Method and apparatus for determining the Wobbe index of gaseous fuels

Apparatus for determining the Wobbe Index of gaseous fuels comprising:

• means for establishing a mixture of gaseous fuel sample with air further comprising,
• a source of air at regulated pressure;
• a source of sample fuel at regulated pressure;
• a source of calibration fuel of known Wobbe Index at regulated pressure;
• means for determining the pressure differential of a flowmeter through which said air constituent of said mixture is caused to flow;
• means for determining the pressure differential of a flowmeter through which said fuel constituent of said mixture is caused to flow;
• burner means for the combustion of said mixture;
• sensing means for sensing the presence of combustibles or oxygen in the products of combustion of said mixture, wherein said sensing means is one exhibiting a rapid change in output signal about a particular combustion product composition wherein said output quantitatively indicative of a certain relative amount of said combustibles or oxygen in said products of combustion;
• means for adjusting the relative amount of fuel in said mixture in response to the output of said sensing means until said sensing means indicates that said products of combustion contain said certain relative amount of said combustibles or oxygen;
• means for determining the Wobbe Index of said fuel from a known relationship between the pressure differential across said fuel and said air flowmeter means and the Wobbe Index of said calibration fuel.

A method for determining the Wobbe Index of gaseous fuels comprising steps of:

• supplying a gaseous fuel sample and air to provide a combustible mixture thereof, said air being of substantially constant amount;
• monitoring the pressure differential of the flow of said gaseous fuel sample through a flowmeter;
• burning said sample in the presence of a means for sensing the presence of combustibles or oxygen in the products of combustion of said mixture, using a sensing means exhibiting a rapid change in output signal about a particular combustion product composition wherein said output is quantitatively indicative of a certain relative amount of combustibles or oxygen in the products of combustion;
• adjusting the relative amount of fuel in said mixture in response to the output of said sensing means until said sensing means indicates that said products of combustion contain said certain relative amount of said combustibles or oxygen;
• determining the Wobbe Index of said fuel from a known relationship between the heating value of the fuel constituents and the amount of oxygen required for the combustion thereof at said particular combustion product composition and the pressure differential across said fuel flowmeter means.