| 摘要 |
PURPOSE: A method for determining mass flow is provided to determine and calculate mass flow by making fluid flow to a restriction portion of a constant flow passage area in a pipe, respectively sensing fluid pressure at a first position upstream of the restriction portion and a second position downstream of it, using a function equation of Reynolds number representing a delivery coefficient determined based on both pressure values and flow calibration data of the restriction portion. CONSTITUTION: A venturi tube(10) is disposed in a pipe(12), a pressure(P1) is detected at a position(14) upstream of the flow restriction portion(minimum diameter d) in the venturi tube(10), and a pressure(P2) is detected at a position(18) of a joint portion downstream of the flow restriction portion. A function equation of Reynolds number Rd related to d representing a delivery coefficient C of the venturi tube(10) is C=a2Rd2+a1Rd+a0, and can be transformed to 0={a2Rd2/(qm/C)}qm2+(a1Rd/C-1)qm+a0 qm/C. The quadratic equation is resolved in relation to the mass flow qm, and positive values of two roots are called qm. a0, a1, and a2 are polynomial coefficients and can be determined in a regression analysis on flow calibration data.
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