A direct jet injector capable of realizing hollow jet under multiple working conditions and a control method thereof

Abstract

The application discloses a direct injection injector capable of realizing hollow spray under multiple working conditions and a control method, which comprises an injector body, a spray cavity arranged in the injector body, a needle valve arranged in the spray cavity, a main control switch arranged at the top of the spray cavity and used for controlling the up-down movement of the needle valve, a valve rod groove arranged at the upper part of the needle valve, a first limiting device and a second limiting device arranged on the injector body and used for limiting the needle valve, and the first limiting device and the second limiting device are arranged in correspondence with the valve rod groove, and the first limiting device is arranged above the second limiting device. The injector can work in the needle valve lift range with strong vortex cavitation, induce hollow jet flow, and improve the fuel atomization quality.

Description

Technical Field

[0001] This invention relates to the field of liquid jet spraying technology, and more specifically to a direct-fire jetting device and control method capable of hollow spraying under multiple operating conditions. Background Technology

[0002] Liquid atomization technology is widely used in aerospace, automotive, environmental protection, medical, agricultural and many other fields, and is a very important practical technology. The injector is an essential key device in the atomization system, and the atomization performance of the system directly depends on the injector.

[0003] Depending on the injection method, injectors can be divided into two types: direct-injection and centrifugal. Direct-injection injectors are widely used in gasoline and diesel engines. In this type of injector, the liquid flows at high speed through the nozzle under pressure differential, forming a solid cone-shaped spray at the outlet. This solid cone nozzle provides stable liquid flow, low pressure loss, and a relatively uniform velocity distribution, making it suitable for high-speed flow applications. However, due to limitations in liquid atomization and the outlet spray cone angle, the atomization effect still needs improvement.

[0004] Centrifugal jets used in liquid rocket engines primarily utilize swirling orifices or swirling channels within the nozzle to cause the liquid to rotate within the nozzle. This rotating liquid film is then ejected from the nozzle as a hollow cone under centrifugal force. Compared to the solid cone spray produced by traditional direct-fire jets, this creates a larger spray cone angle, promoting liquid-air mixing and effectively improving atomization. However, both tangential-hole and vortex-type jets are equipped with complex guide vanes or swirlers, resulting in high manufacturing and maintenance costs. Furthermore, controlling the jet volume is often difficult, making them unsuitable for high-pressure conditions.

[0005] Therefore, how to provide a direct-fire injector and control method that can improve atomization quality and achieve hollow spraying under multiple operating conditions is one of the technical problems that urgently need to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a direct-fire injector and control method that can realize hollow spraying under multiple working conditions, so that the injector can work within the needle valve lift range with strong vortex cavitation, and adopts multi-stage overlapping spray to enhance the vortex cavitation flow inside the injector throughout the liquid spraying process, induce hollow jet, and improve the liquid atomization quality.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A direct-fire injector capable of hollow spraying under multiple operating conditions includes: an injector body; a spray chamber inside the injector body; a needle valve inside the spray chamber; a main control switch at the top of the spray chamber for controlling the up-and-down movement of the needle valve; a valve stem groove at the upper part of the needle valve; a first limiting device and a second limiting device on the injector body for limiting the position of the needle valve; both the first limiting device and the second limiting device are correspondingly arranged to the valve stem groove; the first limiting device is located above the second limiting device.

[0009] Preferably, the first limiting device includes a first push rod, a first stop block, and a first driving mechanism for driving the first push rod to move back and forth and up and down; the injector body has a first guide hole; the first push rod passes through the first guide hole; the first stop block is disposed at the end of the first push rod near the needle valve; the end of the first push rod away from the needle valve is connected to the output end of the first driving mechanism; the first driving mechanism is disposed on the outside of the injector body.

[0010] Preferably, the second limiting device includes a second push rod, a second stop block, and a second driving mechanism for driving the second push rod to move back and forth and up and down; a second guide hole is provided on the injector body; the second push rod passes through the second guide hole; the second stop block is disposed at the end of the second push rod near the needle valve; the end of the second push rod away from the needle valve is connected to the output end of the second driving mechanism; the second driving mechanism is disposed on the outside of the injector body.

