Speaking of this, Chang Haonan stood up directly, came to the side of the curtain, and said while gesturing on the picture:

"In fact, we can see from this diagram that the closer to the instability boundary, the higher the compressor boost ratio, and the higher the boost ratio and higher efficiency, the higher the performance of the engine. However, the presence of the instability control line makes it impossible for the engine to operate in the area between the instability boundary and the instability control line, and most of the time, the engine is able to operate stably in this area. It can be seen that the existence of the instability control line actually makes the performance of the engine unable to be fully exerted. ”

"The short-term stabilization system is a form of open-loop control, which needs to be manually turned on by the pilot, which means that pilots with relatively conservative flying habits may start this system when the engine has not actually reached the instability control line, further reducing the performance potential of the engine, while pilots with aggressive flying habits may not turn on this system until the engine has entered a state of aerodynamic instability, often at this time the working state of the engine has begun to be destroyed, entering an irreversible stall, so that flight safety is greatly reduced."

After explaining the shortcomings of this traditional method, he sat back in his seat and clicked the mouse to release the next page of PPT:

"So when I carried out the 83 project last year, I began to consider whether I could use a more accurate way to control the stability of the engine with less impact on the performance of the engine, and finally summed up two new methods not long ago, namely stability seeking control and active surge control."

"The former is the integration of engine stability checks into the engine's control system, which determines the location of the instability control line by assessing the engine stability in real time, rather than the worst-case scenario assumed at the time of design, allowing the control system to minimize the stability margin and thus improve engine performance."

"And the latter...... Before I get into Active Stability Control, let me mention a brand new concept that I've named myself: Surge Aura. ”

"Surge aura ......"

A light seemed to flash in Yang Wei's eyes:

"You're trying to predict surge in real time?"

It can only be said that the big guy is the big guy, although he is facing a new concept, he still reacts to what Chang Haonan is going to do in the shortest possible time.

The few people who followed Yang Wei immediately showed expressions that were almost shocked.

The essence of surge is a positive feedback self-excitation process, that is, once a certain part starts to surge, then unless it is immediately stopped and restarted in the air, the surge will be "infected" to the entire engine in a very short period of time and cause irreparable damage.

In other words, with traditional methods, by the time you detect engine data anomalies, it's too late.

Accurately predicting a surge is orders of magnitude harder than accurately predicting the weather!

In fact, even after a surge has already occurred, it can be quite difficult to reverse the work point that induces the surge from the data recorded by the engine control system.

Chang Haonan himself should also have experienced this.

So......

How strong does it take to have a strong knowledge of fluid mechanics to boast that you can predict surge in real time?

"That's right."

In the face of Yang Wei's question, Chang Haonan just nodded lightly, and at the same time replaced it with another picture:

"After analyzing and summarizing a series of surge fault data for the J-8 and J-7 aircraft, I noticed that in the stall initiation process before the surge, there will be some disturbance waves with small amplitude formed from the stable flow field, and the impact caused by them is very weak, and it is almost impossible for the pilot to feel it intuitively, but if the working state of the engine is not interfered with at this time, these disturbance waves will continue to increase, and at the end of the initial process will be transformed into rotational stall, and then develop into surge, That's why I call these disturbance waves surge aura. ”

"Therefore, my idea is to detect these surge precursors through a series of sensors and waveform processing techniques, and then to suppress the formation or development of stall precursors by adding additional disturbances to the flow field, delaying the occurrence of rotational stalls."

When Chang Haonan said this, the other people looked at him like they were looking at monsters.

It is equivalent to a person saying that I not only have to accurately predict the weather at a certain time in six months, but also control the weather at this moment through technical means.

This set of theories even sounds like a tightrope walk, let alone directly applied to the field of engineering.

The safety margin is almost the core element of engineering design, and Chang Haonan directly said that he wants to minimize the safety margin and ensure that the safety is pulled to the maximum......

I could only gasp.

And the big guy once again showed the extraordinaryness of the big guy.

Yang Wei touched his chin and pondered for about half a minute, and the first reply he gave was:

"I've actually done a little bit of research on this surge prediction before."

This time it was Chang Haonan's turn to be shocked.

"You are too young to know, but many old people in the 611 Institute know that the kung fu around 90 years, because they were engaged in civilian property at that time, I didn't think it was interesting, so I seriously considered going abroad to work."

Chang Haonan was even more shocked.

This TM has to be retained, otherwise the loss is simply incalculable......

"In short, during that time, I paid attention to the cutting-edge research done by some foreign universities, and I ...... There are two professors named Moore and Gretzer who are far from engineering, and they proposed a model for axial compressors to enter a rotational stall state, including three physical quantities: flow coefficient, pressure coefficient and rotational stall amplitude, which is generally called MG model. ”

The content mentioned later did not surprise Chang Haonan again.

This MG model is basically the starting point for all surge prediction research.

After a slight pause, Yang Wei continued:

"This model is quite useful in the scope of academic research and small tests, but when it comes to the field of engineering, three physical quantities bring three systems of partial differential equations, and the degree of nonlinearity is very high, I once consulted a friend who specializes in mathematics, and he said that one can be used called ......"

"Galyogin?"

All this has entered Chang Haonan's rhythm.

"Yes, the Galerkin method, and then choose a cubic curve as the characteristic curve, convert the system of partial differential equations into ordinary differential equations and solve them, but I personally tried it, and found that the amount of calculation applied is unimaginable, and the final result is not very accurate, in short, I can't see any ......application potential so far."

After listening to this introduction, Chang Haonan was a little embarrassed, and said in his heart, you can't call it a little research at all, and you have already done half of my work......

But on the surface, he only coughed lightly twice:

"Actually, the MG model you just mentioned is the starting point of my whole idea."

"It's just that I recently have some research results on the numerical solution of strong nonlinear partial differential equations, which can be used in the optimization and subsequent solution process of the MG model."

Yang Wei, who had been calm just now, finally couldn't hold back.

"Mathematics...... And research? ”

(End of chapter)