Chapter 462 High-performance film cooling, breaking through the temperature in front of the turbine
After participating in 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, Then definitely go to 606 Institute and 410 Factory.
After all, come and come.
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.
So 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. After getting off the plane, he only showed up at Factory 112. Therefore, after he arrived at Institute 606, in addition to always Except for Hai Yide, the chief engineer who took the lead in organizing the work, no one else was even prepared.
"Why didn't Mr. Chang tell us before he came? Let's clean it up..."
An engineer following Haiyide touched his unshaven temples, 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 teams.
After all, aviation engine 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 this. This way of playing will definitely not work, so 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 the two chairs, and then sat on one of them:
"Although I have not been in Shengjing all the time, since we are the same R&D The team is a family, don’t act like you are welcoming the leader.”
Because the design of aerospace engines involves a large number of complex numerical calculations, the city with the most abundant supercomputing resources in the country is Beijing. , and the compressor research center planned for the future is also located in Beihang University, so a considerable number of R&D personnel are actually stationed in the capital with Chang Haonan.
And he is also a front-line designer. He has a deep understanding of everyone's mental state 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 things that cannot be found.
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 sat down, it was Haiyide who quickly brought the topic back on track:
"Okay, now we are almost here. If you need anything, please ask Mr. Chang in person. If you want to report or inquire, it can save you the trouble of a business trip to the capital. You can quickly say what needs to be said and ask what needs to be asked. "
Although Chang Haonan is usually in BJ, he does not directly refer to Shengjing. Bian left it alone, and each research and development direction was required to submit project progress reports every week, and he would also give feedback as soon as possible, so even though he had not been to 606 Institute for two months, he did not It was a grand occasion where everyone had accumulated a bunch of questions and asked them enthusiastically.
"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 the research, development and design of combustion chamber technology.
He participated in the design of my country's first annular combustion chamber in the Turbojet 14 project. Although in terms of paper performance alone, that still immature design is no better than the past annular combustion chamber. Much better, but because the flame tube is an integral annular cavity, 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 machine, 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 Air intake flow? "
Yin Yongze said as he slid a piece of information along the table in front of 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 dumper.” Because of human The understanding of the combustion process is still relatively unclear, so in terms of combustion aerodynamics and structure, numerical calculations play a relatively small role, and the research foundation for combustion chamber structures is not as good as that of compressors and turbines. Yin Yongze can do this The level of parameterization is indeed quite good.
"Dump the oil pan?"
Yin Yongze was stunned by Chang Haonan's request:
"Our design..."
But he was interrupted by Chang Haonan mid-sentence. ：
“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. Places like cruise missiles and drones require small aero engines to dump fuel. The oil supply pressure of the plate is low, it is not easy to block, and the most important thing is that it is cheap. I 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 will pay attention to it then."
Yin Yongze opened the notebook in front of him and wrote down this request:
"Mr. Chang, the intake air flow rate Things..."
"6%-8% is too much"
Chang Haonan immediately shook his head:
“Now the overall design level has basically determined the structure as a 2-8-1-1 structure or a 3-7-1-1 structure, so that the margin left at each level is It’s very small. If it’s 6% to 8%, it’s almost impossible to add an extra level of high pressure.”
“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 a loss. A considerable part of the compressor power is taken up.
Therefore, although in theory only the amount of cooling gas needs to be increased to achieve better results, in actual aviation 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 including the turbine with greater cooling pressure...
It's still a hammer.
You will let out nearly one-fifth of the air brought in by the compressor, which may be acceptable for engines with output shaft power such as turboprops and turboshafts, but for turbines As for the fan engine, it is basically useless.
And if another level of high pressure is added, it will become 3-8-1-1, which cannot be far behind the current AL31F.
The performance of AL31F is certainly sufficient, but its potential is not.
After all, it is a design from the late 1970s.
“What is the upper limit of your combustion chamber outlet temperature setting?”
The turbine front temperature of turbofan 10 (that is, the combustion chamber outlet temperature) is set at 1200-1250°C. It was Chang Haonan's personal decision, but the cooling system must leave a certain margin. How much margin is left is Yin Yongze's job.
"Leave a 5% margin, 1325°C."
This margin is of course calculated based on the Kelvin temperature.
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, and the demand for air flow increases.”
Now Chang Haonan finally knows where the problem lies;
“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 ones. Holes, in theory, can achieve an effect close to that of slotted cooling, and the air consumption will not increase. You can continue to calculate other structures according to 1325°C. 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, which not only works in high-temperature and high-pressure environments, but also It rotates at high speed and withstands external overload, so 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.
(End of this chapter)