Chapter 846: Teach the French a Lesson
After hearing Liu Yongquan's explanation, Chang Haonan suddenly understood.
This is frightened.
However, I'm afraid it's not exactly what the former said.
In the process of aircraft engine research and development, it is normal for accidents and even some casualties to occur.
After all, France is also a long-established aviation power, so it will not be scared out of its wits simply by blowing up an engine.
But once combined with Liu Yongquan’s pretense during the previous negotiations, the effect is very good——
You have been developing something at home for more than ten years, but others come up and say a problem that you have never heard of.
When I went back and tested it, I found that the situation was exactly the same as the other party's description.
At this time, the focus is no longer on whether the problem at hand can be solved.
Even if he could, he wouldn't be able to feel at ease.
My mentality at this time is definitely:
Since people can see such a big problem at a glance, if they take a closer look, shouldn't they see more?
What's more, there is absolutely no way Snecma would find a solution so quickly.
If there is no comprehensive traceability of the aircraft engine's entire life process, who would have thought that an inconspicuous electrochemical mark during the overhaul process would directly affect flight safety?
You should know that only a very small number of the latest models of engines using CFM56 or its derivative core engines will use heat-resistant coatings that are prone to arcing.
Even General Electric itself may not have solved this problem at the moment, or even discovered it.
Not to mention the French.
Therefore, for the Rafale fighter jet, a project that they could not afford to lose at all, they still chose to find foreign aid.
Thinking of this, Chang Haonan asked directly:
"Then what conditions did they set for coming here this time?"
For him, it is about expanding on the basis of the existing contract.
As long as the price is right.
Talk, you can talk.
And Liu Yongquan was obviously prepared.
After hearing Chang Haonan's question, he immediately took out a file bag from the briefcase at hand:
"I was planning to submit the memorandum of the meeting to the group when I went to Beijing for a meeting next week, but just in time for you to arrive in Shengjing today, I brought it over directly."
After the restructuring, not only the aviation power group itself has stronger independent management rights than the previous head office period, but also the following secondary companies.
Although the decision-making power of the group leadership is still important, at least it is not as demanding as in the past.
Like this time, Institute 606 can first contact Snecma representatives and then report the situation to the group for decision-making.
And if it does not involve foreign trade, it does not involve military products.
For example, Shengfa Group’s QD130 gas turbine for power generation is currently the flagship product.
That's even greater autonomy.
Just report on business performance on a regular basis.
Chang Haonan took the file bag and opened it.
"250 million euros in advance, joint development throughout the life cycle, and sales divided into proportions..."
"Sincerity is okay..."
After reading through the contents of the memo as quickly as possible, he raised his head again and looked at Liu Yongquan:
"Old Liu, what... do you think?"
Although the design of the Turbofan 10 has not yet been officially finalized, there is only enough time to save up enough hours for early batch trials, so Liu Yongquan can already devote a considerable part of his energy to cooperating with the French.
In this way, no matter what decision is made, he, the specific executor, must always be consulted for his opinion.
Liu Yongquan did not answer immediately.
Instead, he lowered his head and thought while walking forward.
After some careful consideration, he spoke:
"In terms of performance indicators, the calibration given by the French is quite conservative. Obviously the temperature in front of the turbine and the stage pressure ratio of the compressor are not bad, but the maximum thrust is only 7.5 tons. There is definitely potential for upgrades."
Chang Haonan nodded:
"Now, have you found the reason why Snecma chose to push down on the M88-2?"
The first model of M88, M88-1, is generally a third-generation and semi-center-thrust engine whose performance meets the technical level.
But the later M88-2 suffered a considerable decline in paper performance.
It is equivalent to using the technology of the third and a half generation, or even part of the fourth generation engine, to create a third generation mid-range version that is comparable to the F404.
While talking, the two of them walked around and came to the overhaul workshop of Liming Factory.
The M88 prototype that the French shipped over at the beginning of the year is kept here.
"Mr. Chang, can you go in and take a look?"
"good."
…
A medium-sized turbofan engine is quietly placed on a special engine bracket.
Its cold end and hot end have been separated, and it has obviously undergone more than one round of disassembly and research——
This is why the French initially had some concerns about joint research and development.
After all, asking someone to dismantle their own engine like this is basically equivalent to asking Miss France to take the initiative to lift up her skirt and expose her underwear.
Chang Haonan stepped forward, bent down and took a closer look.
Design, of course, can't be seen.
Then you have to look at the drawings.
However, it must be said that as an old industrial power, the French are still very capable in the field of production and manufacturing.
