US2083522A - Gas analyzing apparatus - Google Patents

Description

June 8, 1937. J. D. MORGAN GAS ANALYZING APPARATUS Filed Sept 12, 1932 2 Sheets-Sheet 1 14: TORNEY I l------ P June 8, 1937. J. D. MORGAN 2,083,522

GAS ANALYZING APPARATUS Filed Sept. 12, 1932 2 Sheets-Sheet 2 EXHAUST TO ATMOSPHERE RELIEF VALVE. TQ ATMOSPHERE A T0 I MIXING I ESSURF. CHAMBER RELEF CHAMBER FILTER GAS CON OENSER AND COOLER 4 INVENTOR JOHN D. MORGAN ATTORNEY Patented June 8, 1937 GAS ANALYZING APPARATUS John D. Morgan, South Orange, N. J., assignor to Power Patents Company, Jersey City, N. J.,

a corporation of Maine Application September 12, 1932, Serial No. 632,675

2 Claims.

This invention relates to an apparatus for quantitatively measuring the combustible components in a gaseous mixture such as those from domestic and industrial combustion operations,

5 and it has special utility in the examination of exhaust gases from an internal combustion motor of the automotive type resulting from the combustion of hydrocarbon fuels under conditions of under-ventilation. MOre especially the invention concerns the quantitative measurement of combustibles by the controlled catalytic combustion of such gases with or without prior admixture therewithiof additional combustion-supporting fluid, employing catalytic elements disposed in the usual Wheatstone bridge circuit or its equivalent utilizing a galvanometer.

The accuracy of the above type of measuring instrument is dependent in considerable degree, upon the careful control of the rate of flow over the catalytic element of the gases to be analyzed, and the careful and constant regulation of the proportion of gas and air in the said mixture flowing to the combustion cell.

It is well known that exhaust gases from an internal combustion motor flow from the exhaust pipeunder a wide range of pressures and temperatures depending upon the speed at which the motor is being operated and the adjustment of the carbureter andignition system. Various instrumentalities have already been employed for the purpose of insuring a uniform fiow of gas and air under all conditions to the gas analyzer cell. Among such may be mentioned orificed gas sampling devices and fluid flow-inducing means generally connected with the outlet of the analyzer cell. Such devices have generally been open to the objection that the gas line leading from the motor exhaust pipe gradually may be choked up by carbon present in the exhaust gases, in which case the flow-inducing mechanism generally fails to maintain the rate of flow for which the device has been calibrated, and this, often permits of wide variations in the proportions of gas and air flowing to the analyzer.

Among the more important objects of the present invention are to provide in an improved manner for controlling by a pressure-feed type of device the flow of the gas or gas-air mixture to the analyzer cell under conditions preventing unregulated pressure variations occurring in the line connecting the pressureand flow-inducing means and the analyzer cell; to provide for a novel -portable gas analzer of the combustion or the thermal conductivity type embodying a compact strument is not affected by substantial changes in the power operating the flow-inducing means; to provide in novel manner, in such a process and apparatus, for the automatic reactivation of the catalytic element in the analyzer cell prior to each analysis; to provide in novel manner for the rapid and convenient cleaning of .the orifice members when desired; and further to provide in such method and apparatus for quickly cleaning outthe gas line leadingto the gas analyzer from the motor exhaustpipe without in any manner interfering with the adjustments of the various elements of the gas analyzer.

In its broadest scope the invention involves a gas analyzer of the thermal conductivity or of the combustion type which is fully automatic and contains no adjustable valves for air and gas control, and requiring adjustment during an analysis. Important parts of the machine include a motor and generator, a multi-stage pump or its equivalent, dry filters for the gas and for the air when used, a pair of gas analyzer cells disposed in a Wheatstone bridge circuit or its equivalent, a galvanometer or similar device, and certain fluid pressure and electric current regulating means hereinafter described.

The invention will hereinafter be described gas and air mixing and regulating apparatus and associated parts; and

2 I access:

which serves as an instrument panel. The box has a locking device II; and the sides of the box have apertures It therein for ventilation purposes; In the modification shown, the gas analyzing l5 apparatus is mounted upon the front member II for convenience of assembly in producing a small portable unit. Other arrangements of parts, however. ere within the purview of the invention.

