CN217681930U

CN217681930U - Aftertreatment SCR mixer

Info

Publication number: CN217681930U
Application number: CN202221669525.0U
Authority: CN
Inventors: 胡加祥; 赵联
Original assignee: Weichai Power Co Ltd; Weichai Power Emission Solutions Technology Co Ltd
Current assignee: Weichai Power Co Ltd; Weichai Power Emission Solutions Technology Co Ltd
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2022-10-28
Anticipated expiration: 2032-06-30

Abstract

The utility model discloses an aftertreatment SCR blender, including the casing, and set gradually in whirl board, baffle and first baffle in the casing, the whirl board the baffle with first baffle will mixed flow passageway and circulation passageway are separated into to the casing. The center line of the rotational flow part is close to the nozzle mounting position compared with the center line of the rotational flow plate, namely, the rotational flow part is eccentrically arranged, so that the urea nozzle side arranged in the circular flow channel forms a high-pressure side, and a low-pressure side is formed on the opposite side, thereby ensuring that the air flow of the circular flow channel flows from the nozzle mounting position to the opposite side, effectively increasing the mixing path of waste gas and urea spray, improving the mixing uniformity of the air flow, and effectively preventing the urea spray from generating crystallization. In addition, the rotational flow plate provides another circulation path for the air flow on one hand, and on the other hand, turbulence can be formed in the mixed flow channel, so that the mixing degree of the air flow is improved.

Description

Aftertreatment SCR mixer

Technical Field

The utility model relates to a SCR blender technical field, in particular to aftertreatment SCR blender.

Background

At present, in the use process of an SCR mixer, because urea and waste gas are not uniformly mixed, the risk of urea crystallization is high, the oil consumption of the whole vehicle is increased, and NO is subjected to aftertreatment _x The transformation efficiency is reduced, and the like.

Therefore, how to improve the mixing uniformity of urea and exhaust gas becomes a technical problem to be solved urgently by those skilled in the art.

SUMMERY OF THE UTILITY MODEL

The utility model provides a post-treatment SCR blender to improve urea and waste gas mixing homogeneity.

In order to achieve the above object, the present invention provides the following technical solutions:

the utility model provides a post-treatment SCR blender, including the casing to and set gradually whirl board, baffle and the first baffle in the casing, whirl board, baffle and first baffle separate into mixed flow passageway and circulation passageway with the casing, wherein:

the shell is provided with an air inlet for air inlet, an air outlet for air outlet and a nozzle mounting position for mounting a urea nozzle, the air inlet and the air outlet are arranged along a first direction, when the urea nozzle is mounted at the nozzle mounting position, the spraying direction of the urea nozzle is a second direction, and the second direction is mutually crossed with the first direction;

the middle part of the rotational flow plate is provided with a rotational flow part communicated with the air inlet and the mixed flow channel, the edge of the rotational flow plate is provided with a plurality of communicating grooves communicated with the circular flow channel, and the center line of the rotational flow part is closer to the nozzle mounting position than the center line of the rotational flow plate;

the part of the baffle plate close to the nozzle installation position is provided with an air inlet hole which is communicated with the circulation channel and the mixed flow channel; the part of the baffle far away from the nozzle installation position is provided with a communicating hole which is communicated with the circulation channel and the mixed flow channel;

the middle part of the first clapboard is provided with a first exhaust hole which is communicated with the mixed flow channel and the air outlet.

In some possible embodiments, the swirling portion includes a plurality of swirling vanes arranged around a center line of the swirling plate as a circle center, each swirling vane is arranged obliquely from the swirling plate to the flow mixing channel, and a bottom of each swirling vane has an overflowing hole.

In some possible embodiments, the number of swirl vanes is four.

In some possible embodiments, the swirling portion further includes a swirling hole surrounding the plurality of swirling vanes, the swirling hole communicating the air inlet with the mixed flow passage.

In some possible embodiments, the baffle includes a first baffle, a second baffle and a third baffle, the first baffle, the second baffle and the third baffle are annularly arranged around a center line of the rotational flow plate, the first baffle is close to the nozzle mounting position, the air inlet is arranged on the first baffle, the communication hole includes a first communication hole and a second communication hole, the first communication hole is arranged on the second baffle, and the second communication hole is arranged on the third baffle.

