Self-adaptive supporting method and device for U-shaped welded joint during serpentine coil hydraulic bulging

Abstract

The invention belongs to the technical field of hydraulic bulging of a snakelike coil pipe of a refrigeration air conditioner heat exchanger, and provides a self-adaptive supporting method and device for a U-shaped welding joint during hydraulic bulging of a snakelike coil pipe. The device comprises a snakelike coil pipe, a U-shaped welding joint, a pipe end sealing head, a supporting block, a supporting cylinder, a movable cross beam, a hydraulic pipeline, a hydraulic system, a hydraulic medium and a workbench. Liquid filling holes are formed in the pipe end sealing head and the supporting cylinder and communicated with a hydraulic system through a hydraulic pipeline, and pressure p acts on a piston of the supporting cylinder and the inner surface of the S-shaped coil pipe at the same time during hydraulic bulging. The supporting force applied by the supporting cylinder to the U-shaped welding joint is determined by the bulging pressure p, self-adaptive adjustment of the supporting force can be achieved, the tensile force borne by the welding seam is remarkably reduced, and therefore the risk that the welding seam is cracked due to the fact that the welding seam bears too large tensile force is avoided. By adjusting the number and the positions of the supporting cylinders and the shapes of the supporting blocks, the device can adapt to snakelike coil pipes with different lengths, different pipe distances and different welding joint sizes, and is high in flexibility and adaptability.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic expansion of serpentine coils of refrigeration and air-conditioning heat exchangers, and relates to a method and device for adaptively supporting U-shaped welded joints during hydraulic expansion of serpentine coils, and specifically to a method and device for applying adaptive axial support to the U-shaped welded joints by using an external loading unit to offset the axial tension formed at the weld of the U-shaped joint by internal pressure, thereby avoiding the risk of cracking of the weld due to tension. Background Art

[0002] In the refrigeration and air-conditioning industry, the serpentine coil is a core component of heat exchangers such as condensers and evaporators as a pipeline for the circulation of refrigerant. It is welded by several pipe sections and U-shaped welded joints. A large number of fins are installed on the outside of the serpentine coil, which greatly increases the heat exchange area between the heat exchanger and the external environment. The heat carried by the refrigerant is first transferred to the serpentine coil, and the serpentine coil then transfers the heat to the fins. Finally, the outer surface of the fins and the exposed part of the tube transfer the heat to the external environment.

[0003] The matching state between the serpentine coil and the fin is one of the key factors affecting the heat transfer efficiency of the heat exchanger. If the tube and the fin are in a clearance matching state, there is an air gap between the tube and the fin, and the heat is mostly transferred from the tube to the fin by convection and radiation. The heat transfer coefficient is much lower than the heat transfer coefficient in the direct contact state. Therefore, only when the tube and the fin are in close contact can the heat be quickly transferred from the tube to the fin, and the larger the contact area between the tube and the fin, the greater the contact pressure of the contact surface, and the greater the heat transfer coefficient between the two. Correspondingly, the heat transfer efficiency of the heat exchanger is also higher.

[0004] There are many traditional manufacturing methods for heat exchangers, among which the mechanical bulging method mainly has three steps (Zhu Bo. Small diameter pipe Difficulties and solutions in the process of inserting, expanding and welding of tube-fin heat exchangers [J]. Home Appliance Technology, 2017(11):86-88): (1) Inserting, assembling the tube and fin in a clearance fit manner; (2) Expanding, expanding the tube section by mechanical expansion beads to eliminate the gap between the tube and the fin and form an interference fit; (3) Welding, using U-shaped welding joints to connect the tube sections into a whole. The principle of mechanical expansion is to use a push rod to push a mechanical expansion bead with a diameter larger than the inner diameter of the tube into the tube. The expansion bead exerts pressure on the inner wall of the tube to cause the tube to undergo plastic deformation in the axial sequence and increase its diameter, thereby achieving close contact between the outer surface of the tube and the fin. The mechanical expansion method is easy to operate, but the force exerted by the mechanical expansion bead on the inner wall of the tube during expansion is uneven, which is prone to expansion bending and bursting defects.

