A method and device for dissipating heat from a power module of an electric servo system of a high-speed aircraft

Abstract

The application provides a high-speed aircraft electric servo system power module heat dissipation method and device, which comprises a magnetic fluid cooling working medium, a magnetron-driven heat sink, a cooling working medium circulation loop and a heat dissipation cold end heat exchanger. The application can monitor the working signal of the power module, predict the heating state, change the adjustable magnetic field environment in the magnetron-driven heat sink, change the Lorentz force of the magnetic fluid to control the flow rate of the magnetic fluid, adjust the heat dissipation capacity of the magnetron-driven heat sink, and match the heat dissipation requirement of the power module under the dynamic change of the heat flow. In addition, the application can also independently adjust the controlled magnetic field environment and the driving force of the magnetron-driven heat sink corresponding to the power module in the high and low heat flow regions, perform the regional control of the cooling working medium of the magnetron-driven heat sink, change the flow speed of the magnetic fluid in the flow channel in different heat flow regions, realize the non-uniform heat dissipation capacity to match the non-uniform heat flow, and improve the temperature uniformity of the power module.

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation technology for high-power electronic devices, and in particular relates to a thermal control method and device for dynamically adjusting the thermal performance of power devices in electric servo systems of high-speed aircraft in different regions. Background Technology

[0002] The power module is an important component of the electric servo system, the actuator of an aircraft. Its function is to convert the input DC signal into a three-phase AC power supply for driving the motor through its internal IGBT (Insulated Gate Bipolar Transistor) three-phase bridge, realizing the conversion from motor control signal to high-power drive signal. The high-power devices such as IGBTs in this module operate under high current and high switching frequency conditions, generating a large amount of heat due to power loss, which causes the operating temperature of the power module to rise sharply, requiring heat dissipation. As the output power of the electric servo system of high-speed aircraft continues to increase, the heat generation power of the power module has also increased dramatically, making its heat dissipation problem face greater challenges. Due to the working characteristics of the electric servo system in flight control, the heat generation of its power module has the following main characteristics: (1) The heat generation of the power module changes rapidly and dynamically. Due to the adjustment of flight trajectory and flight attitude, the flight control commands sent by the aircraft to the electric servo system are constantly changing dynamically, so the output power and duty cycle of its power devices are constantly changing, and the power loss is closely related to these parameters, causing the heat generation of the power module to change rapidly and dynamically with the flight process. (2) Uneven heating inside the power module. Based on the working principle of brushless motors, the three-phase bridge circuit composed of IGBTs and other components within the power module often employs a lower-power half-bridge modulation method. For example, when using H-PWM_L-ON type half-bridge modulation, the upper half-bridge IGBTs of each phase undergo PWM (Pulse Width Modulation) modulation (generating conduction and switching losses), while the lower half-bridge IGBTs remain constantly on (generating only conduction losses), leading to uneven heating between the upper and lower half-bridges. Furthermore, the continuous unsteady switching between forward / reverse rotation, acceleration / deceleration, and stall states of the motor causes dynamic changes in the PWM duty cycle, conducting bridge arms, and conducting IGBTs, further altering the heat dissipation and heat generation of the components within the power module. These factors result in the power module being in a state of dynamic heat generation variation and uneven heat flow, leading to poor temperature uniformity and complicating the design of its cooling system. Related studies have shown that non-uniform high-temperature operation will lead to increased thermal stress and cracking in high-power devices of power modules, resulting in decreased device reliability and even serious failures such as overheating and burnout. Therefore, it is necessary to design a heat dissipation device that can match the non-uniform heat flow to cool down the power module.

[0003] Currently used heat dissipation methods such as air cooling and water cooling have two problems when applied to the power module heat dissipation of electric servo systems in aircraft: First, their heat dissipation capacity is relatively fixed, with a small adjustable range or slow adjustment speed, lacking rapid dynamic adjustment capability. This makes it difficult to match the heat dissipation performance in real time with the dynamic changes in heat loss of the power module, and it is difficult to meet the requirement of controlling the operating temperature of power devices within a suitable temperature range. Second, the heat dissipation capacity of the above methods is limited, and the device size is too large, which cannot meet the requirements of aircraft for small size, light weight, and compactness of the mounted components. Moreover, the harsh thermal environment inside the cabin of high-speed aircraft makes it difficult to dissipate heat to the environment, and it cannot carry a large amount of cooling fluid for heat exchange. The patent "A Microchannel Heat Dissipation Structure, Manufacturing Method, and Electronic Device" (Patent Publication No. CN 110364501 B) proposes a microchannel heat dissipation structure. This structure fills the flow channels between stacked multi-layer heat dissipation units with an elastomer with a negative thermal expansion coefficient. The deformation of this elastomer with temperature controls whether the conduction between adjacent heat dissipation units is controlled, thereby adjusting the overall heat transfer coefficient of the heat sink and thus achieving heat dissipation capacity adjustment according to heat generation. Its heat dissipation device can achieve temperature control to a certain extent, but for the power module of the high-power electric servo system of high-speed aircraft, the applicability of this method has the following problems: (1) It only has a limited number of thermal performance adjustment states, and cannot flexibly cope with the continuous large-scale temperature rise changes of the power module; (2) The adjustment capability of the heat dissipation performance of this method comes at the cost of increasing the structural volume of the device. The fewer the number of heat dissipation unit stacks, the fewer the adjustable levels, which is difficult to meet the constraints of aircraft volume and weight; (3) As the number of heat dissipation unit stacks increases, the increase in heat transfer efficiency of the heat sink decreases, and for the problem of non-uniform heat flow heat dissipation, its structural matching is not good, and it is difficult to adapt to the non-uniform rapid change of heat dissipation requirements; (4) The mechanical structure and processing are relatively complex, and the performance requirements of the elastomer with negative thermal expansion coefficient are high, resulting in low reliability.

[0004] Therefore, in order to adapt to the heat dissipation of high-power electronic devices such as power modules of electric servo systems for high-speed aircraft, which have high power, high integration, and fast time-varying non-uniform heat flux density, it is necessary to design compact heat dissipation devices with efficient cooling capabilities and controllable thermal performance as needed. Summary of the Invention

[0005] To address the problem of efficient uniform heat dissipation of power modules in aircraft electric servo systems under high power density and non-uniform time-varying heat flow conditions, this invention proposes a heat dissipation method that dynamically matches the heating state of the power module in different regions. A magnetically controlled heat sink device with magnetic fluid as the cooling medium is designed to realize this method. It has the advantages of high compactness, high heat transfer rate, controllable heat dissipation performance, and rapid regional adjustment.

[0006] This invention monitors the operating signals of the power module to predict its heating state, and accordingly modifies the adjustable magnetic field environment within the magnetically controlled heat sink. This alters the Lorentz force exerted by the magnetic field on the magnetofluid, controlling the magnetofluid flow rate and thus regulating the heat dissipation of the magnetically controlled heat sink to match the power module's cooling requirements under dynamically changing heat flux. Furthermore, this invention can also independently adjust the controlled magnetic field environment and driving force of the magnetically controlled heat sink in the high and low heat flux regions (corresponding to the upper and lower bridge arms) of the power module, enabling regional control of the cooling medium in the magnetically controlled heat sink. This changes the flow velocity of the magnetofluid in the channels of different heat flux regions, thereby achieving non-uniform heat dissipation to match non-uniform heat flux and improving the temperature uniformity of the power module.

[0007] This invention achieves continuous adjustment and regional control of the heat dissipation capacity of the magnetically driven heat sink by regulating the flow velocity of the magnetofluid within the heat sink. This matches the dynamic changes and non-uniform distribution of heat generation in the power module, maintaining the overall operation of the power module within a suitable temperature range and improving its temperature uniformity. This effectively addresses the heat dissipation challenges of high-power electric servo systems in aircraft. Furthermore, this invention utilizes cryogenic fuel from the aircraft as the cold-end heat exchange medium, transferring the heat absorbed by the magnetofluid to the cryogenic fuel. This effectively reduces the size and weight of the cold-end heat exchange device and helps improve the overall energy utilization rate of the aircraft. Simultaneously, this invention employs an electrically controlled operating method for the heat sink's driving magnetic field, eliminating the need for pumps or other moving mechanical parts, resulting in high reliability and a long service life.

[0008] The technical solution of this invention is as follows:

[0009] A heat dissipation device for the power module of an electric servo system for a high-speed aircraft includes a magnetic fluid cooling medium, a magnetically controlled heat sink, a cooling medium circulation loop, and a heat exchanger at the cold end.

[0010] The magnetically controlled heat sink includes a heat sink body and a speed control circuit.