In some possible embodiments, there is a gap between the first baffle, the second baffle, and the third baffle.

In some possible embodiments, the air inlet holes are arranged on the first baffle in a plurality of rows, and the number of the air inlet holes in the corresponding row gradually decreases from the air inlet to the air outlet.

In some possible embodiments, the number of the first communication holes is multiple, and the multiple first communication holes are arranged on the second baffle in a display manner; the number of the second communication holes is plural, and the plural second communication holes are arranged in a row on the third baffle.

In some possible embodiments, the number of the first exhaust holes is plural, and the plural first exhaust holes are arranged in a display on the first partition plate.

In some possible embodiments, the air conditioner further comprises a second partition plate provided with a second exhaust hole, the second partition plate is located between the first partition plate and the air outlet, and forms a dispersion channel with the first partition plate.

In some possible embodiments, the number of the second exhaust holes is plural, and the number of the second exhaust holes at a position close to the nozzle mounting position is larger than the number of the second exhaust holes at a position away from the nozzle mounting position, or the aperture of the second exhaust holes at a position close to the nozzle mounting position is larger than the aperture of the second exhaust holes at a position away from the nozzle mounting position.

In some possible embodiments, the first direction is perpendicular to the second direction.

According to the technical scheme, the waste gas enters the shell from the air inlet and is divided into two parts when flowing through the rotational flow plate, one part flows to the rear annular flow channel through the communicating groove, and the other part enters the mixed flow channel through the rotational flow part; the urea sprayed by the urea nozzle is sprayed into the circular flow channel, mixed with the waste gas in the circular flow channel and divided into three parts by the baffle plate, wherein the two parts flow to the two sides of the annular flow channel, and the rest flows to the mixed flow channel through the air inlet hole on the baffle plate; the airflow flowing to the two sides of the annular flow channel is subjected to convection collision through the baffle plate and enters the mixed flow channel through the communication hole, and finally the three parts of airflow are converged in the mixed flow channel and flow to the exhaust port through the first exhaust hole in the first partition plate. Because the center line of the swirling part is closer to the nozzle mounting position than the center line of the swirling plate, namely the swirling part is eccentrically arranged, the urea nozzle side arranged in the circulating channel forms a high-pressure side, and the opposite side forms a low-pressure side, the air flow of the circulating channel flows to the opposite side from the nozzle mounting position, the mixing path of waste gas and urea spray is effectively increased, the mixing uniformity of the air flow is improved, and the urea spray is effectively prevented from generating crystallization. In addition, the rotational flow plate provides another flow path for the air flow on one hand, and can form turbulent flow in the mixed flow channel on the other hand, so that the mixing degree of the air flow is improved.

Drawings

In order to clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below. It is obvious that the drawings in the following description are only examples or embodiments of the invention, and that for a person skilled in the art, other drawings can be obtained from the provided drawings without inventive effort, and that the invention can also be applied to other similar scenarios from the provided drawings. Unless otherwise apparent from the context, or otherwise indicated, like reference numbers in the figures refer to the same structure or operation.

Fig. 1 is a schematic perspective view of an SCR mixer according to an example of the present invention;

fig. 2 is a schematic cross-sectional structural view of an SCR mixer according to an example of the present invention;

fig. 3 is a schematic structural diagram of a swirl plate in an SCR mixer according to an example of the present invention;

fig. 4 is a schematic structural diagram of a first baffle plate in an SCR mixer according to an exemplary embodiment of the present invention;

fig. 5 is a schematic structural diagram of a second baffle plate in an SCR mixer according to an exemplary embodiment of the present invention;

fig. 6 is a schematic structural diagram of a third baffle plate in an SCR mixer according to an example of the present invention;

fig. 7 is a schematic structural diagram of a first partition plate in an SCR mixer according to an exemplary embodiment of the present invention;

fig. 8 is a schematic structural diagram of a second partition plate in an SCR mixer according to an example of the present invention;

wherein 100 is a shell, 200 is a rotational flow plate, 300 is a baffle, 400 is a first clapboard, 500 is a second clapboard, and 600 is a urea nozzle;

