After the eight impeller castings cooled down for a period of time, the three came to the workshop, at this time two impellers were in the process of sand reshing, and a cleaned impeller was placed on the ground.

Looking at the cleaned impeller in his hand, the technical backbone who personally took over the test piece task of Zhong Jianjian became more and more bad, pouted, and then put down the impeller.

"There are many problems, such as bearing holes, sand washing at thin walls, and sand holes."

Shaking his head as he spoke, although he had expected these problems, he didn't expect them to be exposed so quickly, and not only that, but he was concentrated in the first casting, and he couldn't imagine what the next seven castings would look like.

Picked up the casting on the table and saw that there were a lot of problems, Zhong Jianshe looked at it and handed the parts to Yang Hui, Yang Hui actually saw the defects of the casting from afar, but he still took the casting in Zhong Jianjian's hand and observed carefully.

I don't know if I don't see it, the problem is not in those places where there is a problem, but in those places where there is no problem. In the place where there is no problem, it can be seen that the casting is very good, and the roughness is very high, not to mention the roundness of the entire outer ring of the casting, which is very good.

"Construction, you set the requirements for this casting so high?" Yang Hui doesn't know how to cast, but he can see that if this casting is successful, it will definitely catch up with the level of endless precision casting. Obviously, with the current level of the base, there is no way to do it, that is, the country has not yet broken through this technology.

"Yes, this is a one-time molding, like this kind of small parts have a lot of surfaces, there is no way to process the surface, of course, it is okay to use a fitter to polish this by hand, but this is a bit of a fuss, so I chose to improve the casting accuracy."

Now I understand that the problem is simple: since it is impossible to perform secondary processing on the surface of the cast part, the accuracy can only be improved at the time of casting. This is an option, but it is clearly not up to the mark.

At the stall where Yang Hui and Zhong Jianshe were talking, the remaining seven impeller castings were cleaned out, and the two of them were beckoned over to a pile of impellers.

"That's it for the finished product, at present, we can't achieve the accuracy required by the drawing, I promised this test piece request is to see if it can be made, but I obviously underestimated the difficulty."

The person in charge took out one of the impellers in the pile and handed it to Yang Hui and the others.

"This impeller is the best of the eight, there is no sand washing, there are few sand holes, and the seam is supposed to be turned again, so it is not a big problem. You can barely experiment with this. It's a defective product, but it's not a scrap product. ”

After thinking for a long time, this technical backbone said such a sentence, you must know that the castings that went out of this hand have not been defective for many years, and only this time for Yang Hui that they were in a hurry to release this defective product. Only in this way can it be regarded as handing over a casting, if there is no casting, then the follow-up test can not continue.

"Okay, we'll accept this casting, and we'll find a way to control the accuracy requirements when we go back, and we'll trouble you later." At this time, Yang Hui can't say anything, I'm afraid that the second improved casting will have to trouble this, listen to the workers here, this Yijing is the top technical backbone in the factory, and next time no matter what, I will have to trouble this.

Farewell to the factory here, take the only defective product back to the institute, the test is definitely not possible, can only find a way to optimize the impeller, find a way to reduce the casting accuracy requirements.

Put down the casting, find out the design index of the part, now the easiest way is to see if the technical index can be lowered, if you find the technical index that can be lowered, then the comprehensive requirements of the entire impeller may be reduced.

First of all, look at the compressed air efficiency, if the efficiency can be reduced, it is the simplest, and the accuracy requirements of the casting can be directly reduced. However, after looking at the compression efficiency, it can be clearly seen that this indicator has not been reduced, and the efficiency is already close to the minimum air compression requirement required by the combustion chamber.

Look at the design life of 27 hours, this clock construction design left a margin of two hours, now it is to sacrifice the margin of these two hours, directly changed to 25 hours, now the design life of the combustion chamber is 25 hours, the impeller is useless for two more hours, besides, the impeller of the casting is generally not a problem, this thing is more solid and will not have problems under normal operation.

Two hours is not enough, and it doesn't matter much about accuracy.

