A bending device and method for heat exchanger coils

Abstract

The application provides a bending device and method for a heat exchanger coiled pipe, which decomposes the heat exchanger coiled pipe, and decomposes the whole structure into a body spiral part and two end bending parts; a spiral bending device is designed to meet the bending of the body spiral part of the coiled pipe; a pipe end bending device is designed to meet the bending of the pipe end part of the coiled pipe; the spiral bending device comprises a pipe bending unit, an inlet and outlet angle control unit and a pitch control unit, the pipe bending unit implements the bending of the body spiral part of the coiled pipe, the inlet and outlet angle control unit controls the forming angle of the two end bending parts of the coiled pipe, and the pitch control unit controls the pitch of the body spiral part of the coiled pipe. The bending device is adopted to solve the problems of the heat exchanger coiled pipe, such as difficult forming, difficult cleaning of the inner cavity filler, long manufacturing test period of the special mold, poor forming precision of the coiled pipe and the like.

Description

Technical Field

[0001] This invention belongs to the field of pipe bending technology, and specifically relates to a bending device and method for a serpentine tube of a liquid rocket engine heat exchanger. The resulting product has a diameter of 50-500 mm, a wall thickness of 0.5 mm, an ellipticity of less than 10% of the outer diameter after bending, and a bending accuracy of ≤±0.5 mm. Background Technology

[0002] The heat exchanger is a crucial component of a liquid rocket engine, using a serpentine tube to facilitate heat exchange between the fluids inside and outside the tube, thus pressurizing the propellant tank. To achieve efficient heat transfer, the serpentine tube is typically a thin-walled tube, such as φ8×0.5mm or φ10×0.5mm, with a length of 5m to 12m. It basically consists of a spiral section and bent sections at both ends. Because the serpentine tube is thin-walled, it is difficult to meet requirements for ellipticity, wrinkles, and thinning during the bending process. Therefore, during production, internal supports or mandrel supports are generally used to ensure forming quality. The serpentine tube is approximately 5m to 12m long, with a relatively small internal cavity of φ7mm to φ9mm. After bending, it is difficult to completely remove the internal filler or mandrel lubricant, leaving residues that affect engine performance. The inlet and outlet positions and forms of the heat exchanger depend on the specific requirements of different engines. Therefore, bending the serpentine tube generally uses a one-to-one dedicated mold. The mold manufacturing cycle is long, requiring repeated adjustments, which cannot meet the requirements of rapid development and iteration of new liquid rocket engine models.

[0003] Therefore, it is necessary to study the bending process of heat exchanger serpentine tubes and provide a bending device and method for heat exchanger serpentine tubes to solve problems such as difficulty in forming thin-walled tubes, difficulty in cleaning the inner cavity filler, long mold manufacturing cycle, and control of serpentine tube forming accuracy, so as to meet the needs of rapid development and rapid iteration of new heat exchanger models. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the inventors have conducted intensive research and provided a bending device and method for heat exchanger serpentine tubes, which solves the problems of difficulty in forming heat exchanger serpentine tubes of different specifications, tube types and lengths, difficulty in cleaning the inner cavity filling material, long test cycle of special mold manufacturing, and poor forming accuracy of serpentine tubes.

[0005] The technical solution provided by this invention is as follows:

[0006] In a first aspect, a bending device for a heat exchanger serpentine tube includes a spiral bending device and a tube end bending device, which respectively bend the spiral portion of the body and the bent portions at both ends.

[0007] The spiral bending device includes a bending unit, an inlet / outlet angle control unit, and a pitch control unit. The bending unit bends the spiral portion of the serpentine tube body, the inlet / outlet angle control unit controls the forming angle of the bent portions at both ends of the serpentine tube, and the pitch control unit controls the pitch of the spiral portion of the serpentine tube body.

[0008] Secondly, a method for bending a heat exchanger serpentine tube includes the following steps:

[0009] The heat exchanger serpentine tube is disassembled, and the overall structure is broken down into the spiral body and the bent ends.

[0010] Design a spiral bending device to meet the bending requirements of the spiral portion of the serpentine tube body;

[0011] Design a pipe end bending device to accommodate the bending of the serpentine pipe end portion;

[0012] The spiral bending device includes a bending unit, an inlet / outlet angle control unit, and a pitch control unit. The bending unit bends the spiral portion of the serpentine tube body, the inlet / outlet angle control unit controls the forming angle of the bent portions at both ends of the serpentine tube, and the pitch control unit controls the pitch of the spiral portion of the serpentine tube body.

