High-temperature salt mist deposition test bed based on electromagnetic heating and test method thereof

Abstract

The invention aims to provide a high-temperature salt mist deposition test bed based on electromagnetic heating and a test method thereof, and belongs to the field of turbine blade tests. Comprising an inlet section, a test section and an outlet section, the inlet section comprises a mixing contraction section, an air inlet grille is installed at an inlet of the mixing contraction section, a salt mist nozzle is arranged behind the air inlet grille, the salt mist nozzle is connected with a spraying system controller, and the spraying system controller is connected with an air pump and a water storage tank; the test section comprises a metal shell, two ends of the metal shell are respectively connected with the mixing contraction section and the test piece blade, an air inlet heating coil is wound outside the metal shell, and the air inlet heating coil is connected with a temperature system controller; the outlet section comprises a heat exchanger and a fan, an inlet of the heat exchanger is connected with an outlet behind the test piece blade, and an outlet of the heat exchanger is connected with the fan. The temperature control precision is improved, the structure of the turbine blade salt spray deposition test device is simplified, the test cost is reduced, and safe and reliable operation of the test device is guaranteed.

Description

Technical Field

[0001] The present invention relates to a test apparatus and test method thereof, specifically a salt spray test bench and test method thereof. Background Technology

[0002] With the continuous development of marine resources and maritime transportation, gas turbines are widely used in marine development. During operation, the marine environment causes a certain amount of salt to be mixed into the gas turbine intake air. Long-term salt accumulation can significantly affect the strength and morphology of the turbine blades. Salt spray erosion and deposition can have a major impact on the performance and lifespan of the turbine blades, seriously endangering the safe and stable operation of the gas turbine. Therefore, salt spray deposition tests are needed to study its effects and optimize blade design.

[0003] Traditional salt spray deposition test benches typically use gas heating or resistance heating to provide a high-temperature environment. However, these methods suffer from numerous problems, including complex test equipment structures, high testing costs, and the inability to operate safely and stably for extended periods. For example, gas heating suffers from low temperature control accuracy, uneven temperature distribution, the risk of gas leakage, and exhaust pollution of the test environment; resistance heating suffers from low heating efficiency, slow temperature rise, poor temperature uniformity, and the resistance wire's susceptibility to oxidation and breakage in salt spray. Furthermore, regarding parameter control, due to limitations in the test bench's heating mode, existing parameter control systems only support single-aspect temperature control, i.e., adjusting blade temperature by controlling airflow temperature. This fails to address the coupled temperature regulation between airflow and blades, resulting in a lag between blade temperature and airflow temperature, leading to significant temperature matching errors. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature salt spray deposition test bench and its testing method based on electromagnetic heating, which can solve the problems of safety hazards, low heating efficiency, inaccurate temperature control, and uneven temperature distribution in traditional test benches when providing high-temperature environments, and achieve rapid, safe, and efficient simulation of high-temperature salt spray deposition environments.

[0005] The objective of this invention is achieved as follows: This invention discloses a high-temperature salt spray deposition test bench based on electromagnetic heating, characterized by comprising an inlet section, a test section, and an outlet section connected in sequence. The inlet section includes a mixing and shrinking section, with an air intake grille installed at the inlet of the mixing and shrinking section. A salt spray nozzle is disposed behind the air intake grille and connected to a spray system controller. The spray system controller is connected to an air pump and a water storage tank. The test section includes a metal shell, with one end of the metal shell connected to the mixing and shrinking section and the other end of the metal shell fitted with test specimen blades. An air intake heating coil is wound around the outside of the metal shell and connected to a temperature system controller. The outlet section includes a heat exchanger and a fan. The inlet of the heat exchanger is connected to the outlet behind the test specimen blades, and the outlet of the heat exchanger is connected to the fan.

[0006] The present invention may also include: 1. Top extension metal and root extension metal are respectively set at the top and root of the test specimen blade. Top extension metal is wound with top heating coil, and root extension metal is wound with root heating coil. Top heating coil and root heating coil are respectively connected to temperature system controller.

[0007] 2. The metal casing and the test blades are encased inside the insulation casing.

[0008] 3. The metal casing has a fan-shaped cross section with a fan angle in the range of 60° to 120°.

[0009] 4. The section shrinkage ratio of the fan-shaped annular section is 1.2 to 3:1, and the inner wall of the metal shell is equipped with a turbulence-enhancing structure.

[0010] 5. The turbulence enhancement structure is a microrib array with a depth of 0.5-2 mm.

[0011] 6. The operating frequency of the intake heating coil is 10-50kHz, the power density is ≥5kW / m2, and the surface of the intake heating coil is covered with a ceramic insulation layer with a thickness of 0.5mm to 2mm.

