Chapter 8 A new design method! 【Kneel down and beg to read】

At this moment, the classroom door was pushed open, and four more people walked in from the outside.

This teaching building is shared by their entire School of Aeronautical Science and Engineering, so it is not surprising that there are other students in the classroom. If it is before the end of the semester, there may even be twenty or thirty people in the same classroom at the same time, so they are concentrating on their research. The four people involved in the plan didn't care at all.

"Haonan?" The leader of the four people who just came in was Chang Haonan's upper bunk Huang Zhiqiang. Naturally, he recognized the former at a glance: "You are also doing course design here?"

In fact, Huang Zhiqiang came here specially.

Since the beginning of the semester in March this year, Chang Haonan has always looked bitter and resentful. Almost everyone in the dormitory knew that he wanted to design a fighter jet.

But for Huang Zhiqiang, Chang Haonan in that state is not worth worrying about. He knows very well where the opponent's upper limit is, and a person's ability will not be improved because of anger.

And he didn't think that was anything to be angry about.

However, Chang Haonan's uncharacteristically light-hearted attitude this morning made him feel a little uneasy, so he decided to "reconnaissance" to see how far the former had achieved.

"Yes, Lao Liu's class is not sloppy..." Chang Haonan did not raise his head, but continued to draw a sketch of the air inlet and the nose part on the paper, preparing to tell the other three people what they needed to do. things.

In addition to the 10 credits of the aircraft design course, which is second only to the graduation project and will greatly affect the average grade point, Liu Hongbo will also invite many big names in the college to serve as judges in the defense session of the final course design. .

These people are often also the judges during the admission interviews for postgraduate students who are exempt from examination.

There is usually only about a month between the two events.

Therefore, students who are interested in further studies must devote 120% of their energy to this course.

The four people who just came in put the tools and books they brought on a table not far away, and then Huang Zhiqiang, the leader, slowly walked over to Chang Haonan: "By the way, how far have you progressed?"

"We just selected the design plan, so it's early."

Chang Haonan still didn't look up.

He really had no impression of Huang Zhiqiang, and he didn't take him seriously at all.

What I’m going to say next are just some preparatory parts of the design work, so I don’t care about being heard by others.

And whether you can understand it or not is just a matter of words!

However, Zhang Man was very wary of the approaching Huang Zhiqiang, so he took a step to the side quietly, blocking the latter a few steps away from the table.

Huang Zhiqiang tried several times, but in the end he was unable to get over the obstruction because the aisle between the tables and chairs was so narrow.

"cut……"

Although there was no way to take another step forward, the petite Zhang Man could not block his view. Huang Zhiqiang easily saw the two black and white photos on the table and the sketch that Chang Haonan was drawing by hand, so of course I think this is preparation for reproducing the design through photos.

This immediately made him feel relieved again, he shook his head and turned to leave.

"As expected, big losers can only teach little losers. In the end, they have to copy it from the Soviets. Besides, aircraft design is not a sketch. How can you design something based on two photos?"

Huang Zhiqiang thought to himself, and lamented that he had been a little too unfounded just now.

At this time, Chang Haonan didn't know that he had been scolded by others. He had already finished drawing two schematic diagrams and took another piece of paper to list the steps on it.

The other three people also quickly took out their notebooks and pens to prepare notes.

They still remember the way the second-year Ph.D. student whose tutor was an academician herself took notes obediently in front of Chang Haonan yesterday.

"The process is roughly like this. Because we are designing the air inlet and the front fuselage in an integrated manner, I will first select five different design initial values, which are the cone front body, or the half cone of the radome. Corner." Chang Haonan pointed to the tip of the radome on the sketch and marked it with an a symbol: "What the three of you have to do is help me determine the design parameters corresponding to each initial value."

More than twenty years later, this process can be completely handed over to computers, but at this time, at least under their current conditions, many things still have to be calculated by hand, especially the relevant engineering manuals.

Zhou Shuwan and the others nodded like chickens pecking at rice.

"Here are the steps. I'll explain it first. If you don't understand anything, be sure to ask."

Chang Haonan said and wrote (1) on the paper.

"The first step is to set the cone precursor busbar, fix the initialization half cone angle and perform dimensionlessization according to the cone length."

"The second step is for me to do. Average the flow field Mach number in the area near the inlet entrance as the baseline flow field design to calculate the Mach number. Because this is still an airplane after all, so the subsequent design points should be Choose around Mach 1.6, not too high.”

“The third step is to take the intersection of the three-dimensional internal transformation line of the inlet duct in the longitudinal symmetry plane of the cone precursor and the generatrix of the cone precursor as the installation positioning point, and calculate the axis of the incident inner cone shock wave in the inlet duct and the relationship between the axis of the cone precursor and the cone precursor The angle between the axes is used as the installation angle of the air inlet, and the specific calculation method is..."

“In the fourth step, the shape of the upper lip of the inlet is obtained by the intersection of the inner cone shock wave incident on the inlet and the lower surface of the cone precursor, and the shape of the inner lip is obtained by the intersection of the incident inner cone shock wave of the inlet and the lower surface of the cone precursor. The intersection of longitudinal symmetry planes results in..."

"The fifth step is also done by me. Based on the three-dimensional shape of the inlet entrance, streamline tracing is performed in the selected reference flow field to generate the internal profile of the inlet..."

"The air inlet calculated according to these five steps is theoretically the optimal design at the half-cone angle. As for which of these designs is more effective after being installed on the MiG-21 fuselage, we need to do what we did yesterday. I’m going to do a CFD simulation. I’ll run out the results and you guys will be responsible for organizing the data and making charts, so we should be able to find the optimal solution intuitively.”

Of course, among the steps given by the system, there was a process of going to the wind tunnel at the end, but Chang Haonan simply ignored it.

If he could directly apply for resources like a supersonic wind tunnel, would he still be using it to modify the J-7 with three undergraduates?

After Chang Haonan wrote the last step on the paper, he threw the pen aside, stood up and looked at the three teammates in front of him: "Do you understand?"

There was a moment of silence...

"Well... I understood some of it, but I'm not sure what I didn't understand about the parts I didn't understand." Zhou Shuwan scratched his head with a troubled expression: "Let's go to the library first, and then we'll start figuring it out. , I’ll ask you again if I can’t figure it out anymore.”

"Okay." Chang Haonan nodded, and then packed his things on the table into his bag. Zhou Shuwan helped Zhang Man sort out the large amount of information she brought almost out of habit. The four of them Get up and leave quickly.

The classroom was not very large, and Chang Haonan did not lower his voice deliberately when he spoke, so Huang Zhiqiang and the four people sitting next to him also heard the content clearly.

"Brother Qiang, did you hear what Chang Haonan and the others discussed just now?" One of them approached Huang Zhiqiang and asked in a low voice: "What do you mean? It seems like they really have ideas?"

Huang Zhiqiang frowned at this question and glanced at the teammate next to him somewhat unhappily.

He didn’t understand either!