Chapter 14 This can no longer be described by the word "Xueba"
Chang Haonan did not delay for too long. After Liu Hongbo turned back to maintain order, he began his explanation:
"In view of the shortcomings of the J-7, the main fighter of the People's Air Force, which has poor all-weather combat capabilities and does not have beyond-visual-range combat capabilities, our team changed the nose inlet of the original model to a mandibular inlet, leaving the nose A radar with a diameter of no more than 560mm can be installed in the space. At the same time, the flight performance of the aircraft is equivalent to or better than that of the prototype. "
"In addition, with the rapid development of supersonic aircraft, the future has been broken. The boundary between the aircraft and the power unit, and the internal flow and the external flow, therefore, during the design process, we adopted an integrated design scheme of the chin-type inlet/cone front body. After computer simulation verification, it was shown that the inlet/cone front body /The engine matches well, reflecting the advantages brought by integrated design. The design ideas are described as follows. The calculation process is located on pages 14-15 of the design description. Fortran language programming and Fluent software are used in the calculation process..."
“The performance analysis of the integrated model of the inlet/cone precursor is completely conducted by computer. The simulation ideas and methods are as follows...”
"In order to test the reliability of the calculation method used, this article conducts numerical verification using the double ellipsoid model whose detailed performance data is given on pages 213-217 of the textbook. The results are shown in the figure."
"In Under different incoming flow Mach numbers and different incoming flow angles of attack, the results calculated in this article are in good agreement with the experimental data, which shows the credibility of the calculation method used in this article..."
Judge Teacher At first they just listened, but soon they realized that the design was highly complete and well-thought out, and was by no means a half-finished product, so they began to read through the design instructions in front of them and discuss it in low voices from time to time.
When Chang Haonan began to talk about the specific design process, the four of them even opened their notebooks and began to record them quickly.
Of course, the four professors are all involved in CFD simulation. They don’t have to copy everything Chang Haonan said like Yao Mengna. They only need to write down some interesting ideas.
But for other students in the back of the classroom, this scene was already shocking.
On the stage, an undergraduate student was talking nonstop.
In the audience, the four judges were...taking notes?
As for the specific content of what Chang Haonan said, not many people care about it.
I don’t understand it anyway.
Huang Zhiqiang, who was full of confidence in himself just now, was even more stunned when he saw this scene - obviously the reason why the design instructions were only half as thick as those of their group was because there were a large number of steps that were not, or did not need to be, reflected on paper. .
As for the design manual in his hand, which said that the three-dimensional shape design of the inlet entrance "needs to rely on experience", Chang Haonan directly showed an exquisitely drawn half-mold schematic diagram, using two sentences The words made several judges nod their heads.
Just because he doesn't understand doesn't mean that the teachers don't understand. Chang Haonan's ideas are obviously recognized.
“After the design was completed, we compared the aerodynamic performance before and after the improvement, at a speed of Mach 1.5, an angle of attack in the range of 0 to +10° or a sideslip angle of 0 to 6 Within the range of °, the total pressure recovery coefficient of the inlet reaches more than 0.950. "
"The speed is Mach 0.8, and the total pressure recovery coefficient within the same angle of attack or sideslip angle range reaches more than 0.968, which is the same as the speed of Mach 0.8. Within the flow coefficient range matched by the engine, the maximum total pressure distortion index does not exceed 0.14.”
"The performance of the new inlet design at subsonic speeds is improved by about 3% to 8% compared with the original design, and the performance improvement between 1-2 times the speed of sound is more than 10%."
"Compared with the MiG 21MF inlet design that enlarges the intake nose cone and installs a radar, the performance in the full speed range is improved by at least 23%, and the conical front body can accommodate a radar with a maximum caliber of 560mm. According to Existing models are estimated to be enough to lock a fighter-sized target at a distance of about 30-40 kilometers.”
Although the previous content is obscure, the data indicators mentioned by Chang Haonan are familiar to everyone here. The students can still understand it.