[0013] The bending device and method for heat exchanger serpentine tubes provided by the present invention have the following beneficial effects:

[0014] (1) The present invention provides a bending device and method for a heat exchanger serpentine tube, which decomposes the overall structure into a spiral part of the body and a bending part at both ends, and sets up corresponding bending devices to realize segmented bending, thereby reducing the difficulty of forming the serpentine tube.

[0015] (2) The present invention provides a bending device and method for a heat exchanger serpentine tube. In the spiral bending device, the bending unit performs bending of the spiral part of the serpentine tube body, the inlet and outlet angle control unit controls the forming angle of the bending part at both ends of the serpentine tube, and the pitch control unit controls the pitch of the spiral part of the serpentine tube body. The structure of the spiral bending device can achieve strict control of the forming accuracy of the outer diameter of the spiral tube, the forming accuracy of the pitch and the forming accuracy of the angle at both ends.

[0016] (3) The present invention provides a bending device and method for a heat exchanger serpentine tube. In the tube end bending device, the bending die and the clamping die realize the bending of the end tube. During the bending deformation of the end tube, the auxiliary pushing die controls the end tube to not detach from the bending die to assist in the bending of the end tube. The three dies work together to successfully realize the bending of the end tube.

[0017] (4) The present invention provides a bending device and method for a heat exchanger serpentine tube. The grooves of the working surfaces of the bending die and the auxiliary push die are opposite to each other to form an elliptical channel, so that the tube can be transversely ellipticalized by the auxiliary push die. The bending die and the clamping die hold the tube end tube and rotate it around the axis of the bending die. During the bending deformation of the end tube, the transversely elliptical tube is slightly stretched to restore it to a round tube. This solves the problem of the longitudinal ellipticization of the tube reducing the tube forming accuracy during the bending deformation process. The longitudinal ellipticization in the subsequent bending process offsets the pre-transverse ellipticization, ensuring the roundness of the tube during the bending process.

[0018] (5) The present invention provides a bending device and method for a heat exchanger serpentine tube, which controls the wrinkling problem in the bending process of the tube by adjusting the forward speed of the auxiliary pusher of the tube end bending device. The linear speed of the auxiliary pusher is designed to be 50% to 60% of the bending die linear speed to generate a reverse tension, so as to avoid wrinkles and scratches on the inner side of the tube during bending, and the thinning amount is ≤20% of the original wall thickness. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a heat exchanger serpentine tube;

[0020] Figure 2 This is a schematic diagram of the spiral bending device;

[0021] Figure 3 This is a structural schematic diagram of a pipe bending unit;

[0022] Figure 4 This is a schematic diagram showing the distribution of the pipe end bending device. Detailed Implementation

[0023] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0024] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0025] This invention provides a method for bending a heat exchanger serpentine tube, comprising the following steps:

[0026] Step (1): Decompose the heat exchanger serpentine tube, and decompose the overall structure into the spiral part of the body and the bent parts at both ends. Determine the diameter of the spiral part D1 = 50~500mm and the pitch d = 11~30mm; the minimum bending radius of the bent parts at both ends R1≤2D2, where D2 is the outer diameter of the serpentine tube, and the forming accuracy is required to be ±0.5mm.

[0027] See Figure 1The shape of the heat exchanger's serpentine tubes is decomposed, breaking down the overall structure into a spiral body and two bent ends. This decomposition is performed at the end of the spiral, where the bending radius of the tube changes. After decomposition, the relative angles between the two end positions and the number of spiral turns are determined. Figure 1 The relative angle between the two ends is 180°, the number of spiral tube turns is 5, the outer diameter dimension is D1, and the pitch dimension is d; the two ends of the bending part are composed of two bends with bending radii of R1 and R2 respectively; the forming accuracy refers to the outer diameter dimension D1, the pitch dimension d and the inlet and outlet dimensions D2 of the tube end, which is generally required to be ±0.5mm.

[0028] Step (2): Design a spiral bending device to meet the bending requirements of the spiral part of the serpentine tube body, and achieve control over the forming accuracy of the outer diameter of the spiral tube, the forming accuracy of the pitch, and the forming accuracy of the angles at both ends.

