Chapter 1074 Structural pre-deformation design of aircraft engines?

Chang Haonan's bold speculation left Zhang Zhenhua stunned.

At some point, the latter even felt that "the British provided false data" was more realistic.

But if you think about it carefully, it does seem feasible.

After a long time, he reluctantly spoke again:

"Then our next step should be..."

Zhang Zhenhua quickly regained his senses, but the mental shock he had just suffered was obviously not so easy to completely subside, so he quickly asked about the next task.

"Naturally, we should verify this speculation first..."

Chang Haonan answered decisively.

"But you just said..."

“Two-way fluid-structure interaction is indeed difficult, but we verified that we only needed to do a forward analysis.”

Chang Haonan said as he turned the draft paper on the table that was already filled with drawings to the other side:

"Didn't you say that all three teams found that the blades undergo elastic deformation while in operation? This is actually half the battle."

"During operation, there are two main types of loads acting on fan blades: one is the centrifugal load, and the other is the aerodynamic load generated when air flows through the blades. Among them, the centrifugal load is relatively easy to study, and is basically only related to the fan speed. However, the aerodynamic load requires us to comprehensively consider the internal flow conditions, as well as the engine... that is, the external overload of the aircraft itself..."

"..."

Chang Haonan did not choose to gather all the staff together for a meeting, but analyzed the problem directly to Zhang Zhenhua in the office.

On the one hand, this allows the other party to have a process of digestion and output after receiving knowledge input.

On the other hand, Chang Haonan himself did not have any further specific ideas about this issue.

Of course, structural pre-deformation design is naturally among his long-term goals.

However, according to the plan, this should at least be considered after new theoretical breakthroughs are made in the NS equation.

The reason why I followed up on this was largely because I wanted to see what the British had come up with...

……

With the previous experience and Chang Haonan's personal guidance, the preliminary calculation results after considering the blade load were presented to the latter in just three days.

As usual, Zhang Zhenhua presented the calculation results:

"Mr. Chang, after adding the workload into the calculation conditions as you requested, the performance of the entire fan, especially the stage pressure ratio and working stability, has undergone fundamental changes."

"However... we have only estimated the workload and blade material, so the specific index data calculated is still not ideal."

Chang Haonan flipped through the calculation results and took a quick look:

"It's not a big problem. At least in terms of the trend, it has proven that my previous speculation is correct. The British are doing a pre-deformation design on the fan blades. That's enough."

"I never thought... Comrade Bingda would bring me a surprise during his trip to England."

For him, the point is the fact that "performance is improved after deformation caused by applied working load" itself.

As for how much it has improved specifically, it is not that important when a lot of information can only be inferred or even guessed.

Just tracking the research progress of foreign counterparts.

It's not really design.

After a brief pause, Chang Haonan continued:

"I guess the reason why the British handed over some of the data so confidently is that they are sure that we are unlikely to figure out the secrets. If we rashly copy some parameters, it will have the opposite effect."

"And even if this data is leaked, it won't have much direct significance..."

Having said that, he smiled and shook his head.

Given the British character, he should have thought of this earlier.

However, Zhang Zhenhua's expression was quite serious.

In other words, he had been in a low mood ever since he reported the calculation results just now.

"So this is... the inverse of the fluid-structure interaction problem?"

He asked with a rather twisted expression.

This peculiar way of expression made Chang Haonan think for a while, but in the end he nodded:

"If I have to say it, it is indeed true."

"Because the numerical solution process is a semi-black box, it is a bit like the account and password in an online database. When the algorithm is unknown, even if we have the encrypted data, that is, the data after the pre-deformation design, we still cannot restore the valuable information."

However, this is not what Zhang Zhenhua cares about.

After getting Chang Haonan's affirmative answer, he almost stood up with excitement:

"But...how could they do that?"

The internal flow design of an aircraft engine is much more complicated than that of a wing.

Be it CFD or CSM, the fact is that humans have not yet fully studied the theory...even to exaggerate a bit, at the theoretical level, it is just an entry-level problem.

In a field like this, let alone the inverse proposition, even fluid-structure interaction itself was proposed as early as 1933. However, it was not until 1991 that someone used semi-implicit and semi-explicit methods to solve the fluid-structure interaction equations.

As for using the time-discontinuously stabilized spatial finite element method to discretize the fluid-solid coupling model equation to solve the flow problem of two-dimensional structural viscous fluid, it was finally realized after Chang Haonan was reborn, combining the experience of his two predecessors and the help of the system.

The systematic use of fluid-solid coupling to solve the buckling and large deformation problems of three-dimensional structures is a new feature that was only available in TORCH Multiphysics 2.0.

Of course, the earlier NUMECA can also perform calculations in some special cases.

As a result, just over a year later, the British began to do the opposite and use the working blade profile to reverse the processing blade profile?

This situation was indeed a big blow to Zhang Zhenhua.

There is a kind of thing where, after a lot of effort, one finally goes from being far behind to being able to catch up, and it seems that there is a possibility of catching up.

As a result, the other party suddenly accelerated and disappeared.

This kind of blow is indeed quite serious.

However, Chang Haonan remained relatively calm:

"Actually... they may not have done it."

As he answered, he tapped his pen on the table unconsciously, obviously thinking:

"I can only say that this may be the British idea, but ideas are not necessarily something that can be realized."

"Ok?"

The shock in Zhang Zhenhua's eyes gradually turned into confusion.

"You know, aero engines have more than just a few typical working conditions, and the biggest difficulty in structural pre-deformation design is that it is necessary to provide at least an acceptable degree of deformation for each working condition..."

Chang Haonan tried hard to organize his words and make his description as simple as possible:

"In other words, if we really want to achieve a thorough and successful structural pre-deformation design, it is not enough to just select a few working points and optimize them. Instead, we need to exchange and transmit the flow field change information in the fluid domain with the structural deformation information in the solid domain, calculate the structural dynamic equations under the action of generalized forces, and analyze the structural nonlinear transient response of modal superposition to obtain the deformation caused by unsteady aerodynamic forces, so as to estimate the anti-twisted blade shape..."

"Even if we only consider centrifugal force, this process is quite complicated in theory, not to mention that it also involves aerodynamics and temperature... To be honest, almost all of the existing engineering methods were developed by me, so I can boldly judge that it would be almost impossible to accomplish without completely new theoretical tools..."

"So I guess Rolls-Royce will eventually return to the traditional rigid blade design."

As a professional engineer, Chang Haonan naturally has to dare to make judgments.

Besides, whether it was the F135 or the F136 in the previous life, they eventually returned to the traditional rigid design.

This means that at least at this point in time, Rolls-Royce does not have the ability to solve the problem.

After listening to Chang Haonan's analysis, Zhang Zhenhua's emotions recovered a lot.

But I still have some doubts:

"But Mr. Chang, if this is really a fan developed for the F135 or F136, then according to the plan, the JSF project is to have its first flight in 2005 and be put into service in 2008. How could the British have the time to toss around like this?"

Hearing this question, Chang Haonan almost laughed out loud.

He is well aware that there are countless abstract tasks in the entire JSF project.

Until his rebirth, the latest news from Lockheed Martin was that they had abandoned the complete technical status, that is, the block 4 batch of F35.

In other words -

There are some problems that we can't fix anyway, so you just have to make do with them...

"Don't worry, I can make a bet with you."

Chang Haonan suppressed his smile and said to Zhang Zhenhua:

"The JSF project will not be able to form a complete mission capability by 2008, let alone 2018."

"As for the structural pre-deformation design..."

He thought for a moment, then continued:

"For the British, I'm afraid they will only be able to stay on the PPT for a long time..."