[0012] The present invention provides a high-temperature salt spray deposition test method based on electromagnetic heating, characterized in that: the above-mentioned high-temperature salt spray deposition test bench based on electromagnetic heating is used; (1) Turn on the fan to circulate the airflow, and adjust the fan speed to stabilize the airflow; (2) Control the air pump and water tank through the spray system controller to spray salt mist into the airflow through the salt mist nozzle, and adjust the salt mist concentration parameters to the test requirements; (3) Current is passed through the inlet heating coil, top heating coil and root heating coil to heat the airflow and test piece blades respectively using the electromagnetic heating principle; the airflow temperature and test piece blade temperature are monitored in real time, and the current parameters of the inlet heating coil, top heating coil and root heating coil are adjusted according to the feedback to accurately control the temperature to the test set value; (4) Maintain stable test conditions and continue the salt spray deposition test. The test time shall be set according to specific requirements. (5) After the test, turn off the spray system controller and the temperature system controller, continue to keep the fan running, and turn off the fan after the temperature parameter drops to a safe range. Take out the test blades for analysis and testing to evaluate the salt spray deposition and its impact on the test blades.

[0013] The advantages of this invention are as follows: Compared to traditional single-temperature control logic, this invention creatively integrates a fan-shaped annular flow channel structure with electromagnetic heating technology to construct a novel salt spray deposition test platform that combines high-precision temperature control with realistic operating condition simulation capabilities. The non-contact, high-response, and zoned control characteristics of electromagnetic induction heating allow for synchronous heating of the airflow and test specimen, achieving excellent temperature uniformity. By separately controlling the input current of the inlet heating coil and the blade heating coil, decoupled independent temperature control of the airflow and solid test specimen is achieved, breaking the traditional passive mode of "airflow temperature determining blade temperature" and achieving a high degree of matching between airflow and blade temperatures, overcoming the temperature lag problem caused by thermal inertia in traditional methods. Furthermore, the replaceable, multi-size fan-shaped annular turbine blade channel design effectively replicates the complex internal flow structure of a gas turbine, significantly improving the simulation realism and controllability of salt spray deposition behavior. Compared to traditional heating methods, electromagnetic heating eliminates safety hazards such as open flames, and precise current control avoids problems such as localized overheating, resulting in high safety. Simultaneously, reasonable insulation design reduces heat loss, leading to good energy-saving effects. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0015] The invention will now be described in more detail with reference to the accompanying drawings: Combination Figure 1This invention includes an inlet section, a test section, and an outlet section. The inlet section includes an air intake grille 1, a salt spray nozzle 2, and a mixing and shrinking section 3. Other components of the spray system include a spray system controller 12, a water storage tank 13, and an air pump 14. The air intake grille 1 and the salt spray nozzle 2 are installed inside the inlet section cavity, and the cavity outlet is connected to the inlet of the mixing and shrinking section 3. The spray system controller 12, the water storage tank 13, and the air pump 14 are installed outside the inlet section cavity and are connected to the salt spray nozzle 2 via water and air pipelines. The test section includes a metal shell 4, an inlet heating coil 5, a blade heating coil 6, test blades 7, an insulation shell 8, and a temperature system controller 11. The inlet of the metal shell 4 is connected to the outlet of the mixing and shrinkage section 3. The inlet heating coil 5 is wound around the periphery of the metal shell 4. The tail of the metal shell 4 is connected to the test blades 7. The top and root of the test blades 7 are wound with blade heating coils 6. The metal shell 4, inlet heating coil 5, blade heating coil 6, and test blades 7 are all enclosed within the insulation shell 8. The temperature system controller 11 is installed outside the insulation shell 8 and connected to the heating coils inside via wires. The outlet section includes a heat exchanger 9 and a fan 10. The inlet of the heat exchanger 9 is connected to the outlet cavity of the test section via a pipeline, and the outlet of the heat exchanger 9 is connected to the inlet of the fan 10.

[0016] like Figure 1 As shown, the air intake grille 1 is located at the front of the test bench. Its function is to perform preliminary filtration and uniform distribution of the air entering the test bench, ensuring a uniform and stable airflow to subsequent components. The salt spray nozzle 2 is installed after the air intake grille. Its function is to uniformly spray salt spray into the airflow entering the test bench. The spray system controller 12 adjusts the parameters of the water tank 13 and the air pump 14 to provide high-pressure water and high-pressure air, thereby adjusting the spray parameters of the salt spray nozzle and controlling the concentration of salt spray and other indicators to simulate the actual salt spray environment.

