CN116331494A - Air-conditioning system with double evaporators for electric aircraft and control method thereof - Google Patents

Abstract

The invention relates to an electric aircraft double evaporator air conditioning system and its control method in the technical field of aircraft temperature control. Expansion valve, a number of temperature sensors and pressure sensors, as well as pipelines and accessories connecting these devices, etc., the present invention confirms that the evaporator outlet is The physical state of the refrigerant. Compared with the target set state point, by adjusting the corresponding evaporator fan speed or expansion valve or compressor speed, the refrigerant state at the outlet of the evaporator is in the best state, so that the cooling effect of the entire system is the best and the energy consumption is the lowest .

Description

Air-conditioning system with double evaporators for electric aircraft and control method thereof

technical field

The invention relates to the technical field of aircraft temperature control, in particular to an electric aircraft double evaporator air conditioning system and a control method thereof.

Background technique

An air conditioning system needs to be installed on the electric vertical take-off and landing aircraft to meet airworthiness requirements and ventilate the passenger compartment. At the same time, the temperature in the cabin can be adjusted to improve the comfort of the occupants. The power source of the electric aircraft comes from the power battery. The power battery will generate a lot of heat when charging and discharging. If the battery temperature is too high, it will affect the safety of the battery. For safety reasons, the battery needs to be cooled. The battery can be cooled by the air conditioning system.

In the prior art, the air-conditioning system used for aircraft has the following problems: First, when the air-conditioning system must not only cool the passenger cabin, but also cool the battery and other equipment, the overall operating power of the air-conditioning system is required to be relatively high , the power consumption increases and the weight of the system increases, which has a significant impact on the range and load of the electric aircraft; second, the operating status of the evaporator in the air conditioning system is difficult to grasp, and the cooling effect of the evaporator is poor or excessive cooling.

Contents of the invention

In order to solve the disadvantages of the air-conditioning system applied to electric aircraft in the prior art, the present invention discloses an electric aircraft double-evaporator air-conditioning system and its control method. The technical solution of the present invention is implemented as follows:

An electric aircraft double evaporator air conditioning system, comprising a compressor, a condenser, a condenser fan, a first evaporator, a second evaporator, an evaporator fan, a first expansion valve, a second expansion valve and a liquid storage tank; Including first temperature sensor, second temperature sensor, third temperature sensor, fourth temperature sensor, fifth temperature sensor, sixth temperature sensor, seventh temperature sensor, first pressure sensor, second pressure sensor, third pressure sensor , the fourth pressure sensor and the fifth pressure sensor;

The first temperature sensor and the first pressure sensor are arranged at the inlet of the compressor, the second temperature sensor and the second pressure sensor are arranged at the outlet of the compressor, and the sixth temperature sensor is arranged at the air outlet of the condenser. Inlet, the seventh temperature sensor is set at the outlet of the condenser fan, the third temperature sensor and the third pressure sensor are set at the condensate outlet of the condenser, the fourth temperature sensor and the fourth pressure sensor are set at the condensate of the first evaporator Outlet, the fifth temperature sensor and the fifth pressure sensor are arranged at the condensate outlet of the second evaporator.

A control method for an air-conditioning system with double evaporators for an electric aircraft, comprising the following steps: S1, setting the operating phase of the aircraft in the system;

S2. Set the cooling output state of the air conditioning system in each operating stage of the aircraft;

S3, system operation;

S4, the air conditioning system controls the output of the first evaporator and the second evaporator according to each stage of the aircraft;

S5. Each temperature sensor and pressure sensor collects the operation status of each link of the air conditioning system in real time;

S6. The air conditioning system compensates the outputs of the first evaporator and the second evaporator according to the data in S5.

Preferably, in the S1 step, the operating phases of the aircraft include a charging phase, a ground operation phase, a take-off phase, a cruising phase and a landing phase.

Preferably, in the step S2, the cooling output state of the air-conditioning system includes the output ratio of the first evaporator and the second evaporator, and the output priority of the first evaporator and the second evaporator.

Preferably, in the method, the air conditioning system detects the battery temperature and cabin temperature of the aircraft in real time; and adjusts the output of the first evaporator or the second evaporator based on the temperature of the battery or the cabin temperature combined with the operating phase of the aircraft.

