducing agent portion and therefore premature mass conversion.

[0062] The inlet channel 3 leading to the swirl chamber 2 is designed such that the inlet channel 3 adjoins tangentially the conical geometry of the swirl chamber 2. This means that the inlet channel 3 opens tangentially into the swirl chamber 2. Since the inlet channel 3 opens tangentially into the conical geometry of the swirl chamber 2, the introduced dosing medium moves in a circular path towards the nozzle outlet 1, wherein the flow cross section of the swirl chamber 2 continuously tapers towards the nozzle outlet 1.

[0063] The vortex chamber 2 has a conical geometry. This structure is formed by a second cone 5, which represents the lower structure of the vortex chamber 2, and the vortex chamber 2 continues to taper towards the tip. In addition, this arrangement causes the dynamic pressure head to continue to increase.

[0064] The swirl chamber 2 is formed between a conical tip 5 at the bottom of the swirl chamber 2 and a conical recess at the top side of the swirl chamber 2. The conical recess at the top side of the swirl chamber 2 may also be referred to as a funnel, which leads to an outlet hole to the nozzle outlet 1.

[0065] The smooth transition radius 15 between the bottom and the cone 5 ensures that the introduced dosing medium does not slow down too early and lose energy. The inner cone 5 at the bottom of the vortex chamber 2 has a cone angle 16 and a cone end 17 (the cone end can be designed to be rounded or alternatively flattened). The inner cone 5 has the function of rotating the dosing medium relative to the outer contour of the vortex chamber, and in the process continuously increases the speed and thus the pressure, and tears the dosing medium at the cone end 17.

[0066] The effect in this area is a turbulent behavior of the dosing medium. This effect then leads to the compressed dosing medium showing less energy reduction in the edge regions (A) and (B) of the outlet opening of the nozzle outlet 1 of the nozzle 400, while due to this turbulence a full cone jet is formed in the channel region (C), as shown Figure 6 The simulation of the flow in the nozzle body in the nozzle outlet region is shown in FIG.

[0067] As in accordance with Figure 5 As shown in the cross-sectional view of , the sharp transition of the outlet opening 9 to the outer surface 8 has the function of keeping the spray width small. The length of the outlet opening 9 and thus the medium guidance will affect the spray angle because the length consumes energy.

[0068] The orifice diameter is selected so that it maintains back pressure in the system, but in coordination with the pump 200 and tubing lengths, effectively stretches the individual strokes to achieve a long metering stroke given the dosing medium and its viscosity.

[0069] The design of the outlet diameter of the nozzle outlet 1 thus serves to stretch the acceptable spray pressure, since high pressure results in a finer droplet distribution. The arrangement of the inlet channel 3 transversely within the swirl chamber 2 and the deflection of the dosing medium, which has viscous material properties, with the associated cross-sectional and directional changes, result in adhesion forces that stop the dosing medium after the pump stroke, i.e., result in a rapid flattening of the stroke curve.

[0070] Furthermore, the adhesion forces and the aforementioned geometry prevent the dosing medium from flowing through the closed system connected to the pump 200 to or from the nozzle 400. This is supported by the position and orientation of the cone 5 relative to the funnel 12 and the resulting annular gap, which is adjusted by the mounting position 14. The edge radius 10 between the outlet opening to the nozzle outlet 1 and the funnel 12 also has the function of keeping the outflowing dosing medium in rotation, so that the edge region (B) does not form too much inwards and slow down the outflow.

[0071] When installed, the nozzle 400 is surrounded by a cooling body 500 in order to protect it from overheating due to the hot exhaust gas. Figure 7a The cross section of the cooling body 500 for cooling the nozzle 400 is shown. Figure 7b When installed, the nozzle 400 is surrounded by the cooling body 500 .

[0072] Figure 8 The figure shows a cross section of a cooling body 500 in the installed state, with the nozzle 400 accommodated therein. An air gap 24 is formed between the nozzle 400 and the inner wall 25 of the cooling body 500. In order to integrate the cooling body 500 into the coolant circuit of a vehicle, the cooling body 500 has a connecting pipe 20 for supplying coolant and a discharge pipe 23 for discharging the coolant.

[0073] The cooling body 500 surrounds the nozzle 400 and secures it to the exhaust system via a connection point in the form of a flange 19. This connection point is gas-tight with respect to the environment using seals and clamping devices. High temperatures are transferred to the cooling body 500 via the exhaust system through the connection point as convective energy. Furthermore, the cooling body 500 is heated by radiation energy.

