Large-size steel structure welding preheating device

Abstract

The present application relates to the technical field of welding, and discloses a large-size steel structure welding preheating device, which comprises a turbofan jet engine, one end of the turbofan jet engine is an air inlet, and the other end is a rear combustion chamber, a vortex sleeve is arranged outside the turbofan jet engine, a nitrogen air compressor is arranged at the front end of the air inlet, one end of the vortex sleeve is provided with a cold gas discharge pipe, and the other end is provided with a hot gas discharge pipe, the cold gas discharge pipe is located on the same side as the air inlet, and the hot gas discharge pipe is located on the same side as the rear combustion chamber. Compared with the prior art, the present application has the advantages that the turbofan jet engine generates high-temperature gas flow, realizes large-flow and high-flow-speed hot gas flow injection, and has a wider preheating range; the nitrogen air compressor mixes cold nitrogen into the air inlet, reduces the oxygen content of the combustion zone, and reduces the oxidation risk of the preheating area; the hot gas discharge pipe forms a low-oxygen hot nitrogen layer in the periphery of the high-temperature tail gas, reduces heat loss, and further inhibits oxidation.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a preheating device for welding large-size steel structures. Background Technology

[0002] Preheating large steel structures before automated welding is a key process to ensure welding quality, prevent cold cracking, and reduce residual stress.

[0003] Due to size limitations, large steel structures are difficult to heat as a whole, and if overall heating is too energy-intensive, local preheating is usually chosen. Common preheating methods are electric heating and flame heating. Electric heating involves covering the welding area with electric heating tape or resistance heating blanket, while flame heating involves using an oxyacetylene flame or propane flame to sweep and heat the preheating area.

[0004] Currently, electric heating belts and resistance heating blankets have limited coverage. For ultra-large components (such as bridges and storage tanks), they need to be segmented and spliced ​​for heating, which can easily generate temperature gradients. Furthermore, the heating / cooling rate is limited by the thermal conductivity of the material, making it difficult to adapt to the fast welding pace.

[0005] Flame heating may cause oxidation of the base material surface, forming an oxide scale that affects welding quality. Furthermore, the flame loses heat quickly, requiring continuous heating to maintain the temperature, resulting in high energy costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that electric heating has a small coverage area and slow heat conduction in current preheating technologies, while flame heating is prone to oxidation and heat loss. The present invention provides a preheating device for welding large-size steel structures.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: a large-size steel structure welding preheating device, including a turbofan jet, one end of which is an air intake and the other end is a rear combustion chamber. A vortex sleeve is fitted outside the turbofan jet. A nitrogen compressor is installed at the front end of the air intake. One end of the vortex sleeve is set as a cold gas exhaust pipe and the other end is set as a hot gas exhaust pipe. The cold gas exhaust pipe is on the same side as the air intake and the hot gas exhaust pipe is on the same side as the rear combustion chamber.

[0008] An intake ring is provided at the end of the air exhaust pipe and the intake duct. Multiple guide rods are arranged around the intake ring and extend between the air exhaust pipe and the intake duct. A deflector ring is slidably arranged on the guide rod. By sliding, the deflector ring can switch the exhaust direction of the air exhaust pipe between exhausting to the outside of the device and exhausting to the intake duct.

[0009] Furthermore, the deflector ring has an inward-curving deflector channel in the middle and an outward-expanding guide ring at the end. A nitrogen emission grille is arranged around the cold air exhaust pipe, and a nitrogen mixing grille is arranged around the intake duct. The deflector ring slides towards the rear combustion chamber to connect the deflector channel with the inside of the cold air exhaust pipe and the nitrogen emission grille. The deflector ring slides towards the intake duct to connect the inside of the cold air exhaust pipe with the nitrogen mixing grille.

[0010] Furthermore, the cold air exhaust pipe and the air intake converge inward, the rear combustion chamber expands towards the inner wall of the hot air exhaust pipe, and a vortex ring is provided in the middle of the vortex sleeve, with a vortex cavity inside the vortex ring.

[0011] Furthermore, the outlet of the nitrogen compressor is connected to a reduction gearbox, and the end of the reduction gearbox is provided with a compressed nitrogen pipe that is tangentially connected to the vortex cavity. The inlet of the nitrogen compressor is connected to a nitrogen supply pipe.

[0012] Furthermore, an electric cylinder is mounted on the outside of the eddy current sleeve, and the free end of the electric cylinder is fixedly connected to the deflector ring.

