DE102009046280A1 - Method for injecting liquid reducing agent into engine exhaust gas flow, involves injecting liquid reducing agent into exhaust gas flow by injection nozzle - Google Patents

Abstract

The method involves injecting liquid reducing agent into the exhaust gas flow by an injection nozzle, with which the liquid reducing agent is injected into an injection point upstreaming a reduction catalyst for reducing nitrogen oxide components in the exhaust gas. The exhaust gas is discharged from the upstream of the injection nozzle through a bypass flow passage. An independent claim is also included for a device for injecting a liquid reducing agent into an engine exhaust gas flow.

Description

Background / Summary

The after-treatment technology of selective catalytic reaction (SCR) with urea has been the industry's chosen for diesel engine programs to (EPA) to meet the standards of nitrogen oxides (NO _x norms) of the Environmental Protection Agency of of 2010. Using this technology, an aqueous urea solution is often stored on board in a urea tank and injected into the vehicle exhaust via a urea injector, decomposing the injected urea into ammonia (NH ₃ ) and carbon dioxide (CO ₂ ). The ammonia produced is then absorbed on a surface of a downstream SCR catalyst, where it reacts with the NO _x in the exhaust gas for the reaction into nitrogen and water.

The urea solution is often injected into the vehicle exhaust in the form of an atomized spray. Despite the use of mixing systems to keep most of the droplets in the air, a combination of exhaust system space limitations and engine operating conditions may cause some urea droplets to form deposits on the surface of the urea injectors and in the direct exhaust passage (in the exhaust passage). The deposit formation process may be irreversible, causing blockage of the urea injector that results in degradation of the NO _x conversion efficiency of the SCR aftertreatment system. In some cases, the growth of urea deposits in the exhaust passage may cause an increase in engine back pressure and a corresponding loss of engine power.

At low and medium exhaust flows, the larger droplets of injected urea may end up on the surfaces of the exhaust passage where there is a strong and rapid accumulation of urea deposits (see, eg, US Pat. 1 ) takes place. At medium and high exhaust flow rates, the rapidly evaporating smaller droplets of progressively reduced diameter may be swept toward the ceiling surfaces where deposit formation occurs.

The use of various mixing devices has shown a successful reduction of deposit formation processes for both floor and ceiling surfaces of the exhaust passage. Further, the periodic regeneration (eg, cleaning by burning up collected soot from the surfaces) of the diesel particulate filter, which occurs approximately every 10 to 30 hours of vehicle operation, results in operation of the engine such that the exhaust gas temperature exceeds for up to 12 minutes 600 ° C is located. The increased exhaust gas temperature may allow the removal of urea deposits from the floor and ceiling surfaces of the exhaust pipe.

However, the inventors also recognize that some depressed surfaces on the inside of the exhaust pipe or exhaust pipe may still be susceptible to scale formation and accumulation. A common example of this phenomenon is in the dosage injector approach. Installation of a urea dosing injection nozzle, whether at the pipe bend or within a straight section, may result in installation to a mounting boss which holds the injector in place. Opposite the exhaust side of the exhaust pipe, the lug may have a cavity or recess causing the injector position to be slightly removed to minimize exposing the injector to high temperatures. The flow pattern of exhaust gas near the cavity may be altered such that reintroduction of gases into the cavity may occur (see, eg, FIG. 2 ). The extent of the re-introduction can with the operating conditions such. B. exhaust gas flow and temperature, urea dosing rate and ambient temperature, vary. Exhaust gas recirculation near the cavity may increase the tendency for urea deposit formation and accumulation.

As such, systems and methods are provided for injecting a liquid reductant into an engine exhaust to address the aforementioned problems. An exemplary system has an injector nozzle with an outlet for injecting a liquid reductant into the exhaust gas upstream of the reduction catalyst, a gas deflector plate located upstream of the injector, the gas deflector plate configured to have upstream of the baffle a higher pressure zone and downstream of the baffle a zone of lower pressure surrounding the injector outlet, a bypass flow passage configured to divert a portion of the exhaust gas flow from the exhaust passage, the bypass flow passage having an inlet in the higher pressure zone upstream of the baffle, and a header Fluid communication with the bypass flow passage, the accumulator having one or more openings to allow the diverted portion of the exhaust gas to flow from the header openings into the exhaust gas flow, to form a gas shield for the spray, to form a liquid reducing agent.

