Listening to Djokovic's question, Liu Cong's honest smile became even stronger: "This is just a model, and the actual mass-produced parts are much larger than this." ”

"What? You've started mass production of fourth-generation turbofan fan blades?"

It's okay not to listen to this, but as soon as he heard it, Djokovic's whole person was like encountering some indescribable supernatural event, and the whole person couldn't help but tremble.

Of course, not frightened, but frightened.

However, Liu Cong asked with a strange face: "I heard that during the exercise at the eastern foot of the Karakoram Mountain, the military observers of your country have seen the latest improved version of our Y-17, which is equipped with a large bypass ratio turbofan engine WD-60ML with this kind of fan blades, the diameter of this engine is 1.86 meters, the bypass ratio is 9, and the length of a single piece is about 0.75 meters...... Forehead...... You don't really know, do you?"

When asked like this, Djokovic's old face couldn't help but turn red, not only the old Russian expert, but also the executives and experts of the Russian aviation industry present were a little embarrassed.

They really don't know that China's Tengfei Group has mass-produced the fourth-generation turbofan engine fan blades, and if they knew this news, including Djokovic, the entire Russian aviation industry in China would definitely not be as high as before, but would re-recognize and get in touch with the Chinese aviation industry that they regarded as students and juniors in a more equal attitude.

As for why, quite simply, the Russians simply could not make such fan blades of the fourth generation turbofan engine.

Looking at the world, there are only three companies that can really master this technology, General and Pratt & Whitney in the United States, and Rolls-Royce in the United Kingdom.

In addition to these three aviation giants, there is one of them that can't even touch the edge, let alone master it.

If it weren't for that, only these three giants would be able to produce high-thrust aero engines with a bypass ratio of more than 6 on this earth.

To put it bluntly, the three aviation giants have mastered the core technology of large bypass ratio turbofan engine fan blades, and on this basis, the outer bypass can be made bigger and bigger, until the thrust of the outer bypass is increased to about 80% of the thrust of the whole engine, so as to form a third-generation large bypass ratio high-thrust engine with high thrust, low fuel consumption, high reliability and low noise.

In contrast, the former Soviet Union and its successor Russia, of course, also wanted to develop towards a large bypass ratio, but until the collapse of the Soviet Union, the high-thrust engines in the entire Soviet-style system were only the D-18T turbofan engines equipped with the An-124 and An-225 heavy transport aircraft.

The maximum thrust is close to 30 tons, but the bypass ratio is only 5.6, at the moment when the three major aviation giants generally mass-produce high-thrust engines with a bypass ratio of more than 9, 5.6 This value can only be regarded as a high bypass ratio, far from being called a large bypass ratio.

As for Russia, which inherited the Soviet family's business, wanted to boil out the more advanced large-bypass ratio aero engine, the problem was that the continuous economic downturn after the disintegration completely destroyed the Soviet Union's legacy of the family, so that the fighting nation had empty ambitions, but it was difficult to continue, and could only stay in the dusty design drafts and the dreams of those experts in the aviation industry.

The former Soviet Union, a superpower on an equal footing with the United States, had the best aviation technology, and until the end of its life, it did not develop a high-thrust engine with an induction ratio of more than 6.

Did the Soviet Union not pay enough attention to it, or did the fighting people not work hard enough?

No, the fundamental reason is that the fan blades of the turbofan engine are really not too complicated by the large bypass.

If you want the large duct in the front section of the turbofan engine to provide 80% of the thrust of the fan, it is necessary to ensure that the fan speed must be large, so as to ensure that there is enough airflow through the fan to become the reverse thrust of the engine.

The question then becomes, how much speed does the fan need to reach to produce enough thrust and keep the whole engine running smoothly for a long time?

After all, it is impossible for the rotation axis of a fan to provide an infinitely high rotational speed, and even if the axis of rotation does, the fan blades themselves cannot withstand such high centrifugal forces.

What's more, due to the difference between the tip and root stroke of the blade when the fan blade is running, the tip of the blade usually enters supersonic speed when running at high speed, while the blade root is still rotating in the subsonic range.

As we all know, supersonic speed produces shock waves, and in the category of shock waves, the nature of air resistance will change radically, and a kind of shock wave resistance will be formed.

In this way, a unique phenomenon will be produced, that is, the large ducted fan is rotated by the turbine than the first stage of the turbofan engine, but the thrust formed is like a tuberculosis ghost with asthma, which is always a breath off.

Even at extreme times, the rotational speed reaches its peak, and the thrust not only does not reach the theoretical value, but even has a significant sharp decrease.

The reason is that because the tip of the fan blade is the first to enter the supersonic speed, the shock wave resistance will bounce out the air that originally came in as if it were drifting, and the air can only be sucked in by the middle part of the blade, and the efficiency will naturally not go up.

Of course, this is only one of the many disadvantages of fan blades at high speed, as for reducing the service life of the blades, destroying the structural strength of the blades, often causing blade damage and so on.

It is precisely because of these insurmountable bottlenecks that the fan blades of the early turbofan engines are the same as those used by Russia now, since the supersonic speed of the blade tip is so troublesome, it is not enough to let the tip of the blade enter the supersonic speed.

How to control it?

Of course, the stroke of the blade tip was shortened, and so turbofan engines with a bypass ratio of 2 or 4 became popular in the sixties and seventies.

At the same time, increasing the number of blades and reducing the speed of a single blade is also an effective means to reduce the overall speed, of course, in order to strengthen the structural strength of the blade, the middle and root of each blade will also make a raised blade shoulder device.

When put together in this way, it will be found that the first-stage fan of the entire turbofan engine is not so much a fan as a metal wall, but also a hardcore wall with two rings of stiffeners.

Such a turbofan engine is not only too heavy, the thrust-to-weight ratio can not go up, but also the fuel consumption is also amazing, there is no way to go up the efficiency of the front fan, all pointing to the rear turbine to do work to provide thrust, naturally to eat into oil tigers.

As for maintainability, not to mention whether the forty or fifty fan blades will collapse the maintenance personnel if they are removed one by one, the practice of frequently squeezing the turbine to provide thrust is itself constantly reducing the service life of various key components.

It is precisely because of the discovery of the shortcomings of this kind of compromised turbofan engine that the engineers of the aero engine put forward an idea, that is, whether there is a fan blade that can overcome the supersonic shock resistance, so as to use the supersonic speed of the blade tip and the subsonic speed at the same time, so that the bypass ratio of the first-stage fan is expanded, and the air runoff is increased, so as to achieve a significant increase in the overall thrust without increasing the turbine power.

So from the mid-70s, the aviation experts of the aviation powers have been put into this research, the Soviet Union as a superpower at that time naturally followed the trend, as a result, more than ten years later, the relevant theories have come out a lot, but the finished product has not been made, the reason is both simple and helpless, the Soviet Union at that time did not have practical aviation industry design software, can not do complex three-dimensional industrial design, naturally can not create both supersonic and subsonic modern turbine engine fan blades.

Now, China's Tengfei Group is using these blades in large quantities to its own large-bypass ratio turbofan engines, what does this mean?

It's very simple, people have surpassed the original teacher in advanced three-dimensional industrial software - Russia!