Preferably, the normal operating temperature range, the critical temperature operating range and the overheating limit of the battery are set;

When the temperature of the battery is within the normal operating temperature range, there is no need to cool down the battery;

When the temperature of the battery is within the critical temperature operating range, the air conditioning system controls the first evaporator or the second evaporator to cool down the battery;

When the temperature of the battery exceeds the overheat limit, the air conditioning system sends an alarm signal to the system.

Preferably, the normal operating temperature range and critical limits of the cockpit are set;

When the temperature in the cabin is within the normal operating temperature range, there is no need to cool down the cabin;

When the temperature in the cabin exceeds the critical limit, the air conditioning system controls the first evaporator or the second evaporator to cool down the cabin.

Preferably, when the air-conditioning system is cooling the cabin, if the temperature of the battery cannot be lowered to the critical temperature operating range, the cooling of the cabin is stopped.

Preferably, in the step S5, the fourth pressure sensor and the fourth temperature sensor monitor the state of the refrigerant at the outlet of the first evaporator, and the fifth pressure sensor and the fifth temperature sensor monitor the state of the refrigerant at the outlet of the second evaporator ;

In the step S6, the air conditioning system calculates the degree of superheat of the first evaporator or the second evaporator under the current operating state according to the state of the refrigerant at the outlet of the first evaporator or the second evaporator, and compares it with the expected value of the degree of superheat, By adjusting the opening degree of the first expansion valve or the second expansion valve, the superheat degree of the first evaporator or the second evaporator is adjusted to a desired superheat degree value.

The advantages of the present invention are as follows:

1. Through the cooling capacity requirements, operating status, operating phase, safety level and operating characteristics of electric aircraft of different user systems, the operation of the air-conditioning system is managed in an overall manner, so that the operating power consumption of the air-conditioning system is always kept at the minimum. excellent level. Thereby, the overall weight and energy consumption level of the air conditioning system can be reduced, and the flight range and effective load of the aircraft can be improved.

2. By monitoring the state of the refrigerant at the outlet of the first evaporator and the second evaporator, combined with the pressure-enthalpy characteristic diagram of the refrigerant, confirm the physical state of the refrigerant at the outlet of the evaporator. Compared with the target set state point, by adjusting the corresponding evaporator fan speed or expansion valve or compressor speed, the refrigerant state at the outlet of the evaporator is in the best state, so that the cooling effect of the entire system is the best and the energy consumption is the lowest .

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings based on these drawings without any creative work.

Fig. 1 is a schematic structural diagram of an embodiment of an electric aircraft double evaporator air conditioning system;

Fig. 2 is a schematic diagram of the pressure-enthalpy diagram of the refrigerant in an embodiment of the double evaporator air-conditioning system of an electric aircraft;

Fig. 3 is a flow chart of an embodiment of a control method for an electric aircraft double evaporator air conditioning system.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the accompanying drawings. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example

In a specific embodiment, an electric aircraft double evaporator air conditioning system includes a compressor, a condenser, a condenser fan, a first evaporator, a second evaporator, an evaporator fan, a first expansion valve, a second 2. expansion valve, liquid storage tank, pump, first temperature sensor, second temperature sensor, third temperature sensor, fourth temperature sensor, fifth temperature sensor, sixth temperature sensor, seventh temperature sensor, first pressure sensor, a second pressure sensor, a third pressure sensor, a fourth pressure sensor and a fifth pressure sensor;

The first temperature sensor and the first pressure sensor are arranged at the inlet of the compressor, the second temperature sensor and the second pressure sensor are arranged at the outlet of the compressor, and the sixth temperature sensor is arranged at the air outlet of the condenser. Inlet, the seventh temperature sensor is set at the outlet of the condenser fan, the third temperature sensor and the third pressure sensor are set at the condensate outlet of the condenser, the fourth temperature sensor and the fourth pressure sensor are set at the condensate of the first evaporator Outlet, the fifth temperature sensor and the fifth pressure sensor are arranged at the condensate outlet of the second evaporator.

In this embodiment, the pump is connected to the second evaporator for injecting cooling liquid into it.

The principle of this embodiment is shown in Figure 2. When the system is running, the compressor compresses the refrigerant. During this process, the refrigerant is always in a gaseous state, and the temperature and pressure of the refrigerant will increase, which is represented as "compression" in Figure 2. part". During this process, the temperature and pressure changes of the refrigerant are monitored by the first temperature sensor, the first pressure sensor, the second temperature sensor and the second pressure sensor respectively.