[0011] The heat sink body includes a cooling medium channel and an electromagnetic drive device. The heat sink body is arranged on the power module, and the power module is cooled by heat exchange through the magnetic fluid cooling medium in the cooling medium channel. The cooling medium channel is divided into two independent cooling medium channels that flow through the high heat flux region and the low heat flux region of the power module. The electromagnetic drive device can drive the magnetic fluid cooling medium in the cooling medium channel corresponding to the high heat flux region and the low heat flux region respectively to flow at their respective required speeds.

[0012] The speed control circuit predicts the heat generation and distribution of the power module by monitoring the duty cycle of the PWM control signal sent to the power module and the output power current, and collects the current temperature of the power module to assess the heat dissipation requirements of the power module; and controls the electromagnetic drive device to adjust the flow rate of the magnetic fluid cooling medium according to the heat dissipation requirements of the power module.

[0013] The cooling medium circulation loop includes corresponding flow pipes and a cooling medium storage tank; the magnetically controlled heat sink and the heat exchanger at the cold end are connected to the cooling medium storage tank through the flow pipes; the magnetic fluid cooling medium circulates in the flow pipes and storage tank under the drive of the magnetically controlled heat sink. After the magnetic fluid cooling medium absorbs heat and its temperature rises in the magnetically controlled heat sink, it flows out of the magnetically controlled heat sink and flows into the heat exchanger at the cold end along the flow pipe. After the heat exchanger at the cold end cools down by exchanging heat with the outside, it enters the cooling medium storage tank and then enters the magnetically controlled heat sink again along the flow pipe to participate in heat exchange again, continuously circulating to form a cooling medium circulation loop.

[0014] Furthermore, the electromagnetic drive device includes an excitation coil and an iron core that generate a traveling wave magnetic field. The excitation coil and the iron core are arranged on both the upper and lower sides of the cooling working fluid flow channel inside the heat sink body. By applying an excitation current to the excitation coil, the magnetic fluid cooling working fluid is driven to move along the direction of the traveling wave magnetic field. The flow rate of the magnetic fluid cooling working fluid is controlled by changing the frequency of the excitation current.

[0015] Furthermore, the heat exchanger consists of a spiral pipe coiled around the cryogenic fuel delivery pipeline of the aircraft's power system; the magnetic fluid cooling medium, heated by the magnetically controlled heat sink, flows within the spiral pipe of the heat exchanger and exchanges heat with the cryogenic fuel of the aircraft. After its temperature is sufficiently reduced, it enters the cooling medium storage tank.

[0016] Furthermore, the heat sink body is attached to the power module for heat dissipation, and the power module adopts a half-bridge modulation method, presenting a state with high and low heat regions each in half; the electromagnetic drive device is divided into a high heat flux region electromagnetic drive device and a low heat flux region electromagnetic drive device, corresponding to the high heat region and low heat region of the power module, respectively.

[0017] Furthermore, the excitation coil is wound layer by layer on the salient pole of the iron core using a salient pole winding method, generating an independent induced magnetic field along the axial direction of the excitation coil, thereby reducing the influence between the induced magnetic fields generated by adjacent excitation coils.

[0018] Furthermore, the excitation coils are connected in a star configuration, and three-phase alternating currents with a phase difference of 120° are sequentially applied to generate a traveling wave magnetic field. The excitation coils at the same position on the upper and lower sides of the cooling working fluid flow channel inside the heat sink body are connected in the same way and their respective excitation signals are input.

[0019] Furthermore, the speed control circuit includes a controller, a power supply, and a drive circuit; the controller monitors the input PWM control signal and its duty cycle of the power module, and simultaneously measures the power current output by the power module to obtain the predicted heat generation of the power module, thereby determining the heat dissipation capacity required by the magnetically controlled heat sink; the controller generates a corresponding excitation current drive signal according to the heat dissipation capacity required by the magnetically controlled heat sink, and regulates the flow rate of the magnetic fluid cooling medium to enable the magnetically controlled heat sink to provide the required heat dissipation capacity.

[0020] Furthermore, based on the predicted non-uniform heat distribution of the power module, the controller adjusts the heat dissipation capacity in zones through the drive circuits corresponding to the high heat flux region and the low heat flux region, providing excitation current drive signals of different frequencies to the electromagnetic drive devices in the high heat flux region and the low heat flux region, thereby realizing zoned speed control and thus zoned heat dissipation.

[0021] Furthermore, the controller also forms a closed-loop feedback system in the form of feedback signals based on the real-time monitoring of the current actual temperature distribution of the power module, in order to correct prediction deviations and suppress temperature fluctuations.

[0022] A method for heat dissipation of power module in electric servo system of high-speed aircraft includes the following steps:

[0023] Step 1: Collect the duty cycle of the PWM control signal sent to the power module and the output power current information to predict the real-time heat generation and heat distribution of the power module;

[0024] Step 2: Based on the real-time heat generation and heat distribution of the power module obtained in Step 1, the excitation current frequency required for each region of the magnetically controlled heat sink is obtained by utilizing the correspondence between the heat generation of the power module and the excitation current frequency of the magnetically controlled heat sink.

[0025] Step 3: By providing excitation current of the corresponding frequency to the electromagnetic drive devices in each area of ​​the magnetically controlled heat sink, the heat dissipation capacity of the magnetically controlled heat sink is matched with the heat dissipation requirements of different areas of the power module. At the same time, the actual temperature at different locations of the power module is used as a feedback signal to determine whether the temperature of the power module meets the requirements of the desired temperature range. If it does, the heat dissipation performance of the magnetically controlled heat sink is kept unchanged to maintain temperature balance until the acquired PWM control signal or output power current information changes. If it does not meet the requirements, the excitation current frequency of the corresponding electromagnetic drive device is adjusted according to the actual temperature value, thereby regulating the flow rate of the magnetic fluid cooling medium in the corresponding area, changing the heat dissipation performance of the magnetically controlled heat sink, and keeping the temperature of the power module within the normal range.

[0026] Furthermore, the relationship between the heat generation of the power module and the excitation current frequency of the magnetically controlled drive heat sink was obtained through numerical simulation analysis, specifically using the following steps:

[0027] Step a: Build a physical model of the magnetically controlled heat sink in a multiphysics simulation software, including the structural model of the traveling wave magnetic field generator and the structural model of the heat sink.

[0028] Step b: Add electromagnetic field and flow field modules to the structural model of the traveling wave magnetic field generator, and couple them through Lorentz force to build a magnetohydrodynamic coupling model; obtain the magnetohydrodynamic coupling model by numerically solving the magnetohydrodynamic coupling model to obtain the flow rate of the magnetohydrodynamic cooling medium under different excitation current frequencies.

[0029] Step c: After establishing the structural model of the magnetically controlled heat sink and power module, perform mesh generation, set the numerical solution method, and establish a fluid-structure interaction heat transfer model.

[0030] Step d: Select several characteristic points within the heat generation range of the power module and set several excitation current frequencies to construct several sets of heat generation characteristic point-excitation current frequency values; determine whether each set of heat generation characteristic point-excitation current frequency values ​​matches through the following process:

[0031] Step d.1: Using the magnetohydrodynamic coupling model established in step b, obtain the flow rate of the magnetohydrodynamic cooling medium at the excitation current frequency;

[0032] Step d.2: Using the flow rate of the magnetohydrodynamic cooling medium obtained in step d.1 as input, and converting the heat generation at the characteristic point into a heat flow boundary, the temperature of the power module is obtained by solving the fluid-structure interaction heat transfer model. Based on the temperature, it is determined whether the heat generation characteristic point-excitation current frequency numerical group matches.

[0033] Step e: Fit the numerical group of the matched heat generation characteristic points and excitation current frequency to obtain the correspondence between the heat generation of the power module and the excitation current frequency of the magnetically controlled heat sink.

[0034] Beneficial effects

[0035] The beneficial effects of the technical solution of this invention are mainly reflected in:

[0036] 1. Based on the PWM signal and power current of the power module, its heat generation and distribution are predicted, and its temperature is monitored in real time. Accordingly, the excitation current frequency of the magnetically controlled heat sink is controlled to change the flow rate of the magnetic fluid cooling medium, thereby dynamically adjusting the heat transfer capacity of the magnetically controlled heat sink. This forms a method for dynamic regulation of the heat dissipation performance of the magnetically controlled heat sink under closed-loop feedback and predictive control. This method and device can achieve controlled and continuous adjustment of the heat dissipation capacity of the magnetically controlled heat sink, ensuring that the power module is always kept within a suitable operating temperature range. This solves the problem of mismatch in heat dissipation capacity when the heat generation of the power module changes dynamically, and avoids overheating damage to the device.

