A transformer vacuum drying system with jet cycle hot air heating

Abstract

The embodiment of the present application discloses a kind of transformer vacuum drying systems of jet cycle hot air heating, comprising: in the heating row pipe of the vacuum tank inner wall, predetermined position above setting injection device and setting control and measurement subsystem outside the vacuum tank;The injection device is used to the heating row pipe of the vacuum tank inner wall and is set to the supersonic jet stream of injection, forms forced convection heat exchange, and the heat around heating row pipe flows to the bottom of the vacuum tank along the air duct formed by the air duct plate and the inner wall of the vacuum tank, and the transformer device inside the vacuum tank is dried;The control and measurement subsystem is used to measure the pressure inside the vacuum tank, and the inlet and outlet valve opening is adjusted in real time.The system described in the present application can effectively shorten the drying time and reduce energy consumption, while improving the drying quality and efficiency of transformer product, and facilitating the transformation of old transformer vacuum drying equipment.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the field of mechanical equipment manufacturing, in particular to a kind of transformer vacuum drying system of jet cycle hot air heating. BACKGROUND

[0002] At present, the heating method used in the drying process of transformer product mainly has two kinds: one is hot air circulation, pressure change method drying technology with air as heat carrier medium;The other is pressure change method drying technology using gas phase drying treatment equipment for transformer product. The gas phase drying technology belongs to the drying technology of phase change heat transfer, and is mostly applied to the gas phase drying treatment of 110kV and above voltage grade transformer. The hot air heating equipment with air as heat carrier medium is mostly used in the drying process of 35kV and below voltage grade transformer, that is, the transformer is heated by the heat transfer of hot air circulation convection realized by the disturbance of traditional fan in the vacuum drying technology. Among them, the hot air circulation technology can supplement dry air in the inlet air path, and the wet hot air is discharged in the outlet air path according to a proper proportion, so as to reduce the water vapor partial pressure in the vacuum tank, thereby facilitating the moisture discharge of insulating material.

[0003] However, the hot air circulation drying treatment technology and pressure change method drying technology used in the current transformer industry all adopt natural convection, fan circulation forced hot air heating mode. When drying the transformer, there are problems such as easy rusting of the core, uneven temperature distribution, air leakage of fan shaft seal, etc. which result in low heat exchange efficiency and poor quality in the drying process of transformer product. SUMMARY

[0004] Therefore, the embodiment of the present application provides a kind of transformer vacuum drying system of jet cycle hot air heating to solve the problems such as easy rusting of the core, uneven temperature distribution, air leakage of fan shaft seal, etc. when drying the transformer in the prior art.

[0005] In order to achieve the above purpose, the embodiment of the present application provides the following technical scheme:

[0006] The embodiment of the present application provides a kind of transformer vacuum drying system of jet cycle hot air heating, which comprises: a vacuum tank, a heating exhaust pipe is arranged in the inner wall of the vacuum tank, a jet device is arranged at a predetermined position above the heating exhaust pipe in the inner wall of the vacuum tank, and a control and measurement subsystem is arranged outside the vacuum tank;The jet device is used to jet supersonic jet flow to the heating exhaust pipe arranged in the inner wall of the vacuum tank, to form forced convection heat transfer, to make the heat around the heating exhaust pipe flow to the bottom of the vacuum tank along the air duct composed of the air duct plate and the inner wall of the vacuum tank, and to dry the transformer device in the vacuum tank. The control and measurement subsystem is used to measure the pressure in the vacuum tank, to adjust the opening degree of inlet and outlet valve in real time, and to control the pressure field in the vacuum tank.

[0007] Further, the inner wall of the vacuum tank comprises at least one of a side wall, an upper wall, a lower wall and a rear wall.

[0008] Further, a compressed air heater is arranged outside the vacuum tank, which is communicated with the injection device through a hot compressed air main; the compressed air heater is used to compress and heat air, and the processed air is transmitted to the injection device through the hot compressed air main.