[0005] The hydraulic bulging method (Yang Hui. Development and application of tube and tube sheet expansion technology [J]. Dongfang Electric Review, 2013, 27 (2): 32-35. Diao Bingbing, Zhou Jiping, Cao Jin, et al. Research on the application of hydraulic expansion technology in the production of tube-fin oil coolers [J]. Mechanical Design and Manufacturing Engineering, 2016, 45 (8): 91-94) can overcome the problem of uneven force in the mechanical bulging method. Its principle is to use liquid medium to apply uniform load to the inner wall of the tube, and the tube bulges at all positions along the axial direction at the same time, and the deformation is more uniform. Therefore, the contact quality between the tube and the fin obtained by the hydraulic bulging method is better, and the heat exchange efficiency is also higher.

[0006] The steps of manufacturing heat exchangers by hydraulic bulging are different from those by mechanical bulging. After the gap assembly of the tube and fin is completed, the tube sections are first connected as a whole using a U-shaped welded joint, and then the interference fit of the tube and fin is achieved through hydraulic expansion. In this way, only two tube end sealing heads and one liquid filling and pressurization are required to achieve the overall bulging of the serpentine coil.

[0007] However, when hydraulically bulging a serpentine coil with a U-shaped welded joint, the internal pressure will produce significant axial tension at the weld between the U-shaped joint and the pipe section. Taking a plain tube with a circular cross section as an example, the axial force F generated by the pressure p acting on the inner surface of the U-shaped welded joint is p It can be calculated by the following formula:

[0008] F p =2p×S g = p×πD g 2 / twenty one)

[0009] Where D g is the inner diameter of the tube, S g is the hole area in the tube.

[0010] The greater the internal bulging pressure p, the greater the axial force F p The larger the tension is, the greater the tensile force will be at the weld, and the weld is prone to cracking and failure under the tensile force. In order to avoid excessive tensile force at the weld and eliminate the risk of weld cracking under tension, a convenient and effective method and device is needed to apply appropriate supporting force to the U-shaped joint to partially or completely offset the axial force generated by the internal pressure. Summary of the invention

[0011] The purpose of the present invention is to provide an adaptive support method and device for U-shaped welded joints during hydraulic expansion of a serpentine coil, so as to solve the problem that the U-shaped joint welds are prone to cracking due to tension during hydraulic expansion of the serpentine coil, and to achieve high-quality and high-efficiency expansion of the serpentine coil.

[0012] The technical solution of the present invention:

[0013] An adaptive support device for a U-shaped welded joint during hydraulic expansion of a serpentine coil comprises a serpentine coil 1, a support block 2, a support cylinder 3, a pipe end sealing head 4, a movable crossbeam 5, a workbench 6, a hydraulic pipeline 7 and a hydraulic system 8; the movable crossbeam 5 and the workbench 6 are arranged relatively to each other, the workbench 6 is fixed, and the movable crossbeam 5 can move up and down; two pipe end sealing heads 4 are installed on the lower surface of the movable crossbeam 5 and are coaxial with the two pipe ends of the serpentine coil 1; the support block 2 is installed on the piston rod of the support cylinder 3, and the cylinder body of the support cylinder 3 is installed on the upper surface of the workbench 6 and the lower surface of the movable crossbeam 5, and the installation position corresponds to the U-shaped bending vertex of the serpentine coil 1; the pipe end sealing head 4 and the support cylinder 3 are processed with liquid filling holes, and are connected to the hydraulic system 8 through the hydraulic pipeline 7.

[0014] The serpentine coil 1 is composed of a pipe section 1-1 and a U-shaped welded joint 1-2.

[0015] Hydraulic action area S of support cylinder 3 z After determination, the support force F applied to the U-shaped weld joint 1-2 z Determined by the bulging pressure p, and increases with the increase of p, achieving the support force F z Adaptive adjustment.