[0037] 2. An electromagnetically driven system is used to achieve continuous circulation of the magnetofluid. This electromagnetically driven pump, with no moving mechanical parts, is integrated with a microchannel heat sink and attached to the power module substrate, thus forming a magneto-controlled heat sink that performs both fluid drive and heat transfer functions. Compared to traditional mechanical pumps and cooling devices, it not only boasts superior reliability and long lifespan, but its compact, integrated structure is also advantageous for space-constrained electric servo systems in aircraft, facilitating small size and lightweight design.

[0038] 3. The magnetically controlled heat sink adopts a regional independent adjustment method for heat transfer performance. Based on the different heat generation in the high and low heat flux regions of the power module, the flow rate of the magnetic fluid in the corresponding flow channel of the magnetically controlled heat sink in each region is determined and controlled. This achieves dynamic matching between the heat flux of the power module and the heat transfer capacity of the magnetically controlled heat sink in different regions, thereby effectively improving the non-uniform temperature field of the power module, improving the temperature uniformity of the power module, and reducing its internal thermal stress.

[0039] 4. The heat dissipation circulation loop used in this invention exchanges heat with the cryogenic fuel pipeline in the aircraft's power system via an externally wound helical tube. This eliminates the need for a large and complex cold-end heat dissipation device, simplifying the entire system, reducing device size and space occupation, and overcoming the adverse effects of the harsh thermal environment of the aircraft on the outward heat dissipation of the power module. This not only allows for sufficient cooling of the magnetofluid but also enables the secondary utilization of energy lost in the electric servo system through regenerative cooling, contributing to improved overall energy efficiency of the aircraft.

[0040] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0042] Figure 1 This is a schematic diagram of a magnetically controlled heat dissipation device;

[0043] 1-Magnetically controlled heat sink; 2-Magnetic fluid cooling medium storage tank; 3-Cooling cold end heat exchanger; 4-Aircraft engine cryogenic fuel delivery pipeline; 5-Cooling medium circulation loop; 6-Power module.

[0044] Figure 2 This is a schematic diagram of a magnetically controlled heat sink structure;

[0045] 7-Excitation coil in high heat flux region; 8-Core in high heat flux region; 9-Flow channel; 10-Magnetic fluid; 11-Flow channel rib; 12-Core in low heat flux region; 13-Excitation coil in low heat flux region.

[0046] Figure 3 This is a schematic diagram of the excitation coil and iron core structure;

[0047] 7(13)-Excitation coil in high (low) heat flux region; 8(12)-Core in high (low) heat flux region; 9-Flow channel; 10-Magnetic fluid; 11-Flow channel rib.

[0048] Figure 4 This is a side cross-sectional schematic diagram of the power module and the magnetically controlled drive heat sink assembly;

[0049] 1-Magnetic drive heat sink; 6-Power module; 7(13)-High (low) heat flux region excitation coil; 8(12)-High (low) heat flux region iron core; 9-Flow channel; 10-Magnetic fluid; 16-Substrate; 17-Power device; 18-Thermal conductive adhesive; 19-Temperature sensor; 20-DBC (Direct Bonding Copper) layer.

[0050] Figure 5 This is a schematic diagram of a magnetically controlled heat dissipation system based on dynamic matching of thermal performance.

[0051] 3-Cooling cold end heat exchanger; 6-Power module; 7-High heat flux region excitation coil; 13-Low heat flux region excitation coil; 14-High heat flux region excitation coil drive circuit; 15-Low heat flux region excitation coil drive circuit; 21-Controller; 22-Aircraft engine fuel tank; 23-Engine combustion chamber; 24-Magnetic control drive heat sink body; 25-Speed ​​control circuit; 26-DC (Direct Current) power supply.

[0052] Figure 6 This is a flowchart of the magnetically controlled heat dissipation method design.

[0053] Figure 7 This is a block diagram of the dynamic heat loss prediction model for power modules.

[0054] Figure 8 It is a method for determining the numerical simulation parameters of the matching heat generation of the magnetically controlled drive;

[0055] Figure 9 It is a method for determining the matching relationship between excitation current frequency and heat generation;

[0056] Figure 10 This is the control flowchart of the magnetically controlled heat dissipation system. Detailed Implementation

[0057] This invention addresses the heat dissipation requirements of power modules in electric servo systems of high-speed aircraft by proposing a heat dissipation device and method. The method utilizes a magnetofluid as the cooling medium and a microchannel heat sink as the primary heat dissipation device. An electromagnetic drive device without mechanical moving parts is integrated within the microchannel heat sink to drive and control the flow velocity of the magnetofluid, thereby adjusting the required heat dissipation capacity. This achieves dynamic regulation of the heat dissipation capacity required by the non-uniformly changing heat flow of the power module using a magnetically controlled heat sink. Based on the prediction of the dynamic heat generation and distribution of the power module, this method uses the excitation current frequency of the magnetically controlled heat sink as the control variable to regulate the flow velocity of the magnetofluid cooling medium within the heat sink. Using multiphysics simulation and finite element analysis, the matching relationship between the heat generation of the power module and the magnetofluid flow velocity is obtained, thus establishing a thermal control mechanism for the non-uniform dynamic heat flow of the power module.

[0058] The basic principles of this invention will be explained below:

[0059] Part 1: A method for dynamically matching the heat dissipation performance of a magnetically controlled heat sink to the non-uniform dynamic heating state of a power module.

[0060] This invention employs a method of monitoring the current thermal state of the power module and predicting future heat generation. It comprehensively adjusts the cooling fluid flow rate of the magnetically driven heat sink in this invention, thereby regulating the heat transfer performance of the heat dissipation device to control the operating temperature of the power module. The specific method is as follows:

[0061] (1) Monitoring the current thermal status of the power module and predicting future heat generation

[0062] First, a temperature sensor is used to monitor the current heating state of the power module in real time, obtaining the real-time temperature of the power module as a feedback quantity and serving as the main input parameter for the performance control and adjustment of the heat dissipation device. Simultaneously, to perform proactive thermal control based on changes in the real-time heating state of the power module and effectively address future short-term heat flow peaks caused by changes in the power module's operating state, a dynamic heat loss prediction model for the power module, related to its input and output states, is established. Based on its PWM signal, operating current signal, and other parameters, the heat loss of the power module at the next moment is calculated, thereby obtaining a predicted value of heat generation in the short term. This predicted value is then used as an input parameter for the performance adjustment of the heat dissipation device, allowing for advance adjustment of the heat dissipation performance in the corresponding area.

[0063] The method for predicting the heat loss of power modules is as follows:

[0064] Since the three-phase bridge circuit topology and load in the power module are symmetrical, the voltage and current waveforms of each IGBT and freewheeling diode are similar. Therefore, the conduction loss and switching loss of a single IGBT and fast recovery diode in one electrical cycle are as follows:

[0065] P cond(IGBT) =1 / 3·Vce(sat) ·I·δ (1)

[0066] P sw(IGBT) =(E on +E off )·f sw (2)

[0067] P cond(Diode) =1 / 3·V f ·I·(1-δ) (3)

[0068] P sw(Diode) =E rec ·f sw (4)

[0069] In the formula, P cond(IGBT) P cond(Diode) The conduction losses of the IGBT and the fast recovery diode are respectively, P sw(IGBT) P sw(Diode) The switching losses of the IGBT and fast recovery diode are respectively, V ce(sat) Where I is the saturation voltage drop, δ is the output power current, and E is the PWM duty cycle. on and E off For switching energy consumption, V f For forward conduction voltage drop, E rec To reverse the energy consumption, f sw This refers to the switching frequency.

[0070] For a three-phase bridge circuit consisting of six power transistors, due to the use of upper-half-bridge modulation, only one power transistor in each phase arm is in modulation state, resulting in uneven heating between the upper and lower transistors within the same arm. For the upper half of each arm, both the conduction and switching losses of the modulated power transistor must be considered. However, fast recovery diodes operate only once per electrical cycle, and their power loss is negligible. Therefore,

[0071] P IGBT_1 / 3 / 5 =P sw(IGBT_1 / 3 / 5) +P cond(IGBT_1 / 3 / 5) (5)

[0072] P Diode_1 / 3 / 5 ≈0 (6)

[0073] Since the reverse freewheeling fast recovery diode connected in parallel to the power transistor in the lower half of the bridge arm is also in a modulation state, its conduction and turn-off losses need to be considered. However, the power transistor in the lower half of the bridge arm is always conducting during its conduction time, so only its conduction loss needs to be considered (the duty cycle δ = 1 can be assumed). Therefore, the power loss of each lower half of the bridge arm is...