[0013] Furthermore, the turbofan jet is equipped with a transmission box, which contains a gearbox. A gearbox is rotatably mounted on the top of the gearbox, and a second gear, a third gear, a fourth gear, and a fifth gear are respectively mounted on the gearbox.

[0014] Furthermore, a gas turbine is rotatably mounted near the rear combustion chamber end of the transmission box. The gas turbine is equipped with a first drive shaft, which extends into the gearbox and is equipped with a first gear. A second gear meshes with the first gear.

[0015] Furthermore, a starter motor is provided at the bottom of the transmission box, and a ninth gear is provided at the output end of the starter motor, which meshes with the first gear.

[0016] Furthermore, a first centrifugal impeller is rotatably mounted near the intake end of the transmission box, a ducted fan is rotatably mounted inside the intake duct, a second centrifugal impeller is mounted inside the nitrogen compressor, and a first output shaft, a second output shaft, and a third output shaft are rotatably mounted in the center of the gearbox. The first, second, and third output shafts are rotatably connected from the inside out. One end of the first output shaft is poweredly connected to the second centrifugal impeller, and the other end is equipped with a sixth gear. One end of the second output shaft is poweredly connected to the ducted fan, and the other end is equipped with a seventh gear. One end of the third output shaft is poweredly connected to the first centrifugal impeller, and the other end is equipped with an eighth gear. The sixth gear meshes with the third gear, the seventh gear meshes with the fourth gear, and the eighth gear meshes with the fifth gear.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] Turbofan jets generate high-temperature gas flow, enabling high-flow-rate hot gas jet injection with a wider preheating range.

[0019] Hot nitrogen gas ejected from the hot exhaust pipe envelops the high-temperature exhaust gas of the turbofan jet, reducing heat loss.

[0020] By introducing cold nitrogen into the intake manifold through a nitrogen compressor, the oxygen content in the combustion zone is reduced, thereby reducing the risk of oxidation in the preheating zone. A low-oxygen hot nitrogen layer is formed around the high-temperature exhaust gas in the hot gas exhaust pipe, which isolates the air from direct contact with the workpiece and further inhibits oxidation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of the side of the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of the present invention docking with the robotic arm.

[0024] Figure 4 This is a schematic diagram of the internal structure of the turbofan jet engine of the present invention.

[0025] Figure 5 This is a schematic diagram of the internal structure of the pre-combustion chamber of the present invention.

[0026] Figure 6 This is a schematic diagram of the gearbox structure of the present invention.

[0027] Figure 7 This is a schematic diagram of the structure when the cold air exhaust pipe of the present invention is connected to the nitrogen mixing grid.

[0028] Figure 8 This is a schematic diagram of the baffle ring structure of the present invention.

[0029] Figure 9 This is a schematic diagram of the structure when the cold air exhaust pipe of the present invention is connected to the nitrogen exhaust grid.

[0030] As shown in the figure: 1. Turbofan jet engine; 2. Vortex sleeve; 3. Nitrogen compressor; 4. Robotic arm docking fixture; 5. Side support; 6. Electric cylinder; 7. Outer duct housing; 8. Jet housing; 9. Transmission box; 10. Combustion chamber; 11. Intake duct; 12. Ducted fan; 13. First centrifugal impeller; 14. First natural gas pipeline; 15. Baffle blades; 16. Gas turbine; 17. Afterburner; 18. Second natural gas pipeline; 19. Flame stabilizer; 20. Tail cone; 21. Pre-combustion chamber; 22. Ignition port; 23. Ignition device; 24. Third natural gas pipeline; 25. Exhaust duct; 26. Gearbox; 27. Second gear; 28. Third gear; 29. 30. Fourth gear, 31. Fifth gear, 32. First output shaft, 33. Second output shaft, 34. Third output shaft, 35. Sixth gear, 36. Seventh gear, 37. Eighth gear, 38. Starter motor, 39. Ninth gear, 40. Cold air exhaust pipe, 41. Intake ring, 42. Guide rod, 43. Baffle ring, 44. Nitrogen exhaust grille, 45. Nitrogen mixing grille, 46. Gearbox, 47. Vortex ring, 48. Vortex chamber, 49. Compressed nitrogen pipe, 50. Nitrogen supply pipe, 51. Hot air exhaust pipe, 52. Guide ring, 53. Gearbox, 54. Second centrifugal impeller, 55. First drive shaft, 56. First gear, 57. Baffle channel. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings.