[0011] Preferably, there are two valve stem grooves, two first limiting devices, and two second limiting devices; the two valve stem grooves are symmetrically arranged along the central axis of the needle valve; the two first limiting devices are symmetrically arranged along the central axis of the needle valve; and the two second limiting devices are symmetrically arranged along the central axis of the needle valve.

[0012] Preferably, the injector body includes an injector end cap and an injector body; the injector end cap is detachably connected to the top of the injector body.

[0013] Preferably, the bottom of the injector body is provided with a spray hole communicating with the spray chamber; the upper part of the injector body is provided with a liquid injection hole communicating with the spray chamber; and a pressure transmitter is provided in the middle of the injector body.

[0014] Preferably, the space between the bottom of the needle valve and the bottom of the injection chamber forms a pressure chamber.

[0015] Preferably, the top of the needle valve extends to the outside of the injector body and is provided with a displacement detection device for detecting changes in the displacement of the needle valve.

[0016] A control method for a direct-fired injector capable of achieving hollow spraying under multiple operating conditions, utilizing the aforementioned direct-fired injector capable of achieving hollow spraying under multiple operating conditions, includes the following steps:

[0017] Step 1, pre-spraying, includes: 1) The controller turns on the main control switch, causing the needle valve to move upward, and the liquid flows into the spray chamber through the injection hole and is ejected from the spray hole; 2) During the upward movement of the needle valve, the pressure transmitter collects pressure data in real time and transmits it to the oscilloscope recorder. When the pressure fluctuation amplitude at the monitoring point decreases and the fluctuation baseline value returns to the initial value, the controller controls the second limit device to limit the needle valve and prevent the needle valve from moving upward; 3) When the liquid spraying ends, the controller turns off the main control switch, and the needle valve moves downward. When the pressure fluctuation amplitude at the monitoring point decreases and the fluctuation baseline value returns to the initial value, the controller controls the first limit device to limit the needle valve and prevent the needle valve from moving downward, thereby completing the pre-spraying process.

[0018] Step 2, main injection, includes: 1) The controller controls the main control switch to open, causing the needle valve to move upward, while keeping the first limit device and the second limit device in the limit state, until the needle valve rises to the maximum stroke; 2) After the liquid injection is completed, the controller controls the main control switch to close, and the needle valve starts to move downward from the maximum stroke until it drops to the minimum stroke, thereby completing the main injection process.

[0019] Step 3, post-spraying, includes: 1) The controller opens the main control switch, causing the needle valve to move upward, while keeping the first and second limiting devices in their limited positions until the needle valve reaches its maximum lift; 2) After liquid spraying is complete, the controller closes the main control switch, causing the needle valve to move downward from its maximum lift. Simultaneously, the controller releases the first and second limiting devices from their limiting positions until the needle valve is seated, thus completing the main spraying process. This invention achieves the following technical advantages over existing technologies:

[0020] 1) This invention enables the injector to operate within the needle valve lift range where vortex cavitation is strong, inducing a hollow jet and thereby improving fuel atomization quality;

[0021] 2) The present invention can adjust the up and down positions of the first push rod and the second push rod through the first driving mechanism and the second driving mechanism, thereby adjusting the needle valve lift range, so as to adapt to the needle valve lift range requirements under different injection strategies and meet the injection requirements under multiple working conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a direct-fire jetting device that can achieve hollow spraying under multiple working conditions according to the present invention;

[0023] Figure 2 This is a schematic diagram of the pre-injection process;

[0024] Figure 3 Schematic diagram of the main injection process;

[0025] Figure 4 This is a schematic diagram of the post-injection process;

[0026] In the diagram: 1. Injector body; 101. Injector end cap; 102. Injector main body; 2. Injection chamber; 3. Needle valve; 4. Main control switch; 5. Valve stem groove; 6. First push rod; 7. First stop block; 8. First guide hole; 9. Second push rod; 10. Second stop block; 11. Second guide hole; 12. Spray hole; 13. Injection hole; 14. Pressure transmitter; 15. Pressure chamber; 16. Displacement detection device; 17. Pressure sensing element. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Studies of the liquid flow inside the injector show that the generation of vortex cavitation is attributed to the vortex structure in the flow field. The hollow jet induced by the vortex greatly increases the spray cone angle. At the same time, a large number of cavitation bubbles in the vortex cavitation can be convected to the nozzle outlet, thereby tearing the liquid core of the liquid jet, promoting atomization and improving the quality of gas-liquid mixing.

