Vehicle passenger compartment thermal management method and system based on fuel cell stack waste heat recovery
By constructing a virtual heat pack queue to simulate the movement and heat dissipation process of coolant in the pipeline, the arrival of future heat is predicted, which solves the problem of heat transfer lag in the thermal management system of fuel cell vehicles and achieves stable cabin temperature and reduced energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO MEIJIN NEW ENERGY VEHICLE MANUFACTURING CO LTD
- Filing Date
- 2026-03-17
- Publication Date
- 2026-05-26
AI Technical Summary
In the thermal management system of fuel cell vehicles, the delay in heat transfer caused by physical pipeline delays leads to large temperature fluctuations in the passenger cabin, affecting passenger comfort and increasing energy consumption.
By constructing a virtual heat pack queue, the movement and heat dissipation process of coolant in the pipeline can be simulated, the arrival of heat in the future can be predicted, and auxiliary heating equipment can be adjusted in advance to eliminate control lag caused by pipeline transmission delay.
It achieves stable temperature control in the cockpit and reduces energy consumption, avoids excessive heat and frequent start-stop of auxiliary heaters, and extends the life of the fuel cell stack.
Smart Images
Figure CN121848889B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of cabin thermal management technology, and in particular to a vehicle passenger cabin thermal management method and system for recovering waste heat from fuel cell stacks. Background Technology
[0002] As an important branch of new energy vehicles, fuel cell vehicles use the electrochemical reaction of hydrogen and oxygen to generate electricity to drive the motor. At the same time, a large amount of heat energy is generated. In low-temperature environments, how to efficiently utilize the waste heat generated by the fuel cell stack to heat the passenger compartment is the key to improving the overall energy efficiency of the vehicle.
[0003] In related technologies, the thermal management system of fuel cell vehicles typically includes a stack cooling circuit and a passenger cabin heating circuit. The stack cooling circuit removes the heat generated by the fuel cell reaction using coolant. When the passenger cabin requires heating, the heat from the coolant is transferred to the heating circuit via a heat exchanger, or the coolant is directly used to exchange heat through the heating element. To ensure heating efficiency, the system typically monitors the coolant temperature at the stack outlet in real time and adjusts the power of the auxiliary electric heater accordingly to compensate for any heat shortage.
[0004] However, due to the long physical pipeline between the fuel cell stack and the passenger compartment heat exchanger, it takes a certain amount of time for the coolant to flow from the stack to the heat exchanger, and this time varies with the pump speed and pipeline length. The high-temperature coolant detected by the sensor at the stack outlet at the current moment cannot immediately act on the passenger compartment. When the stack load suddenly decreases, resulting in a reduction in heat generation, there is a delay in the coolant temperature at the heat exchanger inlet, which is determined by the pipeline volume.
[0005] If control is based solely on the current fuel cell stack outlet temperature or the current passenger compartment requirements, the power adjustment of the auxiliary electric heater will not match the actual heat received. For example, when the fuel cell stack is operating at high power and generating a large amount of heat, due to pipeline transmission delays, the heat may not have reached the passenger compartment yet. The system may misjudge that the heat is insufficient and start the auxiliary electric heater at full power. Once the high-temperature coolant arrives, it will result in excess heat, overshooting of the passenger compartment temperature, and waste of electrical energy.
[0006] The temporal and spatial misalignment between the control process and the actual heat transfer not only leads to large temperature fluctuations in the passenger compartment, affecting passenger comfort, but also causes frequent start-stop and ineffective work of the auxiliary electric heater, affecting the vehicle's driving range. Therefore, it is necessary to combine the waste heat recovery of the fuel cell stack with thermal management of the vehicle's passenger compartment. Summary of the Invention
[0007] To manage the thermal of a vehicle's passenger compartment, this application provides a method and system for managing the thermal of a vehicle's passenger compartment by recovering waste heat from an electric fuel cell stack.
[0008] According to a first aspect of the embodiments of this application, a method for thermal management of a vehicle passenger compartment based on waste heat recovery from a fuel cell stack is provided, comprising: collecting operating parameters of the fuel cell stack and real-time volumetric flow rate of the coolant at a preset sampling period; the operating parameters include the stack output current, average voltage of individual cells, and total number of series-connected cells; calculating the instantaneous heat generation energy of the coolant injected into the stack within the sampling period using the operating parameters based on the first law of thermodynamics and the principle of electrochemical reaction, and constructing a virtual heat pack queue that maps physical pipelines in a storage space; assigning the instantaneous heat generation energy to the virtual heat pack at the entrance position of the virtual heat pack queue, determining the number of movement steps of the virtual heat pack in the queue based on the real-time volumetric flow rate of the coolant, and iteratively updating the energy state of the virtual heat pack in the queue in combination with the environmental heat dissipation coefficient; calculating the total energy at the end of the virtual heat pack queue within a preset future time window, converting the total energy into a power value corresponding to the time dimension, and obtaining the predicted waste heat power reaching the passenger compartment; determining the basic compensation power of the auxiliary electric heater based on the difference between the current heat demand power of the passenger compartment and the predicted waste heat power, so as to use the basic compensation power for thermal management of the vehicle passenger compartment.
