Chapter 258 Large Bypass Turbofan Engine
Chapter 258 Large Bypass Turbofan Engine
The performance of an aircraft engine is usually judged by its thrust first, and then fuel saving is pursued on this basis.
But here comes the problem. According to the two formulas F (thrust) = W* (C1 outlet airflow velocity – C0 aircraft speed) and efficiency n = 2/1 + (C1/C0), the conclusion can be drawn:
The faster the engine outlet airflow velocity C1, the greater the thrust, but the corresponding efficiency is lower.
In addition to this problem, the bypass ratio also has a very large impact on the aircraft at different flight altitudes and speeds. For example, for a fighter with a small bypass ratio, a bypass ratio of more than 0.7 is more suitable for low altitudes, and a bypass ratio of less than 0.5 is more suitable for high altitudes.
So fuel saving and thrust, large bypass ratio and small bypass ratio are themselves a contradiction, and it is difficult to take all aspects into consideration. This is actually just one of the contradictions between various needs and technologies when designing aircraft engines.
Behind every seemingly subtle design change is the result of a compromise between demand and technology.
Of course, technology is constantly evolving, and scientific research also requires a bold hypothesis and careful demonstration.
Take the large bypass turbofan engine of passenger aircraft and transport aircraft as an example. They have only one air inlet fan, and the diameter is usually more than three meters, so they can inhale a lot of air, most of which enters the outer duct, providing more than 85% of the engine’s thrust.
Therefore, for large bypass engines, the effect of increasing thrust by expanding the outer duct and fan diameter is very obvious, and this is what the F135 engine on the F35 does.
But the side effects are also obvious. If the outer duct and fan diameter are too large, the wind resistance will be large, so it is difficult for aircraft with a large bypass ratio to fly supersonic.
So someone raised a question. Since the aircraft needs a small bypass ratio to obtain greater thrust and speed when taking off or fighting, and pursues a large bypass ratio to save fuel and endurance when cruising, wouldn’t it be a perfect solution to this problem if we make a variable bypass ratio engine? In theory, it is indeed feasible. To put it simply, a turbofan engine is two cylinders of different diameters put together. As long as you make an outer cylinder and a fan that can be retracted, an engine with a variable bypass ratio will come out.
But even if the principle seems simple, it is really difficult to make it.
As soon as you hear the name of this thing, you know that the structure must be very complicated. Let’s not talk about whether it can be made. Just in the high-temperature and high-speed engine, with so many systems and parts added, reliability and life are the most difficult problems.
Therefore, so far, all countries are still in the early stage of research and development, and there is no variable bypass ratio engine that can really be produced.
Compared with the variable bypass technology, which sounds extremely difficult, the variable cycle technology is relatively simple and easy to understand.
There are currently two directions for variable cycle.
One is to enable or disable the afterburner according to the situation. The afterburner is actually a fuel injection combustion device added at the intersection of the hot and cold gases ejected from the inner duct and the outer duct, which uses the unconsumed oxygen in the air to burn again and increase the thrust. In this state, the entire engine is actually no different from a turbojet.
The other is to directly control the ratio of gas entering the inner and outer ducts by adding several gas valves. When high thrust is required for takeoff or penetration, most of the gas is introduced into the combustion chamber of the inner duct for combustion and ejection.
The second method was actually developed by Pratt & Whitney of the United States in 1962. This self-circulating engine named J-58 is also the world’s first variable cycle engine put into use. It is equipped with the SR-71 “Blackbird” strategic reconnaissance aircraft.
And this aircraft equipped with the J-58 self-circulating engine, which looks extremely sci-fi and like an alien product, has indeed become a myth of an era.
It is the first practical jet aircraft that successfully broke through the thermal barrier. Its speed of Mach 3.2 is so fast that even missiles cannot catch up with it. It has been in service for 24 years and has been attacked by thousands of anti-aircraft missiles. However, except for a 5200 missile that damaged it during a reconnaissance mission against Goryeo, the rest were unscathed. Its technological content is still worth fighting for now.
In the competition with the Russians, both sides did come up with a lot of black technology with the whole country’s efforts, and they are still enjoying the benefits brought by that technological competition.
However, in the competitionDuring the competition, ordinary people’s lives were not so good, just like China tightened its belt to develop two bombs, miracles have to pay a corresponding price.