[0009] Further, the injection device is composed of a Laval nozzle and a Laval nozzle.

[0010] Further, the Laval nozzle is a pipeline device with one end tapered and the other end expanded.

[0011] Further, a baffle is arranged between the heating tubes; the baffle is used to make the airflow flow along a preset zigzag route and pass through the surface of each heating tube to sufficiently heat the airflow.

[0012] Further, the control and measurement subsystem comprises a vacuum unit for controlling the pressure field in the vacuum tank.

[0013] Further, the control and measurement subsystem comprises a pressure measuring device for measuring the pressure value inside the vacuum tank.

[0014] Further, the control and measurement subsystem further comprises a valve control device for adjusting the opening degree of the inlet and outlet valves in real time.

[0015] Further, the pressure measuring device is a pressure sensor.

[0016] The transformer vacuum drying system with the injection cycle hot air heating described in the present application can be driven by the supersonic jet ejected by the injection device, instead of the mechanical driving of the internal circulation fan impeller, so that the hot air in the vacuum tank can flow at high speed, forming forced convection heat transfer, which can effectively shorten the drying time and reduce energy consumption, and at the same time, improve the drying quality and efficiency of the transformer product, avoid the problems of rusting of the core, uneven temperature distribution, air leakage of the fan shaft seal and the like during drying of the transformer, and facilitate the transformation of the old transformer vacuum drying equipment currently used in the industry. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description are only examples for illustrating the present application, and for those skilled in the art, other drawings can be obtained from the provided drawings without any creative effort.

[0018] Figure 1 A schematic diagram of the overall structure of a transformer vacuum drying system with jet cycle hot air heating provided by the embodiment of the present application;

[0019] Figure 2 A schematic diagram of the installation position and structure of the jet device in the inner wall of the vacuum tank in a transformer vacuum drying system with jet cycle hot air heating provided by the embodiment of the present application;

[0020] Figure 3 A schematic diagram of the structure of the Laval nozzle in a transformer vacuum drying system with jet cycle hot air heating provided by the embodiment of the present application.

[0021] In the above-mentioned embodiments of the present application, the following abbreviations are used: Figure 1 In the above-mentioned embodiments of the present application, the following abbreviations are used: 301 is an electric heater, 302 is a compressed air heater, 303 is a compressed air inlet, 304 is a hot compressed air main pipe, 305 is a heat conducting oil main pipe, 306 is a heat conducting oil pump, and 307 is a vacuum unit. Figure 2 In the above-mentioned embodiments of the present application, the following abbreviations are used: 101 is the top of the vacuum tank, 102 is the heating pipe, 103 is the Laval nozzle, 104 is the Laval nozzle, 105 is the flow baffle, 106 is the inner wall of the vacuum tank, and 107 is the bottom of the vacuum tank. DETAILED DESCRIPTION

[0022] The specific embodiments of the present application are described below, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the present specification. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the scope of protection of the present application.

[0023] The transformer vacuum drying system disclosed in this application utilizes compressed air jetting to drive the circulation of hot air within a vacuum tank for convective heat exchange, thereby heating the transformer and replacing the disturbance caused by traditional fans. Based on the principle of jet evaporation gas-phase drying, this system proposes a jet-driven hot air circulation vacuum drying technology. Compared to traditional hot air circulation and variable pressure vacuum drying technologies, this system effectively overcomes the shortcomings of poor drying quality and heat exchange efficiency in traditional hot air circulation and variable pressure drying technologies. It improves the technical performance of transformer hot air circulation drying from a physical perspective, significantly enhancing the heating efficiency of the drying equipment, preventing core rusting, improving temperature distribution, and ensuring the vacuum level of the drying system.