Even though Liming Factory has replaced a batch of new equipment, if we only look at the fineness of workmanship, there is still some gap between the Turbofan 10 and the M88-2 in front of us.
However, this seems to show the outrageousness of the French design...
It was only then that Liu Yongquan, who was standing behind Chang Haonan, answered the former's question:
"During this period, we have checked the design data of the M88 engine and this prototype. The preliminary conclusion is that the French had some problems with the matching of the fan and the high-pressure compressor, resulting in the effective pressure ratio of the entire engine not being The pressure is higher than that of just taking it out.”
"The other issue is what you said when you decided on the overall plan of Turbofan 10. The corner area inside the channel has low-energy fluid from the end wall driven by the pressure difference between the pressure surface and the suction surface. These low-energy fluids gather in Flow separation is easy to occur under reverse pressure gradient, and mixing with the mainstream will cause blockage of the compressor channel. "
"In this case, whether the air flow through the compressor is too small, too large, or changes too fast, it may induce corner stall and then surge."
"Of course, more quantitative data will not be known until we send this engine to the 624 Institute for bench testing..."
Chang Haonan already understood.
Although the appearance of this problem is different from that of the original turbojet 14, the essence is very close.
They all relied heavily on other people's compressor designs, but they were beyond their own capabilities and I didn't know how to modify them to suit local conditions.
In the end, basic performance can only be guaranteed by reducing push:
"So they just limited the maximum speed of the engine?"
"right."
Liu Yongquan nodded:
"They directly cut the maximum speed by nearly 20%, avoiding the upper limit of corner stall."
"But no matter what, the lower speed limit is impossible to avoid, so if the M88-2 maintains medium and low thrust for a long time, or the throttle lever moves too violently, it is still possible to cause a rotational stall or even surge."
Hearing this, Chang Haonan couldn't help but smile and turned to look at Liu Yongquan:
"Then they have found the right person..."
Apart from Chang Haonan himself, Liu Yongquan should be the second person with the most experience in dealing with end zone flow problems of axial flow compressors.
The latter, who was suddenly praised, touched his shiny head with some embarrassment:
“Having experience with Turbofan 10, I am relatively confident that we can solve the problems with the M88 compressor by directly modifying the design of the high-pressure compressor.”
"Eh……"
Chang Haonan quickly waved his hand:
"This kind of problem cannot be solved too neatly."
Liu Yong was completely puzzled, but he still waited for Chang Haonan's next explanation.
"We have completed the work in three strokes, five strokes and two divisions. Then the French may think that the work is simple and not feel our level."
Chang Haonan said:
"Moreover, sending the improved plan directly is equivalent to throwing away our bargaining chip, and the subsequent initiative will be in the hands of the opponent."
"So, this matter can be done in three steps."
At this time, Liu Yongquan suddenly interrupted Chang Haonan:
"Wait a minute, Mr. Chang..."
Then he took out a pen and notebook from his pocket:
"You say."
"The first step is to change the current M88-2's electrochemical label to a fluorescent label, and then design several sets of suction holes on the end arm of the engine casing to dispose of the low-energy fluid. This method I should have originally I also said..."
"Open suction will cause a loss of about 8-10% of the inlet flow... Is that true, Mr. Chang?"
Liu Yongquan obviously remembers the knowledge points very well.
"Yes, but after this design, the rotation speed can be added back, so it will be better than the current disabled state. Even if it is installed on the carrier-based Rafale M, it will not have much negative impact on the performance. And there won’t be any big problems with safety.”
Chang Haonan continued:
"The second step, M88-3, is to modify the blade shape at the end of the high-pressure compressor blade to control the total flow loss, especially the distribution of spanwise flow loss, so that the suction surface boundary layer is stronger than the end wall boundary layer. In this way, the set of open suction holes can be eliminated, the performance can be restored to the original M88-1 level, and the lifespan can be extended to normal levels. "
"At this point, we can also conduct some technical verification for our country's fourth-generation mid-range launch."
"The third step is to get to the final model M88-4, and then consider using a swept design and end-arm closed suction to squeeze out the hot-end performance potential of this engine as much as possible and see what level of product we can come up with. Come."
"In this way, for at least the next 8 to 10 years, the power upgrade of the French main fighter jets will be in our hands. Although it is not a final decision, it is at least a powerful bargaining chip..."
Liu Yong quickly wrote down the key points that Chang Haonan said.
When the latter saw this scene, he suddenly thought of a famous scene...
"Repeat it to me."
"The first step is to change the electrochemical labeling to fluorescent labeling..."