[0074] P IGBT_2 / 4 / 6 =P cond(IGBT_1 / 3 / 5),δ＝1 (7)

[0075] P Diode_2 / 4 / 6 =P sw(Diode_2 / 4 / 6) +P cond(Diode_2 / 4 / 6) (8)

[0076] Therefore, the total power loss of the upper half-bridge arm of the power module is

[0077] P total_upper =P IGBT_1 +P IGBT_3 +P IGBT_5 (9)

[0078] The total power loss of the lower half of the bridge arm is

[0079] P total_lower =P IGBT_2 +P IGBT_4 +P IGBT_6 +P Diode_2 +P Diode_4 +P Diode_6 (10)

[0080] In the formula, P total_upper P represents the total loss of the upper half-bridge arm of the power module. total_lower P represents the total loss of the lower half-bridge arm of the power module. IGBT_i and P Diode_i These represent the power losses of each IGBT and fast recovery diode.

[0081] The power module drives the servo motor according to control commands via PWM modulation. The duty cycle (δ) of the PWM signal determines the conduction time within a single cycle. Furthermore, as shown by the formula, the power loss is also closely related to the output power current (I). The saturation voltage drop (V... ce(sat) Switching power consumption (E) on E off Forward conduction voltage drop (V) f ), reverse recovery energy consumption (E) rec Parameters such as output power current (I) and PWM duty cycle (δ) can be obtained by consulting the device's datasheet. Therefore, by using the device's operating parameter table and real-time sampled variables such as output power current (I) and PWM duty cycle (δ), the real-time power loss and its distribution (i.e., the power loss of the upper and lower half-bridges) of the power module can be calculated according to the above formula.

[0082] The calculated real-time power loss of the power module is used as the heat generation information of the power module. Based on its structural dimensions, the instantaneous heat flux and its distribution of the power module can be obtained, which can serve as the input boundary conditions for subsequent joint heat transfer simulation of the power module and the magnetically controlled heat sink. Simultaneously, through subsequent calculations, this information can be used as a basis for regulating the heat sink's heat dissipation performance, controlling its temperature within a suitable range, and independently adjusting the high and low heat flux regions of the power module based on the heat flux information of the upper and lower half-bridges to achieve overall temperature equilibrium. Therefore, when the method and device proposed in this invention are actually working, only the PWM signal and output power current of the power module need to be monitored to calculate the instantaneous heat generation information of the corresponding regions of the upper and lower half-bridges of the power module, thereby determining the required heat dissipation capacity of the heat dissipation device in the corresponding regions of the upper and lower half-bridges.

[0083] (2) Mechanism for regulating the heat dissipation performance of magnetically controlled heat sink

[0084] This invention employs a method of changing the flow rate of a magnetofluid through magnetic control to achieve dynamic adjustment of the heat dissipation performance of a magnetically controlled heat sink.

[0085] The heat sink is mounted and attached to the power module substrate, absorbing and transferring the heat generated by power loss in the power module through heat transfer. During heat dissipation, heat conduction first occurs from the power module to the heat sink housing, followed by heat convection between the heat sink housing and the cooling medium (magnetic fluid) flowing inside, completing the heat transfer from the power module. The cooling medium then transports the heat to the cold end of the heat sink. The convective heat transfer equation for the heat convection process from the heat sink housing to the cooling medium is:

[0086] Q=hAΔT (8)

[0087] In the formula, Q represents the heat transferred, h is the heat transfer coefficient, A is the heat transfer area, and ΔT is the convective heat transfer temperature difference. As can be seen from equation (8), changing the heat transfer coefficient can alter the heat dissipation performance of the heat sink, thereby regulating the heat transferred between the heat sink and the power module. The magnitude of the heat transfer coefficient is related to many factors, such as the flow rate of the cooling medium, the heat sink configuration, and thermophysical parameters. Among these, the flow rate of the cooling medium is the easiest to change and control during operation. Moreover, the heat transfer coefficient is positively correlated with the flow rate of the cooling medium. Increasing the flow rate of the cooling medium through the channels in the heat sink can improve the heat transfer coefficient of the heat sink, thereby changing the amount of heat carried away by the cooling medium as it flows through the heat sink.

[0088] (3) Method for Variable Flow Rate Control of Magnetorheological Fluid Cooling Medium in Magnetically Controlled Heat Sink

[0089] By adjusting the frequency of the excitation current of the traveling wave magnetic field input to the magnetically driven heat sink, the flow rate of the magnetic fluid cooling medium can be controlled, thereby achieving continuous adjustment of the heat dissipation capacity of the magnetically driven heat sink.

[0090] Magnetically controlled heat sinks use magnetorheological fluid as the cooling medium. Due to the magnetic properties of the nanoparticles within the fluid, it can be controlled and driven by a magnetic field, forming the basis for controlling the flow rate of the cooling medium without a mechanical drive device. To drive the magnetorheological fluid to generate controlled motion, a three-phase AC signal, as shown in the following formula, is applied to the three-phase windings (U, V, W) of the excitation coils on both sides of the heat sink flow channel:

[0091] i U =I m cosωt (9)

[0092] i V =I m cos(ωt-120°) (10)

[0093] i W =I m cos(ωt+120°) (11)

[0094] In the formula, i U i V i W Let I represent the instantaneous values ​​of the current in each phase. m ω is the amplitude of the current, and ω is the angular frequency of the alternating current.

[0095] When the above three-phase alternating current excitation is applied to the three-phase winding of the excitation coil, a traveling wave magnetic field with a sinusoidal distribution and movement in space and time will be generated, and its mathematical expression is as follows:

[0096] B = B m sin(ω B t+βx) (12)

[0097] In the formula, B represents the magnetic induction intensity of the traveling wave magnetic field. m It is the amplitude of the magnetic induction intensity of the traveling wave magnetic field, ω B ω is the angular frequency of the traveling wave magnetic field, β is the wave number of the traveling wave magnetic field, and x is the distance traveled by the traveling wave.

[0098] Therefore, when an excitation current is applied to the excitation coil, a traveling wave magnetic field with a certain velocity and magnetic field strength will be generated at the magnetofluid. This traveling wave magnetic field electromagnetically couples with the magnetofluid, inducing an electromotive force in the magnetofluid, which in turn generates an induced current. When the induced current in the magnetofluid interacts with the traveling wave magnetic field, a Lorentz force will be generated, causing the magnetofluid to move along the direction of the traveling wave magnetic field.

[0099] In a traveling wave magnetic field, the relationship between the magnitude of the Lorentz force on the magnetohydrodynamic fluid and the traveling wave magnetic field can be simplified to the following equation:

[0100] F = J × B = f(B) 2 ,δ,V) (13)

[0101] In the formula, F represents the Lorentz force, J is the current density in the magnetohydrodynamic cooling medium, B is the magnetic induction intensity of the traveling wave magnetic field, δ is the conductivity of the magnetohydrodynamic fluid, and V is the velocity of the traveling wave magnetic field.

[0102] It is known that the traveling wave magnetic field velocity, magnetic induction intensity, and magnetohydrodynamic conductivity are the main factors affecting the magnitude of the Lorentz force. From the Lorentz force calculation formula, it can be seen that the magnitude of the Lorentz force can be changed by influencing the traveling wave magnetic field. Therefore, the velocity of the traveling wave magnetic field is:

[0103] V=ωτ / π (14)

[0104] In the formula, ω is the three-phase AC frequency of the input excitation coil, and τ is the pole pitch of the excitation coil.

[0105] As can be seen from the above formula, controlling the electrical frequency supplied to the excitation coil can change the velocity of the traveling wave magnetic field, thereby changing the magnitude of the Lorentz force driving the magnetofluid, and ultimately causing the flow velocity of the magnetofluid to change accordingly.

[0106] (4) Establish the matching relationship between excitation current frequency, magnetofluid velocity, and heat generation of power module.

[0107] To achieve real-time adjustment of the heat dissipation performance of the magnetically controlled heat sink based on the dynamic heating state of the power module, it is necessary to determine the matching relationship between the heat generation of the power module and the heat dissipation capacity of the magnetically controlled heat sink, as well as the matching relationship between the heat dissipation capacity of the magnetically controlled heat sink and the excitation current frequency. Specifically, this involves determining the heat dissipation performance required to maintain the power module at a suitable operating temperature when it is in a certain heating state, and specifying the magnetofluid flow velocity required to meet this heat dissipation performance requirement, as well as the excitation current frequency required to achieve this flow velocity.