In this way, the gas baffle plate creates the zone of higher pressure upstream of the A baffle where the inlet of the bypass passage is located and the zone of lower pressure downstream of the baffle where the injector outlet is located. A pressure differential is thereby formed which allows a portion of the exhaust flow to be diverted through the bypass flow passage to form a gas shield for the liquid reductant spray. The generated gas shield may also serve to facilitate the reintroduction of exhaust gas near the injector outlet, such as, for example, exhaust gas. In an injection nozzle attachment cavity, to reduce the deposit formation and accumulation of liquid reducing agent.

In some examples, the gas deflecting plate has a flange defining a bottom surface and a pair of sidewalls connected to the bottom surface, wherein the flange is configured to direct a portion of the exhaust gas toward the inlet of the bypass flow passage. Further, the one or more apertures of the collector may be circumferentially disposed about the injector outlet, allowing the formed gas shield to be a circular gas shield surrounding the liquid reductant spray.

In some examples, the bypass flow passage is formed between a mounting flange and the injector lug. Further, a channel may be machined into the mounting flange to serve as a bypass flow passage.

In another embodiment, the above problems may be addressed, at least in part, by a method of injecting liquid reductant into an engine exhaust stream, including injecting liquid reductant into the exhaust stream via an injector wherein the liquid reductant is injected at an injection location upstream of a reduction catalyst Reducing NO _x components is injected in the exhaust gas; Discharging exhaust gas from upstream of the injector through a bypass flow passage; and directing the exhaust gas discharged to the injection site where the exhaust gas and the liquid reducing agent both enter the exhaust stream. In this way, it is possible to use the exhaust gas to shield the injector, thereby reducing deposits.

The inventors have recognized the above problems, phenomena and potential solutions. Further, it should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined only by the claims which follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate any disadvantages noted above or in any part of this disclosure.

Brief description of the drawings

1 shows a schematic representation of the occurrence of a urea deposit formation and accumulation in an engine exhaust passage.

2 shows a schematic representation of an occurrence of exhaust gas recirculation in a mounting lumen cavity.

3 shows a schematic representation of an embodiment of an apparatus for treating engine exhaust according to the present application.

4 shows a cross-sectional view of an embodiment of a device for injecting a liquid reducing agent into an engine exhaust gas, which in the apparatus of 5 can be used.

5 shows a perspective view of the device of 6 ,

6 shows a perspective view of the device of 6 in an exploded arrangement.

7 shows a bottom view of the mounting flange of the device of 6 ,

8th shows a schematic representation of a urea injection nozzle, which is mounted on a mounting boss on a pipe bend.

9 shows a schematic representation of a urea injection nozzle, which is mounted on a mounting boss on a straight pipe section.

10 FIG. 10 is a flowchart of an exemplary method of injecting liquid reductant into an engine exhaust according to the present application. FIG.

Detailed description

3 shows a schematic representation of an embodiment of a device 10 for treating exhaust gas of an engine 12 according to the present application. The device 10 can an injection nozzle arrangement 16 for liquid reducing agent, with an exhaust passage or the exhaust pipe 14 of the motor 12 is coupled. The injector assembly 16 for liquid reducing agent may be configured to liquid reducing agent such. B. inject a liquid urea solution in the engine exhaust.

The injector assembly 16 for liquid reducing agent may be in the exhaust passage 14 of the motor 12 at a location upstream of an exhaust gas purification device 18 be arranged. The exhaust gas purification device 18 For example, it may be an SCR catalyst for removing NO _x components in engine exhaust. The details of the injector assembly 16 for liquid reducing agent are with reference to 3 - 7 explained.

The device 10 can be a control unit 20 exhibit that with different sensors 22 , such as As temperature sensors, an oxygen sensor is a _NOx sensor, a pressure sensor and a flow meter, coupled to sense various engine operating conditions. The control unit 20 can also work with different actuators 24 , such as B. various engine valves and throttles, be coupled to control the engine operation. It should be recognized that the engine 12 any suitable engine, such as. As a diesel engine, may be on the device 10 can be used to treat engine exhaust.