[0029] Reference Figure 1-4 As shown, the present invention provides a direct-fire injector capable of hollow spraying under multiple operating conditions, comprising: an injector body 1; an injection chamber 2 inside the injector body 1; a needle valve 3 inside the injection chamber 2; a main control switch 4 at the top of the injection chamber 2 for controlling the up-and-down movement of the needle valve 3; a valve stem groove 5 on the upper part of the needle valve 3; a first limiting device and a second limiting device on the injector body 1 for limiting the needle valve 3; both the first limiting device and the second limiting device are correspondingly arranged to the valve stem groove 5; the first limiting device is arranged above the second limiting device; during the injection process, the needle valve 3 is limited by the first limiting device and the second limiting device, which allows the needle valve 3 to move up or down within a certain lift range of the set range, realizing the pre-spray, main spray and post-spray processes under a certain needle valve lift.

[0030] In this embodiment, the first limiting device includes a first push rod 6, a first stop block 7, and a first driving mechanism for driving the first push rod 6 to move back and forth and up and down; a first guide hole 8 is provided on the injector body 1; the first push rod 6 passes through the first guide hole 8; the first stop block 7 is disposed at the end of the first push rod 6 near the needle valve 3; the end of the first push rod 6 away from the needle valve 3 is connected to the output end of the first driving mechanism; the first driving mechanism is disposed on the outside of the injector body 1.

[0031] In this embodiment, a first guide assembly is provided in the first guide hole 8; the first guide assembly includes a first guide plate; the first guide plate is fixedly connected in the first guide hole 8; a first slider that can slide up and down along the first guide plate is slidably provided on the first guide rod plate; a first sliding hole is provided on the first slider; a first push rod 6 is slidably inserted in the first sliding hole; a through groove is provided on the first guide plate for the first push rod 6 to move up and down.

[0032] In this embodiment, the second limiting device includes a second push rod 9, a second stop block 10, and a second driving mechanism for driving the second push rod 9 to move back and forth and up and down; a second guide hole 11 is provided on the injector body 1; the second push rod 9 passes through the second guide hole 11; the second stop block 10 is disposed at the end of the second push rod 9 near the needle valve 3; the end of the second push rod 9 away from the needle valve 3 is connected to the output end of the second driving mechanism; the second driving mechanism is disposed on the outside of the injector body 1.

[0033] In this embodiment, a second guide assembly is provided in the second guide hole 11; the second guide assembly includes a second guide plate; the second guide plate is fixedly connected in the second guide hole 11; a second slider that can slide up and down along the second guide plate is slidably provided on the second guide rod plate; a second sliding hole is provided on the second slider; the second push rod 9 is slidably inserted in the second sliding hole; a through groove is provided on the second guide plate for the second push rod 9 to move up and down.

[0034] In this embodiment, both the first push rod 6 and the second push rod 9 can move up and down and back and forth, thereby flexibly changing their positions to adapt to the needle valve lift range requirements under different injection strategies, and thus meet the injection requirements under multiple working conditions.

[0035] In this embodiment, both the first drive mechanism and the second drive mechanism are two-axis slides.

[0036] In this embodiment, there are two valve stem grooves 5, two first limiting devices, and two second limiting devices; the two valve stem grooves 5 are symmetrically arranged on the left and right sides along the central axis of the needle valve 3; the two first limiting devices are symmetrically arranged on the left and right sides along the central axis of the needle valve 3; and the two second limiting devices are symmetrically arranged on the left and right sides along the central axis of the needle valve 3.

[0037] In this embodiment, the injector body 1 includes an injector end cap 101 and an injector body 102; the injector end cap 101 is detachably connected to the top of the injector body 102, which facilitates the replacement or maintenance of the components inside the injector end cap 101.

[0038] In this embodiment, the injector end cap 101 and the injector body 102 are connected by threads.

