A reverse thrust mechanism for an aircraft engine

Abstract

The present application belongs to the technical field of reverse thrust mechanism design of aircraft engines, and specifically relates to a reverse thrust mechanism of an aircraft engine, comprising: an outer wall of an outer duct, on which is provided a strip groove; the strip groove extends to the rear end of the outer wall of the outer duct; an outer cover, arranged in the strip groove; a baffle, arranged in the strip groove, located on the front side of the outer cover, with the outer front end of the baffle hinged to the outer side of the outer cover, and having a strip hole thereon; the strip hole extends to the front end of the baffle; an actuator, connected between the outer side of the outer wall of the outer duct and the outer side of the outer cover; a sleeve, one end of which is hinged to the outer side of the outer wall of the outer duct, and the inner side of which has an inner wall protrusion; a connecting rod, one end of which extends into the sleeve, the outer wall of this end has an outer wall protrusion, and the other end is hinged to the outer side of the baffle.

Description

Technical Field

[0001] The present application belongs to the technical field of reverse thrust mechanism design of aircraft engines, and specifically relates to a reverse thrust mechanism of an aircraft engine. Background Art

[0002] In order to shorten the landing distance of the aircraft, an aircraft engine reverse thrust mechanism is designed.

[0003] The current reverse thrust mechanism of an aircraft engine mainly includes a choke door, a pull rod, an actuator and other components. Among them, the choke door is hinged in a slot on the outer wall of the outer duct, the pull rod is hinged between the inner side of the choke door and the inner side of the outer duct, and the actuator is hinged between the outer side of the choke door and the outer side of the outer duct. It has the following features:

[0004] In the forward thrust state, the blocker blocks the slot on the outer wall of the duct, forming a part of the outer wall of the duct. The duct airflow of the aircraft engine can be discharged normally, providing thrust for the aircraft.

[0005] In the reverse thrust state, the actuator drives the choke door to deflect toward the inner side of the outer wall of the outer duct, blocking the outer duct of the aircraft engine, and allowing the outer duct airflow to be discharged from the slots on the outer wall of the outer duct, which can provide reverse thrust for the aircraft, thereby shortening the aircraft's landing run distance.

[0006] The above-mentioned reverse thrust mechanism of the aircraft engine has the following defects:

[0007] 1) The tie rod is hinged between the inside of the choke door and the inside of the duct wall, meaning it is located within the duct and is completely exposed to the duct airflow. The hinged locations at both ends are susceptible to corrosion and have a limited service life. Furthermore, in forward thrust, the tie rod creates significant resistance to the duct airflow, impacting the overall performance of the engine.

[0008] 2) Most of the aerodynamic load will be transmitted to the inner wall of the outer duct through the tie rod, causing the inner wall of the outer duct to bear a large local load. Since the inner wall of the outer duct is mostly designed with honeycomb bonding, the inner wall of the outer duct is easily damaged.

[0009] This application is proposed in view of the above-mentioned technical defects.

[0010] It should be noted that the disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0011] The purpose of the present application is to provide an aircraft engine reverse thrust mechanism to overcome or alleviate at least one of the known technical deficiencies.

[0012] The technical solution of this application is:

[0013] An aircraft engine reverse thrust mechanism, comprising:

[0014] The outer wall of the outer duct has a strip groove thereon; the strip groove extends to the rear end of the outer wall of the outer duct;

[0015] an outer cover, arranged in the strip groove;

[0016] The blocker is arranged in the strip groove and is located on the front side of the outer cover. The outer side of the front end is hinged to the outer side of the outer cover and has a strip hole on it; the strip hole extends to the front end of the blocker;

[0017] An actuator is connected between the outer side of the outer wall of the duct and the outer side of the outer cover;

[0018] A sleeve, one end of which is hinged to the outside of the outer wall of the outer duct and has an inner wall protrusion on the inner side;

[0019] A connecting rod, one end of which extends into the sleeve, the outer wall of which end has an outer wall protrusion, and the other end of which is hinged to the outer side of the blocking door;

