Reduction of airflow pulsation (for reciprocating compressors): Buffer tank solution
The buffer tank is still widely used today because of its excellent effect in suppressing air flow pulsations.
The buffer tank is installed at the compressor cylinder (vibration source) and isolated from the pipeline. Its function is that the pulsating airflow can be reduced in the buffer tank, and the pulsation in the pipeline becomes less significant. The buffer tank can change the inherent frequency of the gas column in the pipeline system, significantly increasing the inherent frequency value between the cylinder and the buffer, thereby avoiding low-order gas column resonance. When the buffer tank is large enough, it acts like a reservoir, providing a pressure stabilization function. The buffer tank is also a low-pass filter, with a strong attenuation effect on high-frequency waves.There are various methods for determining the volume of the buffer tank, and the complexity of these methods varies greatly. The volume of the buffer tanks currently in use is mostly 10 to 15 times the working volume of the cylinder. The farther the buffer tank is from the cylinder, the larger the required volume becomes. Some buffer tanks even have a volume that is 25 to 40 times that of the cylinder's working volume.The closer the buffer tank is installed to the cylinder, the better its buffering effect will be.If the installation space permits, the buffer tank should be directly connected to the inlet and exhaust flanges of the cylinder. The position of the buffer tank's inlet has a more significant impact on the buffering effect. As shown in the figure, the buffering effect of Scheme I is not obvious; while the buffering effect of Scheme II can be improved by 15% to 20%.Scheme Ⅲ is 2 to 3 times more effective than Scheme Ⅰ. Additionally, the horizontal installation of the buffer tank is more effective than the vertical installation.
Domestic scholars have conducted relevant experiments and reached the following conclusion:（1）As the volume of the buffer tank increases, the pressure pulsation value in the pipeline gradually decreases, thereby confirming the fact that increasing the volume of the buffer tank can effectively reduce the pipeline gas flow pulsation.（2）As the length of the pipeline between the compressor cylinder and the buffer tank increases, the pressure pulsation of the gas flow within the pipeline gradually increases.（3）When it is necessary to increase the volume of the buffer tank, increasing the diameter of the buffer tank can better reduce the pressure pulsation in the pipeline compared to increasing the length of the buffer tank. When the length-to-diameter ratio (length/diameter) of the buffer tank is between 1.5 and 2.0, the buffer tank has the best damping effect on the pressure pulsation within the pipeline system.（4）Apart from the volume of the buffer tank, the parameters of the connecting pipes between the compressor cylinder and the buffer tank also have a significant impact on the pressure pulsation of the gas flow within the pipeline. When the length-to-diameter ratio (length/diameter) of the connecting pipe is between 1.25 and 1.75, it can better reduce the gas flow pulsation in the compressor pipeline system. Moreover, when the length-to-diameter ratio of the connecting pipe is greater than 2.5, the pressure pulsation value within the pipeline gradually increases.
The buffer tanks come in two forms: cylindrical and spherical. When the volumes are the same,The buffering effect of the spherical buffer tank is superior to that of the cylindrical one.Whether from the perspective of container stress or in terms of reducing air turbulence, the use of spherical tanks in the high-pressure stage is more advantageous.
