Chapter 1118 Give Me a Week!

Technology is indeed good technology.

But it’s not like you can just sit back and relax.

The greatest significance of this thing is to serve as a guarantee to prevent serious consequences of going out of control after the experiment fails.

Considering the non-rigid connection characteristics of electromagnetic bearings, once this function is triggered, it is equivalent to invalidating the entire experimental data.

Therefore, it does not actually prevent the experiment from failing.

More importantly, the vibration characteristics of the flexible rotor are essentially different from those of the rigid rotor, so it is impossible to put them on directly.

At least the entire control system needs to be overhauled.

Soon, a young graduate student accompanying the team spoke to Chang Haonan:

"Academician Chang, I just took a closer look and it seems that I didn't see the imbalance compensation module you mentioned on this set of equipment?"

Hearing this question, the happy expression on Qu Liangsheng's face suddenly became a little stiff.

This student is very observant, but it would be great if his brain could be as easy to use as eyes...

Because of Chang Haonan's age, even if he deliberately dresses up to be mature, he looks like a normal old blogger at first glance.

Therefore, it is easy to give people the illusion that "we seem to be almost the same".

But he is a serious boss after all, so you should think carefully before you ask!

Fortunately, Chang Haonan himself didn't care much about this and just explained to the other party:

"The principle of unbalance compensation is to calculate the compensation current based on the direction of the unbalanced force, so the control principle needs to be adjusted according to the specific operating conditions. There is a cost... and the test we are about to conduct is originally Check the balance of the fan blades, the speed is not high, of course there is no need to..."

"But if you really want to drive this equipment to 100,000 rpm... it would be better to make some preparations in advance."

In order to prevent his students from asking any weird questions again, Qu Liangsheng quickly picked up the topic:

"Academician Chang, this time I just brought over the analysis results of the unbalanced dynamic response of the flexible rotor by the research team in the past two years. It should be able to provide some help in further improving this equipment."

Since he can be elected as an academician, he naturally has some abilities. He cannot wait for others to solve everything.

Especially in some basic level theoretical research and underlying data accumulation, Qu Liangsheng is confident that no one can surpass him in this aspect at least in China.

While talking, several technicians nearby had completed all preparations before the test, began to close the protective cover, and reminded irrelevant personnel to retreat outside the safety line.

Next, with a whine of high-speed rotation, the test officially began.

Through the thick and narrow glass observation window on the protective cover, everyone can even see the fan blades rotating at high speed.

Soon, the rotation speed reached 10% of the preset value, and the vibration amplitude-speed percentage image on the monitor next to it also began to record dense data points.

"We are still conducting rigid tests, so the vibration situation is relatively simple. There is only one obvious resonance peak, and correspondingly there is only one speed critical point..."

Chang Haonan got closer to Qu Liangsheng and Lu Yongxiang and raised his voice at the same time.

However, compared to the data itself on the screen, the two seemed to be more interested in the testing method. They stared at the rapidly jumping log file in the lower right corner for a long time.

"How did you extract the vibration components of the same frequency?"

Academician Lu turned around and asked.

This question cannot be explained clearly in one or two sentences.

Especially since the venue was too noisy, it was not a good place for discussion.

Moreover, Chang Haonan originally thought that the visit should be almost done, but now he just took advantage of the situation and suggested:

"The conference room is next door, why don't we go there now?"

…

Twenty minutes later.

The group of people sat on both sides of the conference table, listening to a researcher behind the podium introducing the research results——

Academician Qu is 70 years old, so it is naturally impossible for him to stand there in person for half an hour.

"After considering the deformation of the shaft, the flexible rotor will become a complex system with infinite degrees of freedom. Its dynamic model should be described by a system of partial differential equations. The complexity increases significantly, and in most cases it is impossible to find an analytical solution. Therefore, we will only discuss the more typical example for the time being, that is, the disc-type flexible rotor..."

"..."