[0020] The reverse thrust mechanism of an aircraft engine has:

[0021] In the forward thrust state, the sleeve and connecting rod block the strip hole, and the outer cover and the blocking door block the strip groove;

[0022] In the reverse thrust state, the actuator moves, driving the outer cover to move toward the rear end of the outer wall of the outer duct, thereby driving the baffle door to move toward the rear end of the outer wall of the outer duct, and the connecting rod extends outward from the sleeve. When the protrusion of the outer wall collides with the protrusion of the inner wall, the baffle door deflects toward the inner side of the outer wall of the outer duct, and the sleeve and its connecting rod deflect toward the inner side of the outer wall of the outer duct through the strip hole.

[0023] According to at least one embodiment of the present application, in the aforementioned aircraft engine reverse thrust mechanism, both sides of the outer cover and the side walls on both sides of the strip groove are connected by guide rails.

[0024] According to at least one embodiment of the present application, in the above-mentioned reverse thrust mechanism of the aircraft engine, the front section of the outer cover is bent and extended toward the front end of the outer wall of the outer duct, and the inner side is hinged to the outer side of the spoiler.

[0025] According to at least one embodiment of the present application, in the aforementioned reverse thrust mechanism of the aircraft engine, a slot is provided on the inner side of the front end of the outer cover;

[0026] A block is provided on the inner side of the rear end of the choke door;

[0027] The reverse thrust mechanism of an aircraft engine is located at:

[0028] In the forward pushing state, the card block is in the card slot;

[0029] In the reverse thrust state, the card block comes out of the card slot.

[0030] According to at least one embodiment of the present application, the aforementioned aircraft engine thrust reverser mechanism further includes:

[0031] A sealing sheet connected to the sleeve;

[0032] The reverse thrust mechanism of an aircraft engine is located at:

[0033] In the forward pushing state, the sealing sheet blocks the strip hole.

[0034] According to at least one embodiment of the present application, in the aforementioned aircraft engine reverse thrust mechanism, the strip-shaped hole extends to the rear end of the blocker door;

[0035] The reverse thrust mechanism of an aircraft engine also includes:

[0036] The connecting piece is connected to the outside of the blocking door and spans the strip hole.

[0037] According to at least one embodiment of the present application, the aforementioned aircraft engine thrust reverser mechanism further includes:

[0038] The connecting piece is connected to the outside of the blocking door and spans the strip hole.

[0039] According to at least one embodiment of the present application, the aforementioned aircraft engine thrust reverser mechanism further includes:

[0040] The limiting nut is screwed onto the connecting rod to form a protrusion on the outer wall.

[0041] According to at least one embodiment of the present application, in the aforementioned aircraft engine reverse thrust mechanism, the inner wall of the sleeve has an inner protrusion;

[0042] The connecting rod extends into the outer wall of one end of the sleeve and has an outer protrusion;

[0043] The reverse thrust mechanism of an aircraft engine also includes:

[0044] The spring is connected between the inner protrusion and the outer protrusion, and relies on its elastic force to keep the choke door taut through the connecting rod.

[0045] According to at least one embodiment of the present application, the aforementioned aircraft engine thrust reverser mechanism further includes:

[0046] Adjustable nut, threaded onto the connecting rod.

[0047] According to at least one embodiment of the present application, in the aforementioned aircraft engine reverse thrust mechanism, the outer cover and the spoiler are attracted to each other by magnetism.

[0048] According to at least one embodiment of the present application, the aforementioned aircraft engine thrust reverser mechanism further includes:

[0049] Cascade, connected to the front section of the strip slot;

[0050] The rear section of the outer cover bends and extends toward the front end of the outer wall of the outer duct, covering the spoiler and blades.