[0016] The support cylinders 3 have a certain action stroke and the support cylinders are interconnected. The hydraulic medium flows to the support cylinder 3 that needs more hydraulic medium according to the different stress conditions of each support cylinder. Therefore, even if the heights of the U-shaped welded joints 1-2 of the serpentine coil 1 are inconsistent, the support cylinders 3 adapt to the positions of the U-shaped welded joints 1-2 to ensure good support for the U-shaped welded joints 1-2.

[0017] An adaptive support method for U-shaped welded joints during hydraulic expansion of serpentine coils, the technical principle of which is as follows Figure 1-Figure 4 As shown, the contact between the support block 2 on the support cylinder 3 and the serpentine coil 1 is controlled by the hydraulic system 8. During hydraulic bulging, the hydraulic pressure p output by the hydraulic system 8 acts on the piston of the support cylinder 3 and the inner surface of the serpentine coil 1 at the same time; the hydraulic action area S of the support cylinder 3 is controlled. z =πD z 2 / 4 is the inner hole area S of pipe section 1-1 g =πD g 2 / 4 is 1 to 3 times. When the hydraulic system 8 is charged with hydraulic pressure p, the supporting force F generated by the supporting cylinder 3 z =p×S z The axial force generated by the hydraulic pressure p acting evenly on the inner surface of the U-shaped welded joint 1-2 is F p =2p×S g , then, the axial force F acting on a single weld ish Then:

[0018] F h = (F p -F z ) / 2 = p(S g -0.5S z ) (2)

[0019] Among them, D z is the piston diameter of the support cylinder, D g is the inner diameter of pipe section 1-1.

[0020] Therefore, the axial force range of the weld under the support condition of the present invention is -F p / 4~F p / 4, significantly lower than the tensile force F of the weld without support p / 2. When the hydraulic action area S of the support cylinder 3 z Less than 2S g When the axial force on the weld is adjusted to axial pressure.

[0021] Beneficial effects of the present invention:

[0022] (1) The adaptive support force F provided by the present invention z The axial force F generated by the pressure p acting on the inner surface of the U-shaped welded joint p Always maintain a fixed proportional relationship, the support force F z It changes adaptively with the pressure p, significantly reducing the tensile force on the weld, thereby avoiding the risk of cracking due to excessive tensile force on the weld.

[0023] (2) The support method and device provided by the present invention can adapt to the position of the U-shaped welding joint of the serpentine coil, and can ensure good support for the joint.

[0024] (3) The method and device for adaptively supporting U-shaped welded joints during hydraulic expansion of a serpentine coil according to the present invention can realize adaptive support of multiple groups of U-shaped welded joints at the same time, with simple operation, reliable support and high efficiency.

[0025] (4) The method and device for adaptively supporting U-shaped welded joints during hydraulic expansion of a serpentine coil according to the present invention can adapt to serpentine coils of different lengths, different tube spacings and different welded joint sizes by adjusting the number and position of support cylinders and the shape of support blocks. It has high flexibility and strong adaptability.

[0026] (5) The method and device for adaptively supporting a U-shaped welded joint during hydraulic expansion of a serpentine coil according to the present invention can be applied to pipes with different cross-sections, such as Figure 7-Figure 9 The light tube, inner tooth tube and outer tooth tube shown in . BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the adaptive support principle of the U-shaped welded joint provided by the present invention.

[0028] Figure 2 This is the stress analysis diagram of the U-shaped welded joint.

[0029] Figure 3 The cross-sectional view of the support cylinder body ( Figure 1 AA section).

[0030] Figure 4 is the cross-sectional diagram of the tube ( Figure 1 Middle BB section).

[0031] Figure 5 A schematic diagram of the adaptive support device for the U-shaped welded joint during hydraulic expansion of the serpentine coil in the initial state provided by the present invention.

