Chapter 60: Shocking words (two-in-one)
“Of course there is no problem, but I have to know what you are going to say first, so that I can be prepared so that I won’t be unable to get off if any problems arise. Taiwan.”
Lin Shikuan agreed to Chang Haonan’s request without much thought.
The main reason is that he is almost having a psychological shadow on speaking.
After all, others are reporting on xx progress in their work. Even if there is nothing worth saying, everything is going well. Such a comparison makes their group very useless.
"It's nothing, it's just that I have basically determined that the existing wing design needs to be modified to a certain extent. As for the specific data, I am still calculating it. If nothing else, I will probably get it by this time tomorrow."
This explosive news made Lin Shikuan almost breathless.
He did think that Chang Haonan could help them fight a turnaround, but he never expected that it would turn around so quickly...
"Dr. Chang, modifying the wing design is not a small matter. Things, you...are you sure you can come up with a feasible modification plan in just one day?"
"No, no, no, you misunderstood. Of course, it is impossible to know how to modify the wings in one day." Chang Hao. Nan waved his hand and explained: "But it's enough for me to confirm that there is a problem with the wing and it must be modified."
"Cough cough cough——"
Lin Shikuan, who had just managed to catch his breath, held it back again.
This time Chang Haonan did not continue to make shocking remarks, but quietly waited for him to recover.
“But you are half right. If you use traditional design methods, then modifying the wing is indeed a matter that affects the whole body. But if digital design can be realized, then this magnitude The modification will not delay the progress too much. "
"But the Eighty-three Project has not yet achieved full digital design," Lin Shikuan said, rubbing his chest that had just stung due to a violent cough.
"So Lin Gong, you have to speed up the progress and let the other teams of the 83 Project see that the digital design team is not only not a burden, but can also help them greatly improve their efficiency."
Chang Haonan's words made Lin Shikuan's eyes suddenly brightened.
"You are right, Dr. Chang, you are right..."
The latter turned around and strode out of the room, returning to the computer room where everyone was just now.
“Work overtime tonight!”
...
The day passed quickly. After dinner the next day, Lin Shikuan took Chang Haonan and Yao Mengna to a large conference room.
After all, the progress seminar is required by every group involved in the 83rd Project in the 601 Institute. Some groups with more complicated work even have to send several people over.
As soon as the three people entered the door, Yang Fenghao, who was sitting at the head of the long conference table, noticed this.
"Xiao Chang, Xiao Yao, how do you two feel about being in the digital design team? Did Lin Gong help you get familiar with the work?"
Lin Shikuan almost rolled his eyes when he heard this question - he didn't feel that these two people needed him to help them familiarize themselves with the work. In the past day or so, he had been led by the other party to make a lot of progress.
It is no exaggeration to say that this day and a half has done more work than they have done in the past year and a half.
After all, after working overtime last night, everyone in the team was convinced that they were finally heading in the right direction.
"We have been working together for more than a day and feel pretty good. The forest workers are very efficient. They just didn't find the right direction before."
Chang Haonan took advantage of the situation to help Lin Shikuan and others. The man explained, and then received a grateful look from the latter.
When he was just reborn, he had already thought about using the system to improve the power of the entire Chinese scientific research system.
But this can only be done step by step.
Chang Haonan, who was a military screwdriver in his previous life, had no decent management experience at all. Although he had led several projects, they did not require any complicated division of labor and collaboration, so that the system evaluated his management ability. It's level 0 and 0 experience.
This digital design group with a simple structure, generally young members, and no pretensions or baggage is just right for a novice like Chang Haonan to hone his management and organizational skills.
That’s why he found ways to boost the confidence of Lin Shikuan and others.
In fact, since yesterday afternoon, the system has shown that Chang Haonan's management ability experience has been slowly increasing, and it has reached 15 o'clock just after receiving Lin Shikuan's gratitude.
While the three of them were talking to Yang Fenghao, other participating project members also entered the conference room one after another.
After everyone sat down according to previous habits, the seminar officially started soon.
Since Chang Haonan had never been exposed to projects related to the J-8 before, and the August 3rd Project was indeed somewhat legendary to this generation of military workers, he listened to the whole process with great interest.
In general, the test flights of the three prototypes went smoothly, but some groups also mentioned some problems.
