Regarding the pressure reduction performance and flow rate performance of pressure relief valves, and what are the differences from flow control valves? Urgent! Urgent! Urgent! ! !

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1. On the flow regulation performance of pressure regulators: (1) According to the law of conservation of mass, the mass flow rate remains constant before and after a pressure regulator. So what about the volume flow rate? Is it also constant for liquids? Does the volumetric flow rate increase for gases due to changes in density? (2) Is the flow performance of the pressure reducing valve related to Cv? If it is necessary to adjust the flow rate after pressure reduction by the pressure reducing valve, is it then required to install a flow meter and a control valve as well? Can adjusting the pressure reducing valve still achieve the purpose of regulating flow? Select the Cv value based on the required flow rate: a larger Cv value is chosen for higher flow rates, and the opposite for lower flow rates ； Also, how is the Cv value calculated based on the required flow rate? (3) The flow rate of a pressure relief valve is related to the pressure difference. Why do manufacturers say that there is a maximum flow rate when the pressure difference reaches a certain value, and that the flow rate cannot increase further even if the pressure difference increases? Why does an increase in pressure difference lead to an increase in flow rate? (4) The manufacturer says that pressure reduction and flow rate adjustment should be carried out simultaneously. Why is it said that the flow rate remains constant during pressure reduction, and that the pressure difference remains constant during flow rate adjustment? How should this be understood? How is this achieved? In other words, what is the relationship between the pressure relief valve and flow rate? What is the relationship between a flow control valve and pressure? (5) As the opening of the pressure relief valve increases, does its own resistance decrease or increase? Does the flow rate increase or decrease? Does the Cv value increase or decrease? (6) How is the Cv value defined? Is it true that the Cv value is high when the valve is fully open? Does the Cv value increase when the valve is closed partially? (7) The working principle of a pressure reducing valve can be understood as inlet pressure + outlet pressure = spring force; the pressure at the outlet is controlled by adjusting the degree of opening of the flow control orifice inside the valve. The smaller the opening, the less resistance there is for the liquid to pass through, resulting in less pressure loss and a higher outlet pressure. Conversely, a larger opening leads to less pressure loss and a lower outlet pressure. Is this statement correct? The smaller the opening, shouldn’t the resistance be greater and the outlet pressure lower? 2. Regarding the pressure regulation performance of the pressure relief valve? (1) It refers to the characteristic in which, when the flow rate g is constant, fluctuations in the input pressure cause fluctuations in the output pressure. The smaller the fluctuation in output pressure, the better the performance of the pressure reducing valve. The output pressure must be lower than the input pressure by a fixed value in order to remain essentially unchanged regardless of variations in the input pressure. ? Does this ensure that the pressure difference of the pressure relief valve remains constant? And is the flow rate then constant as well? How is it ensured that the flow rate remains constant? (2) Based on the above explanation, the pressure relief valve can adjust the output pressure while maintaining a constant flow rate (pressure characteristic: constant flow rate) ； Can it also adjust the output flow rate while maintaining a constant output pressure (flow characteristic, with a constant input pressure)? How should this sentence be understood? There are quite a few issues; I hope the experts will not hesitate to offer their guidance!