Patent ID: 6893152
Filing Date: 2005-05-17
Classification: G01N

Abstract:
1. A method for the evaluation of the Wobbe index, W, of a fuel gas of a family of gases defined by constituents having a given chemical nature and occurring in variable relative proportions, the method comprising: measuring a mass flow rate of the fuel gas in a sonic flow through a fluid restriction at an absolute measurement pressure and at an absolute measurement temperature, calibrating by measuring a mass flow rate of a reference gas in a sonic flow through the fluid restriction at an absolute reference pressure and at an absolute reference temperature, and evaluating the Wobbe index W as W=A×Y+B, established for the family of gases where Y is the product of three factors, Za, Zb, and Zc, wherein Za is a ratio of the mass flow rate of the fuel gas to the mass flow rate of the reference gas, Zb is a ratio of respective images of the absolute reference pressure and the absolute measurement pressure by a determined polynomial function, and Zc is the square root of a ratio of the absolute measurement temperature and the absolute reference temperature, and A and B are constant for the family of gases.