For example, the WP14 engine is still not mature enough and will induce surge under certain circumstances, especially at high speeds. However, the probability of this problem is very low, so the specific reasons still need to be further investigated.
Still with WP14, the engine life, especially the life of the turbine blades as hot-end components, is not ideal and there is still room for improvement.
In addition, as a typical second-generation high-altitude and high-speed interceptor aircraft, there are problems with the stall angle of attack in a specific speed range and the available overload at high angles of attack, which need to be limited by flight control software to avoid stalling. Or spin state.
Also, the fire control equipment group stated that the imitation progress of the PL11 air-to-air missile, an Aspadian-made model that is matched with the 1471G radar, is so slow that they simply do not have enough ammunition for over-the-horizon attack testing. .
Finally, there is a somewhat peculiar problem. When the J-8-3 uses the innermost pylon of the wing to launch PL8 air-to-air missiles, there is a certain probability of causing the engine to stop.
The reason for this matter is not complicated. The smoke and dust generated when the propellant of the PL8 missile is burned is very heavy, and the interference with the air inlet when the inner pylon is launched may lead to insufficient air intake or turbulent air flow.
It’s just that this is the same problem as the slow progress of the previous PL11 missile, which needs to be solved by the missile research and development unit.
As for the problem of the WP14 engine, it is also not something that the 601 can handle. However, even considering the worst possibility, the J-8-3 can temporarily use the WP13F engine with a smaller thrust, and it will not be completely unable to board. day situation.
So after listening to the previous report, both Yang Fenghata, who presided over the meeting, and the team responsible for these tasks were in a relatively comfortable mood.
“Then finally, let the digital design team talk about their progress.”
Yang Fenghao looked at Lin Shikuan, who was sitting in the back corner of the conference room.
Since the digital design team cannot guide the aircraft design, they have almost become outsiders of the 83rd Project, and have been placed at the end of the report for a long time.
But this time, it was not Lin Shikuan who stood up, but Chang Haonan, who was holding a report in his hand.
This was a new face to most of the people in the conference room. And usually, when the digital design team gives a report, it means that the seminar will end soon and everyone will relax.
Many people have already started chatting quietly among themselves.
“The information design team has completed an aerodynamic simulation of the J-8-3 aircraft in the past period of time.”
“According to our calculation results, the aircraft is on the outermost side When two pylons carry two Aspid air-to-air missiles at the same time, the aileron efficiency will drop sharply under large angles of attack, large aileron deflection angles and large dynamic pressures, and there may even be aileron inverse effects.”
The venue, which was noisy just now, fell silent for an instant.
As soon as these words came out, not to mention the other people present, even Yang Fenghao, who was already aware of Chang Haonan's ability, first thought that there was an error in the simulation.
After all, these two people only arrived at No. 601 at noon the day before yesterday, and it was less than 60 hours until now.
In fact, Yang Fenghata originally planned to introduce them to the project members after the seminar ended today.
Chang Haonan himself faced such a scene for the first time. Now almost everyone's eyes were focused on him, with suspicion, confusion and even confusion in their eyes.
But at this time, it is more important to show confidence and decisiveness.
So he only paused for about two seconds and then continued:
"Based on engineering experience, we can qualitatively know that the changing trend of aileron efficiency and roll rate with dynamic pressure is closely related to the aileron deflection angle and flight angle of attack, but the traditional linear aerodynamic analysis method cannot simulate such results. Therefore, the aerodynamic analysis at high speed and high angle of attack can only be based on experience, supplemented by a large amount of wind tunnel and test flight data.”
“But we introduced external nonlinearity in the analysis process. Aerodynamics, and considering the elastic deformation of the wing structure, we successfully simulated the impact of the angle of attack, wing load and aileron deflection on the aerodynamic efficiency of the wing. The final result was that an aircraft with 4 rounds of A bombs flew at Mach 1.4 At speed, at an angle of attack of 12°, once the aileron deflection exceeds 10°, aileron reaction will occur."
"..."
Chang Haonan's explanation made Yang Fenghata. The idea has become loose.
He knows very well that nonlinear aerodynamic and structural analysis are the areas where the other party is best at.
Even when he agreed to invite Chang Haonan over, it was because of his outstanding abilities in these aspects.
The wing flutter problem of the Y-7 modified passenger plane in Institute 603 also took one day to solve.
......
