Basic theoretical knowledge points of air compressor air

Basic theoretical knowledge points of air compressor air

1. What is the definition of the standard state of air? Answer: The definition of the standard state is: when the air suction pressure is 0.1MPa and the temperature is 15.6℃ (the domestic industry defines it as 0℃), the air state is called the standard state of air. In the standard state, the air density is 1.185kg/m3 (the processing capacity of post-processing equipment such as air compressor, dryer, filter, etc. are all marked with the air flow rate in the standard state, and the unit is written as Nm3/min ).　

　　 2. What is air? What is normal air? Answer: The atmosphere around the earth, we used to call it air. The air under the specified pressure of 0.1MPa, temperature of 20°C, and relative humidity of 36% is normal air. Normal air is different from standard air in temperature and contains moisture. When there is moisture in the air, once the moisture is separated, the air volume will be reduced.

3. What is saturated air and unsaturated air? Answer: At a certain temperature and pressure, the content of water vapor (ie water vapor density) in moist air has a certain limit; the content of water vapor at a certain temperature When the amount reaches the maximum possible content, the humid air at this time is called saturated air. Moist air when the water vapor does not reach the maximum possible content is called unsaturated air.

　　 Fourth, under what conditions does unsaturated air become saturated air? What is "condensation"? And explain its phenomenon. When the unsaturated air becomes saturated air, liquid water droplets will condense in the moist air. This phenomenon is called "condensation". Condensation is common. For example, the air humidity in summer is very high, and it is easy to form water droplets on the surface of the water pipe. In winter morning, water droplets will appear on the glass windows of residents. These are all humid air cooled under constant pressure to reach the dew point. The result of temperature and condensation.

5. What does the partial pressure of water vapor in moist air mean? Answer: Moist air is a mixture of water vapor and dry air. In a certain volume of moist air, the amount of water vapor (by mass) is usually higher than that of dry air. It is much less, but it occupies the same volume as dry air and also has the same temperature. The pressure of humid air is the sum of the partial pressures of the constituent gases (ie, dry air and water vapor). The pressure of water vapor in the humid air is called the partial pressure of water vapor and is denoted as Pso. Its value reflects the amount of water vapor in the humid air. The higher the water vapor content, the higher the water vapor partial pressure. The partial pressure of water vapor in saturated air is called the saturated partial pressure of water vapor, and it is recorded as Pab.

　　 6. What is the humidity of the air? How many kinds of humidity are there? Answer: The physical quantity that indicates the degree of air dryness and humidity is called humidity. Commonly used humidity expressions are: absolute humidity and relative humidity. In the standard state, the mass of water vapor contained in moist air in a volume of 1m3 is called the "absolute humidity" of moist air, and the unit is g/m3. Absolute humidity only indicates how much water vapor is contained in a unit volume of humid air, but cannot indicate the ability of the humid air to absorb water vapor, that is, it cannot indicate the degree of humidity of the humid air. Absolute humidity is the density of water vapor in humid air. The ratio of the actual amount of water vapor contained in humid air to the maximum possible amount of water vapor at the same temperature is called "relative humidity", which is often expressed by φ. The relative humidity φ is between 0 and 100%. The smaller the φ value, the drier the air, and the stronger the water absorption capacity; the larger the φ value, the more humid the air and the weaker the water absorption capacity. The moisture absorption capacity of moist air is also related to its temperature. As the temperature of moist air rises, the saturation pressure increases accordingly. If the content of water vapor does not change, the relative humidity φ of moist air will decrease, that is, the moisture absorption capacity of moist air. increase. Therefore, during the installation of the air compressor room, attention should be paid to maintaining ventilation, lowering the temperature, and no drainage or accumulation of water in the room to reduce the moisture in the air.

　　 Seven. What is humid air? Answer: Air containing a certain amount of water vapor is called humid air, and air without water vapor is called dry air. The air around us is humid air. At a certain altitude, the composition and proportion of dry air remain basically stable, and it has no special significance to the thermal performance of the entire wet air. Although the water vapor content in humid air is not large, the change of content has a great influence on the physical properties of humid air. The water vapor content determines the dryness and humidity of the air. The working object of an air compressor is humid air.

