Chapter 462 High-performance film cooling, breaking through the temperature in front of the turbine

After attending the roll-off ceremony of the first domestic J-11 aircraft, as the chief designer of the turbofan 10 project, Chang Haonan has arrived in Shengjing, and he must visit the 606 Institute and the 410 Factory.

After all, come here.

For China's aviation industry, the turbofan 10 is almost a "zero-based" engine. Although some of the technologies previously developed during the development of the turbojet 14 can be used, there are not many.

As for the older models, they have no reference value at all.

Before the turbojet 14, China did not even have an aerospace engine research and development system in the strict sense.

Therefore, in order to improve efficiency, Chang Haonan adopted an unprecedented parallel operation of the design and production lines on this project, at the cost of increased risks and workload.

"Mr. Chang."

Chang Haonan came to Shengjing on a temporary basis, and he only showed up at Factory 112 after getting off the plane. Therefore, after he arrived at Factory 606, except for Hai Yide, the chief engineer who had been leading the organizational work in Shengjing, other people Not even prepared.

"Why didn't Mr. Chang tell us before he came? Let's clean it up..."

An engineer following Haiyide touched his unkempt sideburns, which had obviously not been taken care of for many days, and then glanced at the design research room, which was almost covered with all kinds of information and diagrams, with a look of embarrassment on his face. expression.

Although engine design work has now been digitized to a considerable extent, this room is actually a place for exchanges and discussions between several of their R&D groups.

After all, aviation development is a complex system engineering. It is impossible to just knead several parts together like kneading clay and then be done. The failed compressor design at the beginning of the Turbojet 14 has proved that this approach will never work. Therefore, even if it is still in the early stages of the project, everyone still needs to frequently communicate with each other under the leadership of the overall design team to prevent the development direction of a certain subsystem from going too far.

In this process, paper materials are often more convenient. After all, there are no online working software these days.

"It's just plain obvious, isn't it?"

Chang Haonan casually put aside a huge drawing that covered two chairs, and then sat on one of them:

"Although I am not always in Shengjing, since we are the same R&D team, we are a family. Don't act like you are welcoming the leader."

Since the design of aeroengines involves a large number of complex numerical calculations, and currently the city with the richest supercomputing resources in the country is Beijing, and the compressor research center planned for the future is also located at Beijing Hang University, there are actually quite a few The R&D personnel are stationed in the capital with Chang Haonan.

Moreover, he is also a front-line designer, and he has a deep understanding of the mental state of everyone during the project process, especially the critical stages of starting and tackling key problems.

If the office is messy, let it stay messy. Once it is sorted out, there will always be something you can't find.

As the chief designer, he is almost everywhere in the entire project. There is no need for him to show his presence by messing around like some leaders do.

After everyone took their seats, Haiyide quickly brought the topic back on track:

"Okay, now we are almost all here. If you have anything you need to report or ask to Mr. Chang in person, it can save you the trouble of a business trip to the capital. So hurry up and say what you need to say and ask what you need to ask."

Although Chang Haonan is usually in BJ, he does not just abandon Shengjing. Each research and development direction must submit project progress reports every week, and he will also give feedback as soon as possible, so although It’s been two months since I’ve been to School 606, but there’s no grand occasion where everyone has accumulated a bunch of questions and is actively asking them.

"Mr. Chang, let us report the situation in the combustion chamber first."

After a brief silence, an engineer who looked about fifty years old spoke first.

Yin Yongze, one of the deputy chief designers of Turbofan 10, is also the person in charge of combustion chamber technology R&D and design.

He participated in the design of my country's first annular combustor in the Turbojet 14 project. Although in terms of paper performance alone, the immature design is not much better than the previous annular combustor, but due to the flame The barrel is an integral annular cavity, so the space utilization rate is higher, the outlet flow field is evenly distributed and the cooling pressure required is relatively small.

Simply put, the potential is greater.

It was precisely because of Yin Yongze's experience that Chang Haonan dared to hand over the combustion chamber, one of the three major components of the core engine, to him.

"When I reported to you last time, we had already set up the high-pressure test platform for the combustion chamber. During this period, we also carried out some preparation work for parametric design. It is expected that the number of high-pressure tests can be reduced to about half of the previous level. The next step is to start developing calculation models and parameterizing the system. However, the combustion power we have determined now is a bit large, and the requirements for cooling intensity are very high. I wonder if the compressor can provide 6%-8% more Intake air flow?”