[0039] In this embodiment, both the first limiting device and the second limiting device are disposed on the injector end cap 101.

[0040] In this embodiment, the length of the valve stem groove 5 is greater than the maximum distance that the needle valve 3 can move up and down within the injection chamber 2.

[0041] In this embodiment, the bottom of the injector body 102 is provided with a nozzle 12 communicating with the injection chamber 2; the upper part of the injector body 102 is provided with an injection hole 13 communicating with the injection chamber 2; a pressure transmitter 14 is provided in the middle of the injector body 102; a pressure sensing element 17 is provided on the pressure transmitter 14; the pressure transmitter 14 is correspondingly arranged with the annular flow channel region in the middle of the injector body 102, and the pressure sensing element 17 on the pressure transmitter 14 is connected to the annular flow channel region to receive pressure change signals, and the voltage signal is converted into a pressure signal by an oscilloscope recorder.

[0042] In this embodiment, the space between the bottom of the needle valve 3 and the bottom of the injection chamber 2 forms a pressure chamber 15.

[0043] In this embodiment, the top of the needle valve 3 extends to the outside of the injector body 1 and is provided with a displacement detection device 16 for detecting the displacement change of the needle valve 3, which can obtain the needle valve lift data during the needle valve lifting-seat process.

[0044] In this embodiment, the displacement detection device 16 is a displacement sensor.

[0045] Studies have shown that the initial formation of cavitation bubbles and the transformation of cavitation morphology affect the pressure fluctuation characteristics inside the injector. Compared with other flow states, vortex cavitation induced by vortex structure causes greater pressure fluctuation amplitude and higher baseline value. Based on this, by combining displacement detection device 16 and pressure transmitter 14, the needle valve lift range in which a stable vortex cavitation flow state appears inside the injector can be obtained.

[0046] This invention also provides a control method for a direct-fired injector capable of achieving hollow spraying under multiple operating conditions. The method, utilizing the aforementioned direct-fired injector capable of achieving hollow spraying under multiple operating conditions, includes the following steps:

[0047] Step 1, pre-injection, includes: 1) The controller controls the main control switch 4 to open, causing the needle valve 3 to move upward. High-pressure liquid flows into the injection chamber 2 through the injection hole 13 and is ejected from the nozzle 12; 2) During the upward movement of the needle valve 3, the pressure transmitter 14 collects pressure data in real time and transmits it to the oscilloscope recorder. When the pressure fluctuation amplitude at the monitoring point decreases and the fluctuation baseline value returns to the initial value, the controller controls the second drive mechanism to drive the second push rod 9 to move towards the needle valve 3. The second push rod 9 drives the second stop block 10 to move towards the needle valve 3 until the second stop block 10 moves towards the needle valve 3. Block 10 moves into the corresponding valve stem groove 5, thereby limiting the needle valve 3 and preventing it from moving upward. During this process, as the height of the needle valve 3 increases, the flow pattern of the liquid inside the injector changes, and cavitation occurs in the area of ​​the nozzle 12 and pressure chamber 15. When there is a strong vortex flow inside the injector, the induced vortex cavitation will reduce the flow area of ​​the nozzle, and the rate of pressure decrease per unit time will slow down. However, the total pressure in the pressure chamber 15 remains unchanged. Therefore, the upstream area of ​​the injector body 102 and the installation position of the pressure transmitter 14 are affected. As the pressure increases, the position of vortex cavitation varies greatly compared to geometric cavitation, thus increasing the disturbance to the liquid flow and increasing the pressure fluctuation amplitude. Therefore, when vortex cavitation exists inside the injector, the pressure fluctuation characteristics in the flow field are significantly different from other flow patterns. After the pressure transmitter 14 collects pressure data and transmits it to the oscilloscope recorder, it shows that the pressure fluctuation amplitude is larger and the fluctuation baseline value is higher. The needle valve 3 continues to rise, the cross-section of the liquid flow channel in the pressure chamber 15 increases, and the linear cavitation stability in the nozzle 12 begins to deteriorate until it disappears completely. 3) When the liquid injection ends, the controller closes the main control switch 4, the needle valve 3 moves downward, and when the pressure fluctuation amplitude at the monitoring point decreases and the fluctuation baseline value returns to the initial value, the controller controls the first drive mechanism to drive the first push rod 6 to move toward the needle valve 3. The first push rod 6 drives the first stop block 7 to move toward the needle valve 3 until the first stop block 7 moves into the corresponding valve stem groove 5, thereby limiting the needle valve 3 and preventing the needle valve 3 from moving downward, thus completing the pre-injection process and determining the range of the needle valve's partial lift.

