"By the way, Yiyi classmate, I forgot to ask you a question just now. I think this question is as important as those formulas, you should be able to solve my puzzles, right? ”

Xiao Yizhan looked at the few words An Zhusheng asked, and knew in his heart that his old friend must have asked that question. He didn't ask this question at the beginning, because he felt that he was not sure whether the question that the two of them wanted to verify was the truth or not. And that problem has now been confirmed by the seven engines produced through subsequent processing. That's right, after each of the seven engines produced later rolled off the assembly line, An Zhusheng did not miss the opportunity to conduct additional tests. Moreover, under his strict requirements, each test is strictly replicated the test conditions of the first test. The results of the test finally convinced the two of them that the engine designed by Shen Yiyi was indeed particularly good. So, naturally, when this question was confirmed, the curiosity of the two old experts could not be hidden. Especially An Zhusheng, an engine expert, he was even more anxious than Xiao Yizhan to know where Shen Yiyi had carried out the exquisite design to make the performance of the engine so outstanding.

Of course, it's not that Xiao Yizhan isn't curious about what Shen Yiyi can do this, it's just that compared to An Zhusheng, who is engaged in engines, he, a person engaged in aircraft design, will not be so eager. However, Old Man Xiao, who had the eager experience of Shen Yiyi's fluid mechanics formulas when he first saw them, can also understand the mood of Old Man An Zhusheng at the moment. Therefore, Old Man Xiao also said on the side: "Yiyi, you must help him solve this confusion, otherwise he will not be able to sleep all night, and his heart is itching like something." ”

Shen Yi nodded: "An Lao, Xiao Lao, if you have any questions, just say it." But it's still the same sentence. If it's too complicated, I really don't have the energy and time to deduce it in detail for you now. After I've finished the things at hand, I'll give the old man time to explain the issues. ”

An Zhu nodded clearly: "Don't worry, if it's too complicated, I won't stare at you and ask." In a moment, you just need to tell me the general direction. If I don't understand this general explanation, then follow what you said. After you're done with the things at hand in a few days, take time to teach us two old men a lesson, so that our two old men can have a good touch on what we haven't been able to figure out for so many years. ”

Shen Yiyi heard what Old Man An said quite mysteriously, and couldn't help but be a little curious. She couldn't help asking, "You two old men don't need to be so mysterious, I don't know what you want to ask." You'd better say it first, let me understand, so that you can have a bottom in your heart, right? ”

An Zhusheng came to his senses at this time, and dared to go around the outside in a big circle. I still haven't told anyone what I want to know.

The old man cleared his throat, sorted out his thoughts, and asked Shen Yiyi questions one by one.

"That's right, Shen Yiyi. The drawings of the engine you draw, we have already helped produce 8 units according to your drawings, you know, according to our regulations, any machine produced in the institute. It must be tested on the test bench before it can be released. ”

Shen Yi nodded slightly, indicating understanding. As a matter of fact. In her later experience, any OEM engine will have a series of factory tests to be done before leaving the factory. For some pure research-oriented institutions such as research institutes, the prototypes they produce are even more able to test and inspect each one because of the small number.

"We tested your engine, and the performance was amazing. What we don't understand is that we look at your design drawings. Compared with the design of other engines of the same type, there is no special structure or design, but what can be said that the performance of your engine will greatly exceed that of other engines in China? ”

An Zhusheng stretched out his hand and motioned for Shen Yiyi, who wanted to answer, not to speak first, so as not to interrupt his whole question.

"And, we thought it was a fortuitous result. So we thought there would be 7 more of the same engine to follow anyway, so let's see if such a standout performance is accidental, or if it really reflects the performance of the engine you designed. However, I did not expect that the performance of the next seven engines was strikingly similar to that of the first engine. From this point on, our understanding is that your engine is really surprisingly good at its performance. But as I said earlier, we looked at your design, and there is nothing different about other traditional designs. What is this for? Can you tell us? ”

After An Zhusheng finished speaking, he looked at Shen Yiyi. He really wanted to know what method this little girl used to make them, who have been working in this industry for so many years, unable to figure out what kind of magic was applied to her engine.