[0074] To compensate for these two heat inputs, the cooling body 500 is temperature-controlled with the aid of coolant from the vehicle's cooling circuit. The coolant is introduced into the interior of the cooling body 500 via a connecting pipe 20. From there, it is directed toward the nozzle outlet 1 and deflected outwards by a deflector plate 22 toward the hot zone. From there, the coolant is directed upward toward the outlet pipe 23 and returned to the cooling circuit. The air gap 24 between the nozzle 400 and the inner wall 25 of the cooling body 500 serves as an air gap barrier.

[0075] The selected geometry of the flow channel in nozzle 400 also ensures targeted drying and crystallization when the metering process is complete and the metering system is no longer metering, i.e., when the pump stroke is stopped. In this case, the delivered dosing medium remains in the entire wetted line. The heat entering from the exhaust duct vaporizes the liquid, and since this is an open system, the moisture content can escape through nozzle outlet 1.

[0076] The commonly used reducing agent in the form of an aqueous urea solution has the following chemical properties: at room temperature and above, it loses its water content by evaporation, forming a gas-permeable crystalline structure. The ammonia content remains in the atmosphere of the pipeline. This effect occurs significantly more rapidly at higher temperatures. Furthermore, at temperatures exceeding 180°C, cracking products are formed that precipitate and are no longer dissolvable by water and / or the commonly used reducing agent.

[0077] In order to prevent crystallized deposits from clogging the nozzle 400 , anti-clogging protection is achieved by targeted drying. Figure 9 A simplified diagram of this process and its physical effects is shown. Arrow 600 indicates the direction of temperature penetration, which is opposite to the flow direction of the dosing medium in the flow channel 415 toward the nozzle outlet 1 of the nozzle 400. Arrow 610 indicates the direction of discharge of water vapor formed by the evaporation of the water content of the reducing agent. In the flow channel 415 of the nozzle 400, due to the influence of temperature, transitional sections 430, 440, 450, and 460 are formed toward the nozzle outlet. The liquid dosing medium is in section 430, followed downstream by section 440 with first water vapor, followed downstream by section 450 with water vapor resulting from the complete evaporation of the water content in section 450, and then downstream by section 460 with urea crystals formed in the flow channel 415 of the nozzle 400. These urea crystals are pushed out by the evaporation pressure.

[0078] The supply line 300 from the pump 200 to the nozzle 400 has a flow cross-section that is greater than or equal to the cross-section of the nozzle inlet 7. If the supply diameter of the line 300 is larger, the nozzle 400 reduces this diameter to 2 mm in the illustrated embodiment. Furthermore, the flow cross-sections of the supply channel 6 and the diffusion chamber 4 are further reduced. The swirl chamber channel has a dimension D = 1.5 mm, and the nozzle outlet 1 has a diameter of 0.7 mm.

[0079] This continuously decreasing flow cross section results in the isolation of the liquid dosing medium. In the drying area, there are water-soluble crystals and a saturated atmosphere consisting of water vapor or ammonia and air. This atmosphere can only be exchanged and further dried via the nozzle opening 1 with a diameter of 0.7 mm, which is additionally sealed with water-soluble crystals or protected as a barrier.

[0080] If higher exhaust gas temperatures act on the nozzle, this may result in the conversion of urea into cracking products.

[0081] In this case, overheat protection devices are required to absorb and dissipate the high temperatures so that no deposits in the form of fission products occur in the metering system and nozzles.

[0082] The cooling body 500 absorbs radiant and convective heat and dissipates it from the nozzle 400 via the coolant (water). The connecting flange 19 conducts the convective and generated radiant heat to the outer shell 26, which is internally moistened with the coolant. The deflector wall deflects the incoming flow first via the inner tube side 25 toward the nozzle outlet 1 and then returns it via the hot side via the connecting pipe 23 to the cooling line system. The inner tube 25 of the cooling body, together with the nozzle body, forms the active air gap cooling device 24 and prevents overheating from reaching the nozzle 400.

[0083] The fixing surface 27 between the nozzle tip and the cooling body 500 is positioned so that it performs both fixing and alignment functions. Furthermore, it is designed as a loose connection, which allows for thermal length compensation and prevents component damage. This sliding-guided fixing surface 27 (where heat transfer is worse than with a fixed connection) serves as overheating protection and is located in the coolant deflection area so that the heat acting on the nozzle body by the muffler can be initiated there.

[0084] Therefore, the physical and chemical characteristics of drying with a reducing agent (32% urea solution and 68% water) usually start from there (the starting drying point). Under the influence of temperature, when the polymer state changes into water vapor, the proportionally distributed water occupies a much larger volume than in liquid form, about a thousand times more.

[0085] As a result, the pressure in the nozzle system continuously increases and can only decrease in the direction of the nozzle outlet.

[0086] Since the drying direction of the nozzle is moving from the nozzle tip 1 to the nozzle inlet 7, as the distance increases, the water in the reducing agent evaporates first, and the ammonia atmosphere and the crystallized small particles (urea crystals) are discharged from the nozzle.

