What is the basis for the critical speed and what does the critical velocity mean

It is estimated that the large shaft is tilted. It is impossible for the unit speed of 12 to be critical until 2500r min. Check it out at an overhaul shop!

When the turbine-generator set reaches a certain speed, and its disturbance frequency is equal to the natural frequency of the unit (free vibration frequency), the unit vibrates violently, and when the speed leaves this speed value, the vibration weakens rapidly to return to normal, and the speed that makes the turbine-generator set vibrate violently is called the critical speed of the turbine-generator rotor.

The rotor of a steam turbine is an elastomer with a certain free vibration frequency. Rotor in the manufacturing process, because the center of the shaft and the center of the rotor can not be completely coincided, there is always a certain eccentricity, when the rotor rotates to produce centrifugal force, centrifugal force will cause the forced vibration of the rotor, when the forced vibration frequency and the rotor natural vibration frequency are the same or proportional, it will produce resonance, so that the amplitude suddenly increases, and the speed at this time is the critical speed.

There are many reasons why the critical speed of a steam engine is large. In general, the bigger the better, because it is better to avoid the second critical speed. In this case, as you said, if the parameters, operation, warm-up, etc. are all controlled, then it should be the problem of the last engine repair.

It is recommended to find an installation company to re-measure, for fear that the center is deviated, or the large shaft is bent.

Also, you see if the oil circuit of the last two tiles is still smooth, and how the oil temperature changes compared to before the repair. Whether the oil quality is qualified.

In the independence test, the cut-off value (also known as the threshold) is determined based on the actual results of the experiment. The relationship between the two variables can be approximated in a straight line only when the absolute value of the correlation coefficient r is greater than the critical value. The critical value refers to the conditions to be met by a certain physical quantity when an object transitions from one physical state to another, which is equivalent to the stationary point often referred to in mathematics.

In some cases, the critical value is equivalent to the maximum value, and we can find the maximum value through the critical point, so as to get twice the result with half the effort. In other cases, there is no necessary link between the maximum and the threshold. Therefore, in the process of solving the maximum value, we can only find the critical point as a way to find the maximum value, and cannot equate it with the solution of the maximum value.

How to determine outliers and thresholds.

Outliers are calculated as follows:

Outliers: Mean (m) 3SD (standard deviation).

The value between 2SD and 3SD, that is, between the normal value and the outlier value, is called the critical value or critical domain.

The critical value is based on the actual application and literal meaning, that is, when the upper limit of the set standard value or the lower limit of the standard value is reached, for example, the standard is 3+ -1mm, and the actual measurement is 4mm or 2mm, which means that your product has reached the critical value in the size of 3+ -1mm. In this case, it is generally easy to exceed the tolerance range, and many quality control systems now do not allow the setting time or the critical value to be adjusted during the adjustment. In this way, there is no guarantee for the quality of the product.

The boundary value of the rejection domain determined from a given level of significance.

Outliers: Mean (m) 3SD (standard deviation).

The critical point is a state determined by physical laws, which can be determined by the physical laws that satisfy the state, and is objectively existing The critical value refers to the conditions to be met by a certain physical quantity when an object transitions from one physical state to another physical state, which is equivalent to the standing point often said in mathematics Therefore, the critical state is used to solve the maximum and minimum values of physical quantities.

The speed that can just complete the circular motion is called the critical velocity The string connects the object to do a circular motion in the vertical direction, and the critical velocity at the highest point is equal to gr. The critical velocity of the highest point of the rod connection is 0 and then the velocity of the lowest point can be found separately according to the kinetic energy theorem.

The critical strength of concrete prepared with ordinary Portland cement shall not be less than 30% of its standard value, C10 concrete shall not be less than 5 megapascals, and concrete mixed with antifreeze shall not be less than 4 megapascals.

After freezing, the fresh concrete can be cured at normal temperature, and the strength can continue to increase, and the initial strength required for more than 95% of the design grade can be reached. The critical strength value of the famous country is generally for ordinary concrete, but the critical strength value will change after the addition of antifreeze.

Tests have shown that the addition of antifreeze can reduce the critical strength value. This is mainly due to the fact that the incorporation of antifreeze can effectively prevent or reduce the harmful effect of frost heave, so the use of concrete can resist the frost heave stress generated without being damaged by frost when it has a small structural strength.

The freezing critical strength of concrete using Portland cement and ordinary Portland cement is not less than 30% of the design strength, and when using slag Portland cement, fly ash Portland cement, pozzolana Portland cement and composite Portland cement, the design strength is not less than 40%.

Each substance has a specific temperature, above which the gaseous substance will not liquefy no matter how much the pressure is increased, and this temperature is the critical temperature. Cooling and pressurization are the conditions for liquefaction of gases. However, only pressurization may not liquefy the gas, depending on whether the gas is below the critical temperature at that time.

Therefore the substance is to be liquefied; The first thing to do is to find a way to reach its own critical temperature. The critical temperature of water is 374, which is much higher than the normal temperature, so it is easy for water vapor to cool down the section before Qi into water

The temperature of the state at the time of the transition is 0° and 100° for water

The DU speed, which causes the rotor to vibrate strongly, is a well-studied problem in rotor dynamics. The center of mass of each micro-segment of the rotor in the rotation system cannot be strictly on the axis of rotation.

