"The GE9 is a good core machine, but the total pressure ratio is too high, and the compressor blades with low aspect ratio are a new topic for us, both in terms of design and manufacturing, since the successful experience of the turbojet 14, there is no need to start a new stove in this kind of place......

Chang Haonan quickly wrote down a few strings of numbers on the paper while introducing:

"At present, the pressure ratio of several mainstream third-generation high-thrust turbofan engines in the world, F100 and AL31F, is in the range of 24-25, and the pressure ratio of F110 is outstanding, and it should be nearly 31. I see that your design, and even use a more efficient bending blade design for the compressor, I am afraid that the pressure ratio will go to 32-33, so that for the two installed objects of our turbofan 10, the adaptability will be very poor......"

After all, it is impossible for the aviation engine to stay on the ground test bench all the time, but to be installed on the aircraft and really take off to fly.

Therefore, even if the aviation power system is really independent in the future and the engine project no longer exists as a supporting aircraft project, it is impossible to design the aviation development without considering the actual situation of the installed object.

A high pressure ratio is indeed a good thing, but it is definitely not a brainless higher the better.

When an engine with an over-high-pressure ratio, especially a turbofan engine, exceeds the speed of sound, the power consumption of the compressor will increase rapidly, resulting in the right shift of the isentropic compression line, the reduction of compressor efficiency, and the reduction of circulating work.

Although the total pressure ratio on paper is still very high, the actual usable effective pressure ratio is lower.

The reaction is that in terms of actual performance, it is a dragon in the low-speed state of this engine, and when the speed is high, it becomes a worm.

Both the F110 and F404/414 have this problem.

How big is the gap?

These two engines with a more advanced technical level are not only inferior to the AL31F and RD93 in terms of thrust curve in the supersonic state, but also inferior to the latter two in terms of fuel consumption.

It's a problem that's constrained by basic physics.

Unless a variable-cycle engine is developed, it is impossible to achieve both performance under various working conditions from the root.

The F119 engine on the F22 chose the opposite design of the F110 for supersonic performance, and the result was that supersonic cruise can be carried out without afterburner, but the fuel consumption in the military push state is extremely high, resulting in the entire aircraft becoming a small short leg in the case of huge internal fuel.

It's not that Pratt & Whitney's designers can't do it.

It's just a trade-off.

The ATF program was born at the height of the Cold War, when the idea was to engage in short, high-intensity combat over Europe and then either shoot down or return home without much range.

It's just that the plan can't keep up with the changes, and when the F22 enters service in 2005, it finds that it has to go to the vast Pacific region to exert its residual heat, and the result is that the performance is out of touch with the demand.

Of course, although it is impossible to solve the problem fundamentally, there are ways to improve it -

It is enough to redesign the aircraft with an adjustable air inlet that is better matched and has a wider range of boost capacity adjustments.

Later, the new model F15 adopted this line of thinking.

As for the F16 and F18......

Laugh to death, what supersonic performance do you want for a medium machine, stay honest and go.

And the current situation is that the overall design of the J-11 is Su-27, and the basic design of the fuselage + air intake channel already has a very anti-sky boost ability, and it is not easy to really lower it.

The J-10 has simply determined to use the non-adjustable DSI inlet channel, and it is also impossible to fix the inlet state in a state of low efficiency and low boost ratio due to small losses.

Therefore, although the turbofan 10 can play freely at the specific technical level, in terms of performance style, it still has to take the route of F100/AL31F, and it is advisable to determine the boost ratio around 25.

The overall design of an aero engine is an extremely complex system engineering, which is reflected before the actual "design" work begins.

"Oh......"

At the end of Chang Haonan's explanation, Hai Yide and Liu Yongquan stared at each other a few times.

Everyone is a professional technician, although I didn't expect this layer with little experience before, but now that others have said it, it will definitely be understood.

"But Mr. Chang, if the boost ratio is restricted, then the overall performance of this engine in the subsonic state, especially the fuel consumption and thrust-to-weight ratio, will definitely be affected......"

The main performance optimization interval of the third-generation fighter is definitely in the high subsonic to transonic segment.

Whether it is the F100, AL31F or RD93, they all sacrifice a certain degree of subsonic performance, especially the RD93, the huge fuel consumption at low speed (or twin engines) and the already small amount of internal oil directly give the MiG-29 the name of the airport defender.

For the Huaxia Air Force, which is expected to conduct high-intensity operations far away from the airport, this is indeed a relatively critical issue.

"Yes, Mr. Chang, J-11 has 9 tons of internal oil, but I don't care about a little fuel consumption, but I look at the body of the J-10, the amount of internal oil should not be very optimistic......"

Haiyide, who was next to him, also expressed the same concern.

In fact, this is one of the main reasons why when the 611 designed the J-10 at the beginning, the two inner pylons were directly bound to the auxiliary fuel tank.

