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Chapter 888 Even the Russians can¡¯t do it

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    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 have started mass production of fourth-generation turbofan engine fan blades?"

    It¡¯s okay not to listen to this. When he heard it, Djokovic felt as if he had encountered some indescribable supernatural event, and his whole body trembled involuntarily.

    Of course I wasn¡¯t scared, but I was shocked.

    But Liu Cong asked with a strange face: "I heard that during the exercise at the eastern foot of the Karakoram Mountains, your country's military observers had seen the latest improved version of our Y-17, which was equipped with a large bypass ratio vortex  The fan engine wd-60ml uses this kind of fan blade. The diameter of this engine is 1.86 meters, the bypass ratio is 9, and the length of a single blade is about 0.75 meters Uh you really don't know, right?"

    When asked this question, Djokovic couldn't help but blush. Not only the old Russian expert, but also the executives and experts in the Russian aviation industry present all had a little embarrassment on their faces.

    They really don¡¯t know that China¡¯s Ascendas Group has actually mass-produced fourth-generation turbofan engine fan blades. If they knew this news, including Djokovic, the entire Russian aviation industry in China would never be like before.  Instead of being superior, they will re-understand and contact the Chinese aviation industry, which they regard as their students and descendants, in a more equal manner.

    As for why, it is very simple. The Russians simply cannot 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.

    Except for the three major airbank giants, there is one of the remaining one who can't even touch the side, let alone master it.

    If not, the only ones on this earth that can really produce high-thrust aero engines with a bypass ratio of 6 or above are these three giants.

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

    In contrast, the former Soviet Union and its successor Russia certainly 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.  The D-18t turbofan engine equipped on the aircraft.

    The maximum thrust is close to 30 tons, but the bypass ratio is only 5.6. At a time when the three major aerospace giants are generally mass-producing high-thrust engines with bypass ratios above 9, the value of 5.6 can only be regarded as a high bypass ratio, far from being a large engine.  Bypass ratio.

    As for Russia, which inherited the Soviet Union's family business, it wants to develop more advanced large-bypass-ratio aircraft engines. The problem is that the sustained economic downturn after the disintegration completely destroyed the family assets left by the Soviet Union, so that the fighting nation has no ambitions, but  It is unsustainable and can only stay in the dusty design drafts and the dreams of experts in the aviation industry.

    The former Soviet Union, a superpower on par with the United States and a leader in aviation technology, did not develop a large thrust engine with a bypass ratio of 6 or above until the end of its life.

    Did the Soviet Union not pay enough attention to it?  Or are the fighting nations not working hard enough?

    No, the fundamental reason is that the fan blades of a large bypass ratio turbofan engine really don't need to be too complicated.

    If you want the front-end large bypass of the turbofan engine to provide 80% thrust compared to the fan, you must ensure that the fan speed must be high, so as to ensure that there is enough airflow through the fan to become the reverse thrust of the engine.

    ?Then the question arises, what speed does the fan need to reach in order to generate enough thrust and ensure that the entire engine runs stably and efficiently for a long time?

    After all, the rotating shaft of the fan cannot provide infinitely high speeds. Even if the rotating shaft can, the fan blades themselves cannot withstand such high centrifugal force.

    More importantly, when the fan blade is running, due to the different strokes of the blade tip and root, the tip part usually enters supersonic speed when running at high speed, while the blade root is still spinning in the subsonic range.

    It is well known that supersonic speeds will produce shock waves. In the shock wave range, the nature of air resistance will undergo fundamental changes, forming a shock wave resistance similar to water drifting.

    This will produce a unique phenomenon, that is, the first-stage large-bypass fan of the high-bypass ratio turbofan engine is rotated by the turbine, but the thrust generated is the same as that of a tuberculosis man with asthma, which is always so different.  One breath.

    Even at extreme times, the rotation speed reaches its peak and the thrust is extremelyBut it cannot reach the theoretical value, and there is even an obvious sharp drop.

    The reason is that the fan blade tip enters supersonic speed first, forming a shock wave resistance that bounces out the air that originally came in. The air can only be sucked in by the middle part of the blade, and the efficiency naturally increases.  Not coming.

    Of course, this is just one of the many disadvantages of high-speed fan blades. 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 because of such insurmountable bottlenecks that the fan blades of early turbofan engines are the same as those used in Russia today. Since it is so troublesome to make the blade tip supersonic, it is better not to let the blade tip enter supersonic speed.

    How to control it?

    Of course, the stroke of the blade tip is 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 rotation speed of a single blade are also effective ways to reduce the overall speed. Of course, in order to strengthen the structural strength of the blades, a raised shoulder device will be made in the middle and root of each blade.

    ??When integrated together, you will find that the first-stage fan of the entire turbofan engine is not so much a fan as a metal wall, and it is also a large hard-core wall with two circles of reinforcing ribs.

    Such a turbofan engine is not only too heavy, and the thrust-to-weight ratio cannot be improved; its fuel consumption is also astonishing. There is no way that the efficiency of the front fan cannot be improved, and all the work is directed to the turbine at the back to provide thrust, so it will naturally become a glutton.

    As for maintainability, let alone removing those forty or fifty fan blades one by one will cause the maintenance personnel to collapse. The practice of frequently squeezing the turbine to perform work to provide thrust is itself continuously reducing the service life of various key components.  .

    It was precisely after discovering the shortcomings of this type of compromised turbofan engine that aviation engine engineers came up with an idea, that is, is there a fan blade that can overcome the supersonic shock wave resistance, thereby combining the supersonic speed of the blade tip with the  It is also used at the same time as the subsonic speed to expand the bypass ratio of the first-stage fan and increase the air runoff, thereby greatly increasing the overall thrust without increasing the turbine power.

    So starting from the mid-1970s, aviation experts from various aviation powers began to invest in this research. As the superpower at the time, the Soviet Union naturally followed the trend. As a result, after more than ten years, many related theories were published, but none of the finished products were available.  The reason why it was not worked out was that it was both simple and helpless. At that time, the Soviet Union did not have practical aviation industry design software and could not do complex three-dimensional industrial design. Naturally, it could not build a modern turbine that could take into account both supersonic and subsonic speeds.  Engine fan blades.

    But now, China's Ascendas Group has used this type of blades in large quantities in its own high-bypass-ratio turbofan engines. What does this mean?

    It¡¯s very simple. They have surpassed the original teacher-Russia in advanced three-dimensional industrial software!

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