The domestic and international development history of fans

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As the name implies, a fan is a machine that generates and distributes wind. Winds can be divided into natural winds and artificially created winds. The former has extremely high energy and power. In the early 18th century, a severe storm struck Europe, uprooting 250,000 trees; the power generated by this storm in just a few seconds exceeded 7.35 million kilowatts. On April 10, 1978, at Hongliu Station in the western part of Hami, Xinjiang, China, a strong wind caused three freight cars weighing 44,000 kilograms to topple off the track with a loud noise, just like toys. As for the typhoons that occur annually in coastal areas, their intensity and the damage they cause to people are even greater. Natural wind is a natural phenomenon of air convection in the atmosphere; it arises from changes in air temperature and density, which create pressure differences, causing air with higher pressure to flow toward areas of lower pressure. The wind contains an energy called “wind energy”. Wind energy, like natural gas, oil, coal, hydropower, ocean energy, solar energy, and geothermal energy, is also a category of energy sources. The measure of wind energy is \"wind pressure\", which is proportional to the square of the wind speed; the higher the wind speed, the greater the wind pressure, and the lower the wind speed, the lesser the wind pressure. In 1905, the British scientist Beaufort used wind speed as a measure to classify winds into 13 levels ranging from 0 to 12; these are known as the Beaufort scale. Each level has a name, ordered from lowest to highest: calm, light breeze, gentle breeze, brise, moderate breeze, strong breeze, gale, storm, hurricane, violent storm, typhoon. This wind scale makes it easy for people to determine the strength of the wind. The wind speed at calm conditions is below 0.2 m/s, while hurricanes have wind speeds ranging from 32.7 to 36.9 m/s; winds of this intensity possess extremely high destructive power. Since 1946, the wind force scale has been expanded to 18 levels; wind speeds from level 13 to 17 are only used when they can be measured with instruments. The wind speed at level 17 is 36.1～61.2 m/s. For a fan, as long as its wind speed is measured, it is possible to determine how strong a wind force the fan can generate. Generally, a level 3 natural wind is sufficient to drive the windmill to generate electricity. Scientists have estimated that approximately 1.5% to 2.5% of the solar energy that reaches the Earth’s surface is converted into wind energy in the atmosphere. The total wind energy present in the entire atmosphere is around 300 million gigawatts, which corresponds to about 26 trillion gigawatt-hours of energy per year. There is at least another 10 to 10 billion kW of wind energy that can be used for power generation, which is four times more than the world’s available hydroelectric resources ； The energy obtained from burning coal worldwide each year is only one-thousandth of the energy provided by wind power during the same period. So, what about the ability to generate mechanical wind? This is the main topic of this article. As for how the fans that generate wind are produced and developed, let’s trace their origins. (1) The origin of fans lies in China. As early as in ancient China, before the Shang Dynasty and Western Zhou Dynasty, a device for forced air circulation was invented, called a blowfan, which was mainly used in the metallurgical industry. 4,800 years ago, our country was already able to manufacture bronzeware — copper knives ； Bronze jue vessels from the early Shang Dynasty sometimes have walls as thin as 2 mm ； By the middle of the Shang Dynasty, two types of alloys—tin bronze and lead bronze—were already in use, allowing for the casting of large cauldrons weighing up to 80 kg. In the later period of the Shang Dynasty, bronze casting reached its peak. China invented iron casting technology as early as the Spring and Autumn Period. During the Yin Dynasty, from the 14th to the 11th century BC, heat treatment techniques involving annealing were already in use. During the Middle Shang period, in the 14th century BC, China used meteoric iron to manufacture weapons and had already adopted heating and forging techniques. The invention, creation, and application of all these technological methods were inseparable from blowers, which served as tools for supplying air. Vent openings have been found on the remnants of Western Zhou Dynasty furnace walls unearthed in Luoyang, and the structural components of the blowers varied depending on the era. In the early days, it was a type of leather bag made from cowhide or horsehide; in ancient times it was called a tuo. External air ducts, which use the expansion and contraction of bladders to achieve air blowing. It was initially a single-cylinder operation, and its method of use can be seen in the Han Dynasty iron-smelting reliefs unearthed in Teng County, Shandong. During the Warring States period or even earlier, devices with multiple bags connected in parallel or series appeared in our country; they were called “pai tuo” during the Han dynasty. During the Beining period, wooden fans were invented. Judging from the drawings of horizontal water pumps and wave-boiling devices in Wang Zhen’s \"Book of Agriculture\" written in 1313 during the Yuan dynasty, its shape resembles that of a wooden box, with the lid being opened and closed to facilitate air circulation. The book \"Tian Gong Kai Wu\", a renowned ancient work on science and technology written by Song Yingxing during the Ming Dynasty in 1634, describes a wooden bellows. It was an ancient piston-type blower that has been in use to this day; it can be considered the precursor of modern reciprocating compressors. Each end of the wooden bellows is equipped with an air inlet, which has a flap on it. There is an air duct on the side of the box, with an air outlet at each end of the duct; a flap is also installed on each outlet. A rod extending outside the box is used to drive the piston back and forth, causing the valve to open and close in order to achieve air blowing. The power for wooden bellows can come from human effort and water power, among others. “A “water bellows” was an ancient smelting blower device powered by water