Before he walked to the test center, the roar of the engine had not stopped, and even Yang Hui heard two engines with different noise frequencies, and he could see that the test center should be running at full capacity.

Along the way, the two of them were in a hurry, but Yang Hui spoke, he had something to ask.

"Construction, do you know the progress of the turbofan 10 engine test in the institute now? It's the end of the year, and it's eight or six years in more than ten days, and we don't have much time. ”

Yang Hui is worried about the turbofan 10 engine test here, Zhong Jianshe is not worried, this guy has been in the second institute and has not run around, unlike Yang Hui, who goes around as a pastemaker.

Naturally, the test progress of the turbofan 10 engine here is more clear: "There is no need to worry, the current turbofan is not only tested on the ground, but also flown for many hours on the H-6 086 test platform." It is said that preparations are now beginning to be made to install the engine on the Jianjiao 7A test, and it will be ready for the installation and take-off test in the middle of next year. ”

Hearing Zhong Jianjian's introduction, Yang Hui understood, the original test of the new engine was so fast, it seems to be quite efficient, and the current turbofan 10 should be the largest investment in the Republic of China A self-developed engine, in fact, it seems to be very effective.

However, this time when I went to the test center, I should pay attention not to the turbofan 10 engine, but to the gear transmission system of the TFE731 engine, which was also tested here, but only to test the transmission system, which did not occupy much resources.

Walking to the TFE731 engine being tested, this engine has just stopped running, and the continuous working time of an engine is a requirement obtained after rigorous testing. The test center here can't mess around with the test, and when the time comes, you have to stop honestly.

The engine stopped. The noise was much quieter, and Zhong Jianshe took the opportunity. Explain to Yang Hui.

"Yang Group, our gear reduction system is not visible here, this is already the transmission system installed on the engine, and there is only a single transmission system in the test center."

Yang Hui glanced at the TFE731 engine on the test bench twice, and then went to the test center with Zhong Jian according to the guidance and under the guidance of Zhong Jianjian.

Walking to the test center, Yang Hui saw a hot scene, compared with the first time he came to the test center to test the small vortex used by the model aircraft. It's definitely a busy chicken and dog jump right now.

"This is one of the first five drivetrains we built, and it looks pretty good, and we have no problem with the technology, but because of the design limitations of the system, it's very difficult for us to use it in the new eight-ton turbofan."

Zhong Jianshe repeated again that this set of gear transmission technology has no upgrade potential, which made Yang Hui very surprised, the gear transmission technology can definitely be used in the eight-ton turbofan, and the gear transmission engines of Pratt & Whitney have been used in the A320 class of passenger aircraft.

It is necessary to know that the engines used in passenger aircraft of the A320 level are already ten tons or more. This shows that geared engines are technically completely feasible.

With deep puzzlement, Yang Hui carefully observed the TFE731 engine gear transmission system on the workbench. Yang Hui felt that the whole person was not good.

This Garrett company really has some ability, to engage in gear transmission technology, between the compressor and the fan, it actually uses a fixed shaft gear train. Seeing this, Yang Hui felt as uncomfortable as eating a fly.

Ability to reduce fixed shaft gear train to this level. And installed between the fan and the compressor, Yang Hui felt that this was also an ability.

At the same time, I sighed: It's no wonder. When Garrett designed the TFE731 engine gearbox, it encountered a very difficult problem of gear heating.

If you want to talk about fixed-shaft gears, in fact, there are a lot of things used in aero engines, the most common is the gear gearbox of turbo engines, which are usually used fixed-shaft gears.

Fixed shaft gears have many advantages, which can achieve multi-stage speed change, but they are not without disadvantages: the volume is relatively large, and it is not very symmetrical, and when it is used in a turbo engine, because it is directly placed between the engine and the propeller, there is still a lot of space, so it is naturally no problem to use.

It is somewhat difficult to use in a relatively compact turbofan engine, which is definitely a point of no return, and the thrust of the TFE731 engine is relatively small, and the power transmitted is not large, so it can be used for the time being.

But to be used in an engine with a thrust of about eight tons, this is absolutely impossible, this detour must be corrected, according to the insight of later generations, Yang Hui knows what is the right way.

Clapping his hands, with a look of contempt, this thing seems to be a bit of a loss when he buys it back, but this is also eight million dollars, just get this thing, Yang Hui regrets it incomparably, why didn't he carefully understand the specific situation of this gear transmission system at that time?

"Don't worry about it anymore, the gear transmission used on the TFE731 does not have much development potential, and Garrett actually uses fixed shaft gears on it, which can be made to show that their attainments in fixed shaft gears are really good, but it is obviously a detour."

As soon as Yang Hui's words came out, Zhong Jianshe was not lightly shaken, and the fixed-shaft gear technology used by Garrett Company now has no future? So what has a future? Since this is the case, why did Yang Hui advocate the introduction of the gearing technology of this engine at that time?

A series of questions made Zhong Jianshe completely confused, and he didn't even know what to ask, there were too many questions, and it was even more difficult to solve.

Yang Hui could only say slowly: "In my opinion, the gear reducer between the fan and the compressor of the turbofan engine can only use planetary gears, which is the only way out." ”

Planetary gears, which are complex gear reducers to manufacture and design, were too few places to use planetary gears in the 80s, and the cost of this thing was too high.

Of course, the benefits of planetary gears are also quite attractive: not only are they small in size; Its transmission accuracy is also quite high, and the general clearance can be less than ten arc minutes (one rotation 360 degrees, one degree 60 arc minutes); The transmission efficiency is also far beyond other gear transmission systems, and the general transmission efficiency of planetary gears is 95% upwards; It also has a fairly high output torque; The operation is also quite smooth, its vibration is low, and the noise is controlled below 65 decibels.

The only disadvantage is that the design is troublesome, the cost is high, and there are relatively high requirements for materials, processing technology, etc., which is why the planetary gears with many benefits do not completely occupy the gear transmission system market.

In the eighties, the general fixed-shaft gear train can also meet the requirements that people need, and there are not too many requirements for high-precision transmission, so that Garrett company did not use planetary gears in the development of TFE731 engine.

But now, Yang has put forward such a bold idea, the planetary gears are installed in the geared turbofan engine, and the advantages of the planetary gears will be vividly reflected at this time, which is simply a match made in heaven.

As for the problems of high cost, troublesome design, and high requirements for materials and processing technology, Yang Hui feels that this is not a problem at all, and with the participation of MTU company, these can be overcome.

Later generations joked that the Germans' heads were full of engine oil and gears, which was used to satirize the rigidity of Germany and at the same time to praise the rigor of the Germans.

But why use the gear metaphor? There's definitely a reason for this (to be continued......