[0108] First, obtaining the specific numerical correspondence between the excitation current frequency and the final magnetohydrodynamic velocity is crucial. Direct analytical solutions are extremely complex, so multiphysics simulation software such as COMSOL Multiphysics is used for numerical calculations. A coupled magnetohydrodynamic model of a magnetically controlled heat sink is then established. This model includes electromagnetic equations such as Maxwell's equations, as well as fluid dynamics equations such as mass conservation, momentum conservation, and energy conservation. Numerical simulations are then performed based on this model, setting different excitation current frequencies to obtain the corresponding magnetohydrodynamic velocities under the given magnetic field. Based on this, the correspondence between the excitation current frequency and the magnetohydrodynamic velocity is established.

[0109] Secondly, determining the specific correspondence between the magnetofluid velocity and the heat generation of the power module also faces the same challenge. Similarly, a fluid-structure interaction heat transfer model of the magnetically controlled heat sink is established in multiphysics simulation software such as COMSOL Multiphysics. This model includes the continuity equation, momentum equation, energy equation, and heat conduction equation in the fluid domain. Using this model, numerical simulations are performed with the magnetofluid velocity and the heat flux and distribution of the power module as the inlet velocity boundary condition and heat flux boundary condition, respectively, to calculate the temperature of the power module. By selecting any set of real-time heat generation of the power module and the magnetofluid velocity in the magnetically controlled heat sink as the boundary conditions of the numerical model, the temperature of the power module under different heat generation and magnetofluid velocities is obtained. The matching of heat generation and magnetofluid velocity is then determined based on whether the temperature meets the requirements, thus obtaining a suitable correspondence between the magnetofluid velocity and the heating state of the power module.

[0110] Through the simulation calculations of the two numerical models above, the correspondence between the excitation current frequency and the magnetofluid velocity was first established. Then, the correspondence between the magnetofluid velocity and the heat generation of the power module was established when the temperature control requirements of the power module were met. In this way, the correspondence between the excitation current frequency, the magnetofluid velocity, and the heat generation of the power module that meet the heat dissipation requirements of the power module can be obtained in series.

[0111] Part Two: Design and Implementation of a Magnetically Controlled Heat Sink Heat Dissipation Device for Dynamically Matching the Heating State of Power Modules by Region to Achieve Different Thermal Performance Zones.

[0112] The heat dissipation system mainly includes: a magnetically controlled heat sink, a cooling working fluid circulation loop, and a heat exchanger at the cold end, each described in detail below.

[0113] Component 1: Magnetically controlled heat sink.

[0114] The magnetically controlled heat sink is the core device of this heat dissipation method, consisting of two parts: the magnetically controlled heat sink body and the speed control circuit.

[0115] (1) Magnetically controlled heat sink body

[0116] The magnetically controlled heat sink consists of a cooling fluid flow channel, an excitation coil and iron core that generate a traveling wave magnetic field, and a casing. The main function of the magnetically controlled heat sink is:

[0117] ① A magnetic fluid is used as the cooling medium to exchange heat with the power module to reduce its temperature.

[0118] Magnetofluids are stable colloids formed by mixing magnetic solid nanoparticles with a base fluid and adding surface dispersants. The presence of solid particles significantly increases the thermal conductivity of the magnetofluid, thereby greatly improving the heat transfer rate per unit volume. It also enables it to flow under the influence of a traveling wave magnetic field.

[0119] ② The electromagnetic drive device generates driving force to pump the magnetofluid to flow in the heat sink.

[0120] As described in Part 1, after applying excitation current to the excitation coils on both sides of the heat sink flow channel, a Lorentz force will be generated through electromagnetic coupling, causing the magnetofluid to move along the direction of the traveling wave magnetic field. This replaces power devices such as mechanical pumps to provide driving force for the magnetofluid, and pumps the magnetofluid to flow in the flow channel of the magnetically controlled heat sink.

[0121] ③ Control the flow velocity of the magnetohydrodynamic fluid as needed to adjust the heat dissipation capacity of the heat sink in real time.

[0122] As described in Part 1, by changing the frequency of the excitation current in the input excitation coil, the flow velocity of the magnetofluid can be adjusted accordingly. The flow velocity of the magnetofluid directly affects its heat dissipation capacity as a cooling medium in a heat sink. Under otherwise constant conditions, the flow velocity of the magnetofluid is positively correlated with its heat dissipation capacity; increasing the flow velocity effectively enhances the heat transfer capacity of the magnetically controlled heat sink. Therefore, when the heat output of the power module changes, the magnetically controlled heat sink can adjust its heat dissipation capacity by changing the frequency of the excitation current in the input excitation coil, thereby controlling the flow velocity of the magnetofluid within the channel.

[0123] ④ Matches the non-uniform heat distribution of the power module, and independently adjusts the heat dissipation capacity of each region.

[0124] As shown above, the heat dissipation capacity of the magnetically controlled heat sink is controlled by the excitation current flowing through the excitation coil. Therefore, based on the known heating characteristics of the power module, the cooling fluid flow channels of the magnetically controlled heat sink are designed as multiple straight-channel parallel connections, with each channel independently flowing through either a high heat flux region or a low heat flux region. Simultaneously, the excitation coil and the iron core are also designed as two independent driving parts, corresponding to the flow channels in the high and low heat flux regions of the power module. This allows for independent adjustment of the magnetofluid flow velocity in the high and low heat flux regions based on the heat generated in each region of the power module, thereby altering the heat dissipation capacity of the magnetically controlled heat sink in different areas and improving the temperature uniformity of the power module.

[0125] (2) Speed ​​control circuit

[0126] The speed control circuit is the control component for adjusting the heat dissipation performance of the magnetically controlled heat sink. It is responsible for controlling the frequency of the three-phase excitation current input to the excitation coil based on the predicted heat generation information and temperature monitoring information of the power module. The main components of the speed control circuit include the controller, power supply, and drive circuit. The heat generation variation of the power module in the electric servo system is caused by changes in the output power of the electric servo system due to factors such as dynamic changes in flight control commands and load power fluctuations. Therefore, the duty cycle of the PWM control signal sent to the power module and the output power current can be monitored to predict its heat generation and distribution. Simultaneously, combined with the collected current temperature of the power module, the heat dissipation requirements of the power module are comprehensively evaluated, and the heat dissipation capacity of the magnetically controlled heat sink is matched and adjusted.

[0127] The aircraft's electric servo system tracks flight control commands and generates corresponding servo outputs by driving the servo motors using PWM control via a power module. Therefore, to predict the heat generation and distribution of the power module, a power loss calculation model needs to be established based on its loss mechanism. Given the PWM modulation method of the power module, this model can predict the dynamic power loss and loss distribution of the power module based on its PWM duty cycle, output power current, and other operating status information. Therefore, by monitoring the PWM control signal and current information input to the power module, its heating characteristics can be analyzed. Then, based on the magnetohydrodynamic flow velocity requirements under different heat generation conditions, a corresponding frequency excitation current is generated and input to the excitation coil of the magnetically controlled heat sink, thereby adjusting the magnetohydrodynamic flow velocity to change the heat sink's heat dissipation capacity. Simultaneously, the power module temperature is collected and fed back to the speed control circuit to correct thermal performance prediction deviations, ultimately forming a dynamic matching heat dissipation mode for the power module's thermal performance based on a closed-loop feedback + predictive control strategy.

[0128] Component 2: Cooling fluid circulation loop

[0129] The cooling fluid circulation loop is a closed-loop flow pipeline, including corresponding flow pipes and a storage tank. The magnetofluid circulates within the flow pipes and storage tank, continuously flowing and carrying away heat from the magneto-controlled heat sink. Driven by the electromagnetic force of the magneto-controlled heat sink, the magnetofluid, having absorbed heat and increased in temperature, flows out of the heat sink and into the cold-end heat exchanger along the flow pipes. After being cooled by heat exchange with the cryogenic fuel in the aircraft's propulsion system, it enters the cooling fluid storage tank, and then re-enters the magneto-controlled heat sink along the flow pipes to participate in heat exchange again, continuously circulating to form a heat transfer loop.

[0130] Component 3: Cooling Cold End Heat Exchanger

[0131] The cold-end heat exchanger consists of a spiral pipe coiled around the cryogenic fuel delivery pipeline of the aircraft's propulsion system. For aircraft using cryogenic fuels such as liquid hydrogen-liquid oxygen or liquid oxygen-methane, the cryogenic fuel is stored in the aircraft's fuel tank and enters the engine via the delivery pipeline. Magnetorheological fluid, heated by a magnetically controlled heat sink, flows within the spiral pipe of the cold-end heat exchanger, exchanging heat with the aircraft's cryogenic fuel. After its temperature is sufficiently reduced, it circulates again along the cooling fluid loop. This not only ensures sufficient cooling of the magnetorheological fluid but also reduces the cost of adding a large cooling structure at the cooling end, providing an effective and reliable heat transfer path. Furthermore, it facilitates the secondary utilization of this lost energy within the aircraft's propulsion system.