[0051] According to at least one embodiment of the present application, in the aforementioned reverse thrust mechanism of the aircraft engine, there are multiple strip grooves and related component structures, which are distributed circumferentially along the outer wall of the outer duct. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of the reverse thrust mechanism of an aircraft engine provided by an embodiment of the present application in a forward thrust state;

[0053] Figure 2 yes Figure 1 A partial view of

[0054] Figure 3 Schematic diagram of an aircraft engine reverse thrust mechanism provided by an embodiment of the present application in an intermediate state between a forward thrust state and a reverse thrust state;

[0055] Figure 4 yes Figure 3 A partial view of

[0056] Figure 5 Schematic diagram of an aircraft engine reverse thrust mechanism provided by an embodiment of the present application in a reverse thrust state;

[0057] Figure 6 yes Figure 5 A partial view of

[0058] Figure 7 This is a partial schematic diagram of an aircraft engine reverse thrust mechanism provided by an embodiment of the present application;

[0059] Figure 8 yes Figure 7 Assembly diagram of the medium structure;

[0060] in:

[0061] 1-outer wall of the outer duct; 2-outer cover; 3-choke; 4-actuator; 5-sleeve; 6-connecting rod; 7-connecting plate; 8-limiting nut; 9-spring; 10-adjustable nut; 11-blade; 12-sealing plate.

[0062] In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. In addition, the drawings are only used for illustrative purposes and should not be understood as limitations on this patent. DETAILED DESCRIPTION

[0063] To make the technical solution and its advantages of the present application clearer, the technical solution of the present application will be described in further detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of the present application and are only used to explain the present application, not to limit the present application. It should be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0064] In addition, unless otherwise defined, the technical or scientific terms used in the description of this application should have the ordinary meanings understood by those of ordinary skill in the art to which this application belongs. The words "upper," "lower," "left," "right," "center," "vertical," "horizontal," "inner," and "outer" used in the description of this application are only used to indicate relative directions or positional relationships, and do not imply that the device or component must have a specific orientation, be constructed, or operate in a specific orientation. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. Therefore, they should not be understood as limitations on this application. The words "first," "second," "third," and similar terms used in the description of this application are used only for descriptive purposes to distinguish different components and should not be understood to indicate or imply relative importance. The words "one," "an," or "the" used in the description of this application should not be understood as absolute limitations on quantity, but should be understood as meaning the presence of at least one. The words "include" or "comprises" used in the description of this application mean that the element or object listed before the word includes the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0065] In addition, it should be noted that, unless otherwise clearly stipulated and limited, the words "install", "connect", "connect" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or a connection between two components. Technical personnel in the field can understand their specific meanings in this application according to the specific circumstances.

[0066] The following is combined with Figures 1 to 8 This application is described in further detail.

[0067] An aircraft engine reverse thrust mechanism, comprising:

[0068] The outer wall 1 of the duct has a strip groove thereon; the strip groove extends to the rear end of the outer wall 1 of the duct;

[0069] An outer cover 2 is provided in the strip groove;

[0070] The blocker 3 is provided in the strip groove and is located on the front side of the outer cover 2. The outer side of the front end is hinged to the outer side of the outer cover 2 and has a strip hole on it; the strip hole extends to the front end of the blocker 3;

[0071] The actuator 4 is connected between the outer side of the outer duct outer wall 1 and the outer side of the outer cover 2;

[0072] The sleeve 5 has one end hinged to the outside of the outer wall 1 of the outer duct and has an inner wall protrusion on its inner side;

[0073] A connecting rod 6, one end of which extends into the sleeve 5, the outer wall of which has an outer wall protrusion, and the other end of which is hinged to the outside of the blocking door 3;

[0074] The reverse thrust mechanism of an aircraft engine has:

[0075] In the forward thrust state, the sleeve 5 and the connecting rod 6 block the strip hole, the outer cover 2 and the blocker door 3 block the strip groove, forming a part of the outer wall 1 of the outer duct. The outer duct airflow of the aircraft engine can be discharged normally to provide thrust for the aircraft.

