Method and apparatus for measuring the strength of the air/fuel mixture supplied e.g. to an I.C. engine

Claim 2

An instrument for providing an indication of the ratio of air to fuel of a combustible mixture being supplied to a combustion system which operates on hydrocarbon fuel, for combustion therein, which instrument comprises: means for effecting the continuous complete combustion of a controlled supply of a hydrocarbon heating fuel with a controlled supply of an oxygen-containing gas to produce heat and a reference gas, said reference gas being a continuous supply of gaseous combustion products containing a known proportion of free oxygen, means for mixing a sample flow of exhaust gas from said combustion system with at least a sample flow of said reference gas in a controlled porportion, and means for effecting a catalytic oxidation reaction of the mixture of the sample flows of exhaust gas and reference gas to oxidise any unburnt components derived from the sample flow of said exhaust gas in the mixture, said means for effecting a catalytic oxidation reaction receiving said heat generated by the combustion of said heating fuel and said oxygen-containing gas to maintain said catalytic oxidation reaction.

Claim 3

An instrument as in claim 1 further comprising a monitoring device for measuring a proportion of free oxygen in the gaseous reaction products of said catalytic oxidation reaction from which measurement together with predetermined data the said air/fuel ratio is derived.

Claim 4

An instrument as claimed in claim 2, wherein said oxygen-containing gas is air, further comprising a portable supply of heating gas for supplying said heating fuel.

Claim 5

An instrument as claimed in claim 2 or 3, in which said monitoring device comprises a quick-response oxygen-sensing cell of the solid-oxide electrolyte type.

Claim 6

An instrument as claimed in claim 4, in which said monitoring cell compirses a zirconia oxygen sensor.

Claim 7

An instrument for measuring the ratio of air to fuel of a combustible mixture being supplied to a combustion system, comprising: a cylindrical housing, a primary catalytic reactor in secure contact alignment within part of said housing comprising a matrix of annular cross section, said matrix having an open-ended central bore, said cylindrical housing having an end thereof closed except for an aperture therein being substantially coaxial with and of substantially the same diameter as said bore, said primary catalytic reactor being disposed a predetermined distance therefrom for forming an annular first mixing chamber, a central housing tube extending through said bore and said aperture, a secondary catalytic reactor in secure contact alignment with part of said tube, said tube having an end thereof substantially closed, said secondary catalytic reactor being disposed a predetermined distance therefrom for forming a cylindrical second mixing chamber, a monitoring cell, said secondary catalytic reactor being disposed a predetermined distance from the other end of said tube, said monitoring cell being securely mounted in a space thereby provided, and said primary catalytic reactor thereby surrounding said secondary catalytic reactor and an operative part of said cell, whereby the operating temperatures of said cell and of said secondary catalytic reactor are produced and maintained by a catalytic reaction at said primary catalytic reactor, and a pair of substantially identical lengths of partly coiled heat exchange tubes, one of said tubes receiving a portion of a flow of combustion products from said primary catalytic reactor and the other of said tubes receiving a portion of a flow of exhaust gas of said combustion system, each of said tubes having a known proportionate resistance to gas flow, being in a heat exchange relationship with the combustion products of said primary catalytic reactor, and providing respective predetermined portions of the flow of said exhaust gas and the flow of said combustion products to said second mixing chamber, wherein a controlled flow of a heating fuel and air is supplied to said first mixing chamber for providing a mixture thereof to said primary catalytic reactor.

Claim 8

An instrument for measuring the ratio of air to fuel of a combustible mixture being supplied to a combustion system, comprising: a cylindrical housing, a primary catalytic reactor in secure contact alignment within part of said housing comprising a matrix of annular cross section, said matrix having an open-ended central bore, said cylindrical housing having an end thereof closed except for an aperture therein being substantially coaxial with and of substantially the same diameter as said bore, said primary catalytic reactor being disposed a predetermined distance therefrom for forming an annular first mixing chamber, a central housing tube extending through said bore and said aperture, a secondary catalytic reactor in secure contact alignment with part of said tube, said tube having an end thereof substantially closed, said secondary catalytic reactor being disposed a predetermined distance therefrom for forming a cylindrical second mixing chamber, a monitoring cell, said secondary catalytic reactor being disposed a predetermined distance from the other end of said tube, said monitoring cell being securely mounted in a space thereby provided, and said primary catalytic reactor thereby surrounding said secondary catalytic reactor and an operative part of said cell, whereby the operating temperatures of said cell and of said secondary catalytic reactor are produced and maintained by a catalytic reaction at said primary catalytic reactor, and a pair of substantially identical lengths of partly coiled heat exchange tubes, one of said tubes receiving a portion of a flow of combustion products from said primary catalytic reactor and the other of said tubes receiving a portion of a flow of exhaust gas of said combustion system, each of said tubes having a known proportionate resistance to gas flow, being in a heat exchange relationship with the combustion products of said primary catalytic reactor, and providing respective predetermined portions of the flow of said exhaust gas and the flow of said combustion products to said second mixing chamber, wherein a controlled flow of a heating fuel and air is supplied to said first mixing chamber for providing a mixture thereof to said primary catalytic reactor.