[0048] Step 2, main injection, includes: 1) The controller controls the main control switch 4 to open, causing the needle valve 3 to move upward, while keeping the first limit device and the second limit device in the limit state, until the needle valve 3 rises to the maximum stroke; 2) After the liquid injection is completed, the controller controls the main control switch 4 to close, and the needle valve 3 starts to move downward from the maximum stroke until it drops to the minimum stroke, thereby completing the main injection process.

[0049] Step 3, post-spraying, includes: 1) The controller controls the main control switch 4 to open, causing the needle valve 3 to move upward, while keeping the first and second limit devices in the limit state, until the needle valve 3 rises to the maximum stroke; 2) After the liquid spraying is completed, the controller controls the main control switch 4 to close, causing the needle valve 3 to move downward from the maximum stroke, while the controller controls the first and second limit devices to release the limit on the needle valve 3, until the needle valve 3 sits down, thus completing the main spraying process.

[0050] In this embodiment, the needle valve lift curve during the fuel injection process can be obtained online through the displacement detection device 16.

[0051] In this embodiment, the needle valve only opens and sets once throughout the entire injection process, which includes pre-injection, main injection, and post-injection, thus reducing the number of times the needle valve impacts the injector body.

[0052] In this embodiment, the needle valve does not sit down when switching between pre-injection, main injection, and post-injection, the nozzle does not seal, and there is overlap in the different injection processes. This compensates for the reduced injection volume caused by the decrease in the maximum lift of the needle valve, while ensuring that there is a strong hollow spray throughout the entire injection process, thus optimizing the oil-air mixing.

[0053] In this embodiment, the controller is a microcontroller.

[0054] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A control method for a direct-fire injector capable of hollow spraying under multiple operating conditions, characterized in that, Direct-fire jets include: The injector body (1) has an internal injection chamber (2); the injection chamber (2) has an internal needle valve (3); the top of the injection chamber (2) has a main control switch (4) for controlling the up and down movement of the needle valve (3); the upper part of the needle valve (3) has a valve stem groove (5); the injector body (1) has a first limiting device and a second limiting device for limiting the needle valve (3); the first limiting device and the second limiting device are both corresponding to the valve stem groove (5); the first limiting device and the second limiting device are both provided. A limiting device is disposed above the second limiting device; the injector body (1) includes an injector end cap (101) and an injector body (102); the injector end cap (101) is detachably connected to the top of the injector body (102); the bottom of the injector body (102) is provided with a spray hole (12) communicating with the spray chamber (2); the upper part of the injector body (102) is provided with a liquid injection hole (13) communicating with the spray chamber (2); a pressure transmitter (14) is provided in the middle of the injector body (102); The control method includes the following steps: Step 1, pre-spraying, includes: 1) The controller controls the main control switch (4) to open, so that the needle valve (3) moves upward, and the liquid flows into the spray chamber (2) through the injection hole (13) and is ejected from the spray hole (12); 2) During the upward movement of the needle valve (3), the pressure transmitter (14) collects pressure data in real time and transmits it to the oscilloscope recorder. When the pressure fluctuation amplitude at the monitoring point decreases and the fluctuation baseline value returns to the initial value, the controller controls the second limit device to limit the needle valve (3) and prevent the needle valve (3) from continuing to move upward; 3) When the liquid spraying ends, the controller closes the main control switch (4), and the needle valve (3) moves downward. When the pressure fluctuation amplitude at the monitoring point decreases and the fluctuation baseline value returns to the initial value, the controller controls the first limit device to limit the needle valve (3) and prevent the needle valve (3) from continuing to move downward, thereby completing the pre-spraying process; Step 2, main injection, includes: 1) The controller controls the opening of the main control switch (4), causing the needle valve (3) to move upward, while keeping the first limit device and the second limit device in the limit state, until the needle valve (3) rises to the maximum lift position; 2) After the liquid injection is completed, the controller controls the closing of the main control switch (4), and the needle valve (3) starts to move downward from the maximum lift position until it drops to the minimum lift position, thereby completing the main injection process; Step 3, post-spraying, includes: 1) The controller controls the opening of the main control switch (4) so ​​that the needle valve (3) moves upward, while keeping the first limit device and the second limit device in the limit state until the needle valve (3) rises to the maximum stroke; 2) After the liquid spraying is completed, the controller controls the closing of the main control switch (4) so ​​that the needle valve (3) starts to move downward from the maximum stroke, while the controller controls the first limit device and the second limit device to release the limit on the needle valve (3) until it sits down, thereby completing the main spraying process.