[0032] Combined with appendix Figure 1 Appendix Figure 2 and attached Figure 3 A large-size steel structure welding preheating device includes a turbofan jet 1 and a vortex sleeve 2. The vortex sleeve 2 is sleeved outside the turbofan jet 1. The side of the vortex sleeve 2 is provided with a robotic arm docking fixture 4, which can dock with an automated robotic arm. The robotic arm controls the turbofan jet 1 to spray high-temperature gas towards the preheating area of ​​the workpiece for preheating. The turbofan jet 1 is a mature existing technology. This application only describes the basic principle and structure.

[0033] Combined with appendix Figure 4 Using the direction shown in the figure as a reference, with the left side of the image being the front and the right side being the rear, the turbofan jet 1 consists of an outer bypass casing 7, a jet casing 8, and a transmission box 9 from the outside to the inside. One end of the outer bypass casing 7 is provided with an air intake duct 11, and the other end is provided with an afterburner 17. The gap between the outer bypass casing 7 and the jet casing 8 that runs through it is called the outer bypass duct, and the gap between the jet casing 8 and the transmission box 9 that runs through it is called the inner bypass duct. At the junction of the air intake duct 11 and the outer bypass casing 7, the outer bypass duct and the inner bypass duct are separated by the jet casing 8. The end of the jet casing 8 extends to the front end of the afterburner 17, where the outer bypass duct and the inner bypass duct converge.

[0034] A gas turbine 16 is rotatably mounted on one end of the transmission box 9 near the rear combustion chamber 17, and a first centrifugal impeller 13 is rotatably mounted on the other end of the transmission box 9 near the intake duct 11. A ducted fan 12 is rotatably mounted inside the intake duct 11.

[0035] A combustion chamber 10 is provided around the outer circumference of the rear of the transmission box 9. A first annular natural gas pipeline 14 is provided in front of the combustion chamber 10. Multiple nozzles are arranged around the first natural gas pipeline 14 and extend into the combustion chamber 10. Multiple igniters 23 are provided in the combustion chamber 10. Baffle vanes 15 are arranged around the rear of the combustion chamber 10. The deflection direction of the baffle vanes 15 is opposite to that of the gas turbine 16.

[0036] Combined with appendix Figure 5 The rear combustion chamber 17 is equipped with a ring-shaped second natural gas pipeline 18 and a flame stabilizer 19. The second natural gas pipeline 18 has multiple nozzles extending to the front of the flame stabilizer 19. The front end of the rear combustion chamber 17 is equipped with a tail cone 20, and the tail cone 20 is equipped with a pre-combustion chamber 21. The bottom of the pre-combustion chamber 21 is equipped with a third natural gas pipeline 24. The third natural gas pipeline 24 is also equipped with an exhaust pipe 25 extending into the outer duct. The pre-combustion chamber 21 is also equipped with an igniter 23. The rear end of the pre-combustion chamber 21 is equipped with multiple ignition ports 22 that are connected to the rear combustion chamber 17.

[0037] Fuel is fed into the combustion chamber 10 and mixed with air for ignition. The high-pressure gas generated by combustion is guided by the baffle blades 15 and drives the gas turbine 16 to rotate. The rotational power of the gas turbine 16 is transmitted to the first centrifugal impeller 13 and the ducted fan 12 through the transmission box 9. The ducted fan 12 rotates to draw in air from the intake duct 11 and simultaneously discharges it to the outer duct and the inner duct. The first centrifugal impeller 13 compresses the air in the outer duct and discharges it into the combustion chamber 10 to mix with the fuel for combustion. After passing through the gas turbine 16, the gas enters the afterburner 17 and mixes with the airflow from the outer duct.

[0038] At the same time, the exhaust pipe 25 mixes part of the airflow in the outer duct with fuel and sends it into the pre-combustion chamber 21. The igniter 23 ignites the fuel in the pre-combustion chamber 21. The flame generated by the combustion is injected into the after-combustion chamber 17 through the ignition port 22 and reignites the mixture in the after-combustion chamber 17. The mixture burning in the after-combustion chamber 17 forms a stable combustion zone after passing through the flame stabilizer 19. The mixture that is newly entering the after-combustion chamber 17 is continuously ignited. After a stable combustion environment is formed in the after-combustion chamber 17, the fuel can be stopped from being added to the pre-combustion chamber 21.

[0039] The above method can continuously generate high-temperature gas flow that is ejected from the rear combustion chamber 17. The high-temperature gas is injected into the vicinity of the area to be welded and can be used for local preheating of large welded workpieces. Since natural gas is relatively easy to obtain and transport, and is also easy to mix with air for combustion, this application selects natural gas as fuel.