[0032] Figure 6 A schematic diagram of an adaptive support device for a U-shaped welded joint during hydraulic bulging of a serpentine coil in a bulging state provided by the present invention.

[0033] Figure 7 FIG. 1 is a schematic cross-sectional view of a light pipe applicable to the present invention.

[0034] Figure 8 It is a schematic cross-sectional view of an internal tooth tube applicable to the present invention.

[0035] Fig. 9 It is a schematic cross-sectional view of an internal tooth tube applicable to the present invention.

[0036] In the figure: 1- serpentine coil, 1-1 pipe section, 1-2 U-shaped welding joint, 2- support block, 3- support cylinder, 4- pipe end sealing head, 5- movable crossbeam, 6- workbench, 7- hydraulic pipeline, 8- hydraulic system. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0038] Example 1

[0039] Combination Figure 1-Figure 7 Description: The present invention proposes an adaptive support method and device for U-shaped welded joints during hydraulic expansion of a serpentine coil, comprising: a serpentine coil 1, a support block 2, a support cylinder 3, a pipe end sealing head 4, a movable crossbeam 5, a workbench 6, a hydraulic pipeline 7, and a hydraulic system 8.

[0040] The serpentine coil is a light tube with a circular cross section. Figure 7As shown; the U-shaped welded joint 1-2 is a component of the serpentine coil 1 and is connected to the pipe section 1-1 by welding; the workbench 6 is fixed and the movable crossbeam 5 can move up and down; the pipe end sealing head 4 is installed on the movable crossbeam 5 and is coaxial with the two pipe ends of the serpentine coil 1; the support block 2 is installed on the piston rod of the support cylinder 3, and the cylinder body of the support cylinder 3 is installed on the workbench 6 or the movable crossbeam 5, and the installation position corresponds to the U-shaped vertex of the serpentine coil 1; the hydraulic action area S of the support cylinder 3 z is the inner hole area of ​​the pipe section S g the pipe end sealing head 4 and the support cylinder 3 are machined with a filling hole and are connected to the hydraulic system 8 through a hydraulic pipeline 7, and the hydraulic medium used in the hydraulic system is hydraulic oil.

[0041] The beneficial effects of this embodiment are: (1) The supporting force applied by the support cylinder 3 to the U-shaped weld joint 2 just balances the axial force generated by the pressure p acting on the inner surface of the U-shaped weld joint. During the expansion process of the serpentine coil 1, the weld is not affected by the axial force, avoiding the risk of cracking of the weld due to tension. (2) The support cylinder 3 has a certain movement stroke and each support cylinder is interconnected, which can adapt to the height changes of each U-shaped weld joint of the serpentine coil, and has low requirements for the position accuracy of the U-shaped weld joint of the serpentine coil. (3) Adaptive support of multiple groups of U-shaped weld joints can be achieved at the same time, which is easy to operate, reliable and efficient. (4) By adjusting the number, position and shape of the support cylinders, serpentine coils of different lengths, different pipe spacings and different weld joint sizes can be adapted, with high flexibility and strong adaptability.

[0042] Example 2

[0043] Combination Figure 5 Description: The present invention proposes an adaptive support method and device for U-shaped welded joints during hydraulic expansion of a serpentine coil, wherein the hydraulic medium uses an easy-to-clean fluid medium such as pure water, emulsion or volatile oil, and the rest is the same as Example 1.

[0044] The beneficial effect of this embodiment is that the fluid medium such as pure water, emulsion, volatile oil, etc. remaining in the serpentine coil 1 after the expansion is completed is easy to clean.

[0045] Example 3

[0046] Combination Figure 1-Figure 6 Description: The present invention proposes an adaptive support method and device for a U-shaped welded joint during hydraulic bulging of a serpentine coil. The hydraulic action area S of the support cylinder 3 is z is the inner hole area S g 1 to 3 times of that in specific embodiment 1 or 2.