101 is an air inlet, 102 is an air outlet, 103 is a nozzle mounting position, 201 is a rotational flow part, 202 is a communicating groove, 203 is a rotational flow hole, 2011 is a rotational flow blade, 2012 is an overflowing hole, 301 is an air inlet hole, 302 is a communicating hole, 401 is a first air outlet hole, and 501 is a second air outlet hole;

300a is a first baffle, 300b is a second baffle, and 300c is a third baffle.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and are not limiting of the invention. The described embodiments are only some, but not all embodiments of the invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

The utility model provides a post-treatment SCR mixer to improve urea and waste gas mixing homogeneity. The following is described in detail with reference to several embodiments.

Referring to fig. 1 to 8, the present invention discloses an aftertreatment SCR mixer in example, including casing 100, and set gradually whirl plate 200, baffle 300 and first baffle 400 in casing 100, whirl plate 200, baffle 300 and first baffle 400 separate casing 100 into mixed flow passageway B and circulation passageway a, wherein: the housing 100 has an air inlet 101 for air inlet, an air outlet 102 for air outlet, and a nozzle mounting position 103 for mounting the urea nozzle 600, the air inlet 101 and the air outlet 102 are arranged along a first direction ox, when the urea nozzle 600 is mounted on the nozzle mounting position 103, the spraying direction of the urea nozzle is a second direction oy, and the second direction oy and the first direction ox are mutually crossed; a swirling part 201 communicating the air inlet 101 with the mixed flow channel B is arranged in the middle of the swirling plate 200, a plurality of communicating grooves 202 communicated with the circular flow channel A are formed in the edge of the swirling plate 200, and a center line O2 of the swirling part 201 is closer to the nozzle mounting position 103 than a center line O1 of the swirling plate 200; an air inlet hole 301 is formed in the position, close to the nozzle mounting position 103, of the baffle 300, and the air inlet hole 301 is communicated with the circulation channel A and the mixed flow channel B; a communication hole 302 is formed in the position, far away from the nozzle mounting position 103, of the baffle 300, and the communication hole 302 is communicated with the circulation channel A and the mixed flow channel B; the middle of the first partition 400 has a first exhaust hole 401 communicating the mixed flow passage B with the outlet 102.

It should be noted that the first direction ox and the second direction oy are arranged to intersect with each other, and the first direction ox and the second direction oy form an acute angle or a right angle along the exhaust gas intake direction. In the drawings, although the first direction ox and the second direction oy are vertically arranged, the present invention is not limited to the vertical form.

When the rear SCR mixer of the utility model is used, the waste gas enters the shell 100 from the air inlet 101, and is divided into two parts when flowing through the rotational flow plate 200, one part flows to the rear circulation channel A through the communicating groove 202, and the other part enters the mixed flow channel B through the rotational flow part 201; after being sprayed into the circulation channel A, the urea sprayed by the urea nozzle 600 is mixed with the waste gas in the circulation channel A and is divided into three parts by the baffle 300, wherein the two parts flow to the two sides of the annular flow channel, and the rest flows to the mixed flow channel B through the air inlet hole 301 on the baffle 300; the air flows flowing to the two sides of the annular flow passage are subjected to convection collision through the baffle plate 300 and enter the mixed flow passage B through the communication hole 302, and finally three parts of air flows are converged in the mixed flow passage B and flow to the exhaust port through the first exhaust hole 401 on the first partition plate 400. Because the center line O2 of the swirling portion 201 is closer to the nozzle mounting position 103 than the center line O1 of the swirling plate 200, that is, the swirling portion 201 is eccentrically disposed, the side of the circulation channel a where the urea nozzle 600 is disposed forms a high-pressure side, and the opposite side forms a low-pressure side, it is ensured that the air flow of the circulation channel a flows to the opposite side from the nozzle mounting position 103, the mixing path of the exhaust gas and the urea spray is effectively increased, the mixing uniformity of the air flow is improved, and the urea spray is effectively prevented from being crystallized. In addition, the swirl plate 200 provides another flow path for the air flow, and on the other hand, a turbulent flow can be formed in the mixed flow channel B, so that the mixing degree of the air flow is improved.