[0040] Combined with appendix Figure 7 A nitrogen compressor 3 is installed at the front end of the intake duct 11. One end of the vortex sleeve 2 is set as a cold gas exhaust pipe 39, and the other end is set as a hot gas exhaust pipe 50. The cold gas exhaust pipe 39 is on the same side as the intake duct 11, and the hot gas exhaust pipe 50 is on the same side as the rear combustion chamber 17. The cold gas exhaust pipe 39 and the intake duct 11 converge inward, and the rear combustion chamber 17 expands towards the inner wall of the hot gas exhaust pipe 50. A vortex ring 46 is provided in the middle of the vortex sleeve 2. A vortex cavity 47 is provided inside the vortex ring 46. The vortex cavity 47 is an annular groove structure. One end of the vortex sleeve 2 is connected to the inside of the vortex sleeve 2. The connection point is close to the hot gas exhaust pipe 50. The connection point between the vortex cavity 47 and the inside of the vortex sleeve 2 converges inward, while the other end expands outward.

[0041] Combined with appendix Figure 7 The outlet of the nitrogen compressor 3 is connected to a reduction tank 45. The end of the reduction tank 45 is provided with a compressed nitrogen pipe 48 that is tangentially connected to the vortex cavity 47. The connection between the compressed nitrogen pipe 48 and the vortex cavity 47 is close to the cold air discharge pipe 39. The inlet of the nitrogen compressor 3 is connected to a nitrogen supply pipe 49.

[0042] The nitrogen compressor 3 compresses externally supplied nitrogen and introduces it into the vortex chamber 47. Since the direction of the nitrogen compression pipe 48 is tangential to the vortex chamber 47, the nitrogen enters the vortex chamber 47 and rotates to form a vortex. Under the constraint of the contour of the vortex chamber 47, the rotating nitrogen flow inside the vortex chamber 47 moves axially towards the hot gas discharge pipe 50 and enters the internal cavity of the vortex sleeve 2. During the process of the nitrogen flow towards the hot gas discharge pipe 50, the airflow near the outer bypass casing 7 is blocked by the outward expansion wall of the afterburner 17 and moves in the opposite direction, while the nitrogen flow near the inner wall of the vortex sleeve 2 is not blocked and flows normally outward through the hot gas discharge pipe 50. The inner airflow, moving in the opposite direction, enters the cold air exhaust pipe 39 and is discharged. As the gas enters the vortex sleeve 2 tangentially, the outer airflow rotates at high speed against the pipe wall due to centrifugal force, while the inner airflow converges towards the central low-pressure area at a lower speed. Based on this, the axial movement directions of the inner and outer airflows are opposite, causing friction between them. The kinetic energy of the outer airflow is converted into heat energy through viscous friction, and the temperature rises to 100–130℃. Meanwhile, the inner airflow loses kinetic energy and expands adiabatically, and the temperature drops to -10 to -50℃. Ultimately, this results in the effect of hot nitrogen airflow being blown out by the hot air exhaust pipe 50 and cold nitrogen airflow being blown out by the cold air exhaust pipe 39.

[0043] Combined with appendix Figure 7 Appendix Figure 8 and attached Figure 9 An intake ring 40 is provided at the end of the cold exhaust pipe 39 and the intake duct 11. Multiple guide rods 41 are arranged around the intake ring 40 and extend between the cold exhaust pipe 39 and the intake duct 11. A deflector ring 42 is slidably arranged on the guide rod 41. A deflector channel 56 is provided in the middle of the deflector ring 42 and an outward guide ring 51 is provided at the end of the deflector ring 42. A nitrogen exhaust grille 43 is arranged around the cold exhaust pipe 39 and a nitrogen mixing grille 44 is arranged around the intake duct 11. The deflector ring 42 slides towards the rear combustion chamber 17 so that the deflector channel 56 connects the inside of the cold exhaust pipe 39 with the nitrogen exhaust grille 43. The deflector ring 42 slides towards the intake duct 11 so that the guide ring 51 connects the inside of the cold exhaust pipe 39 with the nitrogen mixing grille 44.