After the refrigerant is discharged from the compressor, it enters the condenser. The condenser is equipped with a condenser fan, which draws air from the outside to exchange heat for the refrigerant. The refrigerant condenses after cooling down in the condenser, and changes from a gaseous state to a liquid state, with a decrease in temperature and a constant pressure. Shown in Figure 2 as "condensation section". The sixth temperature sensor and the seventh temperature sensor are respectively used to monitor the gas temperature at the inlet and outlet of the condenser air duct. The temperature and pressure of the refrigerant after being condensed and cooled in the condenser are monitored by a third temperature sensor and a third pressure sensor respectively.

After the refrigerant flows out of the condenser, it enters the liquid storage tank. The function of the liquid storage tank is to store the refrigerant when the system is not running, and to dry the refrigerant when the system is running.

After the refrigerant flows out of the liquid storage tank, it enters the expansion valve (in this embodiment, the air-conditioning system controls the refrigerant to enter the expansion valve in three situations: first, it only enters the first expansion valve; second, it only enters the second expansion valve; third , into the first expansion valve and the second expansion valve at the same time. In either case, the change process of the state of the refrigerant in the expansion valve and the subsequent evaporator is the same). The refrigerant expands in the expansion valve, reducing the pressure and temperature accordingly. The refrigerant changes from a completely liquid state to a gas-liquid mixed state that is mainly liquid and contains a small amount of gas.

After passing through the expansion valve, the refrigerant enters the evaporator (there are three situations, first, only enter the first evaporator, second, only enter the second evaporator, third, enter both the first evaporator and the second evaporator) . In the evaporator, the refrigerant exchanges heat with a heat source. The liquid part of the refrigerant continues to absorb heat until it is all converted to a gaseous state. During this period, the pressure of the refrigerant remains unchanged and the temperature rises. The temperature of the heat source is lowered, realizing the effect of cooling the user system. It is indicated as "Evaporation Section" in the figure above.

After the refrigerant flows out of the evaporator, it flows back to the compressor. One evaporation cycle is complete.

In this embodiment, the air conditioning system is divided into an air cooling subsystem and a liquid cooling subsystem according to different cooling requirements of the aircraft. The air cooling subsystem is mainly used for cabin cooling; the liquid cooling subsystem is mainly used for cooling the power battery. The cooling of the power battery affects the operation stability and flight safety of the aircraft, so the air conditioning system of this embodiment firstly meets the cooling demand of liquid cooling; Cold cooling needs have a lower priority than liquid cooling cooling needs.

According to the operating characteristics of the electric aircraft, the operating stages of the aircraft are divided into: charging stage, ground operation stage, take-off stage, cruise stage, and landing stage.

The demand characteristics of cabin cooling and power battery cooling in different stages are shown in the table below:

Charging phase: This phase lasts for a long time (possibly up to several hours). The cockpit is unoccupied and does not require refrigeration. During the charging process of the power battery, heat is released, especially during the fast charging process. All the cooling capacity of the air conditioning system is used to cool the power battery.

Ground operation phase: The duration of this phase is relatively long (about 15 minutes). The discharge power of the battery is small, there is no power output, and the heat release is small, but cooling is still required. At the same time, there are people in the cockpit and there is a need for cooling. At this time, the air-cooling subsystem and the liquid-cooling subsystem in the air conditioning system are both working. The reason for battery cooling in this stage is that the external high temperature environment will affect the power battery, so the battery needs to be cooled.

Take-off phase: This phase lasts very short (about 5 minutes). At this time, the power battery is in the process of high-power discharge, with the largest heat generation and the highest demand for cooling. In consideration of flight safety, only the liquid-cooled subsystem is operated at this stage, and the air-cooled subsystem is not operated. This can effectively reduce the maximum load and design boundary conditions of the air conditioning system, and reduce the weight of the system.

Cruising stage: This stage lasts longer (about 30 minutes). There are people in the cockpit and there is a need for cooling. The battery is in the normal discharge process, and the heat generation is moderate. The total cooling capacity of the air-conditioning system can meet the cooling demands of cabin cooling and battery cooling at the same time. But in order to ensure flight safety, battery cooling needs need to be prioritized.