As a result, when the rotor rotates, there will be lateral disturbances, and at certain speeds it will cause strong vibrations of the system, which in this case is the critical speed.

In order to ensure the normal operation of the system or avoid damage to the system due to vibration, the rotor working speed of the rotating system should avoid the critical speed as much as possible, and if it cannot be avoided, special anti-vibration measures should be taken.

Critical speed to source.

The amplitude of the rotor increases with the increase of speed, and the amplitude du reaches the maximum value at a certain speed, and the amplitude gradually decreases with the increase of speed after exceeding this speed, and is stable in a certain range, and the speed with the largest rotor amplitude is called the critical speed of the rotor. This speed is equal to the original frequency of the rotor, when the speed continues to increase, close to 2 times the frequency of the amplitude will increase again, when the speed is equal to 2 times the frequency is called the second order (stage) critical speed, and so on there are three and four .........

When the outermost ball in the ball mill just rotates with the cylinder without falling, the speed of the ball mill plate at this time is called the critical rotation weight.

Speed. The critical speed of various ball mills is proportional to its diameter d, and the absolute value of the critical speed is not easy to obtain, and only the calculation formula of the theoretical critical speed is widely used.

Critical speed calculation formula:

where d - the inner diameter of the ball mill, m;

n0 – critical speed.

When the non-smooth liner is used, the ball load filling rate is 40% to 50%, and the grinding concentration is large, the calculation result of the formula is relatively close to the reality.

The zodiac signs are determined according to the age of the stars.

Jupiter orbits one day of the twelfth year, and the annual branch order can be determined from Jupiter's position. "Yuhan Shanfang Ji Yishu" believes that every 12 years, "three years old, three years old, three years old, drought", another said that "the world is six years old, six years old, six years old, one hunger".

There is a cycle of the rise and fall of plants and the living environment of animals, and the living conditions of herbivores (rats, cows, horses, sheep) and carnivorous omnivores are very different in different years, and people born in different years can imitate the animals that grow vigorously in that year, thus forming a zodiac animal, so as to presume that the rise and fall of animals is related to the year of Jupiter, and the zodiac and the twelve stars are unified.

The origin of the 12 zodiac signs.

In ancient China, the characteristics of the infestation time and life of the animals were based on the twelve kinds of animals as the twelve zodiac signs, that is, each animal was an hour. Rats are ranked first (with "son"), and the following order is: rat, cow, tiger, rabbit, dragon, snake, horse, sheep, monkey, chicken, dog, pig.

Rats: 11 p.m. to 1 p.m. the next day (i.e., "sub-hour"). At this time, the mouse is the most courageous and the most active, so it is matched with the mouse when it is young.

Ox: 1-3 a.m. (i.e. "ugly hour"). At this time, the cow has eaten enough grass, and the "inverted chewing" is the finest, slowest and most comfortable, so it is matched with the cow when it is ugly.

Tiger: 3-5 a.m. (i.e. "Yin Shi"). According to ancient books, at this time, the tiger is the most active, the most ferocious, and the most hurtful, so it is matched with the tiger at the right time.

Rabbit: 5-7 in the morning (i.e. "Mao time"). At this time, the sun has not yet shown its face, and the light of the moon has not completely receded. The jade rabbit is the name of the moon and is the only animal in the mythology of the Moon Palace, so it is matched with the rabbit when it is mao.

Dragon: 7-9 a.m. (i.e., "hour"). Legend has it that this is the time when the dragons are in the rain, and the dragon is a mythical animal, so the time belongs to the dragon.

Snake: 9-11 a.m. (i.e. "midday"). It is said that at this time, the snake does not hurt people, nor does it wander on the road where people walk, but hides in the grass, so that it belongs to the snake at that time.

Horses: 11 a.m. to 1 p.m. (i.e. "noon"). According to the Taoist priest, at noon, when the sun is at the top, the yang energy reaches the extreme, and the yin energy gradually increases.

In this way, noon belongs to the horse.

Sheep: 1-3 p.m. (i.e. "no time"). It is said that the sheep sprinkle urine most frequently at this time, and the urine spilled can be a kind of madness of its own, so it is not a sheep from time to time.

Monkey: 3-5 p.m. (i.e. "Shen Shi"). At this time, the monkey likes to cry the most, and the sound is the longest and loudest. So Shen Shi is a monkey.

Chicken: 5-7 p.m. (i.e. "unitary time"). At this time, the sunset hill, the chicken began to enter the cage and return to the nest and stay overnight, so it belonged to the chicken.

Dogs: 7-9 p.m. (i.e. "戌時"). When night comes, dogs watch over their homes, vigil vigil is the highest, and produces a special kind of vision and hearing, seeing the farthest and hearing the most clearly. Therefore, it is a dog.

Pig: 9-11 p.m. (i.e. "Boom"). At this time, the pig slept the most, the snoring sound was the loudest, the muscles of the whole body shook the most, and the meat grew the fastest, so it belonged to the pig.

Find a way to kill it when you win, and it kills you when you lose, guess an animal.

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