　　 8. What are the compressed air drying methods? Answer: Compressed air can be pressurized, cooled, adsorbed and other methods to remove the water vapor, and can be heated, filtered, mechanical separation and other methods to remove liquid moisture. The refrigeration dryer is a kind of equipment that cools the compressed air to remove the water vapor contained in it, and obtains relatively dry compressed air. The rear cooler of the air compressor also uses cooling to remove the water vapor contained therein. The adsorption dryer uses the principle of adsorption to remove the water vapor contained in the compressed air.

　　 Nine. What is compressed air? What are its characteristics? Answer: Air is compressible. The air that has been reduced in volume and increased in pressure by the mechanical work of an air compressor is called compressed air. Compressed air is an important power source. Compared with other energy sources, it has the following obvious characteristics: clear and transparent, easy to transport, no special harmful properties, no pollution or low pollution, low temperature, no fire hazard, and no fear Overloaded, able to work in many unfavorable environments, easy to obtain, inexhaustible.

10. What impurities are contained in the compressed air? Answer: The compressed air discharged from the air compressor contains many impurities: ①Water, including water mist, water vapor, and condensed water; ②Oil, including oil pollution and oil vapor; ③Various solid substances , Such as rust mud, metal powder, rubber fines, tar particles and filter materials, fines of sealing materials, etc., in addition to a variety of harmful chemical odor substances.

　　11. What is an air source system? What are its components? Answer: A system composed of equipment that generates, processes and stores compressed air is called an air source system. A typical air source system usually consists of the following parts: air compressor, rear cooler, filter (including pre-filter, oil-water separator, pipeline filter, degreasing filter, deodorizing filter, sterilization filter) Etc.), stabilized gas storage tanks, dryers (refrigerated or adsorption type), automatic drainage and sewage devices, gas pipelines, pipeline valves, instruments, etc. The above equipment is combined into a complete gas source system according to the different needs of the process flow.

　　12. What are the hazards of impurities in compressed air? Answer: The compressed air output from the air compressor contains a lot of harmful impurities. The main impurities are solid particles in the air, moisture and oil. The vaporized lubricating oil will form a kind of organic acid corrosion equipment, which will deteriorate the quality of rubber, plastics and sealing materials, block the small holes, cause valve operation failure, and contaminate products. The saturated moisture in the compressed air will condense into water under certain conditions and accumulate in some parts of the system. This moisture has a rust effect on the components and pipelines, causing the moving parts to jam or wear, and make the pneumatic components malfunction and leak; in cold areas, the freezing of moisture can cause the pipeline to freeze or crack. Impurities such as dust in the compressed air will abrade the relative moving surfaces in the cylinder, pneumatic motor and pneumatic reversing valve, reducing the service life of the system.

　　13. Why do we need to purify compressed air? Answer: Just like hydraulic systems have higher requirements for the cleanliness of hydraulic oil, pneumatic systems also have higher quality requirements for compressed air. The air discharged by the air compressor cannot be used directly by the pneumatic device. The air compressor sucks air containing moisture and dust from the atmosphere, and the temperature of the compressed air increases to above 100°C. At this time, the lubricating oil in the air compressor also partly becomes gaseous. In this way, the compressed air discharged by the air compressor is a high-temperature gas containing oil, moisture and dust. If this compressed air is directly sent to the pneumatic system, the reliability and service life of the pneumatic system will be greatly reduced due to poor air quality, and the resulting loss will often greatly exceed the cost and maintenance cost of the air source treatment device, so choose it correctly Air source treatment system is absolutely necessary.

　　 14. What are the reasons why compressed air is widely used in industry?

　　(1) Storage. It is easy to store large-capacity compressed air as needed.

　　(2) Simple design and control. Pneumatic components are of simple design, so they are suitable for automatic systems with simpler control.

　　(3) Choice of exercise. Pneumatic components are easy to realize linear and rotary motion with stepless speed regulation.

　　 (4) Compressed air generation system, due to the reasonable price of pneumatic components, the cost of the whole set of devices is low, and the pneumatic components have a long life and low maintenance costs.

　　(5) Reliability. Pneumatic components have a long working life, so the system has high reliability.

　　(6) Adaptability to harsh environments. Compressed air is largely unaffected by high temperature, dust, and corrosion, which is beyond the reach of other systems.

　　(7) The environment is clean. Pneumatic components are clean, and there is a special exhaust air treatment method, which has little environmental pollution.

　　(8) Security. It will not cause fire in dangerous places. If the system is overloaded, the actuator will only stop or slip.