Landing phase: The duration of this phase is very short (about 5 minutes). There are people in the cockpit and there is a need for cooling. The battery is in the normal discharge process, and the heat generation is moderate. The total cooling capacity of the air-conditioning system can meet the cooling demands of cabin cooling and battery cooling at the same time. But in order to ensure flight safety, battery cooling needs need to be prioritized.

In this embodiment, the normal operating temperature range of the power battery is set to 20°C-40°C, the critical temperature operating range is set to 40°C-50°C, and the overheat limit is 50°C;

When the temperature of the battery is within the normal operating temperature range, there is no need to cool down the battery;

When the temperature of the battery is within the critical temperature operating range, the air conditioning system controls the second evaporator (that is, the liquid cooling subsystem) to cool down the battery;

When the temperature of the battery exceeds the overheat limit, the air conditioning system sends an alarm signal to the system.

Set the normal operating temperature range of the cockpit at 24°C-30°C and the critical limit at 30°C;

When the temperature in the cabin is within the normal operating temperature range, there is no need to cool down the cabin;

When the temperature in the cabin exceeds the critical limit, the air-conditioning system controls the first evaporator (that is, the air-cooling subsystem) to cool down the cabin.

As shown in FIG. 3 , the air conditioning system judges whether to turn on the liquid cooling function and/or the air cooling function according to the operating state of the aircraft, the battery temperature and the cabin temperature.

At any stage of aircraft operation, when the system monitors that the battery temperature is greater than 40°C, the air conditioning system will turn on the liquid cooling function to cool down the battery. After the system is turned on, if the battery temperature cannot reach below 30°C, 5% of the system cooling capacity will be provided until the battery temperature drops below 30°C. If the cooling capacity of the system reaches the maximum capacity, but the battery temperature still cannot be kept below 50°C, a battery overtemperature warning signal will be sent to the aircraft, and the pilot will control the aircraft to take corresponding remedial measures to ensure the flight safety of the aircraft.

During the ground operation phase, cruise phase and landing phase, when the system detects that the cabin temperature is higher than 30°C, the system controls the air cooling function to turn on, and sets the target cabin temperature to 24°C. When the cooling capacity of the system does not reach the maximum capacity, continuously detect whether the cabin temperature is greater than the target temperature. If it is greater than that, gradually increase the cooling capacity of the air conditioning system with a gradient of 5% until the cabin temperature is less than or equal to the target temperature of 24°C. After the air cooling function is turned on, once the temperature of the battery is detected to be greater than 40°C, the function will be turned off to ensure the stable operation of the battery and the safety of the aircraft.

The method of increasing the cooling capacity of the system includes increasing the speed of the compressor and increasing the speed of the condenser fan.

In this embodiment, the temperature of the power battery is monitored during all operating stages of the aircraft. When the temperature is too high, the liquid cooling function of the air conditioning system is turned on to reduce the temperature of the power battery. When the battery temperature exceeds 50°C, the system sends an over-temperature alarm to the aircraft. signal, and the pilot controls the aircraft to take corresponding remedial measures to ensure the flight safety of the aircraft. If the air cooling function for cabin cooling is turned on, resulting in insufficient cooling capacity of the liquid cooling to maintain the battery temperature at 40°C, then Turn off the air cooling function to ensure the stable operation of the battery.

In this embodiment, during the operation phase of high-power charging and discharging of the battery, the air-cooling and cooling function of the air-conditioning system is turned off, and only the liquid-cooling and cooling function is allowed to operate, which effectively avoids the over-design of the air-conditioning system caused by the sudden increase in the cooling demand of the system in a short period of time, reducing the The weight and power consumption of the air conditioning system increase the payload and cruising range of the aircraft.

In the system architecture of this embodiment, temperature sensors and pressure sensors are installed at the outlets of the two evaporators. Downstream of the first evaporator in the air-cooled refrigeration channel, a fourth temperature sensor and a fourth pressure sensor are installed. Downstream of the second evaporator of the liquid-cooled refrigeration channel, a fifth temperature sensor and a fifth pressure sensor are installed. The role of these two pairs of temperature and pressure sensors is to monitor the state of the refrigerant at the outlet of their respective evaporators. According to the physical property table of the refrigerant pressure-enthalpy diagram, find out the degree of superheat in the current operating state and compare it with the target value of superheat. By adjusting the opening degree of the expansion valve, the actual superheat degree matches the target superheat degree. The target superheat is set to 5°C to ensure that all the refrigerant at the outlet of the evaporator is in a gaseous state and there are no liquid particles, so as to prevent the liquid state from entering the compressor and causing damage to the compressor. The superheat of 5°C fully considers various errors in the system, including sensor measurement errors, system control errors, and expansion valve errors.