The so-called flexible rotor does not mean to make the rotor soft intentionally, but a physical model that is closer to the real situation.

Similar to the relationship between Newton's traditional mechanics and the theory of relativity in describing motion——

For most rotating bodies, their operating speed is much lower than their first-order critical speed, and the deflection deformation caused by the unbalanced force is very small. They can be regarded as a rigid body during the research process, and the design and manufacturing are relatively difficult. Small, only the force balance method or the influence coefficient method is needed to achieve dynamic balance compensation.

However, if the spanwise size of the propaganda body is large and the rotation speed is very fast, then it will undergo deflection deformation that cannot be ignored during the rotation process. Correspondingly, factors such as moment of inertia, gyroscopic effect, and internal damping can no longer be considered. has been ignored, so the issues that need to be considered during design are also much more complex.

If all the above effects are included in the calculation, the coefficient matrix in the motion equation will be so large that it is difficult to estimate, and it will be difficult to perform numerical calculations even in the limited future.

Qu Liangsheng's research is to simplify this process reasonably with the help of some rules, and to reduce the difficulty of calculation as much as possible while ensuring the necessary accuracy.

In fact, he has achieved quite good results.

At least he has successfully established a numerical simulation model for the steady-state and transient unbalanced response of the rotor system.

After the introduction of the young researcher on the stage came to an end, Qu Liangsheng took over the topic and continued:

"At present, our progress is mainly stuck in data extraction technology."

"Comrade Xiao Han has just said that the unbalance amount is linearly related to the same-frequency vibration component of the rotor. This should be very simple, but because of the influence of the bearings, structure, and external environment that support the rotor, the actual shaft vibration signal generated by the rotation of the unbalanced rotor, in addition to the same-frequency vibration component, there is also a large part of noise."

"What's more troublesome is that if the rotor imbalance is large, the equipment can't bear it, but if the imbalance is too small, the signal-to-noise ratio will be very low. , almost all detected signals are interference signals... and the rotor speed is not completely constant, which causes the frequency of the shaft vibration signal caused by the unbalanced centrifugal force to change with the change of the speed, further affecting the accuracy..."

"In short, this process requires a lot of experiments to complete. Because of the hardware conditions, we have not been able to find a particularly appropriate balance between the two... If the conditions here allow Academician Chang, I still hope to restart the experiment quickly, at least to determine the research method..."

"..."

This is also a common problem faced by many Chinese researchers in this era, especially engineering researchers.

I know what to do next, but I just can't do it.

When Chang Haonan was just reborn, he often faced the same situation.

Therefore, he has some unique insights:

"Sharpening the knife does not delay the chopping of wood. I suggest... you can wait for a while."

Chang Haonan raised his head and turned his computer 180° to face the opposite side:

"When we tested the SeA650 engine before, we cooperated with the French to develop an analog narrowband tracking filter technology... The basic principle is also very simple, that is, using switches and capacitors to equal resistance, and then obtaining its frequency response function from the filter transfer function..."

"For example, the case in my picture, the specific result is..."

He rolled the mouse wheel again, and then an expression that filled the entire page appeared on the screen:

"In short, when the filter capacitance value is constant, its quality factor, gain and frequency ratio are also fixed. By adjusting the switching pulse frequency, the center frequency of the bandpass filter can be easily changed."

Although Chang Haonan's description is relatively general, it is obvious that the calculation process behind it is still a bit complicated.

More importantly, it requires high-quality semiconductor components and very rich design experience.

I am afraid it cannot be solved in the short term.

"Why don't we do both?"

As a researcher with a theoretical background, Academician Lu also felt that Chang Haonan's method was more elegant and could save more than two-thirds of unnecessary testing processes.

This is a huge benefit for project cycle and cost.

The only problem is applicability.

"How about this..."

Chang Haonan roughly estimated the difficulty:

"Give me a week to try it. If it doesn't work, it won't be too late to do both. How about it?"