After a brief hesitation for a few seconds, Yang Fenghao coughed twice, drawing everyone's attention to himself.
“Let me introduce, this is Dr. Chang Haonan, who I invited from the research group of Academician Du Yishan of Beijing Hang University to assist in the work. His specialty is the use of numerical methods for aerodynamic simulation and structural simulation.”
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The venue that had just been silent gradually began to be filled with whispers.
Most people don’t know what happened over there at No. 603 School, but the names of Jinghang University and Du Yishan are still somewhat convincing after all.
At least it should be much more reliable than 601 Institute’s own digital design team.
So after Yang Fenghao pointed out Chang Haonan's identity as an outsider, everyone's attitude towards him changed from complete disbelief to hesitation.
Theoretically speaking, Chang Haonan’s explanation just now is indeed tenable.
Aileron refers to a small movable wing surface installed on the outside of the trailing edge of the wing tip. Its main function is to generate rolling torque through differential deflection to make the aircraft perform roll maneuvers. It is one of the most important control surfaces of the aircraft. .
If the rolling moment generated by the aileron and the moment generated by the elastic deformation caused by the aerodynamic force on the wing cancel each other out, the aileron will be unable to continue to control the roll of the aircraft.
When the flight speed continues to increase and exceeds the reaction speed, the rolling moment generated by the aileron will be smaller than the reverse moment generated by the deformation of the wing under the action of aerodynamic force.
That is, when the pilot wants to control the aircraft to roll to the right, the aircraft will roll to the left due to the reverse torque.
This is a very fatal problem for formation flying and air combat.
The simplest solution is naturally to limit the rudder operation of the aircraft in the flight control software - since the aileron angle will be counterproductive if it exceeds 10°, then I write a command to prevent the aircraft from deflecting to more than 10° in the corresponding speed range. 10° is fine.
In fact, many aircraft do this. Even earlier aircraft will simply lock the aileron deflection angle through the mechanical structure to avoid danger from the source.
However, the problem is that although this method ensures flight safety, it also limits the maneuverability, making the aircraft almost become an iron rod that can only make small movements at high speeds.
If what Chang Haonan said is true, it means that the maneuverability of an aircraft with bombs will be severely limited at 1.4 times the speed of sound.
For an interceptor, this is obviously not good news.
"Dr. Chang Haonan, I would like to ask, which method did you use to calculate the impact of wing elastic deformation on efficiency? As far as I know, there does not seem to be a reliable empirical algorithm to deal with this problem?"
On the other side of the conference room, a balding middle-aged engineer wearing a half-sleeved shirt raised his hand and asked.
“You are right, there is indeed no reliable formula to deal with it, but this is exactly the area that the CSD/CFD coupling method is good at solving,”
“First of all, we based on the original The aerodynamic model calculates the aerodynamic performance of the wing under selected flight conditions. At this time, the wing is still regarded as a rigid model for analytical calculation."
"Then, the aerodynamics on the fluid nodes on the wing surface are obtained. The load is interpolated to the structural model nodes through the equivalent node method, and the structural deformation of the wing under this load is calculated. ”
"The third step is to obtain the new coordinates of the wing's characteristic points based on the structural deformation for grid regeneration, establish a new aerodynamic model and then perform the next round of aerodynamic calculations. Repeat the above process until the convergence conditions are met, usually after 6-8 calculations. The convergence result can be obtained. ”
“After the above three steps, the rigid lift and elastic lift of the wing in these two situations can be obtained, thereby calculating the aerodynamic parameters under the selected flight conditions. Wing efficiency. ”
“Finally, by analyzing the lift coefficient and deformation of the wing under various calculation models and flight conditions, the relationship between them and aileron control can be obtained, if necessary. I also brought detailed calculation results."
Yang Fenghao's expression turned serious at this time. He waved to one of his assistants, who then came to the back of the conference room and came from Chang Haonan. I took a few pieces of paper in my hand and placed them one by one under the projector.
Several line charts were projected onto the curtain.
"This..."
"The idea of the iterative method should be correct, but if the result is really like this, the project progress will probably..."
"I didn't expect that the digital design team would still If you can really make something, no matter whether the result is right or not, at least it seems that way..."
"..."
Obviously, although it is impossible because of Chang Haonan's statement alone Just draw a conclusion, but everyone in the conference room has begun to take this calculation seriously.
(End of this chapter)