The ap aratus comprises a motor generator set 50 consisting of a motor 2| and interconnected generator 22, the former being driven by power flowing thereto through circuit 24 controlled by the panel-mounted switch it. Carried upon an end of the generator and generator shaft, and driven 25 by the motor 2|, are a pair of constant. speed pumps 28, 3|, which may be in the form of a multi-stage pump. The respective pumps may be of the same or of diii'erent capacities. The motor generator set and pump assembly shown are cushioned upon rubber and carried by supports 3| secured to the front member or panel of the Mounted upon the rear face of the member is is a' pair of catalytic combustion cells 32, 34 of 35 well known construction. such as described in my copending application Serial No. 482.288, filed September 16, 1930. The cell II is sealed and contains air or other standard gas.- Cell 84 has an inlet 88 and outlet 88 for conveying the gas mixture to be rmconducting the gas to be examinedto the pump 28 in undiluted form, while concurrently removing a large portion of the condensible vapors and solid impurities therein, a novel sampling device ll is connected with the pump through the lines 42, I8, 44. The sampling device ll comprises an open-ended hollow metal tube having spaced semi-circular flanges 41 along its external surface as shown, .for supporting the tube in spaced relation to the walls'of a motor exhaust pipe and for forming bailles for free passage of excess gases around the said tube. The tube ll may be very short without danger of dilution of the exhaust gases by outer air entering the exhaust pipe. The outlet end of the tube 46 discharges tangentially downward into a small collecting chamber is, with the upper end of which the pipe 42 connects. A valved outlet II I permits drainageof condensate from the chamher 48. The outer walls of the chamber 48 may be provided with heat radiating fins I! or the like, as shown. I

- onnected'with the line I is a gas filter and separator 54 having a horizontal baille ll therein and'a removable transparent front cover It. A depending baille t. is mounted below baifle ll adjacent the gas inlet line. The space above the ba'iile II is preferably filled with a dryfiltering medium such as cotton,-glass wool. orthe like.= A removable plug in the base of the separater. permits removal therefrom of any collected moisture. A gas outlet pipe 44 connects theillter with theinlet oi'pump 2l.

-i'lheoutlet of pump is is connected through .line'llwiththegasinletchambcrtlofafiowregulating and mixing device II. The chamber II is permanently open to the-atmosphere through a relatively large aperture l2 therein: and it is also in controlled communication with 5 agasandairmixingchamberllthroughafiow measuring orifice conduit It having therein arotatable' longitudinally-grooved flow-regulating member ll fitting in but movable longitudinallly of said orifice conduit and having an end thereof 10 curved for convenience in moving it. The mixing chamber 14 also is in regulated communication with the air in front of the instrument panel. through a line 80, one end of. which is connected with a dry filter l2 containingcotton or the like 15 and having an aperture It therein, the said filter being coun'l :l'sunk in the front of the panel or member it. The opposite end of line II is connected with a flow-regulating orifice inlet conduit II and regulating member ll, respectively similar 20 to the parts 18, 18 described above.

The inlet end of the pump 3| is in permanent communication with the mixing chamber it through line 88. The outlet of pump II 0011- nects with analyzer inlet line I. through line IO, 25 the latter of which may, if desired, be provided with heat radiation fins or the like 82. Interposed in the line is a pressm-e-resfilating device 94 for controlling the pressure and fiow rate of the gas-air mixture fiowing to the cell ll; In 30 the form shown this regulating device comprises a dead weight valve having a valve seat normally closed by a. ball so selected that its weight is equivalent to the pressure at which it is 'desiredtoan'alyzethegasmixture. Whensuch 35 gas pressure is exceeded, the excess gases force theballfromits seat and fiowtotheatmosphere through apertures ll. Preferably. in present Dracticetheballissoselectedthat itislifted from its seat when for any reason a pressure 4 greater than that corresponding to four inches of water exists in the line, due, for instance, to variations in the speed of the motor operating the pump.