The swirl portion 201 is intended to introduce the exhaust gas introduced through the inlet 101 into the mixed flow path B in a swirling state by the swirl portion 201. The utility model discloses an in the example, whirl portion 201 includes a plurality of whirl blades 2011, and a plurality of whirl blades 2011 arrange for the centre of a circle around whirl board 200's central line O1, and every whirl blade 2011 inclines to mixed flow passageway B from whirl board 200 and arranges, and the bottom of every whirl blade 2011 has overflowing hole 2012. When the exhaust gas entering the swirling portion 201 passes through the overflowing hole 2012, the direction of the exhaust gas entering the mixed flow channel B is changed under the action of the swirling vanes 2011, and in addition, the part of the swirling vanes 2011 located in the mixed flow channel B can also disturb the air flow in the mixed flow channel B to form turbulent flow, so that the mixing degree of the air flow is improved. In an example of the present invention, the swirling portion 201 may also be a spiral structure. The swirling portion 201 may be understood as long as a structure that changes the direction of the exhaust gas can be achieved.

When the swirl portion 201 includes a plurality of swirl vanes 2011, the number of swirl vanes 2011 may be two, three, four, five, or the like. In the illustration, the number of swirl vanes 2011 is four.

In order to further improve the mixing effect, in some examples of the present invention, on the basis of the above-mentioned swirling portion 201, the swirling portion 201 further includes a swirling hole 203 surrounding the plurality of swirling vanes 2011, and the swirling hole 203 communicates the air inlet 101 with the mixed flow channel B. The swirl holes 203 are straight holes, the hole patterns of the swirl holes are square, round, oval and the like, and the direction of the airflow entering the mixed flow channel B from the swirl part 201 is changed, but the airflow passing through the swirl holes 203 is not changed, so that turbulent flow can be formed under the interaction of a plurality of airflows, and the mixing effect is further improved.

The baffle 300 functions to change the flow direction of the air flow entering the circulation passage a to extend the air flow mixing length. A part of the air flow entering the circular flow passage a enters the mixed flow passage B through the intake holes 301, and both parts flow from both sides of the high pressure side to the low pressure side, and enter the mixed flow passage B through the communication hole 302 after reaching the low pressure side.

The baffle 300 has a cylindrical structure, an elliptical cylindrical structure, or the like. In addition, the baffle 300 is an integrated structure or a split structure. When being split type structure, the utility model discloses in some examples, baffle 300 includes first baffle 300a, second baffle 300b and third baffle 300c, first baffle 300a, second baffle 300b and third baffle 300c encircle the central line O1 of whirl board 200, first baffle 300a is close to nozzle installation position 103, inlet port 301 sets up on first baffle 300a, intercommunicating pore 302 includes first intercommunicating pore 302b and second intercommunicating pore 302c, first intercommunicating pore 302b sets up on second baffle 300b, second intercommunicating pore 302c sets up on third baffle 300 c.

When the airflow on the high-pressure side flows to the second baffle 300B in the circulation channel a, the airflow collides with the second baffle 300B and then enters the mixed flow channel B through the first communication hole 302B; when the airflow on the other side of the high pressure side flows to the third baffle 300c in the circulation flow path a, and collides with the third baffle 300c, and then enters the mixed flow path B through the second communication hole 302 c.

The first baffle 300a, the second baffle 300b and the third baffle 300c are integrally connected by fasteners or welding, or the first baffle 300a, the second baffle 300b and the third baffle 300c are of a sectional structure, specifically, a gap exists among the first baffle 300a, the second baffle 300b and the third baffle 300 c. Wherein the gap between adjacent baffles 300 exists in the circumferential direction, and the gap between adjacent baffles 300 exists in the radial direction. The air flow can collide at the position, the mixing degree of the air flow is greatly improved, the air inlet hole 301, the first communicating hole 302b and the second communicating hole 302c on the baffle plate 300 are arranged, the flow cross section of the air flow is increased, and great pressure loss is avoided.

