Method and apparatus for real time gas analysis

Abstract

A method and apparatus for real time gas analysis involving determining individual concentrations of fluid constituents in a mixture of known constituents by measuring properties of the mixture and solving a set of equations, which relate the individual gas concentrations to the measured properties of the mixture, for the unknown individual gas concentrations. The individual concentrations of four gasses in a mixture are determined by: passing the mixture through a flowmeter, a capillary, an orifice, and a sonic oscillator; transducing temperature, pressure and acoustic frequency measurements taken from the sensors; determining the density, viscosity, and the specific heat of the mixture; forming three equations which respectively relate these three properties to individual gas concentrations; and solving the three equations and the constitutive equation which requires that the sum of the concentrations equal unity, for the four unknown individual gas concentrations. A single oscillator can serve as both a sensor (e.g., flowmeter, acoustic velocimeter) and an orifice. The fluidic sensors can be formed as a single chip disposable sensor module. By modifying only the processing software, the same sensors or a subset of the sensors can be used to verify or determine the identity of an unknown gas which is supplied by itself in a pure form or in a mixture of other gasses whose identities are known. By measuring N−1 properties of the gas mixture as a whole, the capabilities of an existing sensor system for measuring M gas concentrations can be extended to measure N additional gas concentrations, provided the identities of the gasses in the mixture are known. Similarly, by modifying only the processing software the same sensor can be used to analyze any sets of gas mixtures.