In some examples, the device may 10 also a mixing device 26 (as in 8th & 9 shown) for mixing the liquid reducing agent spray with the engine exhaust gas. The device 10 may further include a centering device 28 (as in 8th & 9 shown) for centering the liquid reducing agent in the exhaust passage 14 to achieve a better mixing of the spray of liquid reducing agent with the engine exhaust gas. In one example, the device may 28 be a spray centering grid and / or may use angled fins.

3 - 7 are different views of the injector assembly 16 for liquid reducing agent of 5 , As in 4 shown, the injection nozzle assembly 16 an injection nozzle 30 for liquid reducing agent with an injection nozzle outlet 32 for injecting the liquid reducing agent and an injection nozzle attachment 33 for mounting the injector 30 at the exhaust passage 14 exhibit. The injected liquid reducing agent may be in the form of a spray. The injector neck 33 may have a recess, which in this example as injection nozzle approach cavity 34 is shown in a wall of the exhaust passage 14 form. The injector 30 for liquid reducing agent can be mounted on a pipe bend or in a straight pipe section and can in various ways in the exhaust passage 14 be angled.

The injector assembly 16 may further include an exhaust bypass passage 36 with an inlet 40 and an outlet 42 for diverting a portion of the exhaust stream and a gas baffle plate 38 for deflecting the exhaust flow from the injector lug cavity 34 and from the injector outlet 32 exhibit.

The gas deflector plate 38 can be on the wall of the exhaust passage 14 be mounted. The gas deflector plate 38 can a flange 41 (please refer 5 ) configured to expose a portion of the exhaust gas toward the inlet 40 the exhaust bypass passage 36 to lead. The flange 41 can be a bottom surface 43 and a pair of side walls 44 exhibit. The gas deflector plate 38 may be angled in the direction of the incoming exhaust gas flow. The gas deflector plate 38 can at the exhaust passage 14 directly upstream of the inlet 40 the exhaust bypass passage 36 be attached.

The positioning of the gas baffle plate 38 in the exhaust passage 14 can a zone 39 with higher pressure upstream of the gas deflector plate 38 relative to a zone 45 with lower pressure downstream of the gas deflector plate 38 that the injector outlet 32 and the spray of liquid reducing agent surround generate. The pressure difference between the zone 39 with higher pressure and the zone 45 lower pressure can drive some of the exhaust gas into the inlet 40 the exhaust bypass passage 36 enters and through the Abgasumleitungsdurchgang 36 flows to create a gas shield around the liquid reductant spray.

The exhaust bypass passage 36 can also be with a collector 46 at its outlet 42 be coupled. The collector 46 can have one or more openings 48 to allow the diverted portion of the exhaust gas from the collector openings 48 flows into the exhaust gas stream to form the gas shield (see 6 ). In some examples, the one or more openings 48 6 to 9 have openings on the circumference around the injector outlet 32 are arranged so that a circular gas shield, which surrounds the spray of liquid reducing agent, by the bypassed exhaust gas, which from the collector openings 48 comes, can be formed. Further, the bypass exhaust gas flowing out of the header openings may be targeted in a direction appropriate for Reducing agent injection is substantially parallel and aligned with this.

In some examples, the exhaust bypass passage 36 between the injector neck 33 and an injection nozzle attachment flange 51 be educated. A channel 49 can in a bottom 50 of injection nozzle attachment flange 51 machined before it to the injection nozzle approach 33 is welded to as the path of Abgasumleitungsdurchgangs 36 to serve (see 7 ).

In this manner, a portion of the exhaust gas may be diverted to create a gas shield around the liquid reductant spray to reintroduce the liquid reductant spray into the throat cavity 34 and near the injector outlet 32 to prevent. Thus, deposit formation and accumulation of liquid reductant within the injector throat cavity may occur 34 and in the exhaust passage 14 be reduced.

Thus, in one example, the system may be operated to deliver liquid reductant via the injector 30 at an injection point upstream of a reduction catalyst for reducing NO _x components in the exhaust gas into the exhaust gas flow. Further, exhaust gas may be diverted away from the exhaust flow from a point upstream of the injector and then through a bypass flow passage where the diverted exhaust gas is directed to the injection site. Then, at the injection site, the discharged exhaust gas and the liquid reducing agent may both enter the exhaust gas stream. Although this example shows that the exhaust gas is discharged through an angled baffle with respect to the exhaust passage, various other methods of exhaustion may be used to create a pressure differential, such as pressure differential. B. a pitot tube in Bernoulli style. Further, although this example shows that the injection site has a cavity recess formed by an angled injector nozzle configuration, the method may also be applied to systems in which the injector nozzle is disposed in a vertically mounted position with respect to the exhaust passageway. Although this example shows a manifold within the exhaust bypass having multiple parallel flow passages circumferentially disposed about the injection site and from the inlet 40 Finally, a single, non-branching bypass passage can be used.

