Whether the performance of an aircraft engine is good or not is usually to look at its thrust first, and then pursue fuel economy on this basis.

But here's the problem,

According to the two formulas of F (thrust) = W * (C1 outlet airflow velocity - C0 aircraft speed) and efficiency n=2/1 + (C1/C0), it can be concluded that:

The faster the engine outlet velocity C1, the greater the thrust, but the correspondingly lower efficiency.

In addition to this problem, the bypass ratio of the aircraft at different flight altitudes and speeds also has a very big impact, for example, for fighters with small bypass ratios, the bypass ratio is more than 0.7, which is more suitable for low altitudes, and the bypass ratio is lower than 0.5, which is more suitable for high altitudes.

Therefore, fuel saving and thrust, large bypass ratio and small bypass ratio, itself is a contradiction, it is difficult to take into account all aspects, and this is actually only one of the contradictions between various needs and technology when designing aviation engine.

Behind every seemingly subtle design change is a compromise between requirements and technical trade-offs.

Of course, technology is constantly evolving, and scientific research also pays attention to a bold assumption and careful argumentation.

In the case of large ducted turbofan engines for passenger and transport aircraft, they have only one inlet fan, and they are usually more than three meters in diameter, so they can draw in a very large amount of air, most of which goes into the outer duct, providing more than 85% of the engine's thrust.

Therefore, for large ducted engines, the effect of expanding the diameter of the outer duct and fan to increase thrust is very obvious, and the F135 engine on the F35 does just that.

However, the side effects are also obvious, the diameter of the outer duct and the fan is too large, and the windward resistance is greater, so it is difficult for the aircraft with a large bypass ratio to fly at supersonic speeds.

So some people raised a question, since the aircraft needs a small bypass to obtain greater thrust and speed when taking off or fighting, and when cruising, the pursuit of a large bypass is greater than the pursuit of fuel economy and endurance.

Wouldn't it be a perfect solution to this problem if you got an engine with a variable bypass ratio?

Theoretically feasible, the turbofan engine is to put it bluntly, that is, two packages with different diameters and sizes are set together, as long as a retractable outer cylinder and fan are built, a variable bypass ratio engine will come out.

But even this seemingly simple principle is really difficult to make.

As soon as you hear the name of this thing, you will know that the structure must be very complex, not to mention whether it can be made, just in the high-temperature and high-speed engine, adding so many systems and parts, reliability and life are the old and difficult problems.

Therefore, so far, all countries are still only in the initial stage of research and development, and there is no variable bypass ratio engine that can really be taken out.

In contrast to variable duct technology, which is extremely difficult to listen to, variable cycle technology is relatively simple and easy to understand.

There are currently two directions for the variable cycle,

One is to activate or deactivate the afterburner according to the situation, and the afterburner is actually at the intersection of the hot and cold gases sprayed out of the inner duct and the outer duct, and then add an oil injection combustion device to use the oxygen that has not been consumed in the air to burn again and improve the thrust.

The other is to directly control the proportion of gas entering the inner and outer ducts by adding several gas valves, and when high thrust is needed to take off or penetrate the defense, most of the gas is introduced into the combustion chamber of the internal duct to burn and spray.

The second method, in fact, was developed in 1962 by country M Pratt & Whitney, and the self-circulation engine named J-58 was also the world's first variable-cycle engine put into use, and it was equipped with the SR-71 "Blackbird" strategic reconnaissance aircraft.

And this aircraft, equipped with a J-58 self-circulating engine, looks very sci-fi and looks like an alien product, and it has indeed become a myth of the times.

It is the first practical jet aircraft to successfully break through the thermal barrier, the speed of Mach 3.2 can not even catch up with the missile, it has been attacked by thousands of anti-aircraft missiles in 24 years of service, but except for a reconnaissance mission to Goryeo was damaged by a 5200 missile, the rest are all unharmed, and its technological content can still be played even now.

In the competition with Lao Maozi, both of them did hold back a lot of black technology with the power of the whole country, and even now they are still enjoying the afterglow brought by that science and technology competition.

However, in the process of the competition, the life of ordinary people is not so good, just like Huaguo tightening his belt and making two bullets, miracles have to pay a corresponding price.

After the end of the Cold War, Blackbird was overwhelmed by the cost of up to 2 billion knives per aircraft and the monthly cost of 37 million knives, and finally withdrew from the stage of history in 1998.