[0132] The following is a more detailed explanation with reference to the accompanying drawings:

[0133] (I) The specific structure and working method of the magnetically controlled heat dissipation device.

[0134] like Figure 1 As shown, this invention proposes a magnetically controlled drive heat dissipation method and apparatus for a power module 6 of an aircraft's electric servo system. The apparatus mainly consists of a magnetically controlled drive heat sink 1, a cooling fluid storage tank 2, a cold-end heat exchanger 3, and a cooling fluid circulation loop 5. The magnetically controlled drive heat sink 1 generates electromagnetic driving force, causing the magnetic fluid 10 inside it to circulate in the cooling fluid circulation loop 5 in the direction shown in the figure. Through two heat exchanges between the magnetically controlled drive heat sink 1 and the cold-end heat exchanger 3, the magnetic fluid 10 transfers heat from the power module 6 to the aircraft's cryogenic fuel via the cooling fluid circulation loop 5 and the cold-end heat exchanger 3. The cooled magnetic fluid 10 flows into the cooling fluid storage tank 2 and then re-enters the magnetically controlled drive heat sink 1 to participate in heat exchange. In this way, the heat generated by power loss in the power module 6 is continuously removed, maintaining it within a suitable operating temperature range. The heat exchanger 3 at the cold end of the cooling system transfers heat to the cryogenic fuel delivery pipeline 4 of the aircraft engine via a spiral coil. The spiral coil configuration increases the thermal contact area between the heat exchanger 3 and the cryogenic fuel delivery pipeline 4, allowing the magnetofluid 10 to fully exchange heat with the cryogenic fuel. The cryogenic fuel in the aircraft engine fuel tank 22 enters the engine combustion chamber 23 via the cryogenic fuel delivery pipeline 4. During this process, the fuel exchanges heat with the spiral coil to carry away the power loss of the power module 6, generating heat and increasing the initial temperature of the cryogenic fuel. This energy is then reused through regenerative cooling.

[0135] Figure 2This diagram illustrates the internal structure of the magnetically controlled drive heat sink 24 and the relative positions of its components. The magnetically controlled drive heat sink 24 includes a high-heat-flux region excitation coil 7, a low-heat-flux region excitation coil 13, a high-heat-flux region iron core 8, a low-heat-flux region iron core 12, a flow channel 9, and flow channel ribs 11. The magnetically controlled drive heat sink 24 is attached to the power module 6 substrate for heat dissipation. Since the power module 6 often uses a half-bridge modulation method, its upper and lower bridge arms heat up unevenly, resulting in the power module 6 approximately having half high-heat-flux and half low-heat-flux regions. Therefore, the excitation coil and iron core in the magnetically controlled drive heat sink are also divided into two parts according to the heat-generating regions of the power module 6, corresponding to the high and low heat-flux regions of the power module 6. The high-heat-flux region iron core 8 and the low-heat-flux region iron core 12 are symmetrically arranged on the upper and lower sides of the flow channel 9, so that magnetic flux will pass from one side of the high-heat-flux region iron core 8 (or low-heat-flux region iron core 12) through the flow channel 9 to the other side. Both the high-heat-fluidity excitation coil 7 and the low-heat-fluidity excitation coil 13 are wound layer by layer on the salient poles of the iron core. Between the upper and lower parts is the flow channel of the magnetofluid 10, which is isolated by the flow channel ribs 11 to form multiple flow channels 9.

[0136] like Figure 3 The diagram shows the structure of a single high (low) heat flux region excitation coil 7 (13) and a high (low) heat flux region core 8 (12). The high (low) heat flux region excitation coil 7 (13) adopts a salient pole winding method. The salient pole winding method allows for independent assembly of each high (low) heat flux region excitation coil 7 (13), simplifies the manufacturing process, and generates an independent induced magnetic field along the axial direction of the high (low) heat flux region excitation coil 7 (13), resulting in minimal influence between the induced magnetic fields generated by adjacent high (low) heat flux region excitation coils 7 (13).

[0137] Figure 4This describes the main structure and heat conduction process of the power module 6 and the magnetically controlled drive heat sink 1. The excitation coils 7(13) in each high (low) heat flux region are connected in a star configuration, and three-phase alternating currents with a 120° phase difference are sequentially applied to generate a traveling wave magnetic field. The excitation coils 7(13) in the high (low) heat flux regions corresponding to the same position above and below are connected in the same way and input with their respective excitation signals. The traveling wave magnetic field electromagnetically couples with the magnetofluid 10, inducing an electromotive force in the magnetofluid 10, which in turn forms an induced current. The induced current interacts with the traveling wave magnetic field to generate a Lorentz force, driving the magnetofluid 10 to circulate. The magnetofluid 10 exchanges heat with the power module 6, continuously transferring the heat generated by its power loss to the outside to reduce the temperature of the power module 6. The power device 17 is the main source of heat; the heat generated during its operation is mainly transferred to the DBC layer 20, substrate 16, etc., through heat conduction, and then most of the heat is transferred through heat transfer via the magnetically controlled drive heat sink 1, which is closely attached to it. After being absorbed by the magnetic fluid 10 in the flow channel 9, the heat leaves the magnetically controlled heat sink 1 and enters the cooling working fluid circulation loop 5, and is then sent to the cold end heat exchanger 3 for secondary heat exchange at the cold end. The cavity between the excitation coils 7 (13) in multiple high (low) heat flow regions and the iron cores 8 (12) in high (low) heat flow regions is filled with thermally conductive adhesive 18 to increase the heat exchange performance and to fix the excitation coils 7 (13) in high (low) heat flow regions and the iron cores 8 (12) in high (low) heat flow regions.

[0138] Figure 5This is a block diagram illustrating the working principle of the heat dissipation system based on the magnetically controlled heat sink 1. To match the dynamic heating of the power module 6 in real time, the speed control circuit 25 needs to predict the heating state of the power module and monitor its temperature in real time. Based on this, the speed of the cooling medium in the magnetically controlled heat sink body 24 is controlled, causing the flow rate of the magnetic fluid 10 to change dynamically. This achieves a match between the heat dissipation capacity of the magnetically controlled heat sink 1 and the heat generation of the power module 6, thus achieving temperature balance in the power module 6. Specifically, the controller 21 monitors the input PWM control signal and its duty cycle of the power module 6, and simultaneously measures the output power current of the power module 6. Based on this, the predicted heat generation of the power module 6 is obtained through a dynamic heat loss prediction model, thereby determining the required heat dissipation capacity of the magnetically controlled heat sink 1. Since different flow rates of the magnetic fluid 10 correspond to different heat transfer coefficients of the magnetically controlled heat sink body 24, thus determining its corresponding heat dissipation capacity, and the flow rate of the magnetic fluid 10 is positively correlated with the excitation current frequency of its traveling wave magnetic field. Therefore, based on the correspondence between heat dissipation capacity and excitation current frequency, the controller 21 generates a corresponding excitation current drive signal to regulate the flow rate of the magnetic fluid 10, thereby changing the heat dissipation capacity of the magnetically controlled heat sink body 24. Simultaneously, based on the predicted non-uniform heat distribution of the power module 6, the controller 21 performs zoned adjustment of heat dissipation capacity through the excitation coil drive circuit 14 in the high heat flux region and the excitation coil drive circuit 15 in the low heat flux region. It converts the connected DC power supply 26 into three-phase excitation currents of different frequencies, respectively changing the traveling wave magnetic field drive signals supplied to the excitation coil 7 in the high heat flux region and the excitation coil 13 in the low heat flux region, thus achieving the purpose of zoned speed control of the magnetic fluid 10 in multiple parallel flow channels 9. At the same time, the temperature sensor 19 monitors the current actual temperature distribution of the power module in real time to correct prediction deviations and suppress temperature fluctuations. A closed-loop feedback system is formed in the form of feedback signals, serving as real-time control parameters for adjusting the performance of the heat dissipation device. Combining the above two methods, the heat dissipation capability of the magnetically controlled heat sink 1 is dynamically matched to the heat generation of the power module 6, maintaining its temperature within a suitable range. The heat transfer path in this process is as follows: Figure 4 As indicated by the arrow, cryogenic fuel is transferred from power module 6 to the aircraft's propulsion system via magnetofluid 10.

[0139] (II) Design and implementation process of magnetically controlled heat dissipation method.

