If the inlet pressure of the reciprocating machine decreases, does the outlet pressure also decrease?
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I’m a newcomer and not very familiar with reciprocating machines. What happens to the outlet pressure if the inlet pressure decreases? The compression ratio of a reciprocating machine is constant; based on this, the outlet pressure should decrease. However, since the cylinder volume remains unchanged and the amount of compression is also constant, the outlet pressure should not change much. I would appreciate some guidance from those with more experience.
The outlet pressure of a reciprocating pump should vary with the pressure in the outlet pipe, and it can range from 0 to infinity, as long as the pipe can withstand it; therefore, it should be independent of the inlet pressure.
A decrease in the inlet pressure of a reciprocating compressor leads to a reduction in the inlet flow rate of the compressor, resulting in insufficient compression and a decrease in the outlet pressure.
Your idea is correct; if the inlet pressure decreases while the compression ratio remains constant, then the outlet pressure will definitely drop.
Generally, the outlet pressure does not decrease significantly, while the flow rate will drop.
:Those on floors 1, 2, 3, 4, and 5 answered all questions incorrectly; those who gave them points were also criticized. It is suggested that points should only be given after the questions are properly understood, otherwise it will mislead others； What was said on the first floor is correct: the outlet pressure of a reciprocating compressor depends only on the pressure in the outlet system. Theoretically, as long as the motor has sufficient power, the various components of the compressor are strong enough, and the compressor can withstand high temperatures, the outlet pressure can range from 0 to infinity ； A decrease in inlet pressure will only reduce the compressor’s discharge volume and increase the compressor ratio
I disagree with what was said above; it will definitely cause a decrease, as well as pulsations in the gas.
The answers for floors 1, 2, 3, 4, and 5 are all wrong. It is necessary to understand the pressure-boosting principle of reciprocating compressors. It mainly relies on the single-valve function of the exhaust valve to increase pressure. In other words, the exhaust valve opens only when the pressure in the cylinder is greater than the pressure behind the exhaust valve, allowing the gas inside the cylinder to be sent in the backward direction. As the pressure in the back route increases, the pressure in the cylinder must also increase in order to drive the exhaust valve open and supply air to the back route. The process of voltage increase is slow and gradual, not something that happens overnight. The voltage rise process during the commissioning of the unit clearly illustrates this. The pressure ratio is not fixed, but dynamic.
A decrease in intake pressure will only result in a slower increase in pressure in the rear system. In other words, the amount of medium output to the backflow system decreases per unit of time; therefore, the pressure at the compressor outlet must be higher than the system pressure in order to deliver gas into the system. Imagine that the current system pressure is 4 MPa, while the inlet pressure is 1 MPa. The cylinder pressure at this time should be 4.1 MPa or slightly higher. If the inlet pressure drops to 0.8 MPa and the output pressure decreases, the compressor can no longer deliver pressure backward. Considering the on-site situation, let’s think about it again.
The inlet pressure drops too much, the compression ratio increases, and the piston force rises, which is very dangerous
What was said on floor 11 is correct: lowering the inlet too much increases the pressure ratio, which leads to heating problems, that is, an increase in the output temperature.
The output pressure value of the check valve at the outlet of the piston compressor is designed to meet the pressure requirements of the subsequent system. When the inlet pressure decreases, the compression ratio increases in order to achieve the designed output pressure. During the compression process, the amount of air intake increases, the compression time of the gas inside lengthens, the temperature of the gas rises, and the pulsation in the output air volume intensifies. An excessively low inlet pressure is not acceptable, as it can cause damage to the compression mechanism and affect the stability of the subsequent system.
NO, the outlet pressure is determined by the back pressure.
Generally, an interlock for low inlet pressure is required; when the inlet pressure is low, the compression ratio increases and the outlet temperature rises, triggering an interlocked shutdown.
Suggestion 6: Study in more detail the structure of reciprocating compressors – things like motor power and pipe strength. Are the valves inside the compressor really useless? The inlet pressure must not drop below the lower limit specified in the design requirements; otherwise, insufficient suction may cause the outlet valve to fail to open due to high back pressure.
The outlet pressure will not decrease, as it is primarily determined by the exhaust valve and the pressure in the pipeline downstream of the outlet
You can imagine that in a system with compressors operating at partial load, the inlet pressure and gas flow rate are generally lower than under normal conditions, and the outlet pressure is also low.