[0076] In the reverse thrust state, the actuator 4 acts to drive the outer cover 2 to move toward the rear end of the outer wall 1 of the outer duct, thereby driving the spoiler door 3 to move toward the rear end of the outer wall 1 of the outer duct, and the connecting rod 6 extends outward from the sleeve 5. When the protrusion of the outer wall collides with the protrusion of the inner wall, the overall length of the connecting rod 6 and the sleeve 5 reaches the maximum. At this time, the outer cover 2 continues to move toward the rear end of the outer wall 1 of the outer duct, and the spoiler door 3 is constrained by the length of the connecting rod 6 and the sleeve 5, and will deflect toward the inner side of the outer wall 1 of the outer duct, blocking the outer duct of the aircraft engine, so that the outer duct airflow is discharged from the strip groove on the outer wall of the outer duct, which can provide reverse thrust for the aircraft, thereby shortening the landing and rolling distance of the aircraft. During the deflection of the spoiler door 3 toward the inner side of the outer wall 1 of the outer duct, the sleeve 5 and its connecting rod 6 deflect toward the inner side of the outer wall 1 of the outer duct through the strip hole;

[0077] When the reverse thrust mechanism of the aircraft engine changes from the reverse thrust state to the forward thrust state, the actuator 4 can be activated to drive the outer cover 2 to move toward the front end of the outer wall 1 of the outer duct, thereby driving the baffle door 3 to deflect toward the outside of the outer wall 1 of the outer duct. After the baffle door 3 enters the strip groove, it moves toward the front end of the outer wall 1 of the outer duct. During this process, the connecting rod 6 retracts outward into the sleeve 5 and blocks the strip hole. The outer cover 2 and the baffle door 3 block the strip groove, reaching the forward thrust state.

[0078] The aircraft engine reverse thrust mechanism disclosed in the above embodiment is designed to have a strip hole on the baffle door 3, and cleverly uses the sleeve 5 and the connecting rod 6 to constrain the movement trajectory of the baffle door 3, so that the aircraft engine reverse thrust mechanism can be transformed between the forward thrust state and the reverse thrust state. When the aircraft engine reverse thrust mechanism is in the forward thrust state, the sleeve 5 and the connecting rod block the strip hole, forming a part of the outer wall 1 of the outer duct, and will not generate resistance to the airflow of the aircraft engine outer duct, which can effectively ensure the overall performance of the aircraft engine, and is not prone to corrosion and can have a long service life. In addition, the structure composed of the sleeve 5 and the connecting rod 6 is hinged to the outer wall 1 of the outer duct and the baffle door 3, and is not connected to the inner wall of the outer duct. The aerodynamic load it receives will not be transmitted to the inner wall of the outer duct, which can ensure that the inner wall of the outer duct will not be damaged.

[0079] In some optional embodiments, in the above-mentioned aircraft engine reverse thrust mechanism, both sides of the outer cover 2 are connected to the side walls on both sides of the strip groove through guide rails.

[0080] In some optional embodiments, in the above-mentioned reverse thrust mechanism of the aircraft engine, the front section of the outer cover 2 is bent and extended toward the front end of the outer wall 1 of the outer duct, and the inner side is hinged to the outer side of the spoiler 3.

[0081] In some optional embodiments, in the above-mentioned reverse thrust mechanism of the aircraft engine, the inner side of the front end of the outer cover 2 has a card slot;

[0082] There is a block on the inner side of the rear end of the blocking door 3;

[0083] The reverse thrust mechanism of an aircraft engine is located at:

[0084] In the forward pushing state, the card block is in the card slot to prevent the baffle door 3 from tilting outwards and damaging the inner surface of the outer wall 1 of the outer duct;

[0085] In the reverse thrust state, the card block comes out of the card slot.

[0086] In some optional embodiments, the above-mentioned aircraft engine reverse thrust mechanism further includes:

[0087] A sealing sheet 12 is connected to the sleeve 5;

[0088] The reverse thrust mechanism of an aircraft engine is located at:

[0089] In the forward pushing state, the sealing piece 12 blocks the strip hole to ensure the air tightness of the outer wall 1 of the outer duct. In order to ensure the surface of the outer wall 1 of the outer duct, a groove can be provided on the inner side of the flow control door 3 for the sealing piece 12 to be inserted.