Yin Yongze said as he slid a piece of information in his hand along the table to Chang Haonan.

The latter looked through it carefully and found that it was related information on parametric geometric modeling of an annular combustion chamber.

"The pre-processing work has been completed well. In addition, remember that when developing the calculation model later, in addition to the standard centrifugal nozzle, the atomization model can also be used to construct the structure of the centrifugal oil slinger."

Since humans have a relatively unclear understanding of the combustion process, numerical calculations play a relatively small role in combustion aerodynamics and structure, and the research foundation for combustion chamber structures is not as good as that of compressors and turbines, which Yin Yongze can do At this level of parameterization, it is indeed quite good.

"Oil dumper?"

Chang Haonan's request stunned Yin Yongze:

"Our design..."

But he was interrupted by Chang Haonan halfway through:

"Of course the big push like the Turbofan 10 requires the use of centrifugal nozzles, but jet power will definitely become more popular in the future. Small aeroengines are needed for places like cruise missiles and drones, and the oil supply pressure of the oil pan is low and unstable. It’s easy to block, and the most important thing is that it’s cheap, so we just take advantage of the current opportunity to lay a foundation.”

Compared with other aviation development researchers in China in this era, Chang Haonan's biggest advantage, apart from cheating, is his longer-term planning ability.

"Okay, we'll pay attention then."

Yin Yongze opened the notebook in front of him and wrote down this request:

"Mr. Chang, about the air intake flow..."

"6%-8% is too much."

Chang Haonan immediately shook his head:

“现在总体设计层面已经基本把结构确定为2-8-1-1结构或者3-7-1-1结构，这样每一级留出来的余量都很小，6%到8%那几乎要再多加一级高压，肯定不行。”

"But our demand for cooling air flow is indeed much greater. If it doesn't increase..."

Film cooling can be said to be a landmark technology in the history of aero-engine development, but the use of gas for active cooling is not without cost. The gas used for cooling cannot be used for propulsion, which is equivalent to losing a considerable part of the compressor power. .

Therefore, although theoretically better results can be achieved by simply increasing the amount of cooling gas, in actual aircraft engine design, the gas loss rate must still be taken into consideration.

If the inner wall of a combustion chamber consumes at least 6%, then counting the turbine with greater cooling pressure...

And play with a hammer.

If you let out nearly one-fifth of the air that the compressor works so hard to bring in, it may be acceptable for engines with output shaft power such as turboprops and turboshafts, but for turbofan engines, it is basically It's just useless.

而如果再加一级高压，那就要变成3-8-1-1，跟眼下的AL31F根本拉不开差距。

The performance of the AL31F is certainly adequate, but the potential is not.

After all, it is a design from the late 70s.

"What is the upper limit of your combustion chamber outlet temperature setting?"

The temperature in front of the turbine of turbofan 10 (that is, the combustion chamber outlet temperature) is set at 1200-1250c. This is a decision made by Chang Haonan himself, but the cooling system must leave a certain margin. How much margin is left is Yin Yongze's job. .

"Leave 5% margin, 1325c."

This margin is of course calculated in Kelvin.

Then Yin Yongze added:

"This cooling requirement is too high. We can only use slot cooling to replace the round hole cooling on the turbojet 14, which increases the demand for air flow."

Now Chang Haonan finally knew what the problem was;

"Don't use slot cooling. My next plan is to study a high-efficiency formed hole cooling solution for the turbine part. Using special-shaped holes instead of round holes can theoretically achieve an effect close to slot cooling without increasing the air consumption. You guys Let’s continue to calculate other structures according to 1325c. The specific cooling plan will be determined after I develop the porous media model of special-shaped holes.”

Although the temperature at the combustion chamber outlet is undoubtedly the highest part of the entire engine, ultimately converting the energy of the high-energy gas into mechanical work still requires the turbine. The latter not only works in a high-temperature and high-pressure environment, but also needs to rotate at high speed and withstand external overloads. Therefore, the requirements for materials and cooling technology are higher.

If a cooling technology can be used on the turbine, then moving it to the side walls of the combustion chamber is generally not a problem.