The AL31FN is also the AL31F after all, but it has changed some details such as the location of the accessory box slightly, and the engine is still the same engine.

After being installed on the J-10, the range without auxiliary fuel tanks is really unsightly.

However, Chang Haonan shook his head decisively:

"The problem of fuel consumption can be solved by increasing the pre-turbine temperature by another 50-100°C."

It's a pretty simple and crude approach, but it's also the most effective.

Chang Haonan adopted the same approach on the turbojet 14 to ensure the performance of the J-8C at different altitudes and speeds.

"Mr. Chang, the temperature before the turbine of our third-generation big push is now set around 1200 °C, which is already a high threshold for our material science level, if we add ...... more"

Liu Yongquan, as an aviation development designer, naturally considered these problems comprehensively, but looking at Chang Haonan, who was holding a pen next to him, and thinking about the things over there of Turbojet 14, it didn't seem so incredible.

But after a moment of hesitation, he spoke:

"If I go any further, I'm worried that the risk level and schedule of the whole project will get out of control."

1200°C is already the mainstream level of the third generation turbofan engine in the world.

It is indeed difficult to create turbine discs and turbine blades that surpass the level of heat resistance of the United States in a short period of time.

With such a thing as materials science, it is difficult to have any opportunistic opportunities.

Huaxia can now come up with nickel-based superalloy raw materials with similar properties to ReneN5, but it is still the same old problem, if you want to make things, it is useless to have just one piece of raw material, and a series of supporting research such as follow-up processing is also needed for each material, which is also quite time-consuming and resource-intensive.

If you give up the second-generation alloy materials that already have certain supporting research results and industrial practical experience in your hands, and jump directly to the third generation, it is very difficult to say the risks involved.

"Of course, it's still too radical to change the material directly......"

After directly smashing out TORCH Multiphysics with system integrals, Chang Haonan is currently on the verge of "bankruptcy", and there are not so many points to comprehensively raise the level of the entire field of materials science.

This way of improvement is also too blunt, and it does not conform to the logic that Chang Haonan set at the beginning.

Taking a step back, even with the help of the system, the intermediate process will go smoothly, and it will take several years for him to solve the countless problems in the middle, to say the least.

Chang Haonan's plan is to give at least the prototype with the turbofan 10 installed as much as possible a chance to participate in the 50th anniversary National Day parade more than two years later.

It's definitely too late to dry and wait for the materials.

"So I'm going to adopt a new active cooling scheme in the turbine structure, and there is still a lot of potential for the current air film hole cooling, and it is not a big problem to increase the pre-vortex temperature by 50-100°C without changing the matrix material."

After finishing speaking, he didn't pay attention to the stunned few people next to him, but took back the drawing in front of him with a simple schematic diagram:

"As for the thrust-to-weight ratio you just mentioned, let's just abandon the 3-9-1-2 structure, or this structure."

"Huh?"

The other people in the conference room only felt that their brains were on the verge of death because they had received too much information in a short period of time:

"Not with this structure...... Is it a centrifugal compressor? ”

The turbine compressor of the gas turbine can be simply divided into centrifugal and axial flow according to the principle, generally speaking, except for the early stage of the demons, the vast majority of turbojet/turbofan engines have uniformly used the axial flow type, and only some turboprop/turboshaft engines will adopt the centrifugal design.

"Of course not......"

Chang Haonan was a little helpless:

"What I mean is that the use of a higher efficiency single-stage load to reduce the number of stages of the compressor, compress the three-stage fan into a 1-stage or 2-stage fan, and the 9-stage high-pressure compressor into a 6-stage or 7-stage fan, considering that the weight of the entire compression system in an engine accounts for about 60%, if the weight can be reduced by 20% in this part, the thrust-to-weight ratio of the entire engine can be increased by about 10%."

"Do you remember the 'ultra-high load adsorption bending joint leading edge edge blade' that I took out as an example at the last meeting?"

Hai Yide didn't go to the meeting last time, but Liu Yongquan did.

I also listened very carefully.

Therefore, he was the first to react from the confusion just now and nodded:

"Remember, I took notes......"

As he spoke, he pulled out a notebook from the bag he was carrying with him and flipped to one of the pages.

From this slightly dilapidated trace, it can be seen that he may have read a lot during this time.

"That's good."

Chang Haonan lightly tapped the title part of the notebook with his finger:

"This thing is the core technology of our compressor design part."

"The blade design you have learned before, whether it is end bend and end sweep, end wall shape, or edge strip, is still a means of passive control of flow separation."

"The reason why I want to mention the adsorption blade is to use active control means to further improve the single-stage pressure ratio on this basis, so that each stage can play the compression role of one and a half to two stages in the past!"

(End of chapter)