Chapter 310 J-2 with two plans! (For the leader [die

Generally speaking, even if people with an engineering background are good at mathematics, it is often at the application level, and few people are also good at researching mathematics.

In fact, Yang Wei himself has quite good mathematical skills, but when it comes to cutting-edge topics in the field of numerical computing, he still needs the assistance of some experts.

"It's not much of a research..."

Chang Haonan wiped the slight sweat on his forehead because he had just spoken for several long paragraphs:

"Many parts of my research process involve solving nonlinear partial differential equations, but there are currently no very easy-to-use tools, so I tried to see if I could develop one myself."

"If you really want to talk about it, because there are many assumptions and experience summaries in it, the serious mathematics community still does not admit that our kind of research belongs to mathematics..."

"..."

Yang Wei was speechless for a moment.

Looking at the sincere face in front of the young man who was more than ten years younger than himself, the thought of "meeting a match" suddenly came to his mind.

The other few people looked at Chang Haonan with complicated expressions, and then at their deputy chief engineer next to them.

After all, the latter was admitted to university directly after graduating from junior high school. However, he did not do well in the exam and only went to Hokyong Institute of Technology...

"Ahem... let's not mention this. Let's continue talking about your modification and solution method of the MG model, as well as the overall plan."

Chang Haonan nodded and turned the PPT to the next page.

"The new model I modified is not much different from the original MG model in the derivation process. I only need to modify the pressure rise coefficient through the compressor. The biggest difference lies here."

Chang Haonan pointed to a box with a cross in the middle behind the compressor.

After realizing that his artistic level was indeed difficult to save, Chang Haonan gave up on refining his drawings and instead used more schematic diagrams.

The main focus is to maximize strengths and avoid weaknesses.

"This is a component that I temporarily call a closely coupled control valve, also known as a CCV. We assume that there is no gas mass storage between the compressor outlet and the CCV, so a pure pressure drop can be created at the compressor outlet for simulation The impact of our main control stability control strategy on the entire engine operating state."

Speaking of which, Chang Haonan released the improved derivation process of the MG equation step by step below.

……

Ψ'=(W/H)/(4B^2)(Φ/W-1/WΦt(Ψ))H/lc

J‘=J(1-(Φ/W-1)^2-J/4-1/γ^2·4WΦ/(3H))p

……

“In this formula, when J=1, it can represent a pure rotational stall and there is no risk of evolving into surge. When J=0, it is a pure surge, which is what we most need to avoid. condition……"

It was obvious that Yang Wei followed Chang Haonan's thoughts throughout the process and recorded them quickly in his notebook.

Although aircraft design and aero-engine design belong to two different sub-disciplines, for a top boss like him, after mastering one of the fields, he will naturally have some understanding of the other.

Moreover, the maneuverability of third-generation fighter jets, especially some third-and-a-half-generation fighter jets, has shown leaps and bounds. The propulsion system needs to withstand much larger flight attack angles and sideslip angles than before, and the air intake distortion problem it faces is compared to The problem is much more serious for second-generation fighter jets, which also puts forward higher requirements for the design matching of aircraft and engines.

It has become an irreversible trend for aircraft designers to also understand engines.

As one of the best, Yang Wei was naturally prepared for this change.

After he stopped writing, he lowered his head and thought for a few seconds, then raised his head:

"There is a problem here, because the problem of rotational stall must be taken into consideration, so even under certain working conditions, the compressor speed cannot be set as a constant, and the tangential speed at the center radius of the compressor rotor is no longer constant. , how to solve this problem?"

Chang Haonan looked at the part where the other party pointed out the problem:

"Re-establish a dimensionless constant ξ=Ud·T/R, so that the dimensionless constants of the compressor inlet and outlet channels can be obtained through very simple calculations..."

At the beginning, others could keep up with the ideas of these two people, but later on they could only pick and listen to some parts that they were better at.

After confirming that there were no problems with the aerodynamic stability model, Chang Haonan moved on to the next part:

"After completing the engine modeling, the relevant parameters can be determined through experimental data, thereby fitting an engine operating curve that is as close to the actual situation as possible, and thus accurately predicting the engine instability phenomenon."

"I see……"

"After the theoretical part is solved, the remaining problems will be specific to engineering practice."

Chang Haonan closed the PPT that had been placed on the last page and began the final summary.

There are not many websites that can search for pictures these days, and he can't find photos of the AL10FN target engine used by the J-31. As for the turbofan 10, there are not even complete drawings. There is really nothing to put on it. of:

"For example, inside the inlet duct, to detect the initial disturbance of compressor instability, the current preliminary plan is to use the harmonic Fourier coefficient method and the traveling wave energy method. As for which of their specific effects is better, it will only be tested at that time. That’s when I found out.”

"In addition, active stability control, in the final implementation of the control step, still needs to be modified on the engine. The closely connected control valve mentioned in the previous modeling process is designed and added to the back of the compressor. It is ideal. Under such circumstances, this system can make the compressor instability state manifest as a rotational stall at most, without developing into surge. It can even change the compression characteristics of the compression system through the closed-loop control of the CCV, thereby... changing the compression The stable operating range of the system extends beyond the surge boundary and remains stable for a period of time!”

In the previous part, Yang Wei could still keep calm, but this last part made his right hand shake violently, and he almost couldn't hold the pen in his hand.

In other words, through the design of the aircraft control system and limited modifications to the engine structure, the engine's working limit can be exceeded!

Although Chang Haonan said that this kind of chicken-blooded state should not last long, in the ever-changing air battle, the power advantage, even if it only lasts for one minute, can sometimes determine the outcome.

But the only problem now is...

The engine needs to be modified.

"The functions of this system are indeed very tempting..."

Yang Wei closed his notebook and slowly leaned back on the back of his seat, with deep regret in his tone:

"However, this tightly connected control valve...AL31FN is Lurika's design after all. Even if he cooperates with us, considering a series of issues such as project docking, it may be difficult to produce a finished product in a short time."

But Chang Haonan naturally thought of this problem a long time ago and waved his hand directly:

"It doesn't matter. It doesn't have to be done in one step. It can be divided into two steps."

"When using a Russian-made engine for the first flight, we can remove the CCV of the hardware and keep only other parts. First install a youth version, which is a simplified version, and use the most basic and automatic way to adjust the throttle valve to adjust the intake air. Intervening according to the situation, although the effect is slightly worse, at least it can expand the engine envelope to a large extent and ensure flight safety under extreme conditions."

"When the domestically produced third-generation high-thrust turbofan engines mature and are replaced, the full version of the active stability control system can be used."

Yang Wei was stunned by this explanation:

"Your system has very high requirements for flight engine matching. Let's not say whether the turbofan 10 can be developed before the J-10 is officially put into service. Even if it is developed, the design of the inlet will probably have to be significantly changed... …”

Chang Haonan's answer was even more self-liberating:

“It’s just a big change!”

"You can refer to Xiao... uh, what happened when we were working on the August 3rd Project. We first built two non-full-state prototypes using the existing design to evaluate and test the overall situation of the aircraft structure, aerodynamics, flight control, etc. Wait until the domestic matching engine comes out, and then come up with a second version of the design with a modified intake duct. In this way, we only need to test the power and active stability control system, and nothing will be wasted..."

At first, Chang Haonan wanted to say Xiaolong out of habit. After all, it was the most classic model that had its air intake changed during the test flight. However, considering that the project had not yet been completed at this time, he changed his mind midway. .

Yang Wei, who was sitting opposite, had a look of disbelief on his face——

Good guy, our 611 Office asked you to help with Project No. . This is great. You can directly show your sense of ownership and change the progress of our entire project, right?