The intake holes 301 in the first baffle 300a function to allow a part of the air flow on the high pressure side in the circulation passage a to enter the mixed flow passage B through the intake holes 301. The number of the intake holes 301 may be one or more. When being a plurality of, a plurality of inlet ports 301 can arrange wantonly, still can be the matrix form and arrange, still can arrange according to other rules. In an example of the present invention, the inlet holes 301 are arranged on the first baffle 300a in multiple rows, and the number of the inlet holes 301 in the corresponding row gradually decreases from the air inlet 101 to the air outlet 102. With this arrangement, the airflow at the high pressure side can enter the flow mixing channel B from the portion close to the swirl plate 200 as much as possible, so as to mix at the portion of the flow mixing channel B close to the swirl plate 200. The above is the arrangement form of the air inlet holes 301, and the hole type of the air inlet holes 301 can be square holes, round holes, elliptical holes, and the like.

The first communication holes 302B are used to communicate the low-pressure side with the mixed flow channel B, wherein the first communication holes 302B are plural in number, the plural first communication holes 302B may be randomly arranged, and the plural first communication holes 302B may also be arranged on the second baffle 300B in a display manner. The second communication holes 302c serve to communicate the low pressure side with the mixed flow path B, wherein the second communication holes 302c are provided in plural numbers, the plural first communication holes 302B may be arranged arbitrarily, and the plural second communication holes 302c may be arranged in a row on the third baffle 300 c.

The first exhaust hole 401 is used for discharging the mixed airflow in the mixed flow channel B to the exhaust port. The number of the first exhaust holes 401 may be one or more, and when there is one, the aperture of the first exhaust hole 401 is larger; when the number of the first exhaust holes 401 is plural, the plural first exhaust holes 401 are arbitrarily arranged on the first separator 400, and the plural first exhaust holes 401 may also be arranged on the first separator 400 in a display manner.

In order to further optimize the above solution, the post-treatment SCR mixer according to some embodiments of the present invention further includes a second partition 500300 provided with a second exhaust hole 501 on the basis of the above embodiments, wherein the second partition 500300 is located between the first partition 400 and the gas outlet 102, and forms a dispersion channel C with the first partition 400. The airflow passes through the first partition plate 400 and then is fully diffused and mixed in the dispersion channel C, and the airflow can be effectively dispersed more uniformly in the region through the second exhaust holes 501 of the second partition plate 300, so that the ammonia distribution uniformity and the airflow speed uniformity of the airflow are ensured.

The number of the second gas exhaust holes 501 is plural, and the number of the second gas exhaust holes 501 at a position close to the nozzle mounting position 103 is larger than the number of the second gas exhaust holes 501 at a position away from the nozzle mounting position 103, or the aperture of the second gas exhaust holes 501 at a position close to the nozzle mounting position 103 is larger than the aperture of the second gas exhaust holes 501 at a position away from the nozzle mounting position 103. So set up, can make on the whirl board 200 of front end because the eccentric design of whirl portion 201 brings the velocity gradient difference take place the redistribution, effectively improve the ammonia distribution uniformity and the velocity distribution uniformity of this back SCR mixer gas vent cross-section.

The eccentric design of structure whirl baffle 300 can adjust eccentric degree as required, and trompil position can be changed according to the position of arranging of actual urea nozzle 600 mouth to the trompil on the structure baffle 300, and the design of holistic opening can also be changed into according to actual need to the fine and close porous on the porous plate of structure, and the trompil position also can be changed according to the air velocity distribution of structure export cross-section to the trompil of porous plate of structure.

It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings. In the case of conflict, the embodiments and features of the embodiments of the present invention may be combined with each other.

It should be understood that "system," "device," "unit," and/or "module" as used in the present disclosure is a method for distinguishing different components, elements, parts, portions, or assemblies of different levels. However, other words may be substituted by other expressions if they accomplish the same purpose.

