[Q&A Question 323] 2017.12.07
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【Q&A Question 323】December 07, 2017: What are the characteristics of surge in centrifugal compressors? (1) The compressor operates very unstably: when the compressor is running normally, parameters such as discharge pressure and flow rate exhibit small fluctuations at high frequencies. When surge occurs, the pneumatic parameters show periodic variations with large amplitudes and low frequencies, while the average discharge pressure decreases. (2) Fluttering has a strong periodicity: airflow noise, with audible airflow roaring. During normal operation, the sound of the airflow does not change much until surge occurs; at that point, periodic explosive noises appear suddenly. Further reduction in flow rate results in a rumbling sound. (3) Severe machine vibration: The amplitude of vibration in the machine frame, shaft bearings, etc. increases sharply ； (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) For management purposes, if you need to view content from a few days ago, please go through the summary post below. 2017 Q&A Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657794-1-1.html 2017 Daily Image Summary Thread https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1875160 2017 LNG Version Daily Question List https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1804162 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html
1. The outlet pressure and inlet flow rate of the gas medium change significantly, and gas backflow may sometimes occur. It is a dangerous operating condition when the gas medium flows from the compressor outlet back toward the inlet. 2. The pipeline network experiences periodic vibrations with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. 3. The compressor casing vibrates intensely; both the casing and bearings experience severe vibration, along with a loud, periodic airflow noise. Due to these intense vibrations, the lubrication conditions of the bearings are compromised, the bearing shells can be damaged, and even the shaft may break. Friction and collisions between the rotor and stator occur, and the sealing elements suffer serious damage.
① The outlet pressure and inlet flow rate of the gas medium change significantly, and gas backflow may sometimes occur. ② The pipeline network experiences periodic oscillations, with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. ③ The compressor vibrates intensely; both the casing and bearings experience strong vibrations, along with loud, periodic airflow noises.
① The outlet pressure and inlet flow rate of the gas medium change significantly, and gas backflow may sometimes occur. ② The pipeline network experiences periodic oscillations, with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. ③ The compressor vibrates intensely; both the casing and bearings experience strong vibrations, along with loud, periodic airflow noises.
(1) The outlet pressure and inlet flow rate of the gas medium change significantly, and gas backflow may sometimes occur. It is a dangerous operating condition when the gas medium flows from the compressor outlet back toward the inlet. (2) The pipeline network experiences periodic vibrations with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. (3) The compressor casing vibrates intensely; both the casing and bearings experience severe vibration, along with loud, periodic airflow noises. Due to these intense vibrations, the lubrication conditions of the bearings are compromised, the bearing shells can be damaged, and even the shaft may break. Friction and collisions between the rotor and stator occur, and the sealing elements suffer serious damage.
When the pressure or flow rate at the compressor’s suction inlet suddenly drops below the minimum allowable operating level, severe rotational separation of the gas within the compressor occurs, leading to sudden stall (meaning a significant deviation in the flow direction of the gas at the inlet of the blades and in the blade inlet angles). In such situations, the impeller is unable to increase the gas pressure effectively, resulting in a decrease in the pressure at the compressor outlet. However, the pressure in the system piping did not drop instantly, which caused gas to flow back from the system piping toward the compressor; when the pressure in the system piping dropped below the compressor’s outlet pressure, gas flowed back into the system piping. Repeating this process leads to periodic axial, low-frequency, high-amplitude airflow oscillations within the unit and the piping system
Once surge occurs during the operation of a centrifugal compressor, the operation of the unit and the piping system exhibits the following characteristics: 1. The outlet pressure and inlet flow rate of the gas medium change significantly, and in some cases, gas backflow may also occur. It is a dangerous operating condition when the gas medium flows from the compressor outlet back toward the inlet. 2. The pipeline network experiences periodic vibrations with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. 3. The compressor casing vibrates intensely; both the casing and bearings experience severe vibration, along with a loud, periodic airflow noise. Due to these intense vibrations, the lubrication conditions of the bearings are compromised, the bearing shells can be damaged, and even the shaft may break. Friction and collisions between the rotor and stator occur, and the sealing elements suffer serious damage.
1. The outlet pressure and inlet flow rate of the gas medium change significantly, and gas backflow may sometimes occur. It is a dangerous operating condition when the gas medium flows from the compressor outlet back toward the inlet. 2. The pipeline network experiences periodic vibrations with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. 3. The compressor casing vibrates intensely; both the casing and bearings experience severe vibration, along with a loud, periodic airflow noise. Due to these intense vibrations, the lubrication conditions of the bearings are compromised, the bearing shells can be damaged, and even the shaft may break. Friction and collisions between the rotor and stator occur, and the sealing elements suffer serious damage.
1. The pressure at the compressor outlet first rises and then drops sharply, with the flow rate also decreasing rapidly. 2. There are large fluctuations in the current at the site, and the compressor itself emits abnormal noises and vibrations
1. The outlet pressure and inlet flow rate of the gas medium change significantly, and gas backflow may sometimes occur. It is a dangerous operating condition when the gas medium flows from the compressor outlet back toward the inlet. 2. The pipeline network experiences periodic vibrations with large amplitudes and low frequencies, accompanied by periodic \"roaring\" sounds. 3. The compressor casing vibrates intensely; both the casing and bearings experience severe vibration, along with a loud, periodic airflow noise. Due to these intense vibrations, the lubrication conditions of the bearings are compromised, the bearing shells can be damaged, and even the shaft may break. Friction and collisions between the rotor and stator occur, and the sealing elements suffer serious damage.
The aircraft body vibrates, there is significant noise, and the outlet flow rate fluctuates greatly