I have answered this question before, /question/218218015.html Please copy it for reference!
Also, the J-20 has a DSI air intake, definitely not a DIS!
The clam-shaped inlet is also known as "DSI", which means Diverterless Supersonic Intake. The originator is Lockheed Martin, the US F-35 development contractor. It cleverly uses a complex-shaped three-dimensional bulge designed through fluid mechanics calculations to cut the sluggish airflow layer of the boundary layer into two from the middle, leading it to the corners on both sides of the air inlet for release without affecting the A steady stream of predominantly "clean" airflow enters the engine. DSI avoids the air inlet boundary layer separation plate used by the F-22, avoiding a major hidden danger of forward stealth. It can also shield the air inlet to a certain extent, reduce the weight of the fuselage structure, and serve multiple purposes. .
Afterwards, Chengdu Aircraft quickly applied this advanced inlet technology to the improvement of the "Fierce Dragon" aircraft in 2006, and then applied it to the improvement of the J-10 in 2008. and Lockheed Martin become one of the two companies in the world to master and apply this technology.
However, although the DSI drum kit is carefully calculated, it is not adjustable. This means that although fighters using this kind of air intake have the advantages of weight reduction and improved engine efficiency, this advantage can only be fixed in a certain speed range, mainly around high subsonic speeds. In other words, their supersonic performance is restricted. The F-22 uses a traditional air inlet boundary layer separation plate to ensure high supersonic flight performance. The DSI air inlet is generally only suitable for fighters with relatively low flying speeds, such as the F-35 and "Fierce Dragon". Both aircraft are the slowest fighter jets in the past 50 years, with a maximum operating speed of only Mach 1.6.
The latest fourth-generation J-20 uses an original "adjustable DSI air inlet", which has made new innovations and solved the problem of poor DSI high-speed performance. The J-20 air inlet bulge is fixed but there is an adjustable baffle on the side of the inlet, which can effectively change the air intake volume with changes in speed, thereby achieving excellent air intake control capabilities in each major speed range from low to high, making the engine more efficient. Working for the surging ground will also mean better acceleration, climb rate and super cruise capabilities. At the same time, the adjustable baffle is lighter than the traditional air inlet boundary layer separation plate and does not affect the stealth performance.
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