[0017] The airflow carrying salt spray passes through the mixing and contraction section 3, where the salt spray and airflow are further mixed thoroughly, resulting in a more uniform distribution of the salt spray within the airflow and providing stable salt spray airflow conditions for subsequent experiments. The metal casing 4 is constructed as a fan-shaped annular turbine blade channel; this shape more closely resembles the actual working environment of a gas turbine blade, making the test results more valuable. The test section is designed with a double-layer structure. The inner channel, i.e., the outer surface of the metal casing 4, is wound with an intake heating coil 5. Electromagnetic heating is used to heat the airflow and salt spray entering the test section, and the airflow temperature can be precisely controlled by adjusting the current parameters of the intake heating coil 5. Simultaneously, metal structures are extended at the top and bottom of the test blade 7, and blade heating coils 6 are wound around them. These also utilize electromagnetic heating to heat the test blade 7 to the required high temperature, simulating the thermal environment in actual operation. The entire test section is enclosed by an insulation casing 8 to reduce heat loss, improve heating efficiency, and ensure the safety of the experimental personnel. The current through the intake heating coil 5 and the blade heating coil 6 is regulated by a temperature system controller located outside the insulation casing 8. The outlet section is located after the test section. The function of heat exchanger 9 is to reduce the temperature of the airflow after passing through the test section, which protects downstream equipment and allows for heat recovery and utilization, improving energy efficiency. Finally, a high-power fan 10 installed at the rear of the test rig provides sufficient power to drive the airflow within the test rig cavity. By adjusting parameters such as the fan speed, the stability and continuity of the airflow during the test can be ensured.

[0018] The electromagnetic heating system employs dual-loop electromagnetic induction coupling heating and real-time closed-loop temperature control technology, unlike traditional resistance wire or gas heating systems that only heat the airflow or cavity. The electromagnetic coil operates at a frequency of 10-50kHz, with a power density ≥5kW / m², and the coil conductors are coated with a ceramic insulation layer ranging from 0.5mm to 2mm in thickness. The intake heating coil, wound around the outer wall of the metal casing, generates eddy currents within the conductive metal casing through a high-frequency alternating magnetic field, achieving overall heating of the airflow and salt spray mixture with a heating rate exceeding 50℃ / s. Simultaneously, the blade heating coil is directly wound around the extended metal root and tip of the test blade, forming targeted localized electromagnetic heating, allowing the blade body to quickly reach the target temperature without relying on airflow heat transfer. Furthermore, differentiated thermal fields can be created in the blade root and tip regions, inducing deposition effects similar to those observed in actual operation.

[0019] Based on the characteristic of electromagnetic heating that the heating power can be precisely controlled by current, this invention uses a temperature system controller to dynamically adjust the input current of two sets of coils based on feedback from multiple temperature and humidity sensors. This constructs a feedforward-feedback composite control between airflow temperature and blade temperature, actively compensating for the hysteresis effect caused by blade thermal inertia, and achieving synchronous rise and steady-state matching of airflow and blade temperature, with the error controlled within ±5℃.

[0020] The electromagnetic heating coil is installed outside the flow channel of the test device and does not come into direct contact with the internal airflow, which reduces the interference to the internal flow field and salt spray field caused by factors such as flame heat flow and salt deposits on the resistance wire.

[0021] Electromagnetic heating technology offers structural improvements in safety and durability. It is contactless, flameless, and eliminates electrode aging issues, avoiding the risk of resistance wires corroding and breaking in salt spray environments. The heating coil is encapsulated and isolated in a metal casing, protecting it from salt spray corrosion and significantly extending its lifespan. Simultaneously, the high-frequency power supply can be equipped with overload protection and adaptive frequency adjustment to prevent localized overheating.

[0022] The fan-shaped annular turbine blade channel structure more closely resembles real-world operating conditions, achieving geometric simulation and enhanced flow-thermal coupling effects. This invention designs the metal casing as a fan-shaped annular cross-section, with the fan angle ranging from 60° to 120°, simulating the flow channel unit formed by adjacent blades in an actual turbine stage. It supports arranging multiple test blades at their actual circumferential installation angles to form a local annular array, more realistically simulating key flow phenomena affecting salt spray deposition, such as secondary flow, horseshoe vortices, and corner separation.

[0023] The matching structure of the fan-shaped annular turbine blade channel and the mixing contraction section can promote the realism and repeatability of salt spray deposition behavior. This matching structure guides the airflow to accelerate naturally, and the velocity gradient and salt spray particle trajectory can be controlled by changing the mixing contraction section and blade channel of different sizes. The cross-sectional contraction ratio (inlet cross-sectional area / outlet cross-sectional area of ​​the experimental device) of the fan-shaped annular channel is 1.2 to 3:1, and the inner wall of the channel is equipped with a turbulence enhancement structure, which is an array of microribs with a depth of 0.5-2 mm, used to simulate the incoming flow field with different turbulence intensities.

