Chapter 24 Parametric reconstruction of blade airfoil and stacking line

"As expected of Beijing Airlines' top students, you can tell at a glance, but I can't compare with you. I started working right after I went to a technical secondary school, and then I came out to do business with my brother-in-law." Hao Dagang waved his hand.

"I'm being modest. The previous technical secondary schools were no easier to pass than the university entrance exams." Chang Haonan looked at the blade design in his hand: "If you think of nothing else, the wicker leaf shape that combines two Bezier curves is really very good. It’s better than many undergraduate students.”

Wu Yifan next to him suddenly felt that there was something wrong with these words...

"Sigh... What's the point of saying all this? It's not that I can't beat Fuji Electric. Although I don't like notebooks, a small fan can't beat others."

Hao Dagang touched the top of his head and sighed: "I wonder if you can improve it?"

Unknowingly, his name for Chang Haonan has become you.

"Well... Although Bezier curves are used a lot in aircraft airfoils and turbine machinery, the problem is still quite obvious." Chang Haonan replied:

"First, it cannot make local control modifications. Any changes will affect the entire curve. At least half of the 16 parameters in this design are not independent; second, it cannot accurately express quadratic curves such as arcs, so regardless of No matter how you adjust the parameters, the smoothness cannot be guaranteed at the joints between Bezier curves and arcs on the leaf profile."

Seeing that Chang Haonan spoke eloquently, Hao Dagang's face was full of excitement and anticipation: "It seems you have an idea?"

Chang Haonan nodded and looked at Wu Yifan next to him: "Old Wu, sign the contract."

Strictly speaking, Chang Haonan should be regarded as a subcontractor, but Party A of this subcontractor had the knowledge and consent.

After signing, Hao Dagang took out a kraft paper envelope directly from his bag and stuffed it into Wu Yifan's hand.

Deposit, RMB 1000.

At this point, it’s not a small sum of money.

The latter opened the envelope and checked the amount of money, then took out two "Great Unity" coins and put them into his pocket. Finally, he handed the envelope and the remaining money to Chang Haonan, which meant that the deal was concluded.

"I'll leave it to you two to optimize the leaf shape. This time our boss is determined to win the order for Changhong air conditioners. I hope you can bear with me."

After Hao Dagang put away the contract, he stood up and hugged Chang Haonan and Wu Yifan directly. He seemed to be a bit of a gangster.

But it is reasonable. In this era of business, if you dare to run around with cash, you will always have something after all.

After seeing Hao Dagang off, Wu Yifan took off the schoolbag behind him and handed it to Chang Haonan:

"Nan Shen, how long will it take?"

"It's hard to say, but it will only take about a week." Chang Haonan took the backpack, which contained the laptop and floppy disk that he had become very familiar with over the past half month.

"A...week?"

Wu Yifan's hand shook, but fortunately Chang Haonan had already grabbed the strap of the backpack, otherwise the computer inside might have collapsed before it could exert its full value.

"They told me that the original plan took more than two months to design."

"Well, their basic design is actually pretty good. I will use non-uniform rational B-splines (NURBS) to parametrically reconstruct the fan blade airfoil and stacking lines, and just make a few improvements."

"Non-uniform...what?"

Wu Yifan suddenly felt that not only had he not learned well in his professional courses, but he might not have learned Chinese well either.

"I see that you didn't attend class well last semester. Teacher Shi Fa taught you all in his computer-aided geometric design course."

In order to adapt to his current status, Chang Haonan spent half a day reviewing the classes he had taken in the previous semesters. It was impossible to make mistakes this time.

"Ah? I'm stupid..." Wu Yifan suddenly felt a pain in his body. If he could listen to the class well last semester, he would be able to earn five thousand yuan now instead of just one thousand yuan.

But this illusion was soon extinguished.

"Don't think too much. Teacher Shi only teaches the theoretical basis. The difficulty lies in the implementation." Chang Haonan patted Wu Yifan on the shoulder.

In fact, this is not the first time that Chang Haonan has done this job. At the beginning of the 21st century in his previous life, he also used a similar method to design an axial fan with almost the same size for Chang Hong Group.

After all, the predecessor of Sichuan Changhong Group was a military industrial enterprise that manufactured fire control radars. Although it later became a civilian, it is still inextricably linked with the aviation industry. It is not unusual to entrust the latter to help with technical research.

"Okay, I can't earn your money." Wu Yifan shook his head and reluctantly accepted his fate, then took out a notebook from his pocket, wrote down a series of numbers and tore off a page.

"This is my pager number. Once you're done, just ask the paging station to send me a completed message."

In 1996, Chinese display pagers were already very popular. They could not only display numbers, but also receive short messages with a limited number of characters, similar to the Youth Lite version of SMS service.

Chang Haonan had already put on his bag and walked towards the library. He just waved his hand behind to indicate that he heard it.

……

Although the exam week for the second semester of the junior year in the Department of Aircraft Science is very leisurely, it does not mean that the same is true for other majors and grades.

Therefore, the library was undoubtedly overcrowded, and there were even many people sitting on the floor.

So after borrowing a few reference books, Chang Haonan had a simple lunch and went to the computer room again with his things.

Even though he didn't use the system this time, his work efficiency was still quite high. After all, he had a serious scientific research background in his previous life. How could he not even be able to complete such a small project.

It's just that it was supposed to be a step-by-step process, but after doing it, Chang Haonan began to feel a little dissatisfied.

He was less than thirty years old when he worked on the project for Chang Hong. He was a newly graduated engineer. After that, he went through twenty years of experience and completed an overall design under the guidance of the system. The height has naturally far exceeded that of the past.

"It's done, and the performance should meet the requirements, but..."

Chang Haonanqie went out and took a look at the design document - there was no standard format for doing a project for a small business, so he directly used the electronic version of the design document, and then just saved it on the computer and gave it to Wu Yifan.

After all, the design object is just an air conditioner blade, and the rotation speed and gas flow rate are not very fast, so there are a lot of approximations and omissions in the design documents.

"It's not transparent enough..." Chang Haonan said to himself in front of the screen.

These approximations and omissions are certainly acceptable in the field of home appliances, but now he has some new ideas.

I should be able to do better.

The axial flow fan can essentially be regarded as an extremely simple compressor. As an impeller machine, since the air flow in the compressor is a dilation flow, flow separation is more likely to occur and is more serious.

Although axial flow fan blades with stable working conditions do not need to consider stall or surge issues, efficiency losses due to the continuous development and accumulation of the end arm boundary layer and noise caused by refraction of the boundary layer still exist.

In the past, because most OEMs only required fans to meet flow requirements and were not very strict with efficiency, noise and other requirements, no one paid attention to this issue. But now that they have to fight with Fuji Electric In terms of performance...

"It seems that we can refer to some design ideas of aircraft engine turbine compressors?"