As used herein, the terms "a," "an," "the," and/or "the" are not intended to be inclusive and include the plural unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" are intended to cover only the explicitly identified steps or elements as not constituting an exclusive list and that the method or apparatus may comprise further steps or elements. An element defined by the phrase "comprising a component of ' 8230 ' \8230; ' does not exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

In the description of the embodiments of the present invention, unless otherwise specified, "/" indicates an or meaning, for example, a/B may indicate a or B; "and/or" herein is merely an association describing an associated object, and means that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "a plurality" means two or more than two.

In the following, the terms "first", "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

The present invention uses flow charts to illustrate operations performed by a system according to embodiments of the present invention. It should be understood that the preceding or following operations are not necessarily performed in the exact order in which they are performed. Rather, the various steps may be processed in reverse order or simultaneously. Meanwhile, other operations may be added to or removed from these processes.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and the principles of the technology used, and is not intended to limit the present invention. Various modifications and variations of the present invention will be apparent to those skilled in the art. The scope of the present invention is not limited to the specific combinations of the above technical features, but also covers other technical features that are formed by arbitrarily combining the above technical features or their equivalents without departing from the scope of the present invention. For example, the above features and (but not limited to) technical features having similar functions disclosed in the present invention are mutually replaced to form the technical solution.

Claims

1. The utility model provides an aftertreatment SCR blender, its characterized in that, including the casing, and set gradually in whirl board, baffle and first baffle in the casing, the whirl board the baffle with first baffle will the casing is separated into mixed flow passageway and circulation passageway, wherein:

an air inlet hole is formed in the position, close to the nozzle mounting position, of the baffle, and the air inlet hole is communicated with the circulation channel and the mixed flow channel; a communicating hole is formed in the position, far away from the nozzle mounting position, of the baffle plate, and the communicating hole is communicated with the circulation channel and the mixed flow channel;

2. The aftertreatment SCR mixer of claim 1, wherein the swirl portion comprises a plurality of swirl blades arranged around a center line of the swirl plate as a circle center, each of the swirl blades is arranged obliquely from the swirl plate to the flow mixing channel, and a bottom of each of the swirl blades has an overflowing hole.

3. The aftertreatment SCR mixer of claim 2, wherein the number of swirl vanes is four.

4. The aftertreatment SCR mixer of claim 3, wherein the swirl portion further comprises a swirl hole surrounding a plurality of the swirl vanes, the swirl hole communicating the inlet with the flow mixing passage.

5. The aftertreatment SCR mixer of claim 4, wherein the baffles comprise a first baffle, a second baffle, and a third baffle, the first baffle, the second baffle, and the third baffle are circumferentially disposed about a centerline of the swirl plate, the first baffle is proximate to the nozzle mounting location, the air inlet is disposed on the first baffle, the communication aperture comprises a first communication aperture disposed on the second baffle and a second communication aperture disposed on the third baffle.

6. The aftertreatment SCR mixer of claim 5, wherein a gap exists between the first baffle, the second baffle, and the third baffle.

7. The aftertreatment SCR mixer of claim 6, wherein the inlet holes are arranged in a plurality of rows on the first baffle, and the number of inlet holes in a corresponding row decreases in a direction from the inlet to the outlet.

8. The aftertreatment SCR mixer of claim 7, wherein the first plurality of communication apertures is a plurality of first communication apertures arranged in an array on the second baffle plate; the number of the second communication holes is multiple, and the second communication holes are arranged on the third baffle in a display manner.

9. The aftertreatment SCR mixer of claim 8, wherein the first exhaust port is a plurality in number, the first exhaust port being arranged in a display on the first partition.

10. The aftertreatment SCR mixer of claim 9, further comprising a second partition provided with a second exhaust vent, the second partition being located between the first partition and the outlet and forming a dispersion channel with the first partition.

11. The aftertreatment SCR mixer of claim 10, wherein the second exhaust port is plural in number, and the number of the second exhaust ports at a position close to the nozzle mount is larger than the number of the second exhaust ports at a position away from the nozzle mount, or the aperture of the second exhaust ports at a position close to the nozzle mount is larger than the aperture of the second exhaust ports at a position away from the nozzle mount.

12. The aftertreatment SCR mixer of any one of claims 1-11, wherein the first direction is perpendicular to the second direction.