The analyzer cells 8!,havethe usualcata- 46 lytic wires I, III thereimthe same being disposed in a Wheatstone bridge circuit containing fixedresistances I; III; and the balancing or galvanometer line I has therein a pair of fixed resistances lll, III, and a variable resistanceor 5 rheostat iii. For purposes of compactness, the fixed resistances preferably are in the form of short non-magnetic coils mounted closely adjacent the cells-82 and ll,-and the rheostat is positioned midway between the cells, as shown in 55 Fig. 1.

The generator .22 is adjusted to produce an electric current substantially greater than that normally selected for use inthe galvanometer circuit. For the purpose of maintaining a con- Q stant voltage in the galvanometer circuit irrespective of variations in the voltage driving the motor, one or more resistances in the form of carbon filament lamps or amperites i II are arranged in series in the electric circuit connecting the generator with the Wheatstone bridge circult, as shown. Preferably the generator is so regulated that a line voltage to the motor of. volts and a motor speed of 1700 R. P. M. will. produce a current of 10 volts and 1.1 amperes 70 when the catalytic wire in the circuit is at normal operating temperatures,but will produce a current of 10 volts and 1.4 amperes for a few minutes,-at least 1 or 2 minutes-when starting up. The amperites are then so selected as to reduce 75 the voltage under normal operating conditions from 10 volts to 6 volts.

The orifice conduits I6, 84, and cooperating flow-regulating members I8, 86, preferablyare adjusted to permit the induced flow of equal parts of air and gas to the mixing chamber I4 and thence to the pump 38 under suction from the latter. Other proportioning of air to gas is readily accomplished by replacing the flow-regulating members I8, 86 with other similar members having a larger or smaller portion of its longitudinal surface beveled or cut away in the manner shown in Fig. 8. These regulating members are readily replaceable, or removable for cleaning when necessary by unscrewing the hollow caps I28, I22, housing them and then simply sliding the said members longitudinally from their respective conduits. Thus the removal and replacement of the regulating members requires but a moment. The described dilution of the exhaust gases with air has been found to render innocuous any traces of products formed by the decomposition of antiknock substances, such as tetraethyl lead, present in the fuel use'd,-and to prevent injury to the catalyst by these decomposition products.

When the instrument is to be employed without the admixture of supplemental air'for facilitating combustion in the analyzer cell, it will be obvious to those skilled in the art that the air filtering and regulating means and associated parts may be eliminated.

The arrangement as herein described is such that the gas-air mixture (or the gas alone when no secondary air is employed) flows to the distributing pump 38 in preselected regulated proportions under approximately atmospheric pressure regardless of the pressure existing in the line leading from the motor exhaust pipe to the inlet of the sampler pump 28.

For cleaning out the gas sampling line 42 and the sampling device 40 periodically when required, there is provided on the front I4 of the instrument panel a well known type of valve I24 such as widely used on pneumatic automobile tires. The valve is directly connected with the lines 42 and 43 through a metal fitting I26 carried on the instrument panel. Pressures as high as 50 lbs. per sq. in. may safely be imposed upon the line 42 through the valve I24 for the purpose specified, without danger of back pressure through the line 43 and associated parts injuring in any manner the delicate adjustment of the gas analyzer electric circuit or other parts of the apparatus. Wheatstone bridge circuit, as shown in Figs. 1 and 3, preferably is calibrated in terms of the combustion eificiency of the source from which the exhaust gases or waste gases being examined are drawn, this combustion efiiciency being based upon the percentage and composition of combustibles present in the gas flowing to the analyzer.

The instrument, as here shown, is in the form of a very compact small portable unit which may readily be transported fromplace to place and may be employed for checking the calibration of other non-portable gas analyzers located at various places over a wide territory. Its construction here described insures uniform operation and accurate readings even under conditions where, due to irregularities in the current available for driving the motor 20, the amount of gas sample being drawn by the pump 28 substantially varies. Likewise the current flowing through the gal- The galvanometer I28 disposed in thevanometer circuit is maintained at a constant voltage which is at all times lower than that being generated by the generator 22, independently of substantial variations in the generator output due to irregularities in motor operation.