This embodiment realizes the precise implementation control of the degree of superheat of the condensing agent at the outlet of the evaporator, so that the evaporator is always in the working state with optimal performance and the energy consumption of the system is optimal.

Claims (9)

1. The electric aircraft double-evaporator air conditioning system comprises a compressor, a condenser fan, a first evaporator, a second evaporator, an evaporator fan, a first expansion valve, a second expansion valve and a liquid storage tank, and is characterized by further comprising a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, a fifth temperature sensor, a sixth temperature sensor, a seventh temperature sensor, a first pressure sensor, a second pressure sensor, a third pressure sensor, a fourth pressure sensor and a fifth pressure sensor;

the first temperature sensor and the first pressure sensor are arranged at an inlet of the compressor, the second temperature sensor and the second pressure sensor are arranged at an outlet of the compressor, the sixth temperature sensor is arranged at an air inlet of the condenser, the seventh temperature sensor is arranged at an outlet of the condenser fan, the third temperature sensor and the third pressure sensor are arranged at a condensate outlet of the condenser, the fourth temperature sensor and the fourth pressure sensor are arranged at a condensate outlet of the first evaporator, and the fifth temperature sensor and the fifth pressure sensor are arranged at a condensate outlet of the second evaporator.

2. The control method of the electric aircraft double-evaporator air conditioning system is characterized by comprising the following steps of:

s1, setting an operation stage of an aircraft in a system;

s2, setting the refrigerating output state of the air conditioning system in each operation stage of the aircraft;

s3, running a system;

s4, the air conditioning system controls the output of the first evaporator and the output of the second evaporator according to each stage of the aircraft;

s5, each temperature sensor and each pressure sensor acquire the running condition of each link of the air conditioning system in real time;

and S6, the air conditioning system compensates the output of the first evaporator and the output of the second evaporator according to the data in the S5.

3. The method according to claim 2, wherein in step S1, the operating phases of the aircraft comprise a charging phase, a ground operating phase, a takeoff phase, a cruise phase and a landing phase.

4. The method of claim 3, wherein in the step S2, the cooling output state of the air conditioning system includes output duty ratios of the first evaporator and the second evaporator, and output priorities of the first evaporator and the second evaporator.

5. The method of claim 4, wherein the air conditioning system detects the battery temperature and cabin temperature of the aircraft in real time; and adjusting the output of the first evaporator or the second evaporator based on the battery temperature or the cabin temperature in combination with the operational phase of the aircraft.

6. The method of claim 5, wherein a normal operating temperature interval, a critical temperature operating interval, and an overheat limit of the battery are set;

when the temperature of the battery is in a normal operation temperature range, the battery is not required to be cooled;

when the temperature of the battery is in the critical temperature operation interval, the air conditioning system controls the first evaporator or the second evaporator to cool the battery;

when the temperature of the battery exceeds the overheat limit, the air conditioning system sends an alarm signal to the system.

7. The method according to claim 6, characterized in that the cabin normal operating temperature interval and the critical limits are set;

when the temperature in the cabin is in a normal operation temperature range, the cabin is not required to be cooled;

when the temperature in the cabin exceeds a critical limit, the air conditioning system controls the first evaporator or the second evaporator to cool the cabin.

8. The method of claim 7, wherein when the air conditioning system is cooling the cabin, stopping cooling the cabin if the battery temperature cannot be reduced to within the critical temperature operating interval.

9. The method of claim 8, wherein in the step S5, a fourth pressure sensor and a fourth temperature sensor monitor a state of the refrigerant at the outlet of the first evaporator, and a fifth pressure sensor and a fifth temperature sensor monitor a state of the refrigerant at the outlet of the second evaporator;

in the step S6, the air conditioning system calculates the superheat degree of the first evaporator or the second evaporator in the current running state according to the state of the refrigerant at the outlet of the first evaporator or the second evaporator, compares the calculated superheat degree with the desired superheat degree value, and adjusts the superheat degree of the first evaporator or the second evaporator to the desired superheat degree value by adjusting the opening degree of the first expansion valve or the second expansion valve.

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