force. It is said to have been invented by Du Shi, the governor of Nanyang, in the early years of the Eastern Han Dynasty (25–221 AD). Before him, the power for blowing air into smelting furnaces mainly came from human and animal labor. The working components of water pumps have gone through stages such as leather covers, wooden fans, and wooden blowers throughout the course of history. In the Yuan dynasty, water pumps came in two types: the horizontal-wheel type and the main-wheel type. They were mechanisms that converted rotational motion into linear reciprocating motion through a connecting rod. European hydraulic bellows were invented around the 12th century, and they played a role in facilitating the emergence of pig iron in Europe during the 14th century; however, this was many years later than in our country. It is not known exactly in which year before Christ our ancestors invented simple wooden thresher windmills, which have been in use in the south to this day. It has a uniformly wide wooden bellows similar to those found on modern multi-leaf centrifugal ventilator casings, with square openings for inserting grain; there is also a square opening on the left horizontal front side. Wooden wheels are placed inside the bellows, with their wooden shafts extending outward and equipped with cranks. An inclined cut is provided on the lower side of the cranks, and there are gaps between the wheels and the bellows on both the front and back sides to allow air to enter. When the wheel is turned by hand, the millet is poured in through the upper opening. As the wheel does work on the air that enters through the gap between the wheel and the bellows, the gas pressure increases, which pushes the chaff and straw scraps out through the front opening. Due to its higher density, the millet flows into the grain bag through the inclined opening at the lower left side. This wooden thresher windmill was the precursor to modern centrifugal fans, blowers, and compressors. Furthermore, propeller-type windmills were also invented and used in ancient China, and they are the predecessors of axial-flow fans. (II) Advanced fan technology: Although ancient China was the birthplace of fans, prolonged feudal rule suppressed people’s wisdom and hindered the development of industry and agriculture. The backwardness of industrial production led to a decline in science and technology, and thus blowers also declined in popularity. In the 18th century, the Industrial Revolution took place in Europe. With the advent of steam locomotives and rapid progress in the steel and coal industries, ventilators, blowers, and compressors also developed as a result. Some **fan products experience fluctuations along with the ups and downs in steel production ； Some **fan products, on the other hand, fluctuate in accordance with the levels of production of oil and petrochemical products. In 1862, T. Guibell of Britain invented the centrifugal ventilator, whose impeller and casing were concentric circles; the casing was made of brick while the wooden impeller featured backward straight blades. Its efficiency was around 40%, and it was mainly used for ventilation in mines. In 1880, centrifugal fans with spiral casings and backward-curving blades were designed for exhaust ventilation in mines, featuring a relatively complete structure. In 1898, the Irish developed the Sirocco-type centrifugal fan with forward blades, which was widely adopted around the world. In the 19th century, axial flow fans were already used for mine ventilation and air blowing in the metallurgical industry, but the pressure was only 100–300 Pa and the efficiency was only 15%–25%. This type of ventilator began to develop rapidly only after the 1940s. In 1935, Germany was the first to use axial equal-pressure ventilators as boiler ventilators and exhaust fans. In 1948, Denmark developed a axial flow fan with adjustable moving blades in operation. Counter-rotating axial flow fans, meridional acceleration axial flow fans, oblique flow fans, and cross-flow fans have also seen development. Centrifugal compressors were developed on the basis of centrifugal fans, and in the 20th century centrifugal compressors with a pressure ratio of 4.5 appeared. Starting in the 1950s, the centrifugal compressor manufacturing industry developed in the industrially advanced countries of Europe and America. In 1963, the United States produced the first high-pressure centrifugal compressor of 14.7 MPa for use in ammonia synthesis plants; it featured a cylindrical casing instead of a horizontally split casing, and was also known as a cylindrical compressor, capable of withstanding pressures above 10 MPa. In the 1970s, the United States, Italy, and Germany successively developed high-pressure cylindrical compressors with pressures of 60–70 MPa, featuring cylinder wall thicknesses of 280 mm. By the early 1980s, the exhaust pressure had reached 80 MPa. The rotational speed of centrifugal compressors is generally several thousand revolutions per minute, with some reaching over 25,000 revolutions per minute. The required power can reach tens of thousands of kilowatts, and the flow rate has reached 10,000 m³/min. The conventional impellers of centrifugal compressors are designed based on the theory of one-dimensional flow. Starting in the 1960s, three-dimensional flow theory was applied to design spatially twisted blades in order to improve the performance of the impeller stages. Axial flow compressors also first appeared in Europe. At the end of the 19th century, the Britishman C.A. Parsons caused a multi-stage reaction steam turbine to rotate in reverse as an experimental axial flow compressor, but it was not practical due to its low efficiency. At the beginning of the 20th century, Britain manufactured the first axial flow compressor, but its efficiency was still low. It was not until the 1930s that, thanks to the development of aviation, theoretical and experimental research on the gas dynamics of axial flow compressors was carried out, leading to a significant improvement in efficiency. In subsonic regimes (where the flow velocity is below the speed of sound), the pressure ratio is not high, generally not exceeding 1.3. To increase the pressure ratio and flow rate of turbines, transonic and supersonic compressors have been studied and are now widely used in jet engines.