China so called advanced jet engine failed again, flight tests of the J-20 postponed

Fullerene is a form of pure carbon in which atoms are linked together to form a soccer ball-like crystal lattice. Depending on the number of atoms, fullerenes can be lower (from 24x to 70 atoms) and higher (70 or more atoms).

For several years now, there has been a discussion about the advantages of the Chinese J-20 fighter over the Russian Su-57 and the American F-35 . Despite the different aerodynamic design concept, the main disadvantage of the J-20  – its engine – cannot be overcome . The power unit has a serious flaw – it significantly loses traction when the engine reaches operating temperatures.

J-10 with WS-15 engine
J-10 with WS-15 engine

WS-15 engine

The WS-15 engine is being created to replace the Russian AL-31F. The problems of the aircraft engine, which is specially developed for the fifth generation fighters – J-20 and J-31, again caused the cancellation of flight tests of the J-20. This is at least the second postponement.

As you know, the creation of a motor is a complex process and the previous engine is the basis for the next one. Developing the ideal engine is not a one-off process, but the accumulation of technology, experience and, of course, the availability of suitable materials. Until recently, it was customary in the Chinese aircraft industry to first design an aircraft, and then begin to develop an engine for it . Most often, a motor with the required characteristics was simply bought. China has no experience in developing engines on its own. Let us recall the situation with the Ukrainian Motor Sich.

AL-31F engine  currently used in J-20 fighter aircraft
AL-31F engine  currently used in J-20 fighter aircraft

The newest Chinese fighter J-20 was no exception, and at the first stage of testing, only Russian engines were installed on it. The development of their own engine began later.

In May this year, the Chinese media reported on “a breakthrough technology discovered by Chinese scientists.” It was about a fullerene membrane coating for aircraft engine turbines. At the same time, such membranes, as reported, can bring operating temperatures up to 1800 ℃.

At the same time, it was announced that “the problem of thrust loss when the engine reaches operating temperatures has been finally solved” and that the new coating is capable of doubling the service life of engines when operating in low humidity conditions.

But it turned out that the announcement of “the final solution to the problem of engines for fifth generation fighters” was made prematurely. It turned out that when reaching operating temperatures in the engine chamber, processes arise that lead to a significant increase in the sorption qualities of those very membranes. The coating began to absorb the working substance, or became the reason for its thickening with the occurrence of an “unnecessary” chemical reaction. As a result, fuel consumption was prohibitive.

J-20 with test engine, left is AL-31F, right is WS-15
J-20 with test engine, left is AL-31F, right is WS-15

By the beginning of September, China promised to rectify the situation and bring the J-20 from the WS-15 to flight tests. However, now we have to admit again that the problems with the technological component of the aircraft engine have not been resolved.

As it became known, Chinese experts tried to solve the problem of applicability of fullerene films by creating an additional chamber. In this case, it was assumed that the temperature would be uniformly distributed over the increased volume of the structure, which would also reduce the absorbing properties of the membranes. But there were also problems with the additional camera – with the design. As a result, the situation boiled down not only to an increase in the size of the engine, but also to the fact that in order to mount it on the J-20, almost the entire fuel system of the fighter would have to be rebuilt.

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