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, located in Beijing, can simulate extreme 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 supersonic flight conditions up to Mach 30, according to the Chinese Institute of Mechanics, the owner of the facility.
The institute said in a statement on Friday that the tunnel would "support China's research and development of supersonic aircraft and space transportation systems." For comparison, the Mach 10 tunnel at Nasa's Langley Research Center in the US, a major hypersonic test facility, has a test section diameter of nearly 0,8 meters. The larger test portion allows the researchers to put larger aircraft models or even entire instruments 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 supersonic 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 heat and pressure of supersonic 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 high, resulting in a phenomenon known as molecular dissociation. Air molecules break apart into their constituent atoms, which can then react with each other to form new chemical substances.
According to the institute, understanding the complex physics of the flows involved in molecular dissociation is crucial for the development of supersonic aircraft. By studying phenomena in a laboratory environment 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 vehicles are actually built and flown, reducing the risk of breakdowns or accidents. By some estimates, simulating the conditions of a Mach 30 flight inside a large tunnel, requires energy equivalent to that produced by the Three Gorges Dam – an impossibility.
Professor Jiang Zonglin, the lead scientist of 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 known as a "direct-reflected shock wave driver". In traditional supersonic wind tunnels, the airflow is created by a process called "expansion," in which high-pressure gas is rapidly released into a low-pressure chamber, creating a supersonic flow.
However, this method has limitations when it comes to generating the extremely high speeds and temperatures required for ultrasonic testing. Jiang's reflected shock wave driver overcomes these limitations by using a series of precisely timed bursts to create a series of shock waves that reflect each other and converge to a single point.
The result is an intense burst of energy used to control the airflow in the wind tunnel at extremely high speeds. According to the institute, the innovation has paved the way for more advancements by bringing greater accuracy and efficiency to the study of supersonic flight.
By combining data, researchers can better understand how different materials and designs behave in a wide range of flight conditions and use that information to improve the performance and reliability of a hypersonic weapon or aircraft. According to Jiang's team, these facilities could put China many years ahead of its competitors.
Mai Anh (according to SCMP)