[0044] The discharge direction of the cold air discharge pipe 39 can be controlled by changing the position of the deflector ring 42. When discharged through the nitrogen discharge grille 43, the cold nitrogen gas flow is directly discharged to the outside. When discharged through the nitrogen mixing grille 44, the cold nitrogen gas flow enters the intake duct 11 and mixes with the air, and is sucked in by the turbofan jet 1. When the deflector ring 42 is in the middle position between the two situations, it can simultaneously guide the cold nitrogen gas flow to the nitrogen discharge grille 43 and the nitrogen mixing grille 44. A side support 5 is mounted on the outside of the vortex sleeve 2. An electric cylinder 6 is mounted on the side support 5. The free end of the electric cylinder 6 is fixedly connected to the deflector ring 42. The position of the deflector ring 42 is controlled by the extension and retraction of the free end of the electric cylinder 6. By precisely controlling the deflector ring 42, the flow rate of cold nitrogen entering the nitrogen discharge grille 43 and the nitrogen mixing grille 44 can be adjusted to achieve the effect of flow rate regulation.

[0045] When the air drawn into the turbofan jet 1 is mixed with nitrogen supplied by the vortex sleeve 2, the oxygen content participating in the combustion in the combustion chamber 10 and the after-combustion chamber 17 will be reduced, resulting in a reduction in the oxygen content in the final exhaust gas of the turbofan jet 1. This can reduce the degree of oxidation in the local preheating area of ​​the workpiece to a certain extent. At the same time, since the nitrogen entering the intake duct 11 is at a lower temperature, the intake pre-cooling effect of the turbofan jet 1 is achieved, making the airflow density drawn into the turbofan jet 1 greater and the exhaust gas volume after combustion expansion larger. This can improve the power of the gas turbine 16 and optimize the efficiency of the turbofan jet 1. In order to avoid excessive nitrogen entering, the position of the deflector ring 42 is adjusted in real time by the electric cylinder 6 to avoid the formation of fuel-rich combustion in the turbofan jet 1.

[0046] Based on this, the hot gas exhaust pipe 50 and the turbofan jet 1 discharge hot nitrogen in the same direction. Since the structure of the hot gas exhaust pipe 50 is annular, a layer of hot nitrogen can be wrapped around the high-temperature exhaust gas discharged by the turbofan jet 1. This can reduce the mixing of room temperature air with high-temperature exhaust gas to a certain extent. It can not only avoid the increase of oxygen content in the airflow that is finally sprayed onto the workpiece, but also reduce heat exchange with air, avoid heat loss, and increase the preheating temperature.

[0047] Combined with appendix Figure 6 The turbofan jet 1 has a transmission box 9 inside, and a gearbox 52 inside the transmission box 9. A speed change shaft 26 is rotatably mounted on the top of the gearbox 52. A second gear 27, a third gear 28, a fourth gear 29 and a fifth gear 30 are respectively mounted on the speed change shaft 26.

[0048] The gas turbine 16 is provided with a first drive shaft 54, which extends into the gearbox 52 and is provided with a first gear 55. A second gear 27 meshes with the first gear 55.

[0049] The nitrogen compressor 3 is equipped with a second centrifugal impeller 53. The gearbox 52 has a first output shaft 31, a second output shaft 32, and a third output shaft 33 rotating in the center. The first output shaft 31, the second output shaft 32, and the third output shaft 33 are rotated and sleeved from the inside to the outside. One end of the first output shaft 31 is powered to the second centrifugal impeller 53, and the other end is equipped with a sixth gear 34. One end of the second output shaft 32 is powered to the ducted fan 12, and the other end is equipped with a seventh gear 35. One end of the third output shaft 33 is powered to the first centrifugal impeller 13, and the other end is equipped with an eighth gear 36. The sixth gear 34 meshes with the third gear 28, the seventh gear 35 meshes with the fourth gear 29, and the eighth gear 36 meshes with the fifth gear 30.

[0050] Through the above transmission method, the gas turbine 16 can drive the ducted fan 12 and the first centrifugal impeller 13 while also driving the second centrifugal impeller 53 in the nitrogen compressor 3.

[0051] The bottom of the transmission box 9 is equipped with a starter motor 37, and the output end of the starter motor 37 is equipped with a ninth gear 38. The ninth gear 38 meshes with the first gear 55. This device uses the starter motor 37 to start the engine when it is cold.

[0052] The present invention and its embodiments have been described above. This description is not restrictive, and the actual structure is not limited thereto. In conclusion, if those skilled in the art, inspired by this description, design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the scope of protection of this invention.

