An apparatus and corresponding method for determining component flow rates of
a multiphase fluid in a conduit, the fluid consisting of at least three known components,
the method including the steps of: measuring at each of two different positions
along the conduit at least four mixture quantities, typically the sound speed,
the flow velocity of the multiphase fluid, the pressure and the temperature; providing
a speed of sound in each of the components at the measured pressures and temperatures;
providing a trial value for each of either the component flow rates or the phase
fractions; using a predetermined model to calculate values for the measured mixture
quantities based on the trial values for each of either the component flow rates
or the phase fractions; using a predetermined error function to determine an error
value; and using a predetermined optimizing algorithm to determine whether the
calculated values are acceptable, and, if they are not, to provide a new trial
value for each of either the component flow rates or the phase fractions. In some
applications, the error function is the sum of the squares of the difference between
the measured and calculated values at each point.