After the end of the Cold War, the Blackbird cost up to 2 billion dollars per aircraft and the monthly operating cost of 37 million dollars, which made the old M cry out that it could not afford it, and finally withdrew from the stage of history in 1998.
In addition to HP’s J-58, the old American GE company also successfully developed the F-120 variable cycle engine, but it was eventually eliminated due to cost and other reasons. Later, GE learned a lesson and did not blindly pursue high technology, but instead sought cost-effectiveness.
At present, China is also studying and conquering the technologies of reverse thrust, variable cycle, and variable bypass. What has been taken out is the afterburner technology, but it is not the kind that can be started and stopped automatically.
As for Kang Chi,
He is more greedy. Since it is theoretically feasible, he wants it all! However, after he really started working on it, he found that things were far from as simple as he had imagined.
Not to mention anything else, just for him to follow the drawings of the turbofan 20 and reproduce a turbofan 20 would take a lot of effort, not to mention a brand-new black-tech engine.
For the aerospace engine, there are three main cores: design, materials, and technology.
Among them, the design drawings are available, and the country will definitely provide whatever materials you want, but for the technology, if you don’t go to the aerospace industry to learn, it will probably take Kang Chi a year or two to figure it out by himself.
But from the fact that the aviation industry only gave the drawings but not the technology, it can be seen that they still want to keep some tricks for Kang Chi, which is understandable. If someone came to Kang Chi to ask for the drawings and technology of the lithography machine, he would definitely not be happy.
Although Cai Yaobin seemed to be calm when he gave him these “learning materials”, and even feared that he would not be interested, it must have been the military bosses who took great pains to help him get them.
So Kang Chi did not expect to learn these techniques from Xi’an Aircraft Industry Corporation, and could only do it by himself.
How to solve the problem? The only way is to cheat.
So Kang Chi finally chose to downgrade the technology. As long as he could build an engine with these functions, even if the performance was poor, it could only ignite smoothly for one second and allow the system to pop up the panel.
But even so, the whole design process was extremely difficult. Just to design a foldable and retractable outer duct sleeve, Kang Chi spent more than ten days and made dozens of attempts before finally making a roughly feasible one. The development of the entire prototype took more than forty days, and the performance…
[Item: Large Bypass Turbofan Engine]
[Manufacturer: Kang Chi]
[Item Level: 1]
[Experience: 0/50000]
[Item status: intact]
[Item parameters: maximum thrust 8500kgf, maximum reverse thrust 3500kgf, 6-10 variable bypass ratio, manual variable cycle afterburner, service life 1000 hours]
[Analysis items: no analysis items]
[General experience: 493464]
[Mastery points: 71 (+20)]
When Kang Chi saw the panel popped up smoothly by the system, he was delighted, but also a little frustrated.
An intake fan with a diameter of 3 meters, and an engine with so many cutting-edge technologies, the maximum thrust is only 8.5 tons, and the service life of tens of thousands of hours, which is more advantageous for large bypass ratio engines, is even lower than that of turbojet…
It can only be said that aero engines are really difficult.
The key is that aero engines are not like chips. After knowing the principle of chips, it is not difficult to make an integrated circuit with poor performance by hand. However, no matter how good the performance of aero engines is, the first thing to do is to solve the problem of high-temperature combustion and high-speed normal operation, not to mention that so many functional modules must be successfully added, so the starting threshold is very high.
However, with the prototype, the rest is easy to handle. Kang Chi decided to upgrade boldly until he could not upgrade anymore. How can military equipment not have some black technology! Not only this engine, but also the small bypass ratio engine to be developed in the future, as well as the rotating detonation ramjet engine used for close-range ultra-high-speed penetration and rockets, and even the entire drone aircraft carrier and ship-borne equipment cluster plan, he is ready to use black technology to the fullest.
In fact, except for battery technology, Kang Chi has always been restrained in upgrading items, because it is too black technology, and it must upgrade the existing industrial system. It is very troublesome to mass produce, and the cost may not be controlled.
The second is that analyzing black technology is too proficient.
Finally,He was worried that the technology that was too dark in the early stage would easily make people suspicious.
But after several recent attempts, especially the super-strong carbon fiber material technology that was suddenly brought out, not to mention pulling him to dissect it, there was not even a question, which made Kang Chi bolder.
Maybe some people will doubt behind his back, but they will definitely not delve into it, or in other words, when others find it difficult to understand the technology that Kang Chi brought out, the final right of interpretation is already in his hands.