Claim 9

An instrument as claimed in claim 6, in which said pair of tubes are of equal flow resistance whereby the respective flows of gas through said tubes are of an equal volumetric flow rate.

Claim 12

A method as claimed in claim 8 in which the combustion of said heating fuel and said oxygen-containing gas is effected by means of a primary catalytic reactor.

Claim 13

A method as claimed in claim 9 in which the combustion of the mixture of said exhaust gas and said reference gas is effected by means of a secondary catalytic reactor, a matrix of said primary catalytic reactor surrounding said secondary catalytic reactor.

Claim 14

A method as claimed in claim 8, 9 or 10, in which said combustion system is an I.C. engine, and which includes the steps of: automatically calculating from the said oxygen proportions of reference gas and reaction products and other data an equivalence ratio of said combustible mixture supplied to said engine, and providing a read-out of said equivalence ratio.

Claim 15

A method as claimed in claim 11 in which said measuring step further comprises the step of utilizing the heat of combustion of said heating fuel and said oxygen-containing gas to maintain said oxygen-sensing cell at an elevated operating temperature, the gaseous reaction products of said catalytic oxidation reaction being passed thereover.

Claim 18

The apparatus of claim 13, wherein said primary combustion chamber comprises: an inside surface of a substantially cylindrical housing; an outside surface of an axially concentric central tube; and an annular primary catalytic reactor securely contained between said inside housing surface and said outside tube surface; and wherein said secondary combustion chamber comprises: an inside surface of said tube; and a substantially cylindrical secondary catalytic reactor securely contained within said inside tube surface and disposed within the opening through said primary catalytic reactor.

Claim 19

The instrument of claim 13 further comprising an oxygen sensor in thermal proximity with said primary chamber for receiving a flow of said gaseous reaction product from said secondary chamber and effecting a continuous measurement of the proportion of free oxygen thereof at a high temperature by utilizing the heat generated in said primary chamber, the sensitivity of said oxygen sensor being thereby significantly enhanced.

Claim 20

The apparatus of claim 15, wherein said primary combustion chamber comprises: an inside surface of a substantially cylindrical housing; an outside surface of an axially concentric central tube; and an annular primary catalytic reactor securely contained between said inside housing surface and said outside tube surface; wherein said secondary combustion chamber comprises: an inside surface of said tube; and a substantially cylindrical secondary catalytic reactor securely contained within said inside tube surface and disposed within the opening through said primary catalytic reactor; and wherein an operative portion of said oxygen sensor is securely supported within a space in said tube adjacent said secondary catalytic reactor and disposed within the opening through said primary catalytic reactor.

Claim 21

The apparatus of claim 14 or 16 further comprising: means for venting said reference gas from said primary combustion chamber; means for extracting from said reference gas venting means a predetermined flow of reference gas, means for extracting from an exhaust gas venting means a predetermined flow of exhaust gas, and means for mixing the predetermined flows of said reference gas and said exhaust gas to provide a controlled mixture thereof to said secondary combustion chamber.

Claim 22

The apparatus of claim 17, wherein: said reference gas extracting means and said exhaust gas extracting means respectively comprise substantially identical lengths of partly coiled heat exchange tubing through which respective proportional flows of reference gas and exhaust gas are induced to flow under substantially equal pressure differentials, said lengths of tubing having a known proportionate resistance to gas flow and being in heat exchange relationship with said reference gas at an output of said primary combustion chamber within said reference gas venting means, and said reference and exhaust gas mixing means comprises a chamber at one end of said tube adjacent said secondary catalytic reactor for receiving and mixing the proportionate flows of said reference gas and exhaust gs respectively.

Claim 23

The apparatus of claim 18, wherein said lengths of tubing are of equal flow resistance, whereby equal resistance volumetric flow rates are induced therein.

Claim 24

The apparatus of claim 14 or 16 further comprising means for mixing predetermined flows of said heating fuel and said oxygen-containing gas to provide a controlled mixture thereof to said primary combustion chamber.

Claim 25

The apparatus of claim 16, wherein said oxygen sensor comprises a solid oxide electrolyte having zirconia therein.