10 is a flowchart of an example method 100 for injecting liquid reducing agent into an engine exhaust according to the present application. The method can be performed using with reference to 5 - 9 described device 10 be implemented. The procedure 100 can at 102 the use of an injector having an outlet to inject liquid reductant into the exhaust gas upstream of a reduction catalyst for reducing NO _x components in the exhaust gas.

at 104 For example, the method may include using a gas baffle located upstream of the injector to create a high pressure zone upstream of the baffle and a low pressure zone downstream of the baffle surrounding the injector outlet.

at 106 The method may include diverting a portion of the exhaust gas through a bypass flow passage to form a gas shield for the liquid reductant spray, the bypass flow passage having an inlet in the high pressure zone.

at 108 For example, the method may include using a spray centering device to center the spray of liquid reductant in the exhaust gas.

at 110 For example, the method may include using a mixing device to mix the spray of liquid urea with the exhaust gas.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature and that these specific embodiments are not to be considered in a limiting sense, as numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, counter-4 and other types of motors. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various systems and configurations, and other features, functions, and / or properties disclosed herein.

The following claims specifically point to certain combinations and sub-combinations that are considered to be novel and not obvious. These claims may refer to "a" element or "a first" element or the equivalent thereof. Such claims should be understood to include the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be accomplished by Amendment of the present claims or claims by presenting new claims in this or a related application claimed. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also considered to be within the scope of the present disclosure.

An apparatus according to the invention for injecting liquid reducing agent into an engine exhaust gas, comprising:
an injection nozzle having an outlet for injecting liquid reducing agent into the exhaust gas upstream of the reduction catalyst;
a gas baffle disposed upstream of the injector, the gas baffle being configured to generate a higher pressure zone upstream of the baffle and a lower pressure zone downstream of the baffle surrounding the injector outlet;
a bypass flow passage configured to divert a portion of the exhaust flow from the exhaust passage, the bypass flow passage having an inlet in the higher pressure zone upstream of the baffle; and
a header in fluid communication with the bypass flow passage, the header having one or more openings to allow the redirected portion of the exhaust gas to flow from the header openings into the exhaust stream to form a gas shield for the liquid reductant spray.

In this case, preferably, the gas deflecting plate may have a flange fixed to a wall of the exhaust passage at a position downstream of the inlet of the bypass flow passage and upstream of the injector.

In particular, the gas deflecting plate can be angled in the direction of the exhaust gas flow.

More preferably, the flange has a lower surface and a pair of sidewalls connected to the lower surface, the flange being configured to direct a portion of the exhaust toward the inlet of the exhaust bypass passage.

According to a further preferred embodiment, the apparatus further comprises a mixing device, which is arranged downstream of the injection nozzle, for mixing the spray of liquid reducing agent with the exhaust gas flow. There may also be a spray centering grid located downstream of the injector and upstream of the mixer for centering the liquid reductant spray.

An inventive method for injecting liquid reducing agent into an engine exhaust gas contains in particular:
Injecting liquid reductant into the exhaust gas through an injector having an outlet, wherein the liquid reductant is injected upstream of a reduction catalyst for reducing NO _x components in the exhaust gas;
Creating a zone of higher pressure and a zone of lower pressure via a gas baffle located upstream of the injector, the higher pressure zone located upstream of the baffle and the low pressure zone downstream of the baffle and surrounding the injector outlet;
Diverting a portion of the exhaust gas through a bypass flow passage to form a gas shield for the liquid reducing agent, the bypass flow passage having an inlet in the higher pressure zone.

In this case, the liquid reducing agent may be a liquid urea solution and the formed gas shield may be a circular gas shield which surrounds the spray of liquid reducing agent.

Preferably, for this method, the gas deflecting plate has a flange fixed to a wall of the exhaust passage at a position downstream of the inlet of the bypass flow passage and upstream of the injector, and the gas deflecting plate is angled toward the exhaust gas flow.

