Method for measuring the mass flow of a stream of a gaseous medium and fuel supply system

A method is provided for measuring the mass flow of a stream of a gaseous medium of elevated first temperature flowing through a specific pipe, comprising the steps of: a) providing a reference stream of said gaseous medium with a known mass flow and a second temperature being substantially lower than said first temperature; b) mixing said reference stream with said stream of a gaseous medium of elevated first temperature flowing through said specific pipe; c) measuring the resulting temperature of the mixture of said reference stream and said stream of a gaseous medium of elevated first temperature flowing through said specific pipe; and d) determining the unknown mass flow of said stream of a gaseous medium of elevated first temperature flowing through said specific pipe from the known mass flow of said reference stream, said elevated first temperature, said second temperature of said reference stream and said measured resulting temperature according to the formula: M=M*(T1-T3x)/T3x-T2), where Mx is the unknown mass flow, M ref is the known mass flow of said reference stream, T1 is the second temperature, T2 is the elevated first temperature, and T3x is the resulting temperature after mixing.