If you can’t find any problems with a few random words, how can you delve into it?
Upgrade!
[General Experience – 50,000]
[General Experience – 150,000]
[Insufficient experience to upgrade failed, and the civilization has not unlocked the front metal element 376]
The front metal element 376 has not been unlocked? When Kang Chi saw the panel that popped up on the third upgrade system, he was stunned.
The prompt of insufficient general experience is nothing. Two upgrades have used 200,000 experience points. The remaining 290,000 experience points cannot be upgraded. However, the metal element 376 in the front is a bit interesting…
The civilization has not been unlocked, which means that humans have not yet discovered it, and it is not on the periodic table at all. There are only two ways to discover new elements. One is artificial synthesis.
The other is that nature itself exists, but it has not been found, or it does not exist on the earth at all, lying on other planets waiting for human discovery.
But just a digital number, the amount of information is too little, Kang Chi can only put this matter aside for the time being, and carefully look at the upgraded engine parameters.
[Item: Large bypass turbofan engine]
[Manufacturer: Kang Chi]
[Item level: 3]
[Experience: 0/450000]
[Item status: intact]
[Item parameters: maximum thrust 50000kgf, maximum reverse thrust 30000kgf, 6-10 variable bypass ratio, adaptive variable cycle afterburner, service life 20000 hours]
[Analysis items: analyzable]
[General experience: 293464]
[Mastery points: 71]
After seeing the system parameters, Kang Chi couldn’t help but shout: The system is awesome! Although the upgraded engine is larger, the maximum thrust of 50 tons is equivalent to that of three turbofan 20s and 2.56 F117s…
The most important thing is that its current volume is under the condition of 10 bypass ratio. If the bypass ratio is reduced, its volume can be reduced by 40%, and the power is also the greatest in this state.
If the fuselage material is not torn by wind resistance and thrust, it is definitely not a problem to replace four of these things on the Y-20.
And a large transport aircraft that can fly at supersonic speed? Just thinking about it is exciting!
Of course, large supersonic transport aircraft have no practical use except to show off.
The real meaning of this engine is to be able to build a larger transport aircraft.
Or replace the four turbofan 20s on the Y-20 with two turbofan 30s, greatly reducing the dead weight and improving the thrust-to-weight ratio.
The result is that the maximum speed, acceleration and load-carrying capacity can all achieve a qualitative leap.
After the excitement, Kang Chi opened the analysis panel again.
Design analysis requires 10 mastery points.
Material analysis requires 15 mastery points.
Process analysis requires 20 mastery points.
Because the engine technology is too core, Kang Chi did not hesitate to analyze all three projects, and the whole process of knowledge infusion lasted two minutes.
Because it was basically the engine he designed himself, with the previous experience accumulation, the process of information acquisition was relatively easy. Kang Chi only took an hour to absorb and organize all the knowledge and turned it into his own knowledge.
This wave of analysis has made him a leap forward in his design ability for engine design. Although this Class III large bypass turbofan engine is somewhat similar to his previous design, a lot of design optimization and adjustments have been made. Behind every small detail, there are places worth thinking about and learning.
For example, the fan diameter of the air inlet was changed. Kangchi originally achieved this by reducing the number of blades and changing the angle.
But after the system upgrade, this design was directly changed to fold the blades backwards and change the inclination angle of the blades, which looks like a badminton. Although this seems to be aerodynamic,Mechanics, it can also not reduce the number of blades and the amount of air intake, but the design difficulty is several levels higher.
In terms of material analysis, he also obtained a new structural ceramic material that is resistant to high temperature, high strength and corrosion. It is mainly composed of Al203, ZrO3 and C-BN, Si3N4, Sic and other materials, and the production process is also very complicated.
The next step is to seize the time and mass-produce this engine as soon as possible.
The main idea is the same as before, and it is still possible to find a foundry to do it, and try to give full play to the advantages of China’s industrial system.
The second is to improve the efficiency of the Pangu base and maximize the utilization rate of the Pangu base.
However, before that, Kang Chi plans to complete the redesign of the Y-20 first, and then find a way to let Xi’an Aircraft to help him build a fuselage.
When the time comes, install the turbofan 30 and test it directly, giving them a big surprise. In the future, it will be easier to get support for the research and development plan of drone aircraft carriers and ship-borne equipment clusters.
(End of this chapter)