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 must be overhauled.
Soon, a young graduate student accompanying the team said to Chang Haonan:
“Academician Chang, I just observed carefully, and I don’t think I saw you on this set of equipment. Are you talking about the imbalance compensation module? ”
Hearing this question, the happy expression on Qu Liangsheng's face suddenly became a little stiff.
This student is very careful in his observations, but it would be great if his brain could be as easy to use as eyes...
Because of his age, Chang Haonan, even if he deliberately dresses up maturely, looks like a man at first glance. A normal old blogger is not much different.
So 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 it needs to be adjusted according to the specific operating conditions. There is a cost in the control principle... And the test we are about to conduct is to confirm 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 avoid his students asking any weird questions, Qu Liangsheng hurriedly. Picked up the topic:
“Academician Chang, this time I just brought over the analysis results of the research group’s unbalanced dynamic response of the flexible rotor in the past two years. It should be able to further improve this set of Equipment provides some help.”
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 is slightly closer to Qu Liangsheng and Lu Yongxiang raised their voices 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 because the venue is too noisy and is really not a good place for discussion.
And Chang Haonan originally thought that the visit should be almost over, and now he just took advantage of the situation and suggested:
"The conference room is next door, why not... let's go there now?"
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...
Twenty minutes later.
A 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 on it in person. hours.
“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 The analytical solution cannot be found below, so 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 far lower than their own first-order critical speed, which is unbalanced The deflection deformation caused by the force is very small and can be regarded as a rigid body during the research process. The design and manufacturing difficulties are relatively small. Only the force balance method or the influence coefficient method is needed to achieve dynamic balance compensation.
But if the spanwise size of the promotional 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, the moment of inertia, gyroscopic effect, and internal damping Factors such as these can no longer be 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 use some rules to reasonably simplify this process and reduce the computational difficulty 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 introduction of the young researcher on the stage came to an end, Qu Liangsheng took up the topic and continued:
"At present, our progress is mainly stuck in data extraction technology."
"Comrade Xiao Han has just said that the imbalance amount is linearly related to the same-frequency vibration component of the rotor. This should be very simple. , but due to the influence of the bearings, structures, and external environments that support the rotor, in addition to the same-frequency vibration components, a large part of the actual shaft vibration signal generated by the rotation of the unbalanced rotor is noise.”
“What’s even more troublesome is that if the imbalance of the rotor is too large, the equipment will not be able to bear it. But if, conversely, the imbalance is too small, the signal-to-noise ratio will be very low, and almost all detected signals will be interference signals... Moreover, the rotational speed of the rotor is not completely constant, causing the frequency of the vibration signal of the rotating shaft caused by unbalanced centrifugal force to change with the change of rotational speed, further affecting the accuracy..."
"In short, this process requires A large number of experiments can be completed. Due to the limitations of hardware conditions, I have not been able to find a particularly appropriate balance between the two... If the conditions here of Academician Chang allow, I still hope to restart the experiment quickly, at least to give the research method to Make sure..."
"..."
This is also a common problem faced by many Chinese scientific researchers in this era, especially engineering researchers.
I know exactly 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:
“Sharpening the knife will not delay the chopping of firewood. I would suggest... that you can wait for a while.”
Chang Haonan raised his head and at the same time turned his computer 180° to face the opposite side:
“When we were testing the SeA650 engine before, we cooperated with France to develop a simulated narrow-band tracking filter technology... ...The basic principle is also very simple, which is to use the equivalent resistance of the switch and capacitor, and then obtain the frequency response function from the filter transfer function..."
"For example, in the case in my picture, the specific result is... "
As he spoke, 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 The factors, 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 is relatively simple, it is obvious that the calculation process hidden 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 won’t be solved in the short term.
“Why don’t we do it both ways?”
As a researcher with a background in theory, Academician Lu also feels that Chang Haonan’s method is more elegant and can save about two-thirds of the trouble. Necessary testing process.
This is a huge benefit for the project cycle and cost.
The only problem is applicability.
"Let's do this..."
Chang Haonan briefly estimated the difficulty:
"Give me a week to try it. If it doesn't work, it's not too late to try both ways. , how? ”
(End of this chapter)