Method and device for evaluating a fuel gas wobbe index

A method for evaluating the Wobbe index of a fuel gas belonging to a family of gases. The method includes measuring mass flow rates the fuel gas and of a reference gas, which is not necessarily a fuel gas at respective absolute pressures and temperatures and in a sonic flow through a microjet. An evaluation of the Wobbe index (W) of the fuel gas as W=AxY+B uses the results of measurements of the fuel gas and the reference gas and is established for all the gases of the family considered.