[0140] To achieve the above-mentioned working process of the magnetically controlled heat dissipation device, it is necessary to perform the following: Figure 6The magnetic drive heat dissipation method is designed according to the process shown. (1) Based on the heating mechanism of power module 6, its dynamic heating characteristics are analyzed, and a dynamic heat loss prediction model of power module related to input and output states is established to predict the heat generation and its distribution. In this way, the heating status of power module 6 can be obtained from the PWM signal and power current information at different times, which not only provides a basis for the next design, but also can predict the heating status of power module 6 in advance during the operation of the heat dissipation system, thereby improving the control effect. (2) In order to adjust the heat dissipation capacity of magnetic drive heat sink 1 in real time according to the dynamic heating status of power module 6, it is necessary to obtain the matching relationship between the heat dissipation capacity of magnetic drive heat sink 1 and the excitation current frequency, as well as the matching relationship between the heat generation of power module 6 and the heat dissipation capacity of magnetic drive heat sink 1. Since it is difficult to obtain directly through a concise and clear mathematical expression, it is necessary to use numerical simulation tools such as multiphysics simulation software to establish a numerical model through the finite element method for calculation and solution. First, the excitation current frequency corresponding to several heat generation characteristic points of power module 6 is obtained, and then it is fitted into a function of matching relationship between heat generation and excitation current frequency that is easy to implement in controller 21. (3) During the actual thermal control process based on the magnetically controlled heat sink 1, the PWM signal and power current of the power module 6 are measured in real time to predict its heat generation and heat distribution. Based on the heat generation-heat dissipation performance matching function obtained in the previous step, combined with the current temperature feedback of the power module 6, the controller 21 calculates the excitation current frequency required by the magnetically controlled heat sink 1, and controls the excitation coil drive circuit 14 in the high heat flux region and the excitation coil drive circuit 15 in the low heat flux region to generate excitation currents with different frequencies respectively, so as to drive the excitation coil 7 in the high heat flux region and the excitation coil 13 in the low heat flux region respectively, so that the heat dissipation capacity of the magnetically controlled heat sink 1 in the corresponding region matches the heat dissipation requirements of the power module 6 in the region, thereby keeping the operating temperature of the power module 6 in a suitable range and the overall temperature distribution uniform.

[0141] Figure 7This is a block diagram illustrating the principle of the dynamic heat loss prediction model for the power module. Based on the input PWM signal and output power and current information received by the power module 6 at different times, the dynamic heat generation and its distribution as a function of duty cycle and output power are obtained. The power loss generated by the power module 6 during operation mainly comes from two parts: the IGBT and fast recovery diode of the power device 17, including conduction loss and switching loss. Since the electric servo system uses PWM modulation to change the voltage at the servo motor terminals, thereby adjusting the direction, torque, and speed of the servo motor, the conduction arm, duty cycle, and output power continuously change, causing the conduction loss and switching loss values ​​and their ratio to continuously change, resulting in dynamic changes in the heat generation of the power module 6. To obtain the dynamic loss of the power module 6, a dynamic heat loss prediction model is built based on its working principle and circuit structure. Parameters such as saturation voltage drop, switching energy consumption, forward conduction voltage drop, reverse recovery energy consumption, and current are obtained from the device datasheet and used to form a lookup table for real-time calculation. Then, using the obtained device operating parameter table and real-time sampled variables such as load current and PWM duty cycle, the real-time power loss of the power module 6 is calculated.

[0142] According to the specific working process of the magnetically controlled heat sink 1, by changing the frequency of the traveling wave magnetic field excitation current, the flow rate of the magnetofluid 10 is changed to match the heat generation of the power module 6. Figure 8 and Figure 9 This paper demonstrates a parameter determination method and process for obtaining the matching relationship between excitation current frequency and heat generation based on numerical simulation analysis. To establish the matching relationship between the heat generation of power module 6 and the excitation current frequency of magnetically controlled heat sink 1, a simulation model is first built in the multiphysics simulation software COMSOL. Figure 8The multiphysics simulation model is shown. The calculation process of the multiphysics simulation model is as follows: (1) Determine the physical model of the magnetically driven heat sink body 24. According to the structural design of the traveling wave magnetic field generator, determine its coil winding method, number of turns, pole pitch, core size and other parameters; according to the heat sink structure design, determine its flow channel cross-sectional size, number of flow channels, material properties and other related parameters. (2) Establish the magnetohydrodynamic coupling model and the fluid-structure coupling heat transfer model respectively. In the COMSOL simulation software, add the electromagnetic field and flow field module and couple them through the Lorentz force. Then, build the magnetohydrodynamic coupling model according to the determined configuration parameters. The corresponding magnetohydrodynamic 10 flow velocity can be obtained by setting different excitation current frequencies. Subsequently, in the fluid flow and heat transfer module, after establishing the geometric model according to the structure of the magnetically driven heat sink 1 and the power module 6, perform mesh generation, set the numerical solution method, establish the fluid-structure coupling heat transfer model, and calculate the temperature and distribution information of the power module 6 with the magnetohydrodynamic 10 flow velocity and the heat generation and distribution of the power module 6 as input variables. (3) Perform numerical calculation and solution. First, an excitation current frequency value is input, and the flow velocity of magnetohydrodynamics 10 is obtained by solving the magnetohydrodynamic coupling model. Then, this flow velocity value is input into the fluid-structure interaction heat transfer model as a velocity inlet boundary condition. Simultaneously, the heat generated by power module 6 is converted into a heat flux boundary condition, thereby obtaining the temperature of power module 6 through solution. Then, the following steps are performed... Figure 9 The matching process is shown below. Several feature points are selected within the heat generation range calculated by the dynamic heat loss prediction model of power module 6. Numerical simulation is performed using the established multiphysics simulation model to obtain the temperature of power module 6 under different heat generation and excitation current frequencies. The temperature is used to determine whether the heat generation and excitation current frequency match. The required excitation current frequency for each heat generation feature point is iteratively calculated, resulting in several sets of matching numerical values. These sets are then fitted to obtain a function with heat generation as the independent variable and excitation current frequency as the dependent variable, thus establishing the correspondence between the heat generation of power module 6 and the excitation current frequency.

[0143] Figure 10The control flow of the magnetically controlled heat dissipation system is as follows. After completing the design of the magnetically controlled heat dissipation method, the obtained PWM signal and output power current correspondence with the heat generation and distribution of the power module 6, the correspondence between the heat generation of the power module 6 and the excitation current frequency of the magnetically controlled heat sink 1, and the designed thermal control strategy and algorithm are integrated into the controller 21 to realize the dynamic thermal control of the magnetically controlled heat dissipation system. After the heat dissipation system starts working, the controller 21 continuously collects PWM signals and power current information to predict the real-time heat generation and heat distribution of the power module 6. Then, based on the correspondence between the power module 6 and the excitation current frequency, the controller 21 controls the drive circuit 14 (15) to invert the DC power supply 26 into a three-phase excitation current of the corresponding frequency value to drive the excitation coil 7 (13) in the high (low) heat flow area, so that the heat dissipation capacity of the magnetically controlled heat sink 1 matches the heat dissipation requirements of different areas of the power module 6. At the same time, multiple temperature sensors 19 between the contact surface of the magnetically controlled heat sink 1 and the power module 6 monitor the actual temperature at different locations of the power module 6 in real time and transmit it to the controller 21 as a feedback signal to form a closed-loop negative feedback system. The controller 21 determines whether the temperature of the power module 6 meets the desired temperature range. If it does, the system repeats the process and maintains the heat dissipation performance of the magnetically controlled heat sink 1 unchanged to maintain temperature balance until the acquired PWM signal or power current changes. When the actual temperature of the power module 6 is detected to be higher than the suitable temperature range, the controller 21 increases the frequency value of the three-phase excitation current and drives the excitation coil 7 (13) in the high (low) heat flow area according to the actual temperature value. It regulates the traveling wave magnetic field in the corresponding area to accelerate the flow speed of the magnetic fluid 10, thereby improving the heat dissipation capacity of the magnetically controlled heat sink 1 at the corresponding position. In the same time, it absorbs and transfers more heat energy, thereby reducing the temperature of the power module 6 to the suitable temperature range. Conversely, when the actual temperature of the power module 6 is detected to be lower than the suitable temperature range, the flow speed of the magnetic fluid 10 is slowed down through the reverse process, reducing the heat dissipation capacity of the magnetically controlled heat sink 1 at the corresponding position, thereby maintaining the temperature of the power module 6 within the normal range.

[0144] During the regulation process, the high and low heat flow regions of the magnetically controlled heat sink 1 are controlled separately and independently. The controller 21 will control the drive circuit 14 (15) to generate excitation currents of different frequencies according to the heat generation of the high and low heat flow regions and pass them into the excitation coil 7 of the high heat flow region and the excitation coil 13 of the low heat flow region. The flow rate of the magnetic fluid 10 in the flow channel 9 of the corresponding region will be adjusted respectively, so that the flow rate of the flow channel 9 at the corresponding position matches the heat generation of the region, thereby achieving the purpose of zoned regulation of the heat dissipation capacity of the magnetically controlled heat sink 1 and improving the temperature uniformity of the power module 6.