In addition to HP's J-58, GE of the United States also successfully developed the F-120 variable-cycle engine, but it was eventually eliminated because of cost and other reasons.

At present, Huaguo is also studying and overcoming the technologies of reverse thrust, variable cycle, and variable duct, and what has been taken out is afterburner technology, but it is not the kind that can automatically start and stop.

As for Kangchi,

He's greedy, and since it's theoretically possible, he's going to have them all!

It's just that after he really got it, he found that things were far from being as simple as he imagined.

Not to mention anything else, just for him to follow the drawings of the turbofan 20 and reproduce a turbofan 20 would have to take a lot of effort, let alone a new black technology engine.

For Hangfa, there are three main cores: design, materials and technology.

Among them, the design drawings are available, and the materials will definitely be provided by any country that they want, but if you don't go to the aerospace industry to study, it will be difficult for Kangchi to figure it out by itself.

However, it can be seen from the fact that the aviation industry only gives drawings but not processes, and they still want to keep a hand on Kangchi, which can also be understood, if anyone comes up to Kangchi to ask for the drawings and technology of the lithography machine, he will definitely not be happy.

Although Cai Yaobin seemed to be indifferent when he gave him these 'learning materials', and he was even afraid that he would not be interested, but the military bigwigs must have worked hard to get them for him.

Therefore, Kangchi did not expect to learn these processes by going to Xifei, so he could only do it by himself.

The only way to solve the worries is to open the hanging.

So Kangchi finally chose to downgrade the technology, as long as it can build an engine with these functions, even if the performance is poor, it can only ignite smoothly for one second, so that the system can eject the panel.

But even so, the whole design process is extremely difficult, just to design a foldable and scalable duct sleeve, it took more than ten days, dozens of attempts to finally barely come up with a feasible, the entire prototype research and development took more than 40 days, and the performance......

[Item: Large Ducted Turbofan Engine]

【Manufacturer: Kangchi】

[Item Level: 1]

[Experience: 0/50000]

[Item Condition: Intact]

[Item parameters: maximum thrust 8500kgf, maximum reverse thrust 3500kgf, 6-10 variable duct ratio, manual variable cycle afterburner, service life 1000 hours]

[Parsed item: No parsed item]

[General Experience: 493464]

[Mastery Points: 71 (+20)]

When seeing the panel that the system popped up smoothly, Kangchi was delighted, but inevitably had a little frustration.

An air inlet fan with a diameter of 3 meters, and so many cutting-edge engines, the maximum thrust is only 8.5 tons.

Moreover, the service life of tens of thousands of hours that the large duct has advantages over the engine is lower than that of the turbojet......

It can only be said that it is really difficult to develop the aircraft.

The key is that Hangfa is not like a chip, after the chip knows the principle, it is not difficult to rub an integrated circuit with poor performance by hand, but no matter what the performance of Hangfa is, it is first necessary to solve the problem of high-temperature combustion and high-speed normal operation, not to mention the successful addition of so many functional modules, so the starting threshold is very high.

But with a prototype, the rest is pretty much the rest.

Kangchi decided to boldly upgrade until it couldn't be upgraded, how could military equipment be black technology!

Not only this engine, but also the small bypass ratio engine to be engaged in in the future, as well as the short-range ultra-high-speed detachment defense penetration and the rotary detonation ramjet engine used in the rocket, and even the entire UAV aircraft carrier and shipboard equipment cluster plan, he is ready to fill up the black technology.

In fact, in addition to battery technology, Kangchi has always been more restrained in the upgrading of items, because it is too dark technology, it must upgrade the existing industrial system, which is very troublesome in mass production, and the cost may not be controllable.

The second is that it is too expensive to analyze black technology.

Finally, I am worried that I will come up with too black technology in the early stage, which is easy to make people suspicious.

But through the last few attempts, especially the super carbon fiber material technology that was suddenly taken out, let alone pulling him to unravel, there was not even a word of questioning, which made Kangchi's courage suddenly a lot bigger.

There may be people who will doubt it behind their backs, but they will definitely not delve into it, or when the technology that Kangchi has come up with is difficult for others to understand, the final interpretation is already in his hands.

You can't find a problem with a few casual words, how can you dig deeper?