Shen Yiyi thought about it one by one, and probably understood what the problem in the heart of Old Man An Zhusheng was. She asked Mr. An: "Old An, you are from the 606 Institute, shouldn't you study this kind of piston engine?" ”

An Zhusheng nodded: "Yes, we don't study this kind of engine." But don't forget, we also started with traditional engines. So what a piston engine looks like, we still have a basic concept. In addition, over the years, we will also go to other units to participate in some review meetings, and this knowledge is still there. So don't try to fool me. I'm not that easy to deceive. In the end, he also reminded Shen Yi one by one.

Shen Yiyi smiled and said, "Don't think I'm going to lie to you." I'm just going to ask you about your major, but I'm afraid you'll never understand what you're talking about in a while. Now that you understand what a piston engine is all about, I'm relieved. ”

"You just said that the performance of our engine greatly exceeds the performance of existing engines, and I think the range of this excess is not unlimited, at least it cannot break through the efficiency of the Carnot cycle." Shen Yiyi will be particularly cautious when talking about this kind of theoretical thing. She is afraid that a slip of the tongue will affect the overall understanding of the idea.

Old Man An nodded as a matter of course. The Carnot cycle is a proprietary knowledge point that is well known to people in heat mechanics, which basically reflects the theoretical limit of the conversion of chemical energy into mechanical energy. So of course, no matter how good the performance of Shen Yiyi's engine is, it is impossible to break through this limit. This is where the second law of thermodynamics comes into play.

As soon as Shen Yi saw that Old Man An could understand and there was no doubt, he continued to speak with confidence.

"So, since our performance has not broken through the Carnot cycle, then the so-called better performance than the existing engine is nothing more than that our loss is smaller, so our mechanical energy loss is also smaller. Do you agree with that? ”

An Zhusheng nodded in agreement, and urged: "Don't be wrong, keep talking." I know that your mechanical energy loss is small, but how do you do it? The people under me told me that in the assembly of some of your parts, you found that some poor work was selected unreasonably, was this intentional or accidentally drawing the wrong one? ”

Shen Yiyi admired in his heart. It's really an old expert, and you can see the problem at once. Her choice of tolerances was really the answer she had come up with when she was thinking about the question asked by Old Man An just now.

"Yes, the tolerances you mentioned were actually specially selected by me. I'm sure your technicians will tell you that this machine of mine is very easy to install, but I thought it would leak, but it didn't, right? ”

Listening to Shen Yiyi's question, Mr. An Zhusheng recalled carefully, and it seemed that someone had really reported to him that the engine processed according to Shen Yiyi's drawings this time seemed to be particularly easy to assemble, and he did not use the hammer that our Chinese workers and masters liked to use. Old Man An nodded: "You are right, it is true." But does it have anything to do with the performance of your engine? ”

Shen Yi nodded: "Of course it matters." And to be honest with you, An, I guess that's actually what makes my designs different from the ones you've seen before. ”

Looking at Old Man An's wide-eyed eyes, Shen Yiyi continued: "Actually, the person who draws the engineering drawings must know that the tolerance of the parts is very important. However, most people choose tolerances from the Mechanical Design Manual, and probably few people would think that this approach may not be appropriate. ”

"My understanding is that the tolerances in the Mechanical Design Manual only represent the minimum requirements for manufacturing tolerances, not the optimal requirements. In fact, if that kind of tolerance is applied to each part, the accumulated tolerances are quite considerable when the product is actually formed. Such accumulated tolerances will inevitably affect the performance of the final product. Therefore, when we select tolerances, we should take into account the performance factors of the final product and reconsider our method of selecting tolerances. ”

When Mr. An Zhusheng heard Shen Yiyi's statement, he suddenly had a vague concept: "So, in fact, the mixing of tolerance bands when you were designing at that time was actually intentional, and the purpose was to ensure the performance of the final product?" ”

Shen Yiyi cocked his thumb: "The old man is right!" That's what I thought. In fact, for the whole engine, I set an overall tolerance index, and then assigned it to each part, especially the tolerances of the connection parts, according to this principle. I guess the biggest reason why the performance of my 8 engines produced according to the drawings is not much different, but it is better than the same type of engine. (To be continued......)

PS: The customer is here again. I'll try to keep it up as long as I can.

Everyone's support!

I would also like to thank all the students who voted.

Xie Lu Xie cartoon kiss's reward. You gave me the strength to continue creating.