Then an indicator that made Yang Hui cry and laugh suddenly appeared in front of Yang Hui. Zhong Jianjian, a lovely comrade, actually considered the impeller's ability to withstand inhaled foreign bodies, and considered the possibility of hitting birds, in order to be able to return safely after the engine inhaled foreign bodies, Comrade Zhong Jianshe increased the strength and hardness of the impeller by more than one grade.

"My Comrade Zhong Jianjian, you have also considered hitting the bird, how big is this model aircraft, and if it can hit the bird, I want to say how small the probability is." Looking at Zhong Jianjian, who was still calculating the impact of the two hours of cutting down on the final manufacturing accuracy, Yang Hui could only ask with kind words.

"The probability of hitting a bird・・・・・・ Oh, it's that I think too much, where does this model aircraft come from so easy to hit a bird, it's all because I read a paper on the engine inhaling foreign objects and hitting birds a few days ago, and I was confused." Zhong Jianshe naturally understands his own problem at one point, and he thinks a lot about it and calculates more data.

"Team leader, wait a minute, I'll calculate where the strength and hardness requirements of the impeller can be reduced without considering inhalation of foreign bodies and hitting birds" At this time, Zhong Jianshe remembered an impeller scheme that he had given up, and he was very excited.

As for the impact of the impeller life on the manufacturing accuracy, which has been calculated for half of the time, it is natural to give up immediately, and this strength and hardness are the main ones that have a major impact on the manufacturing accuracy.

"Come out, haha, do you know the team leader, if you don't consider the inhalation of foreign bodies, after the strength and hardness of the impeller are reduced, it will be in line with the other impeller I designed."

As he spoke, Zhong Jianshe dug around his own pile of scratch paper, and finally found a ball of scratch paper that had been ravaged and curled up into a ball, and carefully unfolded the paper.

What catches his eye is a fairly simple impeller meter, but one of the several sets of data next to it is the compressive efficiency of this impeller, Yang Hui himself can't believe that the air efficiency of this simple impeller is about 1.4 times that of the complex impeller just now, and this data has a lot to do.

"The team leader is this impeller, you look at this design, I have calculated, the compression efficiency is very high, but the strength of this blade structure is very low, as long as there is a slight intervention of external force in high-speed rotation, it will definitely be broken immediately. So I was reluctant to give up on the impeller at the time. ”

At this time, Zhong Jianshe was like a child offering treasure, introducing this plan that he had given up to Yang Hui, and now he is waiting for Yang Hui to praise him fiercely.

Yang Hui now has no time to praise Zhong Jianjian, Yang Hui is also very happy with this obviously over-efficient compressor wheel, and is playing the idea of this impeller.

Such a high compression efficiency must not be wasted, and this turbojet can be changed into a pseudo turbofan in the future.

Speaking of which, I have to talk about a very famous engine, General Dynamics (GE) F404 turbofan engine, yes, it is advertised outside that this is a turbofan engine, But careful people can find that this is a turbofan with a channel ratio of only 0.34, and in fact, the original channel ratio of this engine is only 0.2, which is installed on the YF17 fighter, and the 0.2 external channel airflow is used to cool the outer wall of the engine, so it does not participate in combustion.

For example, Pratt & Whitney's PW1120, people still call themselves turbojet, PW1120 is actually a low-pressure compressor continuous deflation of the vortex jet, see it, and then taste it carefully: low-pressure compressor continuous deflation. Reflected no, this guy is the same as F404, leaking turbojet.

Well, speaking of which, I will understand how to use the current impeller with a super high compression ratio. It is to install a deflation valve on the casing behind the centrifugal impeller, and from then on, this miniature turbojet can also name itself a turbofan engine like F404, becoming an air leak turbojet. This is almost no one to play in later generations, without him, the technical content is too high, but I didn't expect that now I accidentally hit such a powerful impeller, which is really a lost horse, and I don't know if it's a blessing.

Although according to this impeller, it is possible to make a leakage turbojet (that is, the turbofan said by GE), but Yang Hui does not plan to do this, it is still the old reason, there is no time to change the design, and the second is to make technical reserves.

So we still have to find a way to cover up the performance of this impeller, so it's simple, and then change it in the direction that can make manufacturing simple. Although this is a very simple impeller, it would be better to make it simpler.

"Construction, according to the requirements of this combustion chamber, to reduce the compression efficiency, and at the same time to make the impeller simpler."