In the practice of the invention for analyzing motor exhaust gases, the end of the sampling device 40 is thrust into the exhaust pipe leading from the motor the combustion efficiency of which is to be measured. The switch 26 on the instrument panel is closed, thus causing the motor generator set to function and both the pumps 28 and 38 to begin operation. Flow of gases from the exhaust pipe to the pump 28 is produced in part by the suction of the pump 28, and under some conditions in part by pressure developed in the exhaust pipe from the motor. The exhaust gases flow tangentially into the chamber 48 of the sampling device where they are substantially cooled and where a considerable portion of their moisture and solid suspended matter is deposited. The gases then flow through lines 42 and 43 to and through the separator and filter 54, and thence to the inlet of pump 28.

The filtered gas is forced by the pump 28 into the chamber 68 where substantially atmospheric pressure exists due to the continuous free escape of excess gases therefrom through the aperture I2. A small regulated amount of the gas is drawn through the mixing chamber 14 under the action of the pump 30, the latter of which concurrently draws air through the filter 82, line 88, and regulating orifice chamber 84 to the mixing chamber I4. The gases then flow through the pump under a pressure continuously maintained higher than that at which they are to be an alyzed in the cell 34. flows to the cell past the pressure-reducing valve whereby pressure above that selected for the examination is released.

Preferably in the examination of motor exhaust gases employing the combustion type of gas analyzer, a pressure equivalent to 4 inches of water is maintained upon the gases flowing through the combustion cell 34. The use of heat-radiating fins upon the line leading from the pump to the analyzer cell facilitates introduction of the gases to the latter at an approximately uniform temperature at all times. Any small variations in gas temperature are such as do not measurably affect the accuracy of the instrument readings.

When the test is begun by closing the switch 26, the catalytic wires I08, I02, are at low temperatures, and the generator produces a 10 volt current which is then reduced to a 6 volt current of a relatively high amperage,in the neighborhood of 1.4 amperes,and which flows through the catalytic wires for a short period of 1 or 2 minutes. This heats the catalytic elements to This gas mixture then i temperatures generally within the range of from 1600 to 1925 F.,--following which the increased resistance of the highly heated catalytic elements reduces the current flowing in the Wheatstone bridge circuits to the normal selected operating current, preferably of 1.1 amperes, at a constant voltage of 6 volts, which is then maintained irrespective of ordinary variations in voltage of the current driving the motor. The operating temperatures of the catalytic elements preferably are then maintained around 1120 t0 1380 F. The reduction of the current generated to one of constant voltage in the Wheatstone bridge circuit irrespective of variations in the generator output,is effected by the amperites H5.

4 a i 5mm device, and the-specific form of pressure-release valve and flow-regulating orifice members sescribed; nor is it essential that the specific arrangementof parts in the Wheatstone bridge circuit described be employed. Furthermore the specific voltages and 'amperages specified in the above-mentioned specific embodiment of themvention may be materially departed from. The invention set out in the accompanying claims is i a susceptible of modification within the scope of the latter;

- Iclaim:

to the atmosphere, an orifice inlet conduit from,

the atmosphere leading 1m and mixing. chamher, a flow-measuring orifice conduit-communicably connecting the pressure relief chamber and the mixing chamber. and a pair of freely rotatv able longitudinally slidable flow-regulating mem- 5 bars respectively disposed longitudinally within the flow-measuring orifice conduit and the orifice inlet conduit from atmosphere and dimensioned to limit ,to a calibrated amountthe finw capacity of each of saidvorifiees. o

2. In gas analyzing apparatus, a fiow-icgulah ing device comprising an orifice. block, a presvsure relief chamber within said block having an outlet leading to atmosphere and having an inlet to which gas to be analysedvis supplied 15 under pressure, a mixing chamber within said block having an outlet from which gas, is removed under suction, an orifice conduit communicably connecting said pressure relief chamber and said mixing chamber, an aperture ex- 20 tension of said orifice conduit ported out through a wall of said block. a freely rotatable longitudinally slidable flow-regulating member disposed longitudinally of said orifice conduit and dimensioned to limit to a calibrated amountthe fiow- 25 capacity of said conduit, and a removable plug closure for the aperture whereby to aiford access for the rapid removal and replacement of said flow regulating member.

- JOHN 1:. mm.

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