[0009] In this way, by constructing a virtual heat pack queue and simulating its movement and heat dissipation process in the pipeline, the fluid heat transport process is digitally reconstructed. This allows for the prediction of the actual heat energy arriving at the heat exchanger in the future, thereby enabling the adjustment of auxiliary heating equipment in advance. This eliminates the control lag caused by the transmission delay of physical pipelines, improves the stability of temperature control, and reduces energy consumption.
[0010] Optionally, the instantaneous heat generation energy of the fuel cell injected with coolant during the sampling period can be calculated using operating parameters, including: determining the instantaneous heat generation energy as the product of the first, second, third, and fourth product terms; the first product term is the total number of individual cells connected in series inside the fuel cell; the second product term is the output current of the fuel cell at the current sampling time; the third product term is the voltage difference, which is equal to the theoretical thermal neutral voltage constant of the electrochemical reaction of the hydrogen fuel cell, minus the average voltage of the individual cells in the fuel cell at the current sampling time; and the fourth product term is the duration of the sampling period.
[0011] Optionally, the number of movement steps of the virtual heat packs in the queue is determined based on the real-time volumetric flow rate of the coolant, including: obtaining the total volume of the pipeline from the fuel cell outlet to the inlet of the crew compartment heat exchanger, and using the ratio of the total pipeline volume to the preset length of the virtual heat pack queue as the physical volume of a single virtual heat pack; using the product of the real-time volumetric flow rate of the coolant and the sampling period as the flow volume of the current period; and rounding the ratio of the flow volume to the physical volume corresponding to a single virtual heat pack to obtain the number of movement steps.
[0012] In this way, by discretizing the continuous fluid into virtual heat packs of fixed volume and converting the flow rate into the number of movement steps, the complex fluid dynamics problem is transformed into a simple queue indexing operation, which reduces the computational load of the embedded controller and ensures the accuracy of heat transfer location updates when the flow rate changes.
[0013] Optionally, the energy state of the virtual hot packs in the queue is iteratively updated in conjunction with the environmental heat dissipation coefficient, including: for each virtual hot pack at a position index in the virtual hot pack queue, determining the thermal energy of the corresponding hot pack at the upstream source position at the previous moment; using the difference between 1 and the heat dissipation factor as the thermal decay coefficient; the numerator of the heat dissipation factor is the product of the natural convection heat transfer coefficient of the pipe wall to the environment, the outer surface area of the pipe micro-element corresponding to a single virtual hot pack, and the sampling period duration; the denominator of the heat dissipation factor is the product of the specific heat capacity of the coolant, the density of the coolant, and the physical volume corresponding to a single virtual hot pack; multiplying the thermal energy of the corresponding hot pack at the upstream source position at the previous moment with the thermal decay coefficient to obtain the thermal energy of the virtual hot pack at the current position index.
[0014] In this way, the heat exchange between the pipe wall and the environment is considered while simulating the movement of the heat pack, and the energy value of the heat pack is dynamically corrected, so that it can adapt to different ambient temperature conditions, avoid overestimating the waste heat power due to ignoring heat dissipation along the path, and further improve the control accuracy.
[0015] Optionally, the total energy is converted into a power value corresponding to the time dimension to obtain the predicted waste heat power reaching the cabin, including: determining the end data segment in the virtual heat pack queue corresponding to a future preset time window, the end data segment containing multiple consecutive virtual heat packs; accumulating the current energy values of all virtual heat packs in the end data segment to obtain the total energy; dividing the total energy by the duration of the future preset time window, and multiplying the obtained quotient by the heat exchange efficiency coefficient of the heat exchanger to obtain the predicted waste heat power.
[0016] Optionally, thermal management of the vehicle's passenger compartment is performed using the base compensation power, including: determining a dynamic smoothing factor to characterize the severity of load fluctuations in the fuel cell stack, multiplying the base compensation power by the dynamic smoothing factor to obtain the target operating power of the auxiliary electric heater, and controlling the auxiliary electric heater to operate at the target operating power.
[0017] In this way, the introduction of a dynamic smoothing factor can smooth the heating power under the condition of drastic fluctuations in the stack load, avoid frequent power jumps in the heater due to overly sensitive feedforward control, and extend the service life of power devices.
