Located in the mountainous Huairou district north of Beijing, the JF-22 wind tunnel is 4 meters (13 feet) in diameter and can generate airflow speeds of up to 10 kilometers (6.2 miles) per second, according to a final assessment conducted on May 30.
The JF-22, based in Beijing, can simulate harsh flight conditions at 30 times the speed of sound. Photo: SCMP
That makes it the largest and fastest wind tunnel in the world, capable of simulating hypersonic flight conditions up to Mach 30, according to the China Institute of Mechanics, the facility's owner.
The tunnel will “support China’s research and development of hypersonic aircraft and space transportation systems,” the institute said in a statement Friday. By comparison, the Mach 10 tunnel at Nasa’s Langley Research Center in the United States, a major hypersonic test facility, has a test section of nearly 2 feet in diameter. The larger test section allows researchers to put larger aircraft models or even entire aircraft into the wind tunnel to obtain more accurate flight data.
The JF-22 is an integral part of the Chinese government’s goals to achieve by 2035. By then, Beijing hopes to deploy a fleet of hypersonic aircraft that can carry thousands of passengers into space each year or anywhere on the planet within an hour. But such aircraft must be able to withstand the extreme temperatures and pressures of hypersonic flight, while maintaining a stable flight trajectory and a safe, comfortable environment for passengers.
At five times the speed of sound, the air molecules around the plane begin to compress and heat up, resulting in a phenomenon known as molecular dissociation. The air molecules break down into their constituent atoms, which can then react with each other to form new chemicals.
Understanding the complex physics of the flows involved in molecular separation is crucial to the development of hypersonic aircraft, according to the institute. By studying the phenomena in a laboratory setting using facilities such as wind tunnels, researchers can learn how hypersonic vehicles interact with their surroundings and develop new technologies to improve their performance and safety.
Wind tunnel testing can also help identify potential problems or design flaws before a vehicle is actually built and flown, reducing the risk of failure or accident. By some estimates, simulating Mach 30 flight conditions inside a large tunnel would require the same amount of energy as the Three Gorges Dam—something that is simply not possible.
Professor Jiang Zonglin, the lead scientist on the JF-22 project, came up with an innovative solution. To generate the high-speed airflow required for hypersonic testing, Jiang proposed a new type of shock wave generator called a “direct-reflection shock wave driver.” In traditional hypersonic wind tunnels, the airflow is generated by a process called “expansion,” in which high-pressure gas is rapidly released into a low-pressure chamber, creating a hypersonic flow.
However, this method has limitations when it comes to generating the extremely high speeds and temperatures required for ultrasonic testing. Jiang's Reflective Shockwave Driver overcomes these limitations by using a series of precisely timed explosions to create a series of shock waves that reflect off each other and converge at a single point.
The resulting burst of intense energy is used to manipulate airflow in a wind tunnel at extremely high speeds. The innovation, according to the institute, paves the way for further advances by bringing greater precision and efficiency to hypersonic flight research.
By combining the data, researchers can gain a better understanding of how different materials and designs perform under a range of flight conditions and use that information to improve the performance and reliability of hypersonic weapons or aircraft. These facilities could put China years ahead of its competitors, Jiang’s team said.
Mai Anh (according to SCMP)
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