[0090] In some optional embodiments, in the above-mentioned aircraft engine reverse thrust mechanism, the strip hole extends to the rear end of the blocker door 3, dividing the blocker door 3 into two parts to avoid interference with the movement of the sleeve 5 and connecting rod 6 combination structure;

[0091] The reverse thrust mechanism of an aircraft engine also includes:

[0092] The connecting piece 7 is connected to the outside of the flow-blocking door 3 and spans the strip hole to divide the flow-blocking door 3 into two parts and connect them together. In addition, it can prevent the combined structure of the sleeve 5 and the connecting rod 6 from tilting outward, ensuring that the combined structure of the sleeve 5 and the connecting rod 6 blocks the strip hole in the forward pushing state.

[0093] In some optional embodiments, the above-mentioned aircraft engine reverse thrust mechanism further includes:

[0094] The limit nut 8 is screwed onto the connecting rod 6 to form a protrusion on the outer wall. The maximum value that the overall length of the connecting rod 6 and the sleeve 5 can be adjusted by screwing the limit nut 8, thereby adjusting the constraint on the movement of the spoiler 3 and adjusting the inclination angle of the spoiler 3 in the outer duct of the aircraft engine when controlling the reverse thrust state.

[0095] In some optional embodiments, in the above-mentioned aircraft engine reverse thrust mechanism, the inner wall of the sleeve 5 has an inner protrusion;

[0096] The connecting rod 6 extends into the outer wall of one end of the sleeve 5 and has an outer protrusion;

[0097] The reverse thrust mechanism of an aircraft engine also includes:

[0098] The spring 9 is connected between the inner protrusion and the outer protrusion, and relies on its elastic force to keep the baffle door 3 taut through the connecting rod 6, so that the baffle door 3 can be constrained in the strip hole in the forward thrust state, avoiding the baffle door 3 from being deflected toward the inner side of the outer wall 1 of the outer duct due to gravity, affecting the aerodynamic performance of the outer duct of the aircraft engine, and avoiding the relative movement of the sleeve 5 and the connecting rod 6 from getting stuck.

[0099] In some optional embodiments, the above-mentioned aircraft engine reverse thrust mechanism further includes:

[0100] The adjustable nut 10 is screwed onto the connecting rod 6 and can adjust the preload force of the spring 9 by turning it.

[0101] In some optional embodiments, in the above-mentioned aircraft engine reverse thrust mechanism, the outer side of the sleeve 5 is grooved to expose the limit nut 8, the adjustable nut 10 and other parts to facilitate installation and adjustment.

[0102] In some optional embodiments, in the above-mentioned reverse thrust mechanism of the aircraft engine, the outer cover 2 and the baffle door 3 rely on magnetism to attract each other. Specifically, they can use magnets to attract each other so that the baffle door 3 can be constrained in the strip hole in the forward thrust state to prevent the baffle door 3 from being deflected toward the inner side of the outer wall 1 of the outer duct due to gravity, thereby affecting the aerodynamic performance of the outer duct of the aircraft engine.

[0103] In some optional embodiments, the above-mentioned aircraft engine reverse thrust mechanism further includes:

[0104] Cascade 11, connected to the front section of the strip groove;

[0105] The rear section of the outer cover 2 bends and extends toward the front end of the outer wall 1 of the outer duct, covering the baffle door 3 and the blade cascade 11.

[0106] In some optional embodiments, in the above-mentioned aircraft engine reverse thrust mechanism, there are multiple strip grooves and related component structures, which are distributed circumferentially along the outer wall 1 of the outer duct. Their specific number, size and distribution position can be designed by relevant technical personnel according to specific actual conditions when applying the technical solution disclosed in this application, and no more detailed explanation will be given here.