[0018] Optionally, the dynamic smoothing factor is determined as follows: the difference between the current output current of the fuel cell and the previous output current is divided by the sampling period to obtain the current change rate; the square of the current change rate is multiplied by a preset sensitivity coefficient to obtain the fluctuation impact term; a preset positive number is added to the fluctuation impact term to obtain the target denominator term; and the reciprocal of the target denominator term is used as the dynamic smoothing factor.
[0019] Optionally, the method further includes: after detecting the off signal of the vehicle's ignition switch, traversing all valid positions of the virtual heat packs in the virtual heat pack queue, and accumulating the energy values of the virtual heat packs to obtain the total residual heat energy value; if the total residual heat energy value is greater than a preset energy threshold, controlling the electronic water pump to operate in low power mode and turning on the air conditioning blower until the water temperature at the heat exchanger inlet is lower than the safe temperature threshold.
[0020] In this way, the high-temperature coolant remaining in the pipeline can be fully utilized for a final round of heating or cooling after the vehicle is turned off, which protects the components of the vehicle system and maximizes the use of residual heat.
[0021] Optionally, the method further includes: controlling the cooling circuit to enter a small circulation mode and forcibly turning on the auxiliary electric heater before the ambient temperature is lower than a preset cold start threshold and the vehicle is started; calculating the estimated arrival time required for the hot fluid to be transferred from the outlet of the auxiliary electric heater to the inlet of the fuel cell stack based on the current fluid flow rate; and adjusting the output power of the auxiliary electric heater in advance according to the allowable temperature rise rate limit of the fuel cell stack inlet before the arrival time ends.
[0022] In this way, by using the same set of virtual heat pack transmission principles in reverse, the time and temperature of the heated coolant reaching the fuel cell stack can be precisely controlled during the cold start phase, preventing thermal shock from damaging the internal membrane electrodes of the fuel cell stack and extending the fuel cell stack life.
[0023] According to a second aspect of the present application, a vehicle passenger compartment thermal management system for recovering waste heat from fuel cell stacks is provided, comprising: a processor and a memory, wherein the memory stores computer program instructions, and the computer program instructions, when executed by the processor, implement the steps of the vehicle passenger compartment thermal management method for recovering waste heat from fuel cell stacks provided in the first aspect of the present application.
[0024] The technical solutions provided by the embodiments of this application may include the following beneficial effects: by constructing a virtual heat pack queue and simulating the movement and heat dissipation process of the virtual heat pack in the pipeline, the digital reconstruction of the fluid heat transport process is realized, which can predict the actual heat energy arriving at the heat exchanger in the future, thereby adjusting the auxiliary heating equipment in advance, eliminating the control lag caused by the transmission delay of the physical pipeline, improving the stability of temperature control and reducing energy consumption, and effectively realizing the thermal management of the vehicle's passenger compartment while recovering the waste heat of the fuel cell stack.
[0025] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0026] Figure 1 This is a flowchart illustrating a vehicle passenger compartment thermal management method for recovering waste heat from fuel cell stacks, according to an exemplary embodiment.
[0027] Figure 2 This is a schematic diagram of the stack load current variation of the fuel cell in the embodiments of this application;
[0028] Figure 3 This is a schematic diagram comparing the power response of the embodiments of this application with that of the prior art under conditions of sudden load increase;
[0029] Figure 4 This is a schematic diagram illustrating the structure of a vehicle passenger compartment thermal management system for recovering waste heat from an electric fuel cell stack, according to an exemplary embodiment. Detailed Implementation
[0030] To manage the thermal performance of a vehicle's passenger compartment, embodiments of this application provide a method and system for managing the vehicle's passenger compartment by recovering waste heat from an electric fuel cell stack. Figure 1 This is a flowchart illustrating a vehicle passenger compartment thermal management method for recovering waste heat from a fuel cell stack, according to an exemplary embodiment. Figure 1 As shown, the method includes the following steps.
[0031] In step S101, the operating parameters of the fuel cell stack and the real-time volumetric flow rate of the coolant are collected at a preset sampling period.
[0032] Operating parameters include stack output current, average voltage of individual cells, and total number of cells in series. Data acquisition mainly relies on the controller local area network bus communication between the vehicle controller and the fuel cell control unit. The preset sampling period can be set, for example, between 0.1 seconds and 0.5 seconds.
[0033] The output current of the fuel cell stack can be acquired by a high-precision Hall current sensor connected in series in the high-voltage DC output circuit of the fuel cell stack. The average voltage data of each cell comes from the fuel cell stack inspection controller. The fuel cell stack inspection controller monitors the voltage of hundreds of individual cells inside the fuel cell stack in real time, calculates their arithmetic average, and sends it to the bus. The total number of cells connected in series is a fixed parameter, which is usually stored in memory.
[0034] The real-time volumetric flow rate of the coolant can be directly measured by a turbine flow meter or electromagnetic flow meter installed on the main circuit, or estimated by looking up a table based on the pressure-flow characteristic curve of the water pump by collecting the real-time speed, operating current and inlet-outlet pressure difference of the electronic water pump.
