| 摘要 |
PROBLEM TO BE SOLVED: To determine 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. SOLUTION: 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. This 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.
|
