The military-industrial scientific research system of the academic master.

Technology, indeed good technology.

But it doesn’t mean you can just sit back and relax.

The greatest significance of this thing is that it serves as a backup to prevent serious consequences of getting out of control after the experiment fails.

Considering the non-rigid connection characteristics of electromagnetic bearings, once this function is triggered, the entire experimental data will be invalidated.

So, it actually cannot prevent the experiment from failing.

More importantly, the vibration characteristics of the flexible rotor are fundamentally different from those of the rigid rotor, so it is impossible to put it on directly without any changes.

At least the entire control system needs to be overhauled.

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

"Academician Chang, I just took a closer look and I don't think I saw the unbalanced compensation module you mentioned on this equipment?"

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

This student is very observant, but if only his brain could be as good as his eyes...

Because of his age, even if Chang Haonan deliberately dresses maturely, at first glance he looks no different from a normal old man.

Therefore, it is easy to give people the illusion that "we are similar".

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

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

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

"But if you really want to drive this equipment to 100,000 rpm...it's better to do some preparation in advance."

In order to prevent his students from asking any more strange questions, Qu Liangsheng quickly took over the conversation:

"Academician Chang, I just happened to bring here the analysis results of the research team on the dynamic response of flexible rotor imbalance in the past two years. It should be able to provide some help in further improving this equipment."

Since he was elected as an academician, he must have the ability. It is impossible for him to wait for others to solve everything.

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

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

Next, with a humming sound 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-rotation speed percentage graph on the nearby display began to record dense data points.

"We are still conducting a rigidity test, so the vibration situation is relatively simple, with only one obvious resonance peak and correspondingly only one critical speed point..."

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

However, compared to the data on the screen itself, the two seemed to be more interested in the testing methods and 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 just one or two sentences.

In particular, the scene was too noisy and was not a good place for discussion.

Moreover, Chang Haonan originally thought that the tour was almost over, so he took the opportunity to suggest:

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

……

Twenty minutes later.

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

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

"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 set of partial differential equations. The complexity increases significantly, and in most cases, no analytical solution can be found. Therefore, we will only discuss a more typical example, that is, a disk-type flexible rotor..."

"..."

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

Similar to the relationship between Newton's traditional mechanics and relativity in describing motion -

For most rotating bodies, their operating speed is much lower than their first-order critical speed, and the flexural deformation caused by the unbalanced force is very small. They can be regarded as a rigid body during the research process. The design and manufacturing difficulty is relatively small, and dynamic balance compensation can be achieved by using the force balance method or the influence coefficient method.

However, if the spanwise dimension of the promotional body is large and the rotation speed is very fast, then it will undergo non-negligible flexural deformation during the rotation process. Accordingly, factors such as the moment of inertia, gyroscopic effect, and internal damping can no longer be ignored. Therefore, the issues that need to be considered during the design are also much more complicated.

If all the above effects are taken into account, the coefficient matrix in the equation of motion will be so large that it will be difficult to estimate, and it will be difficult to solve numerically even in the finite future.

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

In fact, he has achieved quite good results.

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

After the young researcher on the stage finished his introduction, Qu Liangsheng took over the topic and continued:

"Our progress is currently mainly stuck on data extraction technology."

"Comrade Xiao Han has just said that the unbalance amount is linearly related to the rotor's co-frequency vibration component. This should be very simple, but due to the influence of the bearings and structure supporting the rotor, as well as the external environment, the actual shaft vibration signal generated by the rotation of the unbalanced rotor contains a large part of noise in addition to the co-frequency vibration component."

"What's more troublesome is that if the rotor is too unbalanced, the equipment will not be able to handle it. But if the imbalance is too small, the signal-to-noise ratio will be very low, and almost all the detected signals are interference signals... In addition, 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 speed, further affecting the accuracy..."

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

"..."

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

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

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

Therefore, he has some unique insights:

"It takes time to sharpen the knife before you chop wood. I suggest... that we wait a little longer."

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

"When we were testing the SeA650 engine, we worked with the French to develop an analog narrowband tracking filter technology... The basic principle is very simple, which is to use switches and capacitors to equal resistance, and then obtain its frequency response function from the filter transfer function..."

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

He scrolled the mouse wheel again, and 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 explanation was relatively general, it is obvious that the calculation process behind it is still a bit complicated.

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

I'm afraid it can't be solved in the short term.

"How about...we do both?"

Academician Lu, a researcher with a theoretical background, 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 to project cycle and cost.

The only question is suitability.

"How about this……"

Chang Haonan roughly estimated the difficulty:

"Give me a week to try it out. If it doesn't work, then it won't be too late to try both at the same time. How do you think?"