[0107] The hinge mentioned in this application can be hinged with pins through the cooperation of single and double ear structures, or it can be hinged with various bearings. The specific design can be made by relevant technical personnel according to the actual situation when applying the technical solution disclosed in this application, and no more detailed explanation will be given here.

[0108] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to in detail.

[0109] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or replacements to the relevant technical features, and the technical solutions after these changes or replacements will fall within the scope of protection of the present application.

Claims

1. An aircraft engine reverse thrust mechanism, characterized in that: include: An outer wall (1) of the duct has a strip groove thereon; the strip groove extends to the rear end of the outer wall (1) of the duct; An outer cover (2) is arranged in the strip-shaped groove; A flow-blocking door (3) is provided in the strip-shaped groove and is located on the front side of the outer cover (2), with the outer side of its front end hinged to the outer side of the outer cover (2) and having a strip-shaped hole thereon; the strip-shaped hole extends to the front end of the flow-blocking door (3); An actuator (4) is connected between the outer side of the outer wall (1) of the outer duct and the outer side of the outer cover (2); A sleeve (5) has one end hinged to the outside of the outer wall (1) of the outer duct and an inner wall protrusion on the inner side; A connecting rod (6), one end of which extends into the sleeve (5), the outer wall of which has an outer wall protrusion, and the other end of which is hinged to the outside of the blocking door (3); The aero-engine reverse thrust mechanism comprises: In the forward thrust state, the sleeve (5) and the connecting rod (6) block the strip-shaped hole, and the outer cover (2) and the flow-blocking door (3) block the strip-shaped groove; In the reverse thrust state, the actuator (4) moves, driving the outer cover (2) to move toward the rear end of the outer wall (1) of the outer duct, thereby driving the baffle (3) to move toward the rear end of the outer wall (1) of the outer duct, and the connecting rod (6) extends outward from the sleeve (5). When the protrusion of the outer wall collides with the protrusion of the inner wall, the baffle (3) deflects toward the inner side of the outer wall (1), and the sleeve (5) and its connecting rod (6) deflect toward the inner side of the outer wall (1) of the outer duct through the strip hole.

2. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: The two sides of the outer cover (2) are connected to the side walls on both sides of the strip-shaped groove through guide rails.

3. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: The front section of the outer cover (2) bends and extends toward the front end of the outer wall (1) of the outer duct, and the inner side is hinged to the outer side of the flow control door (3).

4. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: Also includes: A sealing sheet (12) connected to the sleeve (5); The reverse thrust mechanism of the aero-engine is located at: In the forward pushing state, the sealing sheet (12) blocks the strip-shaped hole.

5. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: The strip-shaped hole extends to the rear end of the flow-blocking door (3); The aero-engine reverse thrust mechanism further comprises: A connecting piece (7) is connected to the outside of the flow-blocking door (3) and spans the strip-shaped hole.

6. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: Also includes: A limiting nut (8) is screwed onto the connecting rod (6) to form the outer wall protrusion.

7. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: The inner wall of the sleeve (5) has an inner protrusion; The connecting rod (6) extends into the outer wall of one end of the sleeve (5) and has an outer protrusion; The aero-engine reverse thrust mechanism further comprises: A spring (9) is connected between the inner protrusion and the outer protrusion, and relies on its elastic force to keep the flow-blocking door (3) taut through the connecting rod (6).

8. The aircraft engine thrust reverser mechanism according to claim 7, characterized in that: Also includes: An adjustable nut (10) is screwed onto the connecting rod (6).

9. The aircraft engine reverse thrust mechanism according to claim 1, characterized in that: The outer cover (2) and the flow-blocking door (3) are attracted to each other by magnetism.

10. The aircraft engine thrust reverser mechanism according to claim 1, characterized in that: Also includes: A blade cascade (11) connected to the front section of the strip-shaped slot; The rear section of the outer cover (2) bends and extends toward the front end of the outer wall (1) of the outer duct, covering the baffle (3) and the blade grid (11).

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