So the back of the classroom, which had been silent when the design process was discussed just now, quickly started to boil again.
In the mid-1990s, beyond visual range combat was the most urgent issue for the Air Force. It can be said that whether there is a beyond visual range combat capability is the difference between 0 and 1.
Because of this, for a long time, "pointed aircraft" that can be equipped with large-caliber radars have been synonymous with advanced. Only a small number of J-8Bs and Su-27s have this feature. But today, they actually saw an improved J-7 that also had the same characteristics and could be installed with radar!
Don’t look at the figure of 30-40 kilometers, which seems small. You must know that the AIM7F air-to-air missile, the main force of the US military in the 1990s, has a maximum range of only 40 kilometers for a head-on attack. The Aspie that our country purchased from Italy The Thunderbolt 11 copied by Germany and based on this has a range of only 30 kilometers, so this 560mm nose is enough for now.
Not to mention that on this basis, the flight performance of the aircraft has not only not been reduced, but has been improved!
“If this improved J-7 is paired with the Thunderbolt 11, it will be almost the same as the F16! The F16 can fly more than 30 kilometers with the AIM7.” Most people who study aviation have a negative impression of the Air Force. I still have some understanding
"Well, there may still be a certain gap in terms of range, after all, the size of the aircraft." The other person seemed to be more rational, but there was obviously excitement in his tone.
“Hey, what’s the problem with short range? We don’t bully others like the Yankees. Let’s see, if we can have 200 aircraft at the beginning of the year, no, we can have 100 improved models like this. J-7, those two aircraft carriers definitely don’t dare to be so rampant!”
This sentence instantly won the unanimous approval of the people around them.
Although our country's aviation industry is still relatively backward, the supply of J-7 can still be opened up. However, the current model of J-7 has lagged behind when it was manufactured, so it can only maintain a small amount of production.
For a time, although everyone's views were not unified, almost everyone in the classroom began to discuss the aircraft's performance, cost, manufacturing difficulty and even the prospects of equipping the troops.
In fact, not only the students behind, but also several judges and teachers began to consider whether this improved model really has the possibility of being implemented?
"Xiao Chang, although your design still has some room for improvement, personally speaking, there is nothing to ask. If I were to do it, I would definitely not be able to come up with anything better than this. A better plan."
Professor Li Guang, the oldest of the four judges, took off his reading glasses and looked at Chang Haonan with relief in his eyes: "So I want to ask, what do you think about this? Are there any problems that need to be solved in the manufacturing of the aircraft? ”
This is almost impossible to give a higher evaluation. You must know that this course only requires aerodynamic design. Manufacturing issues, It is not included in the assessment scope.
Chang Haonan has already been prepared for this.
"Hello Professor Li, we have considered this issue at the beginning of the design. 60% of the parts of this improved model can be used in common with the original model. The performance requirements of the new parts generally do not exceed the level of the MiG 21MF. However, considering the weight of the radar, in order to maintain aerodynamic balance, some composite materials need to be used to reduce weight in the air inlet and radome. The amount of composite materials accounts for about 2% of the total material of the aircraft body. "
2% of the composite materials. Materials are not new to China Aviation Industry. They have already had experience with the J-7M, J-8B and J-7.
So this answer is basically equivalent to ‘there is no problem that needs to be solved’, but it seems not modest enough to say so directly, so I found a problem that is not a problem.
“I think if conditions permit, can we build a scale model and go to Mianyang to try it in the wind tunnel?”
Liu Hongbo’s voice was not very loud, and It was said to three other teachers, but someone still heard it.
The wind tunnel in Mianyang is not just a small experiment in a school laboratory. Going there to test, even if it is just a scale model, means that the plan really has the potential to take root.
You must know that this is just a junior year course design!
The discussion that had been silent started again, but this time, more people’s attention shifted to Chang Haonan.
Obviously, the word "student master" is no longer enough to describe such a person.
(End of this chapter)