For a pipe with two outlets, when pressure rises, one outlet is opened to maintain stable pressure, while the flow rate at the other outlet decreases

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This post was last edited by iamafailor on 2019-11-14 at 16:21. The pressure of p-1 is controlled by the PCV; the shut-off valve for p-3 remains at a constant opening. When there are slight fluctuations in the pressure of p-1, the PCV takes action to adjust it smoothly, keeping the pressure of p-1 within a range of ±0.1 MPa. The problem is that when the PCV is opened further, the flow meter shows that the gas flow rate at p-3 decreases. Why does the gas flow rate at p-3 decrease when the PCV is opened further, even though the pressure of p-1 stays unchanged? Shouldn’t the airflow at p-3 remain constant if the pressure stays the same? One more thing: they are all 10-inch gas pipelines. Please ignore the following content. What is the principle behind this? Detailed description: “Two outlets of a pipeline” – “one pipeline” refers to the inlet at the expansion end of the expansion compressor, while “two outlets” refer to the JT valve and nozzle of the expansion machine. In actual operation, the JT valve and nozzle are used; the JT valve automatically controls the pressure at 2 MPa, whereas the nozzle maintains a fixed opening degree manually. Whenever the upstream pressure changes, the JT valve automatically adjusts its opening degree (the variation is very small, within ±0.1 MPa, and it may adjust between 30% and 40%). I noticed that when the JT valve is opened more, the speed of the expansion machine decreases, which means that the amount of gas passing through the nozzle decreases. This goes beyond my understanding of traditional processes – for a nozzle, the upstream pressure should remain constant, so why does the amount of gas change? Both more and less gas are consumed automatically by the JT valve; then why does the amount of gas passing through the nozzle change? Is the amount of gas through the nozzle related to the amount of gas upstream or to the pressure? Dear teachers, please help explain this in simple terms. Okay, I’ll explain it simply: what I want to know is the principle behind this, no flowcharts are needed. There are two branches on the main pipeline, and the main pipeline has a stable gas pressure. If the valve of the first branch is opened wider while the other valve remains closed, why does the gas flow in the second branch decrease after the first branch’s valve is opened wider? (The gas pressure in the main pipeline remains stable.)