2. A direct-fire jetting device for implementing the method described in claim 1, enabling hollow spraying under multiple operating conditions, characterized in that, include: The injector body (1) has an internal injection chamber (2); the injection chamber (2) has an internal needle valve (3); the top of the injection chamber (2) has a main control switch (4) for controlling the up and down movement of the needle valve (3); the upper part of the needle valve (3) has a valve stem groove (5); the injector body (1) has a first limiting device and a second limiting device for limiting the needle valve (3); the first limiting device and the second limiting device are both corresponding to the valve stem groove (5); the first limiting device is located above the second limiting device.

3. A direct-fire jetting device capable of hollow spraying under multiple operating conditions according to claim 2, characterized in that, The first limiting device includes a first push rod (6), a first stop (7), and a first driving mechanism for driving the first push rod (6) to move back and forth and up and down; a first guide hole (8) is provided on the injector body (1); the first push rod (6) passes through the first guide hole (8); the first stop (7) is provided at the end of the first push rod (6) near the needle valve (3); the end of the first push rod (6) away from the needle valve (3) is connected to the output end of the first driving mechanism; the first driving mechanism is provided on the outside of the injector body (1).

4. A direct-fire jetting device capable of hollow spraying under multiple operating conditions according to claim 2, characterized in that, The second limiting device includes a second push rod (9), a second stop (10), and a second driving mechanism for driving the second push rod (9) to move back and forth and up and down; a second guide hole (11) is provided on the injector body (1); the second push rod (9) passes through the second guide hole (11); the second stop (10) is provided at the end of the second push rod (9) near the needle valve (3); the end of the second push rod (9) away from the needle valve (3) is connected to the output end of the second driving mechanism; the second driving mechanism is provided on the outside of the injector body (1).

5. A direct-fire jetting device capable of hollow spraying under multiple operating conditions according to claim 2, characterized in that, The valve stem groove (5), the first limiting device and the second limiting device are all two in number; the two valve stem grooves (5) are symmetrically arranged on the left and right along the central axis of the needle valve (3); the two first limiting devices are symmetrically arranged on the left and right along the central axis of the needle valve (3); the two second limiting devices are symmetrically arranged on the left and right along the central axis of the needle valve (3).

6. A direct-fire jetting device capable of hollow spraying under multiple operating conditions according to claim 2, characterized in that, The injector body (1) includes an injector end cap (101) and an injector body (102); the injector end cap (101) is detachably connected to the top of the injector body (102).

7. A direct-fire jetting device capable of hollow spraying under multiple operating conditions according to claim 6, characterized in that, The bottom of the injector body (102) is provided with a spray hole (12) communicating with the spray chamber (2); the upper part of the injector body (102) is provided with a liquid injection hole (13) communicating with the spray chamber (2); and the middle part of the injector body (102) is provided with a pressure transmitter (14).

8. A direct-fire jetting device capable of hollow spraying under multiple operating conditions according to claim 2, characterized in that, The space between the bottom of the needle valve (3) and the bottom of the injection chamber (2) forms a pressure chamber (15).

9. A direct-fire injector capable of hollow spraying under multiple working conditions according to claim 2, wherein the top of the needle valve (3) extends to the outside of the injector body (1) and is provided with a displacement detection device (16) for detecting the displacement change of the needle valve (3).

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