[0024] The process of the method of the present invention is as follows: (1) Turn on the fan to circulate the airflow in the test bench, and adjust the fan speed to a suitable value to stabilize the airflow.

[0025] (2) Spray salt mist into the intake airflow through a salt mist spraying device and adjust the salt mist concentration and other parameters to the test requirements.

[0026] (3) Current is passed through the inductor coil, and the airflow and turbine blade test pieces are heated by electromagnetic heating principle. The airflow temperature and blade temperature are monitored in real time by temperature sensors, and the current and other parameters of the inductor coil are adjusted according to the feedback to accurately control the temperature to the test set value, such as heating the airflow temperature to 800℃ and the blade temperature to 900℃.

[0027] (4) Keep the test conditions stable and continue to conduct salt spray deposition tests. The test time is set according to specific needs, such as 10 hours.

[0028] (5) After the test, turn off the salt spray device and the current of the inductor coil, continue to run the fan for a period of time, and turn off the fan after the temperature and other parameters in the test bench drop to a safe range. Take out the turbine blade test piece for analysis and testing, and evaluate the salt spray deposition and its impact on the blade.

Claims

1. A high-temperature salt spray deposition test bench based on electromagnetic heating, characterized in that: The system comprises an inlet section, a test section, and an outlet section connected in sequence. The inlet section includes a mixing and shrinking section, with an air intake grille installed at the inlet. A salt spray nozzle is located behind the air intake grille and connected to a spray system controller. The spray system controller is connected to an air pump and a water storage tank. The test section includes a metal casing. One end of the metal casing is connected to the mixing and shrinking section, and the other end is fitted with test specimen blades. An air intake heating coil is wound around the outside of the metal casing and connected to a temperature system controller. The outlet section includes a heat exchanger and a fan. The inlet of the heat exchanger is connected to the outlet behind the test specimen blades, and the outlet of the heat exchanger is connected to the fan.

2. The high-temperature salt spray deposition test bench based on electromagnetic heating according to claim 1, characterized in that: The test specimen blades are provided with top extension metal and root extension metal, respectively. The top extension metal is wound with a top heating coil, and the root extension metal is wound with a root heating coil. The top heating coil and the root heating coil are respectively connected to the temperature system controller.

3. The high-temperature salt spray deposition test bench based on electromagnetic heating according to claim 1, characterized in that: The metal casing and the test blades are encased inside the insulation casing.

4. The high-temperature salt spray deposition test bench based on electromagnetic heating according to claim 1, characterized in that: The metal casing has a fan-shaped cross-section with a fan angle ranging from 60° to 120°.

5. A high-temperature salt spray deposition test bench based on electromagnetic heating according to claim 4, characterized in that: The section shrinkage ratio of the fan-shaped annular section is 1.2 to 3:1, and the inner wall of the metal shell is equipped with a turbulence-enhancing structure.

6. A high-temperature salt spray deposition test bench based on electromagnetic heating according to claim 5, characterized in that: The turbulence enhancement structure is a microrib array with a depth of 0.5-2 mm.

7. A high-temperature salt spray deposition test bench based on electromagnetic heating according to claim 1, characterized in that: The operating frequency of the intake heating coil is 10-50kHz, the power density is ≥5kW / m2, and the surface of the intake heating coil is covered with a ceramic insulation layer with a thickness ranging from 0.5mm to 2mm.

8. A high-temperature salt spray deposition test method based on electromagnetic heating, characterized in that: The high-temperature salt spray deposition test bench based on electromagnetic heating as described in claim 1 is adopted; (1) Turn on the fan to circulate the airflow, and adjust the fan speed to stabilize the airflow; (2) Control the air pump and water tank through the spray system controller to spray salt mist into the airflow through the salt mist nozzle, and adjust the salt mist concentration parameters to the test requirements; (3) Current is passed through the inlet heating coil, top heating coil and root heating coil to heat the airflow and test piece blades respectively using the electromagnetic heating principle; the airflow temperature and test piece blade temperature are monitored in real time, and the current parameters of the inlet heating coil, top heating coil and root heating coil are adjusted according to the feedback to accurately control the temperature to the test set value; (4) Maintain stable test conditions and continue the salt spray deposition test. The test time shall be set according to specific requirements. (5) After the test, turn off the spray system controller and the temperature system controller, continue to keep the fan running, and turn off the fan after the temperature parameter drops to a safe range. Take out the test blades for analysis and testing to evaluate the salt spray deposition and its impact on the test blades.

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