[0024] The following is a detailed description of embodiments of the transformer vacuum drying system heated by jet circulating hot air as described in this application. Figure 1 and 2 The figures shown are schematic diagrams of the overall structure of a transformer vacuum drying system heated by jet circulating hot air according to an embodiment of this application, and the installation position and structure of the jetting device in the inner wall 106 of the vacuum tank within the system. The specific implementation process includes the following parts: a vacuum tank, a heating pipe 102 disposed in the inner wall 106 of the vacuum tank, a jetting device disposed at a predetermined position above the heating pipe 102 in the inner wall 106 of the vacuum tank, and a control and measurement subsystem disposed outside the vacuum tank. The jetting device is used to jet a supersonic jet onto the heating pipe 102 disposed in the inner wall 106 of the vacuum tank, forming forced convection heat transfer. This causes the heat on the surface of the heating pipe 102 to be blown away by the supersonic jet ejected from the nozzle, and the heat around the heating pipe 102 flows from top to bottom along the air duct formed by the preset air duct plate and the inner wall 106 of the vacuum tank to the bottom 107 of the vacuum tank. Figure 2 The material (at position B) is fully released into the internal space of the vacuum tank, and then flows inward and upward along a predetermined direction to uniformly heat the transformer product, thereby achieving the drying process of the transformer product inside the vacuum tank. It should be noted that the inner wall of the vacuum tank includes at least one of the following: the side wall, the upper wall, the lower wall, and the rear wall (i.e., the side opposite the vacuum tank door), which is not specifically limited here.

[0025] At the highest point of the air duct plate (i.e. Figure 2The high-speed flow of the air current generates a low pressure, which sucks the gas in the vacuum tank to the inlet of the air duct, thereby forming a circulation effect. Specifically, at the total inlet of the air duct on the inner wall 106 of the vacuum tank, the high-speed flow of the air current in the air duct can form a local low pressure with a suction effect, and then the gas at the top of the pipeline is sucked into the air duct. Further, in the air duct, along with the supersonic jet sprayed by the jetting device, the heat on the surface of the heating pipe 102 is carried to the lower outlet of the air duct, blows into the inside of the vacuum tank, and forms a turbulent flow of hot air around the transformer product to perform heat exchange.

[0026] It should be noted that the circulation effect is not achieved by the traditional fan circulation. In the traditional fan circulation, the air flow of the fan loses the blowing effect on all the heating pipes 102 below after passing through the shielding of the uppermost first heating pipe 102. In the system of the present application, the compressed gas can be sprayed into the vacuum tank from the Laval nozzle 104 by using the jetting circulation hot air heating structure, and the high-speed air flow can obtain a supersonic air flow by the acceleration effect of the high-pressure air sprayed from the Laval nozzle 104, thereby achieving a better circulation and heat exchange effect.

[0027] In addition, in order to make the inside of the vacuum tank dynamically balanced to the best water outlet pressure state, the control and measurement subsystem is further included in the embodiment of the application, and the amount of gas drawn by the control and measurement subsystem needs to be matched with the amount of gas entering the inside of the vacuum tank, so that the dynamic balance state is reached in the vacuum tank, thereby ensuring the stable water outlet pressure state. Therefore, the control and measurement subsystem needs to accurately measure the pressure in the inside of the vacuum tank and finely adjust the opening degree of the inlet and outlet valves in real time, and intelligently control the pressure field in the vacuum tank. Specifically, the control and measurement subsystem includes a vacuum unit 307, a pressure measuring device, a valve control device, etc. The vacuum unit 307 is used to control the pressure field in the vacuum tank. The pressure measuring device can be used to measure the pressure value in the inside of the vacuum tank. The valve control device is used to adjust the opening degree of the inlet and outlet valves in real time. The pressure measuring device can be a pressure measuring device such as a pressure sensor, a vacuum pressure gauge, a liquid level meter, etc.