[0145] The contents of this invention not described in detail are existing technologies known to those skilled in the art.

[0146] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A heat sink for a power module of an electric servo system of a high-speed aircraft, characterized in that: The magnetic fluid cooling medium, the magnetic control driven heat sink, the cooling medium circulation loop and the heat dissipation cold end heat exchanger are included. The magnetic control driven heat sink includes a heat sink body and a speed regulation control circuit. The heat sink body includes a cooling medium flow channel and an electromagnetic driving device; the heat sink body is arranged on the power module, and the power module is heat exchanged and dissipated by the magnetic fluid cooling medium in the cooling medium flow channel; the cooling medium flow channel is divided into two groups of independent cooling medium flow channels flowing through the high heat flow area and the low heat flow area of the power module; the electromagnetic driving device can drive the magnetic fluid cooling medium in the corresponding cooling medium flow channel of the high heat flow area and the low heat flow area to flow at a required speed respectively. The speed regulation control circuit predicts the heat generation and distribution of the power module by monitoring the duty cycle of the PWM control signal sent to the power module and the output power current, collects the current temperature of the power module, and evaluates the heat dissipation requirement of the power module; the electromagnetic driving device is controlled according to the heat dissipation requirement of the power module to adjust the flow speed of the magnetic fluid cooling medium. The cooling medium circulation loop includes corresponding flow pipelines and a cooling medium storage tank; the magnetic control driven heat sink and the heat dissipation cold end heat exchanger are connected to the cooling medium storage tank through the flow pipelines; the magnetic fluid cooling medium circulates in the flow pipelines and the storage tank under the driving of the magnetic control driven heat sink, flows out of the magnetic control driven heat sink after absorbing heat and increasing temperature, flows into the heat dissipation cold end heat exchanger along the flow pipelines, is cooled by heat exchange with the outside in the heat dissipation cold end heat exchanger, and then enters the cooling medium storage tank, and then enters the magnetic control driven heat sink again along the flow pipelines to participate in heat exchange, thereby forming a cooling medium circulation loop.

2. The power module heat sink for high speed aircraft electric actuation system according to claim 1, wherein: The electromagnetic driving device includes excitation coils and cores generating traveling wave magnetic fields, and the excitation coils and cores are arranged on the upper and lower sides of the cooling medium flow channel in the heat sink body; the magnetic fluid cooling medium is driven to move along the direction of the traveling wave magnetic field by applying excitation current to the excitation coils; and the flow speed of the magnetic fluid cooling medium is controlled by changing the frequency of the excitation current.

3. The power module heat sink for high speed aircraft electric actuation system according to claim 1, wherein: The heat dissipation cold end heat exchanger is composed of spiral pipelines coiled on the low-temperature fuel delivery pipeline of the aircraft power system; the magnetic fluid cooling medium heated by the magnetic control driven heat sink flows in the spiral pipelines of the heat dissipation cold end heat exchanger, exchanges heat with the low-temperature fuel of the aircraft, and then enters the cooling medium storage tank after the temperature is sufficiently reduced.

4. The power module heat sink for high speed aircraft electric actuation system according to claim 2, wherein: The heat sink body is attached to the power module for heat dissipation, the power module adopts a half-bridge modulation mode, and presents a high and low heat area state; the electromagnetic driving device includes a high heat flow area electromagnetic driving device and a low heat flow area electromagnetic driving device, which correspond to the high heat area and the low heat area of the power module respectively.

5. The power module heat sink for high speed aircraft electric actuation system according to claim 4, wherein: The excitation coil adopts salient pole winding method and is wound on the salient pole of the core layer by layer to generate independent induction magnetic field along the axial direction of the excitation coil, thereby reducing the influence between the induction magnetic fields generated by adjacent excitation coils; the excitation coils are connected in star shape and are sequentially connected with three-phase alternating current with a phase difference of 120° to generate a traveling wave magnetic field; the excitation coils corresponding to the same position on the upper and lower sides of the cooling medium flow channel in the heat sink body are connected in the same way and are input with respective excitation signals.

6. The power module heat sink for high speed aircraft electric actuation system according to claim 1, wherein: The speed control circuit comprises a controller, a power supply and a driving circuit; the controller monitors the input PWM control signal of the power module and the duty cycle thereof, simultaneously measures the power current output by the power module, and further obtains the predicted heat generation of the power module, so as to determine the heat dissipation capacity required to be provided by the magnetron-driven heat sink; The controller generates a corresponding excitation current driving signal according to the heat dissipation capacity required to be provided by the magnetron-driven heat sink, and adjusts the flow rate of the magnetic fluid cooling medium, so that the magnetron-driven heat sink provides the required heat dissipation capacity.

7. The power module heat sink for high speed aircraft electric actuation system according to claim 6, wherein: The controller adjusts the heat dissipation capacity of the high heat flow area and the low heat flow area according to the non-uniform heat generation distribution of the predicted power module, provides excitation current driving signals with different frequencies to the electromagnetic driving devices in the high heat flow area and the low heat flow area, realizes regional speed control, and further realizes regional heat dissipation.

8. The power module heat sink for high speed aircraft electric actuation system according to claim 7, wherein: The controller also forms a closed-loop feedback system in the form of a feedback signal according to the current actual temperature distribution of the power module monitored in real time, corrects the prediction deviation and suppresses temperature fluctuations.

9. A method for dissipating heat from a power module of an electric servo system of a high-speed aircraft using the device of any one of claims 1 to 8, characterized in that: The method comprises the following steps: Step 1: collecting the duty cycle of the PWM control signal sent to the power module and the output power current information, and predicting the real-time heat generation and heat distribution of the power module; Step 2: according to the real-time heat generation and heat distribution of the power module obtained in step 1, using the corresponding relationship between the heat generation of the power module and the excitation current frequency of the magnetron-driven heat sink, obtaining the required excitation current frequency of each region of the magnetron-driven heat sink; Step 3: by providing excitation current with corresponding frequency to the corresponding electromagnetic driving devices of each region of the magnetron-driven heat sink, the heat dissipation capacity of the magnetron-driven heat sink matches the heat dissipation demand of different regions of the power module; at the same time, the actual temperature at different positions of the power module is taken as a feedback signal to determine whether the temperature of the power module meets the expected temperature interval requirement, if it does, the heat dissipation performance of the magnetron-driven heat sink remains unchanged to maintain temperature balance until the collected PWM control signal or output power current information changes; if not, adjust the excitation current frequency of the corresponding electromagnetic driving device according to the actual temperature value, and then adjust the flow rate of the magnetic fluid cooling medium in the corresponding region to change the heat dissipation performance of the magnetron-driven heat sink, so that the temperature of the power module is maintained in the normal interval.

10. The method of claim 9, wherein: The corresponding relationship between the heat generation of the power module and the excitation current frequency of the magnetron-driven heat sink is obtained by numerical simulation analysis, which specifically adopts the following steps: Step a: build a physical model of the magnetron-driven heat sink body in a multi-physical field simulation software, including a structure model of a traveling wave magnetic field generating device and a heat sink structure model; Step b: Add electromagnetic field and flow field modules in the traveling wave magnetic field generating device structure model and couple them through Lorentz force to obtain a magneto-hydrodynamic coupling model; solve the magneto-hydrodynamic coupling model to obtain the flow velocity of the magnetic fluid cooling medium corresponding to different excitation current frequencies; Step c: After establishing the structure model of the magnetically controlled driving heat sink and power module, perform mesh division, set the numerical solution method, and establish a fluid-solid coupling heat transfer model; Step d: Select several characteristic points in the heat generation range of the power module and set several excitation current frequencies to construct several heat generation characteristic point-excitation current frequency numerical groups; Determine whether each heat generation characteristic point-excitation current frequency numerical group matches through the following process: Step d.1: Obtain the flow velocity of the magnetic fluid cooling medium corresponding to the excitation current frequency by using the magneto-hydrodynamic coupling model established in step b; Step d.2: Take the flow velocity of the magnetic fluid cooling medium obtained in step d.1 as input and convert the heat generation of the characteristic point into a heat flow boundary, solve the temperature of the power module through the fluid-solid coupling heat transfer model, and determine whether the heat generation characteristic point-excitation current frequency numerical group matches according to the temperature; Step e: Fit the matched heat generation characteristic point-excitation current frequency numerical group to obtain the corresponding relationship between the heat generation of the power module and the excitation current frequency of the magnetically controlled driving heat sink.

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