Upgrade!

[General XP-50000]

[General XP-150000]

[Lack of experience failed to upgrade, and civilization did not unlock the pre-376 metal element]

Didn't unlock the front metal element No. 376?

When he saw the panel that popped up from the third upgrade system, Kangchi was stunned.

The hint of lack of general experience is nothing.,It took 200,000 experience to upgrade twice.,The remaining 290,000 or so experience really can't be upgraded.,But this front-mounted No. 376 metal element is a bit interesting......

Civilization has not been unlocked, which means that human beings have not yet discovered things that are not on the periodic table at all, and there are only two paths to the discovery of new elements.

One is synthetic.

One is that nature itself exists, but it has not been found, or there is no one on the earth at all, lying on other planets waiting for humans to discover it.

But just a number number, the amount of information is too little, Kangchi can only put this matter aside for the time being, and take a closer look at the upgraded engine parameters.

[Item: Large Ducted Turbofan Engine]

【Manufacturer: Kangchi】

[Item Level: 3]

[Experience: 0/450000]

[Item Condition: Intact]

[Item parameters: maximum thrust 50000kgf, maximum reverse thrust 30000kgf, 6-10 variable bypass ratio, adaptive variable cycle afterburner, service life 20000 hours]

[Parse item: Analyzable]

[General Experience: 293464]

[Mastery Points: 71]

After seeing the system parameters, Kangchi couldn't help but shout: The system is awesome!

Although the upgraded engine is larger again, the maximum thrust of 50 tons is worth 3 turbofan 20 and 2.56 F117......

The most important thing is that its current volume is in the case of 10 bypass ratio, if the bypass ratio is reduced, its volume can be reduced by 40%, and the power in this state is also the largest.

If the fuselage material will not be torn apart by wind resistance and thrust, directly replace the four of these things on the Y-20, and supersonic flight will definitely not be a problem.

And a large transport aircraft that can fly at supersonic speeds?

It's exciting just thinking about it!

Of course, large supersonic transport aircraft have little practical role other than being able to load and force.

The real meaning of this engine is to be able to build a much larger transport aircraft.

Or the four turbofan 20 on the Yun 20 are directly replaced with two turbofan 30, which greatly reduces the dead weight and improves the thrust-to-weight ratio.

The result is a qualitative leap in top speed, acceleration and load capacity.

After the excitement, Kangchi opened the analysis panel again.

Design parsing, which requires the cost of mastery points: 10.

Material analysis, requires the cost of mastery points: 15.

Process analysis, need to consume mastery points: 20.

Because the engine technology is too core, Kangchi did not hesitate to analyze all three items, and the whole process of knowledge infusion lasted two minutes.

Because it is basically an engine designed by himself, with the accumulation of pre-experience, the process of information acquisition is relatively easy, and it only took one hour for Kangchi to absorb and sort out all the knowledge, and turn it into his own knowledge.

Although this Class III large ducted turbofan engine as a whole is a bit similar to his previous design, a large number of design optimizations and adjustments have been made, and behind every small detail, it is worth pondering and learning.

For example, the fan diameter of the air inlet was changed, and Kangchi originally achieved it by reducing the number of blades and changing the angle.

However, after the system was upgraded, the design was directly changed to fold the blades backwards, and at the same time change the tilt angle of the blades, which looks like a shuttlecock, although it looks aerodynamic, and can not reduce the number of blades and the amount of air suction, but the design difficulty is several levels higher.

In terms of material analysis, he also obtained a new structural ceramic material with high temperature resistance, high strength and corrosion resistance, which is mainly composed of Al203, ZrO3 and C-BN, Si3N4, Sic and other materials, and the production process is also very complex.

The next step is to hurry up and mass produce this engine as soon as possible.

The main idea is the same as before, if you can find an OEM, you can do OEM, and try to give full play to the advantages of Huaguo's industrial system.

The second is to improve the efficiency of the Pangu base and fill the utilization rate of the Pangu base.

However, before that, Kangchi plans to complete the redesign of the Yun-20 first, and then find a way to ask Xifei to help him build a fuselage.

When the time comes, the turbofan 30 will be installed and the direct test flight will give them a big surprise for the whole wave, and it will be easier to get support for the research and development plan of the UAV carrier and carrier-based equipment cluster in the future.

(End of chapter)