[0035] As an electrochemical reaction device, fuel cells have extremely high transient response speed in their heat generation characteristics. When a vehicle driver presses the accelerator pedal, the current of the fuel cell stack can change drastically within milliseconds, causing the heat generation of the fuel cell to rise rapidly in a short period of time.
[0036] In step S102, based on the first law of thermodynamics and the principle of electrochemical reaction, the instantaneous heat generation energy of the fuel cell injected with coolant during the sampling period is calculated using operating parameters, and a virtual heat pack queue mapping the physical pipeline is constructed in the storage space.
[0037] In one embodiment, calculating the instantaneous heat generation energy of the fuel cell injected with coolant during the sampling period using operating parameters includes: determining the instantaneous heat generation energy as the product of a first product term, a second product term, a third product term, and a fourth product term; the first product term is the total number of individual cells connected in series within the fuel cell stack; the second product term is the output current of the fuel cell stack at the current sampling time; the third product term is the voltage difference, which is equal to the theoretical thermal neutral voltage constant of the electrochemical reaction of the hydrogen fuel cell, minus the average voltage of the individual cells in the fuel cell stack at the current sampling time; and the fourth product term is the duration of the sampling period.
[0038] The formula for calculating heat production energy is: ,in, Indicates the sampling period The total heat energy generated by the internal fuel cell stack, measured in joules; This represents the total number of batteries connected in series. This refers to the output current of the fuel cell stack. The theoretical thermally neutral voltage constant is, for example, 1.48 volts for a standard proton exchange membrane fuel cell when the product is liquid water. t represents the average voltage of a single cell, and t represents the duration of the sampling period.
[0039] For example, when 350, current 200 amps, single-unit voltage The voltage is 0.65 volts, and the sampling period is... When the sampling period is 0.1 seconds, the heat energy generated during the sampling period is joule.
[0040] Based on the law of conservation of energy, the chemical energy of the hydrogen consumed by a fuel cell is derived from... This indicates that a portion of this energy is converted into electrical energy. The remaining portion is converted into heat energy.
[0041] Traditional calorimetry based on inlet and outlet temperature difference and flow rate has a lag. The specific heat capacity of coolant is very large and the temperature sensor itself has a heat capacity, which causes the measured temperature difference change to often lag behind the actual heat generation change by several seconds or even several minutes. The delay of calculating the heat generation through electrical parameters is even lower. It can calculate the exact energy value of the injected water flow before the heat causes the water temperature to rise, and achieve heat source sensing with a lower delay.
[0042] In one embodiment, a virtual hot pack queue that maps to the physical piping is constructed by initializing a fixed-length one-dimensional array or doubly linked list in the microcontroller's random access memory. This queue simulates the physical piping from the fuel cell stack outlet to the inlet of the cabin heater core heat exchanger.
[0043] Total length of the queue The number of nodes is set according to the physical size of the pipeline and the required calculation accuracy. For example, it can be set to 1000 nodes. Each node, or virtual heat pack, represents a small fluid element in the pipeline. The head of the queue, i.e., the position with index 0, corresponds to the fuel cell outlet, and the tail of the queue, i.e., the position with index 999, corresponds to the heat exchanger inlet. Each node stores the current thermal energy value and the corresponding temperature value carried by the fluid segment.
[0044] Discretizing a continuous fluid into a series of independent fluid packets using the Lagrange method simplifies complex fluid dynamics problems into a queue shifting operation, a mature technique in computer science. This reduces algorithm complexity and allows the solution to run on low-cost embedded controllers.
[0045] In step S103, the instantaneous heat generation energy is assigned to the virtual heat pack at the entrance of the virtual heat pack queue. The number of movement steps of the virtual heat pack in the queue is determined according to the real-time volumetric flow rate of the coolant. The energy state of the virtual heat pack in the queue is iteratively updated in combination with the environmental heat dissipation coefficient.
[0046] In one embodiment, determining the number of movement steps for virtual heat packs in the queue based on the real-time volumetric flow rate of the coolant includes: obtaining the total volume of the pipeline from the fuel cell outlet to the inlet of the crew compartment heat exchanger, and using the ratio of the total pipeline volume to the preset length of the virtual heat pack queue as the physical volume of a single virtual heat pack; multiplying the real-time volumetric flow rate of the coolant by the sampling period as the flow volume of the current period; and rounding the ratio of the flow volume to the physical volume corresponding to a single virtual heat pack to obtain the number of movement steps.
[0047] It can measure the total volume of physical pipelines. For example, 15 liters, queue length For example, if it is 1000, then the physical volume represented by a single virtual heat pack Increase; in the current sampling period Within 0.1 seconds, if the traffic If the flow rate is 60 liters per minute, or 1 liter per second, then the volume flowing through is... Increase, number of steps moved Calculated as Rounding to the nearest integer results in 7 steps.