[0029] See Figure 2 and Figure 3 The spiral bending device includes a bending unit, an inlet / outlet angle control unit, and a pitch control unit. The bending unit bends the spiral portion of the serpentine tube body, the inlet / outlet angle control unit controls the forming angle of the bent portions at both ends of the serpentine tube, and the pitch control unit controls the pitch of the spiral portion of the serpentine tube body.

[0030] The pipe bending unit includes two rows of parallel feeding rollers 1 and three bending rollers 2. At least one set of opposing driving rollers is included in the two rows of feeding rollers 2, and the rest are driven rollers. The feeding rollers 2 are machined with arc-shaped grooves around their circumference. The two rows of feeding rollers are opposite each other to form a straight pipe conveying and shaped channel. The three bending rollers 3 are machined with arc-shaped grooves around their circumference. Two bending rollers 2 are opposite each other to receive the straight pipe conveyed by the feeding rollers 1, and the other bending roller 3 performs bending guidance on the straight pipe so that the bending radius of the straight pipe reaches the bending degree required by the spiral part of the serpentine pipe.

[0031] The entrance / exit angle control unit includes a vertical slide rail 8, a horizontal slide rail 7, and a distance sensor 9. The vertical slide rail 8 is mounted on the horizontal slide rail 7, and the distance sensor 9 is mounted on the vertical slide rail 8. The vertical slide rail 8 and the horizontal slide rail 7 drive the distance sensor 9 to move in the height and horizontal directions, adjusting the position of the distance sensor so that its stopping position is directly opposite the end position of the conduit bend. When the spiral section bend is completed and the conduit passes the distance sensor, the distance sensor sends a signal to control the bending unit to stop bending, thus completing the spiral section bend of the serpentine tube.

[0032] The pitch control unit is a support shaft (6, 10) with a set height, located on the side of the bending unit. During bending, the bent section rests on the support shaft. The height difference between the support shaft and the straight conduit being transported in the bending unit is the pitch value of the spiral section of the serpentine tube. The support shaft rotates with the bent tube to avoid damaging the conduit. Pitch control is achieved by adjusting the height of the support structure, with an adjustable accuracy of 0.01mm and a pitch control accuracy of ±0.1mm.

[0033] Step (3): Design a pipe end bending device to meet the bending requirements of the serpentine pipe end, so that the special-shaped bend will not interfere with the equipment when bending, and bend without filling the inner cavity, meeting the following requirements: the ellipticity of the bend at the end of the serpentine pipe is ≤10% D2, the thinning amount is ≤20% of the original wall thickness, and there are no wrinkles or scratches.

[0034] See Figure 4 The pipe end bending device includes a bending die 5, a clamping die 4, and an auxiliary pushing die 3. The radius of the arc surface of a local area of ​​the bending die 5 is the same as the radius of the arc surface of the bending section of the serpentine pipe end, serving as a bending template for the bending section of the serpentine pipe end. The clamping die 4 and the auxiliary pushing die 3 are located around the bending die 5. The working surfaces of the bending die 5, the clamping die 4, and the auxiliary pushing die 3 are machined with arc-shaped grooves. The grooves on the working surfaces of the clamping die 4 and the bending die 5 face each other, forming a circular channel to locally clamp the end guide tube. During the bending process, the guide tube in the clamping die and the bending die does not move. The working surface of the auxiliary pushing die 3 is a long arc surface. The grooves on the working surfaces of the bending die 5 and the auxiliary pushing die 3 face each other, forming an ellipse. The elliptical channel has its major axis in the horizontal direction, with a length greater than the outer diameter of the end conduit, and its minor axis in the vertical direction, with a length less than the outer diameter of the end conduit. This allows the conduit to achieve lateral ellipticization as it passes through the auxiliary push mold 3. The bending mold 5 and clamping mold 4 hold the end conduit and rotate it around the axis of the bending mold 5, bending and deforming the end conduit. During the bending and deformation process, the laterally elliptical conduit is slightly stretched and restored to a round conduit. The auxiliary push mold 3 is close to the free end of the end conduit and always moves in the opposite linear direction to the free end of the end conduit during the bending and deformation process. This reduces friction on the conduit while controlling the end conduit to not detach from the bending mold 5, thus assisting in the bending of the end conduit.

