FLOW RATE MEASUREMENT METHOD AND APPARATUS

摘要

Method and apparatus capable of accurately measuring a flow rate using Gaussian quadrature even under a small number of measurement points are provided. An average for the y-coordinate of values of normal-directional component with respect to the cross-section represented by vz0(x, y) among an estimated flow velocities in a flow passage cross-section is used as Vz0(x), and a weighting function of Gaussian quadrature is set to Vz0(x)L(x), where L(x)=ymax(x)−ymin(x). Further, an average for y of values of normal-directional component with respect to the cross-section of an actual flow velocity represented by vz(x, y) is used as Vz(x), and an integrand is set to Vz(x)/Vz0(x). These values are used to determine an approximate value of a flow rate according to Gaussian quadrature. In addition, a method of virtually offsetting zero-point of the flow velocity distribution to apparently avoid a problem such as reverse flow is provided.

主权项

1. A method for measuring a flow rate Q of a fluid flowing through a flow passage, the flow rate Q being represented by the following Formula:Q=∫Ssvz=∫xminxmaxx∫ymin(x)ymax(x)yvz(x,y)=∫xminxmaxxVz(x)L(x)where,Vz(x)=∫ymin(x)ymax(x)yvz(x,y)ymax(x)-ymin(x)L(x)=ymax(x)-ymin(x) (where: S represents a flow passage cross-section, wherein a position within the flow passage cross-section S is represented as (x, y); vz represents a normal-directional (z-directional) component with respect to the flow passage cross-section S of a flow velocity of the fluid, wherein vz(x, y) represents a normal-directional component at a position (x, y) of a flow velocity of the fluid at the position (x, y) on the flow passage cross-section S; and ymin(x) and ymax(x) represent, respectively, a minimum value and a maximum value of the y-coordinate when the x-coordinate is fixed on the flow passage cross-section S, wherein xmin and xmax represent, respectively, a minimum value and a maximum value of the x-coordinate on the flow passage cross-section S), the method comprising: determining a node xi and a coefficient wi for Gaussian quadrature (where i represents a natural number of 1 to N, where N represents an arbitrary natural number equal to or greater than 1), using a weighting function Vz0(x) L(x) represented by,
Vz0(x)L(x) where,Vz0(x)=∫ymin(x)ymax(x)yvz0(x,y)ymax(x)-ymin(x) where vz0(x, y) represents an estimate value of a normal-directional component of a flow velocity at each position (x, y) within the flow passage cross-section S; determining Vz(xi) and Vz0(xi) for respective nodes xi; and determining an approximate value QN of the flow rate Q, the approximate value QN being represented by using the following Formula:QN=∑i=1NwiVz(xi)Vz0(xi).