sonic velocity of flow restriction orifice plate
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Throttle orifice plate I. Overview Due to its advantages such as simple structure, ease of processing, low manufacturing costs, and convenient installation, the throttle orifice plate can be used to control flow rates or reduce pressure by replacing control valves, provided that the process requirements are met. This approach helps to significantly reduce investment and operational maintenance costs. As a result, it is widely used in industrial installations abroad, playing an important role in ensuring the safe operation of these systems. However, at present, the use of flow control orifice plates in domestic process units is still insufficient, showing a gap compared to foreign countries. Where it is necessary to limit flow or reduce pressure, control loops are mostly used to achieve this. In some places, it is only necessary to keep the fluid flow within a specified range without any need for adjustment, and the accuracy requirements regarding this flow are not high either; in such cases, flow-limiting orifice plates can be used as a substitute. Therefore, it is necessary to fully understand the advantages of flow-limiting orifice plates in the design of process equipment, and to pay attention to their application. . The flow control orifice plates are designed and manufactured in accordance with standards such as GB2624, HG/T 20570, GD2000, GD87, etc. II. Measurement Principle The flow-limiting orifice plate can be used as a flow measurement element to determine flow rates, or as a throttling element to regulate flow rates and reduce pressure. When there is a certain pressure difference before and after the orifice plate, as the fluid flows through it, for a given orifice size, the flow rate through the orifice plate increases as the pressure difference increases. However, when the pressure difference exceeds a certain value (known as the critical pressure difference), the flow velocity of the fluid through the throat of the orifice plate reaches the speed of sound. At this point, no matter how much the pressure difference increases, the flow rate through the orifice plate remains constant and does not increase any further. ? ? ? ? ? ? ? ? ? ? ? The flow control orifice plate operates on this principle to limit the flow rate of the fluid and reduce pressure. I’m just wondering, why does it need to reach the speed of sound? ? ?
When reaching the speed of sound, choked flow occurs.
This is apparently called the sound barrier. In simple terms, as the flow velocity of a fluid increases, its resistance also increases linearly; however, when the speed approaches the speed of sound, the resistance increases exponentially, which is what leads to the formation of the sound barrier. Breaking through this sound barrier requires greater power, and a shock wave is generated during the process.
I’ve studied it, but I still don’t quite understand it; P
To delve deeper into the subject, one must first understand why the speed of sound is that value. When the speed of sound reaches that value, thrust and drag reach equilibrium, for similar reasons to why the maximum speed controlled by flow restriction reaches the speed of sound
From the continuity equation for flow, the energy conservation equation, and the equations for isentropic processes, the following relationship can be derived: A represents the cross-sectional area, u is the flow velocity, and Ma is the Mach number. When Ma is 1, the cross-sectional area increases and the flow velocity increases as well.
Is the liquid the same? Reach the speed of sound?