[0028] Further, in the embodiment of the present application, the vacuum tank outside of the injection circulating hot air heating transformer vacuum drying system is also provided with a compressed air heater 302, an electric heater 301, a heat conducting oil pump 306, an electric control device, a valve and a connecting pipeline, etc., and the control and measurement subsystem further comprises a computer control device which can automatically control the pressure field inside the vacuum tank by adjusting the valve control device for real-time adjustment of the inlet and outlet valve opening and the vacuum unit according to the measured pressure inside the vacuum tank. The compressed air heater 302 is communicated with the injection device through a hot compressed air main pipe 304; the compressed air heater 302 is used for compressing and heating air and transmitting the processed gas to the injection device through the hot compressed air main pipe 304. Based on the above design, the hot compressed air main pipe 304 in the system uses external source gas. Since the hot compressed air main pipe 304 uses external source gas, the high-speed airflow blown out by the injection device can continuously blow away the heat on the heating exhaust pipe 102, and the heat exchange can still be carried out under a relatively high vacuum degree, thereby avoiding the situation that the heat exchange cannot be carried out or the heat exchange is low due to the small gas density in the traditional natural convection, fan circulating forced hot air heating process.

[0029] In the embodiment of the present application, the injection device is composed of a Laval nozzle 103 and a Laval nozzle 104. The Laval nozzle 104 is an important technical component of the injection cycle of the present application, which is a pipeline device with one end (left end) tapering and the other end (right end) expanding. By adopting the classic aerodynamic model of the Laval nozzle 104, the compressed airflow can be shot out as high-speed airflow. Specifically, since the Laval nozzle 104 is a pipeline device tapering at one end and expanding at the other end, the minimum cross section is called the throat, and the airflow reaches the speed of sound at the throat, generating supersonic airflow. As shown in Figure 3 P1— the pressure of the compressed air input into the injection device by the hot compressed air main pipe 304; P2— the pressure of the expanded gas; P b — back pressure (the actual pressure inside the vacuum tank at the time); P cr — the critical pressure of the nozzle throat.

[0030] It should be noted that for steady pipe flow, the fluid mass flowing through any cross section is equal, i.e. ρvA=C, where C is a constant, and the density ρ, the velocity v and the cross section A are in the same cross section of the flow pipe, and after taking the logarithm of the equation ρvA=C and differentiating, we get:

[0031]

[0032] From the Euler motion equation of steady one-dimensional flow:

[0033] vdv=-dp / ρ (2)

[0034] And the differential form of the speed of sound: dp / dρ=a 2 (The changes in p and ρ follow an adiabatic isentropic process) Combined into

[0035] or

[0036] Substituting into equation (1), we get:

[0037]

[0038] Where M is the Mach number, M = v / a; Equation (3) is the basic relationship of isentropic flow of one-dimensional compressible flow in a variable cross-section pipe. This formula shows that in high-speed airflow, in order to increase the flow velocity, dv / v > 0, and the increase or decrease of the area change dA / A depends on the M number.

[0039] If the airflow inside the pipe is subsonic (i.e., M < 1), the coefficient on the left side of equation (3) is negative, then dA / A < 0, and the pipe cross-section should contract; if the airflow inside the pipe is supersonic (i.e., M > 1), the coefficient on the left side of equation (3) is positive, then dA / A > 0, and the pipe cross-section should expand. At the sonic cross-section, M = 1, dA = 0.

[0040] The above results indicate that to accelerate subsonic airflow into supersonic airflow, the pipe structure must first contract and then expand. Therefore, based on this principle, in the embodiments of this application, a Laval nozzle is designed and manufactured and installed on the Laval nozzle 103. Under the action of a pressure difference of about 0.3 MPa, the high-temperature air (about 150°C) inside the nozzle is injected onto the heated pipe 102, forming a supersonic airflow that carries away the heat.

[0041] like Figure 1 The diagram shown is an overall structural schematic of a transformer vacuum drying system heated by jet circulating hot air according to an embodiment of this application. The specific implementation process also includes the following components: an electric heater 301 for heating the heat transfer oil, a heat transfer oil main pipe 305 for conveying the heated heat transfer oil to the heating pipe 102, and a heat transfer oil pump 306 for providing power for the conveying of the heat transfer oil.

