Chapter 310 J-10 with two plans! (Additional update 15 for the leader [the deadbeat])
Generally speaking, even if people with an engineering background are good at mathematics, it is often reflected in 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.
“There’s no research to speak of...”
Chang Haonan wiped the slight sweat on his forehead because he had just spoken for several long paragraphs:
< br>
"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."
< br>“If you really want to talk about it, because it contains many assumptions and experience summaries, the serious mathematics community still does not admit that our kind of research belongs to mathematics...”
“…”< br>
Yang Wei was speechless for a moment.
Looking at the sincere face in front of him, a young man who was more than ten years younger than himself, he suddenly felt like he had met his match.
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 college directly after graduating from junior high school. However, he did not do well in the exam and only went to Hokyung Institute of Technology...
"Ahem... let's not mention this. Let's continue talking about you. The correction and solution methods of the MG model, as well as the overall plan."
Chang Haonan nodded and turned the PPT to the next page.
“There is not much difference in the derivation process between the new model I modified and the original MG model. 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 connected control valve, which is a CCV. We assume that there is no storage of gas quality between the compressor outlet and the CCV, so a pure valve can be created at the compressor outlet. Pressure drop is used to simulate the impact of our main control stability control strategy on the entire engine operating state."
Having said this, Chang Haonan released the improved MG equation step by step below. derivation process.
……
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))ρ
……
“In this formula, when J= When J=0, it can represent a pure rotational stall and there is no risk of evolving into surge, while when J=0, it is a pure surge, which is the operating condition we need to avoid most..."
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 are two different branches of 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 angles of attack and sideslip angles than before. Faced with The air intake distortion problem is much more serious than that of second-generation fighter jets, which also places higher requirements on the design matching between the aircraft and the engine.
Aircraft designers also need to understand engines, which has become an irreversible trend.
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, and 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 to Constant, and the tangential velocity 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:< br>
“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...”
In the beginning , others can still keep up with the ideas of these two people, but later on they can only pick some parts that they are better at and listen to them.
After confirming that there were no problems with the aerodynamic stability model, Chang Haonan moved on to the next part:
“After completing the modeling of the engine, the relevant parameters can be determined through experimental data to fit the An engine operating curve that is as close to the actual situation as possible, so as to accurately predict the engine instability phenomenon."
"So that's it..."
"After the theoretical part is solved, the rest is left. The next question will be specific to engineering practice.”
Chang Haonan closed the PPT that had been placed on the last page and started the final summary.
There are not many websites that can search for pictures these days, and he can't find photos of the AL31FN target engine used by the J-10. As for the turbofan 10, there are not even complete drawings. There is really nothing to put on it. ’s:
“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 them has better specific effects? , then we will only know after testing.”
“In addition, the final implementation of active stability control requires modifications to the engine, as mentioned in the previous modeling process. A tightly connected control valve is designed and added to the back of the compressor. Under ideal conditions, this system can make the compressor instability state manifest as a rotational stall at most, without developing into surge. The compression characteristics of the compression system can even be changed through the closed-loop control of the CCV, thereby... extending the stable operating range of the compression system beyond the surge boundary and maintaining stability for a period of time! ”
Previous part, Yang! Wei could still keep calm, but this last item 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 according to Chang Haonan, this chicken-blooded state should not last long, but 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 changed.
“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 a deep regret in his tone:
"However, this tightly connected control valve...AL31FN is Liulika'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."
However, Chang Haonan naturally thought of this problem a long time ago and waved his hand directly:
"It doesn't matter. There is no need to do it 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. Although the effect is slightly worse, it can at least expand the engine envelope to a large extent and ensure flight safety under extreme conditions."
"Wait until the domestically produced third-generation high-thrust turbofan. After the engine matures and is replaced, the full version of the active stability control system can be used. ”
This explanation stunned Yang Wei:
“Your system has very high requirements for flying engines. Let’s not talk about whether the turbofan 10 can be developed before the J-10 is officially put into service. Even if it is developed, , then the design of the air intake will probably have to be changed a lot..."
And Chang Haonan's answer was even more self-indulgent:
"It just needs to be changed a lot!"
“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, and evaluated the overall situation of the aircraft structure, aerodynamics, flight control, etc. And test, wait until the domestic supporting engine comes out, and then come up with a second version of the design with modified intake duct, so that only the power and active stability control system can be tested again, and nothing will be wasted..."< br>
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. 10. This is great. You can directly show your sense of ownership and help us. The entire project schedule has been changed, right?
(End of this chapter)