[0035] During the bending process of the end conduit, the conduit tends to become longitudinally elliptical, gradually lengthening in the height direction to become the major axis and shortening in the horizontal direction to become the minor axis. To ensure that the ellipticity of the bent portion of the serpentine tube end is ≤10% D2, an auxiliary push mold is used as a counter-deformation mold to pre-ellipse the round tube laterally, with the horizontal direction as the major axis and the vertical direction as the minor axis. The pre-ellipticization is offset by the longitudinal ellipticization during the subsequent bending process, thus ensuring the roundness of the conduit during the bending process.

[0036] To address the wrinkling issue during the conduit bending process, the forward speed of the auxiliary pusher die in the tube end bending device is adjusted. Through process bending tests, the linear speed of the auxiliary pusher die is designed to be 50%–60% of the bending die linear speed, generating a reverse tension to prevent wrinkles and scratches on the inner side of the tube during bending, with a thinning amount ≤20% of the original wall thickness.

[0037] The two curved sections of the serpentine tube, as decomposed in step 1, contain two bends with bending radii R1 and R2. The bending die and clamping die hold the inner side of the bend near the spiral section. The clamping length is set to 20-30mm through trial and error to ensure stable clamping, prevent damage to the tube, and minimize the thickness of the clamping die and bending die.

[0038] This invention also provides a bending device for a heat exchanger serpentine tube, including a spiral bending device and a tube end bending device, which respectively bend the spiral portion of the tube body and the bent portions at both ends. The specific structure is consistent with the corresponding content above, and will not be repeated here.

[0039] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0040] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A bending device for a heat exchanger serpentine tube, characterized in that, It includes a spiral bending device and a tube end bending device, which respectively bend the spiral part of the body and the bending parts at both ends; The spiral bending device includes a bending unit, an inlet / outlet angle control unit, and a pitch control unit. The bending unit bends the spiral portion of the serpentine tube body, the inlet / outlet angle control unit controls the forming angle of the bent portions at both ends of the serpentine tube, and the pitch control unit controls the pitch of the spiral portion of the serpentine tube body. The bending unit includes two parallel rows of feeding wheels and three bending wheels. The two rows of feeding wheels include at least one set of opposing driving wheels, and the rest are driven wheels. The feeding wheels are machined with arc-shaped grooves around their circumferences. The two rows of feeding wheels form a straight guide tube and a three-dimensional channel. The three bending wheels are machined with arc-shaped grooves around their circumferences. Two bending wheels are opposite each other and receive the straight guide tubes conveyed by the feeding wheels. The other bending wheel guides the straight guide tube to bend so that the bending radius of the straight guide tube reaches the bending degree required for the spiral part of the serpentine tube. The inlet / outlet angle control unit includes a vertical slide rail, a horizontal slide rail, and a distance sensor. The vertical slide rail is installed on the horizontal slide rail, and the distance sensor is installed on the vertical slide rail. The vertical and horizontal slide rails drive the distance sensor to move in the height and horizontal directions, adjusting the position of the distance sensor so that its stopping position is directly opposite the end position of the conduit bend. When the spiral section bends completely and the conduit passes the distance sensor, the distance sensor sends a signal to control the bending unit to stop bending. The pitch control unit is a support shaft with a set height, located on the side of the bending unit. During the bending process, the bent part rests on the support shaft. The height difference between the support shaft and the straight conduit conveyed in the bending unit is the pitch value of the spiral part of the serpentine tube.

2. The bending device for the heat exchanger serpentine tube according to claim 1, characterized in that, The pipe end bending device includes a bending die, a clamping die, and an auxiliary pushing die; The radius of the arc surface of the bending die in a local area is the same as the radius of the arc surface of the pipe end bending section, serving as the bending template for the pipe end bending section. The clamping die and the auxiliary pushing die are located outside the bending die. The working surfaces of the bending die, clamping die, and auxiliary pushing die are machined with arc-shaped grooves. The grooves on the working surfaces of the clamping die and the bending die are opposite each other, forming a circular channel to locally clamp the end guide tube. During the bending process, the guide tube in the clamping die and the bending die does not move. The working surface of the auxiliary pushing die is a long arc surface. The grooves on the working surfaces of the bending die and the auxiliary pushing die are opposite each other, forming an elliptical channel. The major axis of the elliptical channel is located in the horizontal direction, and the length of the major axis is greater than the outer diameter of the end guide tube. The minor axis is located in the vertical direction, and the length of the minor axis is less than the outer diameter of the end guide tube, so that the guide tube achieves transverse ellipticization after passing through the auxiliary pushing die. The bending die and the clamping die clamp the pipe end guide tube and rotate it around the axis of the bending die, bending and deforming the end guide tube. During the bending and deformation process, the transversely elliptical guide tube recovers into a circular guide tube. The auxiliary pusher is located near the free end of the end conduit and moves in the opposite linear direction to the free end of the end conduit during the bending deformation of the end conduit, controlling the end conduit to not detach from the bending die and assisting in the bending of the end conduit.