[0048] In the current computation cycle, all data in the queue needs to be shifted 7 index positions backward. The 7 empty positions at the head of the queue will be used to calculate the instantaneous heat generation energy. If the heat generation energy is 5810 joules, then the energy will be evenly distributed among these 7 new heat packs, with each heat pack carrying approximately 830 joules.
[0049] The flow rate of vehicle coolant changes dynamically with the water pump speed and flow resistance. When flowing at high speed, heat transfer is fast, and the virtual heat pack should move backward quickly; when flowing at low speed or idling speed, heat transfer is slow, and the number of steps the heat pack moves is reduced.
[0050] By dynamically mapping flow rate into steps, the position of the hot water in the virtual queue is always synchronized with the position of the hot water in the real pipeline, regardless of the vehicle's operating conditions, thus solving the problem of transmission delay under variable flow rate.
[0051] In one embodiment, the energy state of virtual hot packs in the queue is iteratively updated in conjunction with the environmental heat dissipation coefficient, including: for each virtual hot pack at a position index in the virtual hot pack queue, determining the thermal energy of the corresponding hot pack at the upstream source position at the previous moment; using the difference between 1 and the heat dissipation factor as the thermal decay coefficient; the numerator of the heat dissipation factor is the product of the natural convection heat transfer coefficient of the pipe wall to the environment, the outer surface area of the pipe micro-element corresponding to a single virtual hot pack, and the sampling period duration; the denominator of the heat dissipation factor is the product of the specific heat capacity of the coolant, the density of the coolant, and the physical volume corresponding to a single virtual hot pack; multiplying the thermal energy of the corresponding hot pack at the upstream source position at the previous moment with the thermal decay coefficient to obtain the thermal energy of the virtual hot pack at the current position index.
[0052] During the heat transfer process, the pipe walls dissipate heat to the low-temperature environment. For the first [unit / item] in the queue... A hot pack, whose energy update expression is: ,in, For the updated current energy, This refers to the energy of the heat pack before it moved, i.e., at the previous moment. The overall heat transfer coefficient is positively correlated with vehicle speed; for example, the faster the vehicle speed, the stronger the air-cooling effect and the faster the heat dissipation. This represents the tube wall surface area corresponding to a single heat pack. This refers to the specific heat capacity of the coolant. The value is the density, and the term in parentheses is the thermal decay coefficient, which is usually less than 1.
[0053] The heat dissipation of the pipeline is not negligible in long-distance transmission, and the heat dissipation rate is greatly affected by ambient temperature and vehicle speed. If this physical process is ignored, the model predicts that the heat reaching the passenger compartment will be significantly higher than the actual value, causing the controller to reduce the auxiliary heating power, ultimately making the user feel cold.
[0054] By using a discretized Newton's law of cooling model, the corresponding heat loss is deducted in each step of the movement, which improves the physical fidelity of the model and ensures that the final predicted power is the net power after environmental correction, thus guaranteeing the accuracy of control.
[0055] In step S104, the total energy at the end of the virtual heat pack queue within a future preset time window is calculated, and the total energy is converted into a power value corresponding to the time dimension to obtain the predicted waste heat power reaching the passenger compartment. Based on the difference between the current heat demand power of the passenger compartment and the predicted waste heat power, the basic compensation power of the auxiliary electric heater is determined so as to use the basic compensation power for thermal management of the vehicle passenger compartment.
[0056] In one embodiment, converting the total energy into a power value corresponding to the time dimension to obtain the predicted waste heat power reaching the passenger cabin includes: determining the end data segment in the virtual heat pack queue corresponding to a future preset time window, the end data segment containing multiple consecutive virtual heat packs; accumulating the current energy values of all virtual heat packs in the end data segment to obtain the total energy; dividing the total energy by the duration of the future preset time window, and multiplying the obtained quotient by the heat exchange efficiency coefficient of the heat exchanger to obtain the predicted waste heat power.
[0057] Suppose a vehicle needs to predict available heat over the next 5 seconds. Based on the current flow rate, assuming it moves 7 steps every 0.1 seconds, the next 5 seconds (50 cycles) correspond to the end of the queue. The total energy is obtained by summing the energy values of these 350 heat packs that are about to leave the queue and flow into the heat exchanger. For example, 150,000 joules, then the average power Watts. Considering heat exchanger efficiency. For example, with a value of 0.9, the final predicted power is 27,000 watts.
[0058] The regulation of the auxiliary electric heater and blower of the controlled object should not be based on instantaneous pulses, but on the average energy supply over a period of time. The integration of the time window reflects the macroscopic trend of energy flow, and it can be clearly seen that a huge heat flow will arrive within the next 5 seconds. Therefore, it is not necessary to turn on the auxiliary heating at full power, thus avoiding overshoot and waste.