Preferably, the gas deflecting plate has a flange having a lower surface and a pair of sidewalls connected to the lower surface, wherein the blade is configured to direct a portion of the exhaust gas flow toward the inlet of the bypass flow passage.

Further, according to a further preferred method, the mixing of the spray of liquid urea with the exhaust gas is provided via a gas deflecting plate located upstream of the injection nozzle.

A further preferred engine exhaust gas treatment apparatus comprising:
a reduction catalyst for reducing NO _x components in the exhaust gas;
an injection nozzle having an outlet for injecting the liquid urea solution;
a gas baffle disposed upstream of the injector and configured to generate a higher pressure zone upstream of the baffle and a lower pressure zone downstream of the baffle surrounding the injector outlet;
a bypass passage configured to divert a portion of the exhaust flow from the exhaust passage, the bypass flow passage having an inlet in the higher pressure zone upstream of the baffle; and
a header in fluid communication with the bypass flow passage, the header having one or more openings disposed circumferentially about the outlet of the injector to allow the redirected portion of the exhaust gas to flow from the header openings into the exhaust gas stream to form a gas shield for the spray from the liquid urea solution.

Claims (10)

A method of injecting a liquid reductant into an engine exhaust stream, comprising: injecting liquid reductant into the exhaust stream via an injector, wherein the liquid reductant is injected at an injection location upstream of a reduction catalyst for reducing NO _x components in the exhaust; Discharging the exhaust gas from upstream of the injector through a bypass flow passage; and directing the exhaust gas discharged to the injection site where both the discharged exhaust gas and the liquid reductant enter the exhaust stream. The method of claim 1, wherein the exhaust gas is exhausted via an angled baffle, wherein the liquid reductant is injected at an angle with respect to the exhaust gas flow, the bypass flow passage having a manifold with a plurality of parallel flow passages circumferentially disposed about the injection location , and wherein the injection point has a recess. Device for injecting liquid reducing agent into an engine exhaust, comprising: an injection nozzle ( 30 ) with an outlet ( 32 ) for injecting liquid reducing agent into the exhaust gas upstream of the reduction catalyst ( 18 ); a gas deflector plate ( 38 ) located upstream of the injection nozzle ( 30 The gas baffle plate is configured to define a zone of higher pressure upstream of the baffle (FIG. 38 ) and a lower pressure zone downstream of the baffle plate that separates the injector outlet (FIG. 32 ) surrounds; a bypass flow passage ( 36 ) configured to capture a portion of the exhaust flow from the exhaust passage (Fig. 14 ), the bypass flow passage having an inlet ( 40 ) in the higher pressure zone upstream of the baffle; and a collector ( 46 ) in fluid communication with the bypass flow passage, the collector having one or more ports ( 48 ) to allow the diverted portion of the exhaust gas to flow from the header openings into the exhaust stream to form a gas shield for the liquid reductant spray. The device of claim 3, wherein the liquid reducing agent is a solution of liquid urea. Apparatus according to claim 3, wherein the collector ( 46 ) is configured to allow the diverted exhaust gas from the manifold openings ( 48 ) flows in a direction aligned with a direction of the liquid reductant spray. Apparatus according to claim 4, wherein the one or more openings ( 48 ) of the collector ( 46 ) on the circumference around the injection nozzle outlet ( 32 and wherein the formed gas shield is a circular gas shield surrounding spray of liquid reductant. The apparatus of claim 6, wherein the one or more header openings have 6 to 9 holes formed circumferentially about the injector outlet (10). 32 ) are arranged. Apparatus according to claim 3, wherein the bypass flow passage (16) 36 ) between an injection nozzle attachment ( 33 ) and a mounting flange ( 51 ) for mounting the injection nozzle ( 30 ) on a wall of the exhaust passage ( 14 ) is trained. Apparatus according to claim 8, wherein a channel ( 49 ) in the mounting flange ( 51 ) is machined to control the bypass flow passage ( 36 ) to build. Apparatus according to claim 3, wherein the gas deflecting plate ( 38 ) a flange ( 41 ) disposed on a wall of the exhaust passage at a position downstream of the inlet of the bypass flow passage (12). 36 ) and upstream of the injection nozzle ( 30 ) is attached.

Images