3. A method for bending a serpentine tube in a heat exchanger, characterized in that, Includes the following steps: The heat exchanger serpentine tube is disassembled, and the overall structure is broken down into the spiral body and the bent ends. Design a spiral bending device to meet the bending requirements of the spiral portion of the serpentine tube body; Design a pipe end bending device to accommodate the bending of the serpentine pipe end portion; The spiral bending device includes a bending unit, an inlet / outlet angle control unit, and a pitch control unit. The bending unit bends the spiral portion of the serpentine tube body, the inlet / outlet angle control unit controls the forming angle of the bent portions at both ends of the serpentine tube, and the pitch control unit controls the pitch of the spiral portion of the serpentine tube body. The bending unit includes two parallel rows of feeding wheels and three bending wheels. The two rows of feeding wheels include at least one set of opposing driving wheels, and the rest are driven wheels. The feeding wheels are machined with arc-shaped grooves around their circumferences. The two rows of feeding wheels form a straight guide tube and a three-dimensional channel. The three bending wheels are machined with arc-shaped grooves around their circumferences. Two bending wheels are opposite each other and receive the straight guide tubes conveyed by the feeding wheels. The other bending wheel guides the straight guide tube to bend so that the bending radius of the straight guide tube reaches the bending degree required for the spiral part of the serpentine tube. The inlet / outlet angle control unit includes a vertical slide rail, a horizontal slide rail, and a distance sensor. The vertical slide rail is installed on the horizontal slide rail, and the distance sensor is installed on the vertical slide rail. The vertical and horizontal slide rails drive the distance sensor to move in the height and horizontal directions, adjusting the position of the distance sensor so that its stopping position is directly opposite the end position of the conduit bend. When the spiral section bends completely and the conduit passes the distance sensor, the distance sensor sends a signal to control the bending unit to stop bending. The pitch control unit is a support shaft with a set height, located on the side of the bending unit. During the bending process, the bent part rests on the support shaft. The height difference between the support shaft and the straight conduit conveyed in the bending unit is the pitch value of the spiral part of the serpentine tube.

4. The bending method for the heat exchanger serpentine tube according to claim 3, characterized in that, The pipe end bending device includes a bending die, a clamping die, and an auxiliary pushing die; The radius of the arc surface of the bending die in a local area is the same as the radius of the arc surface of the pipe end bending section, serving as the bending template for the pipe end bending section. The clamping die and the auxiliary pushing die are located outside the bending die. The working surfaces of the bending die, clamping die, and auxiliary pushing die are machined with arc-shaped grooves. The grooves on the working surfaces of the clamping die and the bending die are opposite each other, forming a circular channel to locally clamp the end guide tube. During the bending process, the guide tube in the clamping die and the bending die does not move. The working surface of the auxiliary pushing die is a long arc surface. The grooves on the working surfaces of the bending die and the auxiliary pushing die are opposite each other, forming an elliptical channel. The major axis of the elliptical channel is located in the horizontal direction, and the length of the major axis is greater than the outer diameter of the end guide tube. The minor axis is located in the vertical direction, and the length of the minor axis is less than the outer diameter of the end guide tube, so that the guide tube achieves transverse ellipticization after passing through the auxiliary pushing die. The bending die and the clamping die clamp the pipe end guide tube and rotate it around the axis of the bending die, bending and deforming the end guide tube. During the bending and deformation process, the transversely elliptical guide tube recovers into a circular guide tube. The auxiliary pusher is located near the free end of the end conduit and moves in the opposite linear direction to the free end of the end conduit during the bending deformation of the end conduit, controlling the end conduit to not detach from the bending die and assisting in the bending of the end conduit.

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