[0059] The current thermal demand power of the passenger cabin is calculated by the air conditioning main control logic. Its inputs include the target temperature set by the user, the actual temperature measured by the in-vehicle sensors, and the ambient temperature. The control algorithm usually adopts proportional-integral-derivative control.
[0060] For example, the control algorithm output shows that 10,000 watts of heating power is needed to maintain the interior temperature at 22 degrees Celsius. If the predicted waste heat power is 8,000 watts, then the difference of 2,000 watts is the basic compensation power that the auxiliary electric heater should bear.
[0061] Thermal management of the vehicle's passenger compartment using base compensation power includes: determining a dynamic smoothing factor to characterize the severity of load fluctuations in the fuel cell stack; multiplying the base compensation power by the dynamic smoothing factor to obtain the target operating power of the auxiliary electric heater; and controlling the auxiliary electric heater to operate at the target operating power.
[0062] In one embodiment, the dynamic smoothing factor is determined as follows: the difference between the current output current of the fuel cell and the previous output current is divided by the sampling period to obtain the current change rate; the square of the current change rate is multiplied by a preset sensitivity coefficient to obtain the fluctuation impact term; a preset positive number is added to the fluctuation impact term to obtain the target denominator term; and the reciprocal of the target denominator term is used as the dynamic smoothing factor.
[0063] Dynamic smoothing factor The formula for calculation is: ,in The sensitivity coefficient is a preset positive constant used to adjust the sensitivity to volatility. The current at the current moment; The current at the previous moment.
[0064] When the fuel cell stack is operating in steady state, the rate of change of current is close to 0, and the denominator is close to 1. When the value is close to 1, the auxiliary electric heater outputs power exactly according to the predicted difference, responding quickly. However, when the fuel cell stack is under severe load conditions, such as rapid acceleration with a very high rate of change in current, the denominator increases rapidly, leading to... As the power approaches zero, the target power of the auxiliary electric heater is forcibly reduced.
[0065] Although the feedforward control has a fast response, the predicted waste heat power will also fluctuate drastically when the fuel cell stack fluctuates violently. If the high-voltage auxiliary electric heater is adjusted to follow this violent fluctuation, for example, by jumping from 0 watts to 5000 watts and then back to 0 watts, it will cause arc erosion of the high-voltage relay contacts, shortening the hardware life, and at the same time cause ripple jitter of the high-voltage bus voltage of the whole vehicle.
[0066] By introducing a suppression factor based on the rate of change of current, the operation of the auxiliary electric heater is temporarily frozen or smoothed when the operating conditions change drastically, and precise compensation is performed after the operating conditions stabilize. While ensuring the accuracy of thermal management, the health management of the high-voltage electrical system is also taken into account, achieving a balance between control performance and hardware lifespan.
[0067] Figure 2 This is a schematic diagram of the stack load current variation of the fuel cell in an embodiment of this application, as shown below. Figure 2 As shown, under exemplary operating conditions, the vehicle maintains low-load idling speed for 0 to 20 seconds; in the range of 20 to 50 seconds, the vehicle is in a rapid acceleration or hill-climbing condition, and the fuel cell current rises nonlinearly and rapidly to 300A; after 50 seconds, it maintains a higher power steady-state operation.
[0068] Figure 3 This is a comparative diagram of the power response of the embodiments of this application and the prior art under conditions of sudden load increase, as shown in the figure. Figure 3 As shown, with the target thermal demand power of the cabin remaining constant, the arrival time of residual heat lags behind the change in the fuel cell load current due to pipeline transmission delay.
[0069] When existing technologies, such as traditional feedback control, are used to adjust the heating power of PTC, the reliance on feedback from the outlet water temperature sensor makes it impossible to detect heat waves that are already in the pipeline but have not yet arrived. This results in the PTC still operating at full power when a large amount of waste heat is entering, causing the total power to exceed the limit, leading to cabin temperature overshoot and energy waste.
[0070] like Figure 3 As shown, the vehicle passenger compartment thermal management method for recovering waste heat from fuel cell stacks provided in this application embodiment uses data from a virtual heat pack queue to predict the rising trend of waste heat in advance. Before the waste heat actually arrives, the power of the PTC can be actively reduced. The immediacy of the electrical energy response can effectively compensate for the lag in heat transfer, ensuring constant cabin heating while avoiding potential overheating.
[0071] In one embodiment, after detecting the off signal of the vehicle's ignition switch, the system can traverse all valid virtual heat packs in the virtual heat pack queue and accumulate the energy values of the virtual heat packs to obtain the total residual heat energy value. If the total residual heat energy value is greater than the preset energy threshold, the system controls the electronic water pump to operate in low-power mode and turns on the air conditioning blower until the water temperature at the heat exchanger inlet is lower than the safe temperature threshold.