[0042] In the embodiment of the present application, air is processed by dehumidification, filtration, compression and heating to form a compressed air flow into the left and right upper corner of the vacuum tank Laval nozzle 103, and then through the Laval nozzle to form a supersonic air flow. The principle of the jet cycle structure includes: the compressed gas obtained after the compression and heating treatment by the compressed air heater 302 is sprayed from the jet device composed of the Laval nozzle 103 at the highest position and the Laval nozzle, and the supersonic jet flow is obtained, which carries away the heat on the heating pipe 102 and drives the air in the inner wall 106 of the vacuum tank to continue to flow downward, thereby effectively solving the technical problem that the wind pressure obtained by the circulating fan cannot effectively realize vacuum drying in the prior art. In the air duct, a baffle 105 can be arranged between every two heating pipes 102. When the high-pressure air flow flowing from top to bottom flows through the baffle 105, the baffle 105 can make the high-pressure air flow flow along a predetermined zigzag route and be heated by the surface of each heating pipe 102. Under the action of the Laval nozzle effect channel, the air at the top 101 of the vacuum tank is sucked into the air duct inlet. The air finally reaching the air duct outlet at the bottom of the vacuum tank is fully heated high-speed hot air, which enters the bottom 107 of the vacuum tank to start circulating heating, ensures that the air pressure in the vacuum tank is sufficient, and drives the air to move from top to bottom and flow to the lower part through various obstacles.

[0043] It should be noted that in the specific implementation process, a jet device can be added to each heating pipe 102 according to the principle of aerodynamics, so that hot air can only enter the heating pipe 102 from one inlet above for heat exchange; the number of jet devices can also be appropriately reduced, such as 4-6 heating pipes 102 forming a unit, and a jet device is arranged at a proper position above the heating pipe 102, which is not limited here.

[0044] The transformer vacuum drying system with jet cycle hot air heating described in the present application can be driven by the supersonic jet flow ejected by the jet device, replacing the mechanical drive of the internal circulating fan impeller, so that the hot air in the vacuum tank can flow at high speed, forming forced convection heat exchange, which can effectively shorten the drying time and reduce energy consumption, improve the drying process quality and efficiency of transformer products, and avoid problems such as rusting of the core, uneven temperature distribution, air leakage of the fan shaft seal, etc. during drying of the transformer, and facilitate the modification of the old transformer vacuum drying equipment currently used in the industry.

[0045] The above specific implementation further details the purpose, technical solution and beneficial effects of the present application. It should be understood that the above description is only a specific implementation of the present application and does not limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made on the basis of the technical solution of the present application shall be included in the protection scope of the present application.

Claims

1. A jet cycle hot air heated transformer vacuum drying system comprising: Vacuum tank, the heating row pipe is arranged in the inner wall of the vacuum tank, characterized in that: the injection device is arranged at the predetermined position above the heating row pipe arranged in the inner wall of the vacuum tank, and the control and measurement subsystem is arranged outside the vacuum tank; the injection device is used to inject supersonic jet flow to the heating row pipe arranged in the inner wall of the vacuum tank, to form forced convection heat exchange, to make the heat around the heating row pipe flow to the bottom of the vacuum tank along the air duct formed by the preset air duct plate and the inner wall of the vacuum tank, and to uniformly heat the transformer device inside the vacuum tank; the control and measurement subsystem is used to measure the pressure inside the vacuum tank, to real-time adjust the opening degree of the inlet and outlet valves, and to control the pressure field inside the vacuum tank. The injection device is composed of two parts of Laval nozzle and Laval nozzle, and the control and measurement subsystem includes a vacuum unit for controlling the pressure field inside the vacuum tank.

2. The jetted cycle hot air heated transformer vacuum drying system of claim 1, wherein, The inner wall of the vacuum tank includes at least one of the side wall, the upper wall, the lower wall and the rear wall of the vacuum tank.

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