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?"


    Upon 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 to confirm The balance of the fan blades and the speed are 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 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 pretty good results.


    At least the numerical simulation model of the steady-state and transient unbalance 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:


    "Currently our progress is mainly stuck on data extraction technology."


    "Comrade Xiao Han has just said that there is a linear relationship between the unbalanced amount and the same-frequency vibration component of the rotor. This should be very simple, but due to the influence of the bearings, structure, and external environment supporting the rotor, the unbalanced rotor In addition to the same-frequency vibration components, a large part of the actual shaft vibration signal generated by rotation 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 the imbalance is too small, the signal-to-noise ratio will be very low, and almost all detected signals will be interference signals...and the speed of the rotor will It 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 rotation speed, further affecting the accuracy..."


    "In short, this process requires a lot of testing to complete. Due to hardware constraints, I have never been able to find a particularly appropriate balance between the two... If the conditions here allow for Academician Chang, I still hope to restart the testing quickly. At least determine the research methods..."


    “…”


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


    I clearly 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:


    "The sharpening of the sword will not waste the time of chopping wood. I would suggest... that you can wait for a while."


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


    "When we were testing the SeA650 engine before, we cooperated with the French 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 the capacitor, and then obtain the filter transfer function. Frequency response 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 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 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 both?"


    As a researcher with a theoretical background, Academician Lu also feels that Chang Haonan''s method is more elegant and can save about two-thirds of the unnecessary testing process.


    This is a huge benefit for the project cycle and cost.


    The only problem is suitability.


    "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 about it?"


    (End of chapter)