[0047] The beneficial effects of this embodiment are: z<2S g Under the condition, there is a certain tensile stress in the straight section of the serpentine coil 1, and under S z >2S g Under these conditions, there is a certain compressive stress in the straight pipe section of the serpentine coil 1. By specially designing the hydraulic action area of ​​the support cylinder 3, the stress state of the serpentine coil 1 can be regulated.

[0048] Example 4

[0049] Combination Figure 5-Figure 9 Description: The present invention proposes a method and device for adaptively supporting a U-shaped welded joint during hydraulic expansion of a serpentine coil. The serpentine coil 1 is a tube with internal teeth or external teeth, and the cross-sectional shapes are as follows: Figure 8 and Fig. 9 As shown, the rest is the same as Example 1, 2 or 3.

[0050] The beneficial effect of this embodiment is that it can realize adaptive support of U-shaped welded joints during the hydraulic bulging process of serpentine coils with different cross-sectional shapes.

Claims

1. An adaptive support device for U-shaped welded joints during hydraulic bulging of serpentine coils, characterized in that: The adaptive support device comprises a serpentine coil (1), a support block (2), a support cylinder (3), a pipe end sealing head (4), a movable crossbeam (5), a workbench (6), a hydraulic pipeline (7) and a hydraulic system (8); the movable crossbeam (5) and the workbench (6) are arranged relative to each other, the workbench (6) is fixed, and the movable crossbeam (5) can move up and down; two pipe end sealing heads (4) are installed on the lower surface of the movable crossbeam (5) and are coaxial with two pipe ends of the serpentine coil (1); the support block (2) is installed on the piston rod of the support cylinder (3), and the cylinder body of the support cylinder (3) is installed on the upper surface of the workbench (6) and the lower surface of the movable crossbeam (5), and the installation position corresponds to the U-shaped bending vertex of the serpentine coil (1); the pipe end sealing head (4) and the support cylinder (3) are processed with liquid filling holes, and are connected to the hydraulic system (8) through the hydraulic pipeline (7).

2. The adaptive support device according to claim 1, characterized in that: The serpentine coil (1) is composed of a pipe section (1-1) and a U-shaped welding joint (1-2) which are welded together.

3. The adaptive support device according to claim 1, characterized in that: The serpentine coil (1) is a smooth tube, an inner tooth tube or an outer tooth tube.

4. The adaptive support device according to claim 1, characterized in that: The hydraulic medium in the hydraulic system (8) is pure water, emulsion or volatile oil.

5. An adaptive support method for U-shaped welded joints during hydraulic bulging of serpentine coils, characterized in that: The contact between the support block (2) on the support cylinder (3) and the serpentine coil (1) is controlled by a hydraulic system (8); during hydraulic bulging, the hydraulic pressure p output by the hydraulic system (8) acts on the piston of the support cylinder (3) and the inner surface of the serpentine coil (1) at the same time; the hydraulic action area S of the support cylinder (3) is controlled. z =πD z 2 / 4 is the inner hole area S of the pipe segment (1-1) g =πD g 2 / 4 is 1 to 3 times; when the hydraulic system (8) is charged with hydraulic pressure p, the supporting force F generated by the supporting cylinder (3) z =p×S z The axial force generated by the hydraulic pressure p acting evenly on the inner surface of the U-shaped welded joint (1-2) is F p =2p×S g , then, the axial force F acting on a single weld is h Then: F h =(F p -F z ) / 2=p(S g -0.5S z ) Among them, D z is the piston diameter of the support cylinder, D g is the inner diameter of pipe section (1-1).

6. The adaptive support method according to claim 5, characterized in that: When the hydraulic action area S of the support cylinder (3) z Less than 2S g When the axial force on the weld is adjusted to axial pressure.

7. The adaptive support method according to claim 5, characterized in that: Hydraulic action area S of support cylinder (3) z After determination, the support force F applied to the U-shaped weld joint (1-2) z Determined by the bulging pressure p, and increases with the increase of p, achieving the support force F z Adaptive adjustment.

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