Chapter 309 Boss Yang Wei was shocked
Having said this, Chang Haonan stood up directly, came to the curtain, and said while gesticulating on the picture:
"Actually, we started from It can be seen from this figure that the closer the area is to the instability boundary, the higher the compressor boost ratio. The higher boost ratio and higher efficiency mean that the engine has higher performance, but instability control. The existence of the line prevents the engine from operating in the area between the instability boundary and the instability control line. However, most of the time, the engine can operate stably in this area. It can be seen that the existence of the instability control line actually makes the engine unstable. The performance cannot be fully exerted. "
"The short-term stability enhancement system is in the form of open-loop control and needs to be turned on manually by the pilot, which means that pilots with relatively conservative flying habits may not have reached the engine before it actually arrives. This system is activated when the control line becomes unstable, further reducing the engine's performance potential. Pilots with aggressive flying habits may not activate this system until the engine has entered aerodynamic instability. Often the engine's working state has already begun at this time. It was damaged and entered an irrecoverable stall, which greatly compromised flight safety."
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: < br>
“So when I was working on the 83rd Project last year, I began to consider whether we could use a more precise method that would have less impact on engine performance to control engine stability. Finally, I summarized two new methods not long ago. The methods are stability seeking control and active surge control. "
"The former integrates engine stability check into the engine control system and determines instability control by evaluating engine stability in real time. line position, rather than the worst-case scenario assumed during design, allowing the control system to minimize stability margins, thereby improving engine performance."
"And the latter... Before introducing active stability control, Please allow me to first mention a new concept named by myself - surge precursor."
"Surge precursor..."
A flash appeared in Yang Wei's eyes. Light:
"Are you going to predict surge in real time?"
It can only be said that the boss is the boss. Although he was facing a completely new concept, he still realized what Chang Haonan was going to do in the shortest time.
The few people who followed Yang Wei immediately showed expressions that were almost horrified.
The essence of surge is a positive feedback self-excited process. That is to say, once a certain part starts to surge, unless it is stopped and restarted immediately, the surge will occur in a very short time. Be "infected" to the entire engine interior and cause irreparable damage.
In other words, for traditional methods, when you detect abnormal engine data, it is actually too late.
Accurately predicting surge is orders of magnitude more difficult than accurately predicting weather!
In fact, even after surge has occurred, it is quite difficult to reversely find the operating point that induces surge from the data recorded by the engine control system.
Chang Haonan himself should have some experience of this.
So...
How much knowledge in fluid mechanics do you need to dare to boast that you can predict surge in real time?
"That's right."
Faced with Yang Wei's question, Chang Haonan just nodded lightly and replaced it with another picture:
"Targeting the J-8 After analyzing and summarizing a series of surge failure data that occurred on the JH-7 aircraft, I noticed that during the stall initiation process before the surge occurred, there would be some disturbance waves with smaller amplitudes starting from the stable state. Formed in the flow field, their influence itself is very weak, and it is almost impossible for the pilot to intuitively feel it. However, if there is no interference with the working state of the engine at this time, these disturbance waves will continue to strengthen and transform into The rotation stalls and then develops into surge, so I call these disturbance waves surge precursors."
"So, my idea is to detect these surge precursors through a series of sensors and waveform processing technology. Then, additional disturbances are added to the flow field to suppress the formation or development of stall precursor waves and delay the occurrence of rotational stall."
When Chang Haonan talked about this, the other people looked at him. It’s almost like watching a monster.
It is equivalent to a person saying that I not only want to accurately predict the weather at a certain time six months from now, but I also want to control the weather at this time through technical means.
This theory sounds a bit like extreme tightrope walking, let alone its direct application in the engineering field. The four words safety margin are almost the core element of engineering design, but Chang Haonan directly stated that he wanted to keep the safety margin to the minimum while ensuring the highest safety...
I can only take a breath of air.
As for the boss, he once again showed how extraordinary he is.
Yang Wei touched his chin and pondered for about half a minute, and the first reply he gave was:
"I actually did a little research on this surge prediction before."
This time It was Chang Haonan's turn to be shocked.
“You are too young, so you may not know, but many old people in the 611 Institute know that around the 1990s, because they were all engaged in private property, I didn’t think it was interesting, so I thought about it very seriously. About working abroad.”
Chang Haonan was even more shocked.
This guy has to be retained, otherwise the loss will be immeasurable...
"In short, during that time, I paid attention to some cutting-edge research done by foreign universities, which was... the kind that was far away from engineering. Two professors named Moore and Glazer proposed a model for an axial flow compressor to enter a rotating stall state, including three physical quantities: flow coefficient, pressure coefficient and rotating stall amplitude, which is generally called the MG model. "
What was said later did not exceed Chang Haonan's expectations.
This MG model is basically the starting point for all surge prediction research.
After a short pause, Yang Wei continued:
"This model is relatively easy to use in academic research and small experiments, but when it comes to the engineering field, three physical quantities bring three systems of partial differential equations, and the degree of nonlinearity is very high. I once asked a friend who specializes in mathematics After consultation, he said that he could use a method called..."
"Galiao Jin Method?"
All this has entered Chang Haonan's rhythm.
“Yes, the Galerkin method, and then select a cubic curve as the characteristic curve, convert the partial differential equations into a system of ordinary differential equations and then solve it, but I personally tried it and found that the applied calculation The quantity is unimaginably large, and the accuracy of the final results is not high. In short, there is no application potential so far..."
After listening to this introduction, Chang Haonan felt a little ashamed and said to himself: This can’t be called a little research at all, half of my work has been done...
But on the surface, he just coughed twice:
“Actually, the MG model you just mentioned is the starting point of my whole idea.”
“It’s just that about strong nonlinearity I have recently produced some research results on numerical solutions to partial differential equations, which can be used in the optimization and subsequent solution process of the MG model.”
Yang Wei, who had been calm and composed just now, finally became a little unbearable. .
"Do you still have research on mathematics...?"
(End of this chapter)