Claims

1. A large-scale steel structure welding preheating device, comprising a turbofan jet engine (1), one end of the turbofan jet engine (1) is an air inlet (11), and the other end is a rear combustion chamber (17), characterized in that: The turbofan jet engine (1) is externally sleeved with a vortex sleeve (2), a nitrogen compressor (3) is arranged at the front end of an air inlet channel (11), one end of the vortex sleeve (2) is provided with a cold air discharge pipe (39), and the other end is provided with a hot air discharge pipe (50), the cold air discharge pipe (39) is on the same side as the air inlet channel (11), and the hot air discharge pipe (50) is on the same side as the rear combustion chamber (17); A vortex ring (46) is arranged in the middle of the vortex sleeve (2), the vortex ring (46) is internally provided with a vortex cavity (47), a speed reduction tank (45) is arranged in communication with the outlet of the nitrogen compressor (3), and a compressed nitrogen pipe (48) is arranged at the tail end of the speed reduction tank (45) and is tangentially communicated with the vortex cavity (47); a nitrogen supply pipeline (49) is connected to the inlet of the nitrogen compressor (3); The cold air discharge pipe (39) and the air inlet channel (11) are provided with an air inlet ring (40) at the end portion, a plurality of guide rods (41) are arranged around the air inlet ring (40) and extend between the cold air discharge pipe (39) and the air inlet channel (11), a baffle ring (42) is slidably arranged on the guide rod (41), and the baffle ring (42) can switch the exhaust direction of the cold air discharge pipe (39) between the outside of the device and the air inlet channel (11) by sliding; The baffle ring (42) is internally provided with a converging baffle channel (56), the baffle ring (42) is externally provided with a diverging flow guide ring (51), the cold air discharge pipe (39) is provided with a nitrogen discharge grid (43) around the circumference, the air inlet channel (11) is provided with a nitrogen mixing grid (44) around the circumference, and the baffle ring (42) is slid towards the rear combustion chamber (17) to make the baffle channel (56) communicate the inside of the cold air discharge pipe (39) with the nitrogen discharge grid (43), and the baffle ring (42) is slid towards the air inlet channel (11) to make the flow guide ring (51) communicate the inside of the cold air discharge pipe (39) with the nitrogen mixing grid (44).

2. The large size steel structure welding preheating device according to claim 1, characterized in that: The cold air discharge pipe (39) and the air inlet channel (11) converge inwardly, and the rear combustion chamber (17) expands toward the inner wall of the hot air discharge pipe (50).

3. The apparatus for preheating welding of large-sized steel structure according to claim 2, characterized in that: The vortex sleeve (2) is externally provided with an electric cylinder (6), and the free end of the electric cylinder (6) is fixedly connected with the baffle ring (42).

4. The apparatus for preheating welding of large-sized steel structure according to claim 1, characterized in that: The turbojet (1) is from outside to inside in turn outer channel shell (7), jet shell (8) and transmission case (9), the transmission case (9) is close to the first centrifugal impeller (13) of air inlet channel (11) one end rotation setting, air inlet channel (11) inside rotation is equipped with channel fan (12), nitrogen compressor (3) is equipped with second centrifugal impeller (53), transmission case (9) inside is equipped with gear box (52), gear box (52) central rotation is equipped with first output shaft (31), second output shaft (32) and third output shaft (33), first output shaft (31), second output shaft (32) and third output shaft (33) are rotated from inside to outside sleeve joint, first output shaft (31) one end and second centrifugal impeller (53) power connection, the other end is equipped with the sixth gear (34), second output shaft (32) one end and channel fan (12) power connection, the other end is equipped with the seventh gear (35), third output shaft (33) one end and first centrifugal impeller (13) power connection, the other end is equipped with the eighth gear (36).

5. The apparatus for preheating welding of large-sized steel structure according to claim 4, characterized in that: The gear box (52) top rotation setting variable speed shaft (26), variable speed shaft (26) is equipped with second gear (27), third gear (28), fourth gear (29) and fifth gear (30) in turn, wherein third gear (28) and sixth gear (34) mesh, fourth gear (29) and seventh gear (35) mesh, fifth gear (30) and eighth gear (36) mesh.

6. The apparatus for preheating welding of large-sized steel structure according to claim 5, characterized in that: The transmission case (9) is close to gas turbine (16) of combustion chamber (17) one end rotation setting, gas turbine (16) is equipped with first transmission shaft (54), first transmission shaft (54) extends to gear box (52) inside and is equipped with first gear (55), first gear (55) and second gear (27) mesh.

7. The apparatus for preheating welding of large-sized steel structures according to claim 6, characterized in that: The transmission case (9) bottom is equipped with starting motor (37), and the output end of starting motor (37) is equipped with ninth gear (38), and ninth gear (38) and first gear (55) mesh.

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