[0072] When the driver presses the stop button and the vehicle enters the power-off process, although the fuel cell stack stops reacting, a large amount of high-temperature coolant remains in the pipes and fuel cell stack itself. The vehicle system does not immediately cut off the power, but instead scans the virtual hot pack queue in memory.
[0073] If the total residual heat energy displayed in the queue exceeds, for example, 500 kJ, it indicates that there is considerable heat hidden in the pipeline. The water pump can be controlled to maintain a low speed, for example, 10 liters per minute, and the warm air blower can be kept on.
[0074] When a fuel cell shuts down, a large amount of high-temperature coolant may still remain in the pipeline. If the pump is stopped directly, the local high temperature may damage the seals. By calculating the total residual heat energy, it can be intelligently determined whether it is necessary to perform a post-blowing operation, thus preventing the heat immersion effect after the fuel cell stack is shut down, i.e., the local boiling or overheating damage to the membrane electrode caused by the cessation of coolant flow. The generated heat is fully utilized to provide continuous warm air for passengers as they leave the vehicle, or to maintain the cabin temperature in the early stages of vehicle parking and delay frost formation, which not only improves the safety of the system but also maximizes the energy utilization efficiency.
[0075] In one embodiment, the cooling circuit can be controlled to enter a small circulation mode and the auxiliary electric heater can be forcibly turned on before the ambient temperature is lower than the preset cold start threshold and the vehicle is started; the estimated arrival time required for the hot fluid to be transferred from the outlet of the auxiliary electric heater to the inlet of the fuel cell stack can be calculated in reverse according to the current fluid flow rate; and the output power of the auxiliary electric heater can be adjusted in advance according to the allowable temperature rise rate limit of the fuel cell stack inlet before the arrival time ends.
[0076] In extremely cold startup scenarios, such as -30 degrees Celsius, the fuel cell stack requires an external heat source for preheating. At this time, the auxiliary electric heater serves as the heat source, and the heat is transferred to the fuel cell stack through pipelines. By using the same virtual queue principle as the previous steps and reversing the flow definition, it is possible to accurately calculate when the first wave of hot water heated by the auxiliary electric heater will arrive at the fuel cell stack inlet.
[0077] Assuming the calculated arrival time is 20 seconds and the maximum allowable temperature rise rate of the fuel cell stack is 5 degrees Celsius per minute, the power of the auxiliary electric heater can be linearly reduced starting at the 15th second.
[0078] Thermal shock during cold start is one of the main causes of fuel cell lifespan degradation. If cooling only begins when hot water contacts the inlet sensor of the fuel cell stack, the huge temperature difference will cause the membrane electrode material to crack due to uneven thermal expansion and contraction. By using a virtual heat pack transfer model to predict arrival time, the auxiliary electric heater can be proactively adjusted, ensuring that the fuel cell stack does not exceed the safety boundary while heating up rapidly, thus extending the service life of the fuel cell stack.
[0079] Figure 4 This is a schematic diagram illustrating the structure of a vehicle passenger compartment thermal management system 1000 for recovering waste heat from an electric fuel cell stack, according to an exemplary embodiment. (Refer to...) Figure 4The vehicle passenger compartment thermal management system 1000 for recovering waste heat from fuel cell stacks includes a processor 1100 and a memory 1200. The memory 1200 stores computer program instructions, which, when executed by the processor 1100, implement all or part of the steps of the vehicle passenger compartment thermal management method for recovering waste heat from fuel cell stacks in this application.
[0080] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.
[0081] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.
Claims
1. A method for thermal management of a vehicle's passenger compartment based on waste heat recovery from an electric fuel cell stack, characterized in that, include: The operating parameters of the fuel cell stack and the real-time volumetric flow rate of the coolant are collected at a preset sampling period. Operating parameters include stack output current, average voltage of individual cells, and total number of cells in series; Based on the first law of thermodynamics and the principle of electrochemical reaction, the instantaneous heat generation energy of the fuel cell injected with coolant during the sampling period is calculated using operating parameters, and a virtual heat pack queue mapping the physical pipeline is constructed in the storage space. The instantaneous heat generation energy is assigned to the virtual heat pack at the entrance of the virtual heat pack queue. The number of steps the virtual heat pack moves in the queue is determined based on the real-time volumetric flow rate of the coolant. The energy state of the virtual heat pack in the queue is iteratively updated in combination with the environmental heat dissipation coefficient. The total energy at the end of the virtual heat pack queue within a preset future time window is calculated, and the total energy is converted into a power value corresponding to the time dimension to obtain the predicted waste heat power reaching the passenger cabin. Based on the difference between the current heat demand power of the passenger cabin and the predicted waste heat power, the basic compensation power of the auxiliary electric heater is determined so as to utilize the basic compensation power for thermal management of the vehicle passenger cabin.
2. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, The instantaneous heat generation energy generated by the injected coolant in the fuel cell stack during the sampling period is calculated using operating parameters, including: The instantaneous heat generation energy is determined as the product of the first, second, third, and fourth product terms; the first product term is the total number of individual cells connected in series within the fuel cell stack; the second product term is the output current of the fuel cell stack at the current sampling time; the third product term is the voltage difference, which is equal to the theoretical thermal neutral voltage constant of the electrochemical reaction of the hydrogen fuel cell, minus the average voltage of the individual cells in the fuel cell stack at the current sampling time; the fourth product term is the duration of the sampling period.
3. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, The number of steps to move for the virtual heat pack in the queue is determined based on the real-time volumetric flow rate of the coolant, including: Obtain the total volume of the piping from the fuel cell stack outlet to the inlet of the cockpit heat exchanger, and use the ratio of the total piping volume to the preset length of the virtual heat pack queue as the physical volume of a single virtual heat pack. The product of the real-time volumetric flow rate of the coolant and the sampling period is used as the flow volume of the current period; the ratio of the flow volume to the physical volume corresponding to a single virtual heat pack is rounded to obtain the number of movement steps.
4. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, The energy state of virtual hot packets in the queue is iteratively updated based on the environmental heat dissipation coefficient, including: For each virtual hot packet at a location index in the virtual hot packet queue, determine the thermal energy of the corresponding hot packet at the upstream source location at the previous time step of the location index. The difference between 1 and the heat dissipation factor is used as the thermal attenuation coefficient; the numerator of the heat dissipation factor is the product of the natural convection heat transfer coefficient of the pipe wall to the environment, the outer surface area of the pipe micro-element corresponding to a single virtual heat pack, and the sampling period; the denominator of the heat dissipation factor is the product of the specific heat capacity of the coolant, the density of the coolant, and the physical volume corresponding to a single virtual heat pack. Multiply the thermal energy of the corresponding heat pack located at the upstream source position at the previous moment by the thermal attenuation coefficient to obtain the thermal energy of the virtual heat pack located at the current position index.
5. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, The total energy is converted into a power value corresponding to the time dimension to obtain the predicted residual heat power reaching the passenger cabin, including: Determine the end data segment in the virtual hot packet queue corresponding to a future preset time window. The end data segment contains multiple consecutive virtual hot packets. Accumulate the current energy values of all virtual hot packets in the end data segment to obtain the total energy. The predicted waste heat power is obtained by dividing the total energy by the duration of a future preset time window and multiplying the quotient by the heat exchanger's heat exchange efficiency coefficient.
6. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, Thermal management of the vehicle's passenger compartment using base compensation power includes: A dynamic smoothing factor is determined to characterize the severity of load fluctuations in the fuel cell stack. The base compensation power is multiplied by the dynamic smoothing factor to obtain the target operating power of the auxiliary electric heater, and the auxiliary electric heater is controlled to operate at the target operating power.
7. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 6, characterized in that, The dynamic smoothing factor is determined in the following way: The difference between the current output current of the fuel cell stack and the output current of the fuel cell stack at the current moment is divided by the sampling period to obtain the current change rate. The square of the current change rate is multiplied by the preset sensitivity coefficient to obtain the fluctuation effect term. The preset positive number is added to the fluctuation effect term to obtain the target denominator term. The reciprocal of the target denominator term is used as the dynamic smoothing factor.
8. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, The method further includes: After detecting the off signal of the vehicle's ignition switch, iterate through all the virtual hot packs in the virtual hot pack queue at all valid positions, and accumulate the energy values of the virtual hot packs to obtain the total residual heat energy. If the total residual heat energy exceeds the preset energy threshold, the electronic water pump will be controlled to operate in low power mode, and the air conditioner blower will be turned on until the water temperature at the heat exchanger inlet is lower than the safe temperature threshold.
9. The vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to claim 1, characterized in that, The method further includes: When the ambient temperature is below the preset cold start threshold and the vehicle is started, the control cooling circuit enters the small circulation mode and the auxiliary electric heater is forcibly turned on. The estimated arrival time required for the hot fluid to travel from the auxiliary electric heater outlet to the stack inlet is calculated in reverse based on the current fluid flow rate; the output power of the auxiliary electric heater is adjusted in advance according to the allowable temperature rise rate limit at the stack inlet before the arrival time ends.
10. A vehicle passenger compartment thermal management system for recovering waste heat from fuel cell stacks, characterized in that, include: A processor and a memory, the memory storing computer program instructions that, when executed by the processor, implement the vehicle passenger compartment thermal management method for waste heat recovery from fuel cell stacks according to any one of claims 1-9.