Take Off My Aviation Era

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

"What? You have started mass production of fan blades for the fourth-generation turbofan engine?"

It's okay not to listen to this. Upon hearing this, Djokovic's whole person shuddered involuntarily as if he had encountered some indescribable supernatural event.

Of course it was not scared, but shocked.

But Liu Cong asked with a strange expression: "I heard that during the exercise at the eastern foot of the Karakorum Mountains, your country’s military observers had already seen the latest improved version of our Yun-17, equipped with a large bypass than the vortex. The fan engine WD-60ML uses 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... Uh... You don't really know, do you?"

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

They really didn’t know that China’s Ascendas Group actually mass-produced fourth-generation turbofan engine fan blades. If they knew this news, including Djokovic, the entire Russian aviation industry in China would definitely not be as good as before. It is generally high above, but with a more equal attitude to re-understand and contact the Chinese aviation industry that they regard as students and juniors.

As for why, it's very simple. The Russians simply can't make this fourth-generation turbofan engine fan blade.

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

In addition to the three major aviation development giants, there is one that can't be touched at all, let alone master it.

If this is not the case, it is only these three giants that can really produce high-thrust aero engines with bypass ratios above 6.

To put it bluntly, it is the three major aviation giants who have mastered the core technology of large bypass ratio turbofan engine fan blades. Based on this, the outer bypass can be made larger and larger until the thrust ratio of the outer bypass is increased. To about 80% of the thrust of the entire engine, a third-generation high-thrust engine with high thrust, low fuel consumption, high reliability and low noise is formed.

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

The maximum thrust is close to 30 tons, but the bypass ratio is only 5.6. Now that the three major aviation giants generally mass-produce large thrust engines with bypass ratios above 9, the value of 5.6 can only be regarded as a high bypass ratio, which is far from a big one. Bypass ratio.

As for Russia, which inherited the Soviet family business, it wanted to get a more advanced large bypass than aero engines. The problem is that the continued economic downturn after the disintegration completely destroyed the legacy of the Soviet Union, so that the fighting nation had no ambitions. It is unsustainable and can 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 and the existence of the top aviation technology, did not produce a large thrust engine with a bypass ratio of 6 or more until the end of its life.

Is the Soviet Union not paying enough attention? Or is the fighting nation not working hard enough?

No, the root cause is that the large bypass is really not too complicated than the fan blade of a turbofan engine.

If you want the large duct of the turbofan engine to provide 80% of the thrust than the fan, you must ensure that the fan speed must be large, so as to ensure that there is enough airflow through the fan to become the engine's reverse thrust.

Then the question is, how much speed does the fan need to reach to generate enough thrust and to ensure the stable and efficient long-term smooth operation of the entire engine?

After all, the rotating shaft of the fan cannot provide an infinitely high speed. Even if the rotating shaft can, the fan blade itself cannot withstand such a high centrifugal force.

More importantly, when the fan blades are in operation, due to the different strokes between the tip and the root of the blade, the tip of the blade usually enters supersonic speed during high-speed operation, and the blade root will rotate in the subsonic range regardless of the root.

It is well known that supersonic speed will produce shock waves. In the shock wave category, the nature of air resistance will undergo a fundamental change, which will form a shock wave resistance like water drift.

This will produce a unique phenomenon, that is, the large bypass fan is rotated by the turbofan engine, but the thrust formed is the same as that of an asthmatic tuberculosis ghost, which is always worse. In one breath.

Even at extreme times, the speed reached its peak, and the thrust not only failed to reach the theoretical value, but even dropped significantly.

The reason is that the blade tip of the fan first enters the supersonic speed, forming shock wave resistance, and bounces the air that originally came in as if it is splashed. The air can only be sucked in by the lower part of the blade, and the efficiency is naturally improved. Not coming.

Of course, this is just one of the many disadvantages of the fan blades at high speeds. As for reducing the service life of the blades, destroying the structural strength of the blades, and often causing damage to the blades, there are many disadvantages.

It is precisely with such insurmountable bottlenecks that the fan blades of the early turbofan engines are the same as the methods used in Russia now. Since the tip of the supersonic speed is so troublesome, it is enough not 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, so turbofan engines with a bypass ratio of 2 or 4 became popular in the 1960s and 1970s.

At the same time, increasing the number of blades and reducing the speed of a single blade are also effective means to reduce the overall speed. Of course, in order to strengthen the structural strength of the blades, the middle and root of each blade will also be equipped with a convex shoulder device.

So integrated together, you will find that the first-stage fan of the entire turbofan engine is not so much a fan, not to mention a metal wall, but also a **** wall with two loops of reinforcing ribs.

This kind of turbofan engine is not only too heavy, and the thrust-to-weight ratio is too high; the fuel consumption is also astonishing. There is no way that the front fan can't increase in efficiency. All of them point to the turbine behind to provide thrust.

As for maintainability, let alone if those 40 or 50 fan blades are removed one by one will they cause the maintenance personnel to collapse. It is the practice of frequently squeezing the turbine to provide thrust ~www.readwn.com~ itself is constantly reducing each The service life of such key components.

It is precisely for discovering the various deficiencies of this type of compromised turbofan engine that the engineers of the aeroengine put forward an idea, that is, whether there is a fan blade that can overcome the resistance of the supersonic shock wave, so as to compare the supersonic speed of the blade tip with The subsonic speed is also used at the same time to expand the bypass ratio of the first-stage fan and increase the air runoff, so as to achieve a substantial increase in the overall thrust without increasing the turbine power.

Since the mid-1970s, aviation development experts from various aviation powers have been involved in this research. The Soviet Union, as a superpower at the time, naturally followed the trend. As a result, after more than ten years, many related theories have been published, but none of the finished products The reason for not finding it is simple and helpless. At that time, the Soviet Union did not have practical aerospace industry design software, and could not do complex three-dimensional industrial design. Naturally, it could not create a modern turbine that could take into account both supersonic and subsonic speeds. Engine fan blades.

Now, China's Ascendas Group has applied these types of blades to its large bypass ratio turbofan engines in large quantities. What does this show?

Quite simply, they have surpassed the original teacher-Russia in advanced 3D industrial software!

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