Publish Time: 2022-10-31 Origin: Site
As a closed indoor space, the cabin body also has its own "air conditioner", but in the industry this system is called "environmental control system", or environmental control system for short. Temperature regulation is only one of the sub-functions of the environmental control system, and the environmental control system can also regulate physical quantities related to the environment such as pressure and humidity.
Why do aircraft need to use environmental control systems in the sky to control environmental variables such as temperature, pressure and humidity? This is determined by the nature of the atmosphere.
In fact, in addition to the human body needing to be in a suitable temperature range, all kinds of equipment on the aircraft also have their own working temperature range. Exceeding the corresponding range will cause discomfort to the human body or equipment and affect the flight safety of the aircraft.
Similarly, the human body and airborne equipment also have certain requirements for environmental-related physical quantities such as pressure, humidity, and oxygen content. The pressure, humidity, and oxygen content cannot be too large or too small, and they need to be within a suitable range. . The environmental control system uses different methods to control these variables in a suitable range in different areas according to different control requirements, so as to achieve a good environmental state between man and machine.
For some time since the Wright Brothers built the first airplane in 1903, the cockpits used on airplanes were open, with no environmental controls.
With the improvement of the structure and performance of the aircraft, the flight altitude is getting higher and higher, and at the same time, accompanied by the danger of low temperature, low air pressure and hypoxia at high altitude, life support requires the cockpit to be changed to an airtight cockpit, and then the environmental control system should be used. Instead, the aforementioned variables related to environmental parameters are controlled to ensure the normal operation of humans and airborne equipment.
Aircraft refrigeration system
There are two main types of aircraft refrigeration systems: air circulation refrigeration systems and evaporative circulation refrigeration systems. The air circulation system dissipates heat according to the principle of converting heat energy into mechanical work; the heat in the evaporative circulation system is dissipated during the evaporation of the liquid refrigerant. Both systems can be used individually or in combination.
The air source in the air circulation refrigeration system is mainly provided by the air drawn from the engine. The high-temperature and high-pressure gas provided by the engine is initially cooled by a series of heat exchangers, and then expanded and cooled by the cooling turbine to obtain low-pressure air and fed into the cabin. The role of the cooling turbine is to convert thermal energy into useful work and drive equipment such as compressors and fans. Most military aircraft and passenger aircraft use air circulation refrigeration systems. It should be noted here that the premise of using an air circulation refrigeration system is the air source. In addition to the above-mentioned engine bleed air (the most important), it also includes APU bleed air and ground bleed air.
The evaporative cycle refrigeration system has the same principle as the evaporative compression refrigeration cycle air conditioning system on the ground, and uses the state change of the refrigerant to transfer energy. The refrigerant absorbs the heat of the cooling medium in the evaporator and vaporizes it, and in the condenser, it releases heat and condenses through the cooling of the cooling medium. Purpose. As the cooling capacity required by modern aircraft continues to increase, advances in evaporative compression refrigeration technology and research on new refrigerants make evaporative cycles widely used in auxiliary refrigeration units of large passenger aircraft and high-performance military aircraft.
Why is there personal ventilation on an airplane? Since the aircraft space itself is relatively confined, it is very important to maintain relative air circulation in this case. However, passengers feel different wind speeds under different air supply temperatures. For example, in summer, passengers feel that it is very pleasant to blow some wind; but in winter, it will feel cold. The human body's feeling can be improved by the local airflow direction and size, taking into account the majority of passengers while addressing the individual needs, so there is a personal vent on the top of each occupant's head, which can be manually controlled to change the direction of airflow and size, to achieve the purpose of improving the comfort of the local environment.