[0087] This effect continues until the temperature and pressure reach equilibrium and the liquid no longer evaporates. The atmosphere in the pipe is saturated and small crystal structures form due to the precipitation of components in the saturated atmosphere. These crystal structures can form in the pipe up to the nozzle.

[0088] When the piston pump starts again, it delivers the liquid to the pipeline with stable pressure. The crystal structure in the pipeline and nozzle quickly dissolves in the liquid and is discharged into the muffler through the nozzle tip.

Claims

1. A reducing agent injection nozzle (400) for injecting a reducing agent into an exhaust gas flow of an internal combustion engine for selective catalytic reduction, the reducing agent injection nozzle having a nozzle body, flow channels (6, 7) formed in the nozzle, through which the reducing agent delivered to the reducing agent injection nozzle is guided from a connecting channel of the reducing agent injection nozzle to a nozzle outlet (1), It is characterized by: A swirl chamber (2) is formed upstream of the nozzle outlet (1), and the swirl chamber (2) gradually becomes thinner in a direction toward the nozzle outlet (1).

2. The reducing agent injection nozzle (400) according to claim 1, characterized in that The vortex chamber (2) is formed between a conical tip (5) at the bottom of the vortex chamber (2) and a conical recess at the top side of the vortex chamber (2).

3. The reducing agent injection nozzle (400) according to claim 1 or 2, characterized in that: The reducing agent injection nozzle (400) for introducing the reducing agent into the vortex chamber (2) has at least one, in particular two, introduction channels (3), which are arranged offset on the circumference of the vortex chamber (2) and lead tangentially to the vortex chamber (2).

4. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that A diffusion chamber (4) is arranged upstream of the vortex chamber (2), and the diffusion chamber (4) is indirectly or directly connected to the connecting channel (7) of the reducing agent injection nozzle (400). In particular, starting from the connecting channel (7) of the reducing agent injection nozzle (400), one or more branch channels (6) leading to the diffusion chamber (4) are arranged.

5. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that A diffusion chamber (4) is arranged upstream of the swirl chamber (2), wherein the diffusion chamber (4) is formed by a rotationally symmetrical annular gap between an inner nozzle body (410) and an outer nozzle body (420).

6. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that A diffusion chamber (4) is arranged upstream of the vortex chamber (2), wherein the vortex chamber (2) is fluidically connected to the diffusion chamber (4) via at least one inlet channel (3), in particular via one or more inlet channels (3) opening tangentially into the vortex chamber (2).

7. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The swirl chamber (2) opens into the nozzle outlet (1), wherein the nozzle outlet (1) is formed by a cylindrical bore.

8. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The flow cross section of the connecting channel (7) of the reducing agent nozzle (400) is greater than or equal to the flow cross section of the diffusion chamber (4) downstream of the connecting channel (7).

9. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that A diffusion chamber (4) is arranged upstream of the vortex chamber (2), wherein a flow cross section at an outlet of the diffusion chamber (4) is greater than or equal to a flow cross section at an inlet of the vortex chamber (2).

10. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The flow cross section at the outlet of the vortex chamber (2) is greater than or equal to the flow cross section of the nozzle outlet (1).

11. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The nozzle body is received by a cooling body (500), in particular, an air gap (24) is formed between the nozzle body and the cooling body (500).

12. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The nozzle body is accommodated by a cooling body (500), wherein the cooling body (500) has at least one inlet connection piece (20) and at least one outlet connection piece (23) for the coolant, and the cooling body (500) can be connected to a coolant circuit via the at least one inlet connection piece (20) and the at least one outlet connection piece (23).

13. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The nozzle body is received by a cooling body (500), wherein the cooling body (500) has a flange (19) on its outer side, by means of which it can be mounted, in particular gas-tightly mounted, on an exhaust duct of an internal combustion engine.

14. The reducing agent injection nozzle (400) according to any one of the preceding claims, characterized in that The nozzle body has a fastening surface (27) via which thermal energy of an exhaust gas flow from an internal combustion engine can be introduced into the nozzle body.

15. A reducing agent metering system for injecting a reducing agent into an exhaust gas flow of an internal combustion engine for selective catalytic reduction, the reducing agent metering system comprising at least one metering pump (200), wherein the reducing agent in a reducing agent tank (100) is sucked from the tank (100) via a suction line by means of the at least one metering pump, conveyed via at least one pressure line (300), and introduced into the exhaust gas flow of the internal combustion engine via at least one nozzle (400). It is characterized by: The at least one nozzle (400) is formed by a reducing agent injection nozzle (400) according to any one of the preceding claims.

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