US2733697A - downs - Google Patents

Description

Feb, 7, 1956 DQWNS, JR 2,733fi97 CARBURETOR AIR DRYER Filed Deq. 50, 1954 INVENTOR. G .F. DOWNS JR.

BY wwn A r i on/V51 5 United States Patent CARBURETOR AIR DRYER George F. Downs, Jr., Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Application December 30, 1954, Serial No. 478,681

13 Claims. (Cl.123--119) This invention relates to a means and method for preventing carburetor icing in an internal combustion engine. More specifically it is directed to the dehydration of the. air drawn into the carburetor during the engine warm-up period.

'It has been observed that an internal combustion 2,733,697 Fatented Feb. 7, 1956 suitable for use in the invention. Figure 3 is a plan view of a portion of the engine of Figure 1 showing another modification of the invention and illustrating schematically an electrical control circuit. Figure 4 is a cross section of a desiccant container suitable for use in the present invention.

engine having a carburetor will stall while being warmed up when certain combinations of atmospheric temperature and humidity exist. This stalling, known as 'cold stalling is caused by the formation of ice on the throttle plate and adjacent parts of the carburetor, and especially around the idling jet and the throttle plate. The ice results from the cooling effect of the vaporization of fuel within the carburetor and from the pseudo-adiabatic expansion of carburetor air in the metering venturi and past the edges of the throttle plate, the cooling causing moisture in the incoming air to accumulate as ice in the carburetor. For example, normal fuel vaporization within the carburetor can cause a temperature reduction of the metal parts of the carburetor up to 50 F. below that of the entering air. The result is that after a period of light load operation, when the throttle is closed to the idle position, ice already formed on the throttle plate and adjacent walls, plus ice which then forms, restricts the narrow air openings to cause engine stalling. Cold stalling ordinarily occurs when the atmospheric temperature isin the range of about 30 to 60 F. and the relative humidity is greater than about 60 per cent. The general approach to this problem in the prior'art has been to add a various anti-icing agents to the fuel 'as illustrated for example, by U. S. 2,600,113.

The present invention takes an entirely different approach to this problem. This invention proposes to eliminate icing or cold stalling by dehydrating the air to the engine during'the critical-period of engine warmup when icing is most likely to occur. This invention may also alleviate accelerated corrosion conditions during this period. The invention provides a desiccant through which air is drawn during the warm-up period, means for the air to by-pass the desiccant after warm up, and means to regenerate the desiccant after a period of use.

Accordingly the principal object of this invention is to provide a means and method of dehydrating the air injected into the carburetor of an internal combustion engine. T

An additional object of the invention is to provide a combination of means for dehydrating the air drawn into a carburetor during the warm-up period and for regenerating the desiccant after the warm-up period is over.

The invention can best be described by an examination of the accompanying drawing which shows several forms Referring to Figure 1, engine 10 includes an exhaust manifold 11 to which is attached a desciccant container 12 of cylindrical shape and having a screened inlet opening 13. Container 12 is filled with a suitable desiccant such as silica gel. The other end of container 12 (opposite inlet 13) is closed; this forces air which enters through 13 to leave through conduit 14 which opens into air cleaner intake 16. The junction of container 12 and conduit 14, like inlet 13, is provided with a screen 13a (Figure 4) to confine the desiccant within container 12 but without unnecessarily restricting the air flow therethrough. A first butterfly valve 15 is located in conduit 14 and is controlled through arm 18]) by a temperature sensing spring element 18 illustrated in Figure 2. A second butterfly valve 19 is located in the intake 16 and is controlled in similar manner through arm 17b by element 17. i

In operation, elements 17, 18 are set so that when engine 10 is started coldvalve 19 is closed and valve 15 is open thus forcing all combustion air to pass through desiccant container 12 before reaching the engine, thus removing 'a substantial portionof the free moisture and preventing any build up of ice within the carburetor.

When the engine reaches a temperature sufficient to pre engine is warmed up sufiicient to eliminate the possi-' bility of cold stalling the desiccant has performed its function and the air subsequently drawn into the carburetor bypasses the desiccant.

As shown in Figure 2, spring element 18 consists of a rectangular box which attaches to the engine by a threaded stem 40; this screws into a tapped hole in the intake manifold. The inner end of coil spring 41 is' held in a slot in the end of arm 18a, the outer end 42 being held in a fixed but adjustable position by a peg (not shown) in cap 43. The latter is flanged at its base 44 and secured by lugs 45; hence, the tension of the spring 41 for any given position of arm 18a can be adjusted by the position of cap 43, the setting of which determines the relative position of the outer end of the spring with respect to the inner end. For example, if it is desired that the manifold attain a rather high temperature before arm 18a is actuated the spring 41 would be relaxed accordingly by the setting of the around its axis of rotation to reciprocating motion in.

arm 18b.

Referring to the modification of Figure'3, butterfly" valve 19 is controlled by an electrical circuit comprising engine ignition switch 21, timer reset switch 22(optional),

solenoid 20, thermal switch 23, and electrical energy source 24. Valve 19 is opened by spring '25 and closed by the action of solenoid 20 and mechanical linkage 26, valve being controlled by spring unit 18 and linkages 18a, 1812 as described in connection with Figure '1. When ignition switch 21 is turned to the onpo sition timer 22 is energized, completing the circuit; thus solenoid is energized and closes valve 19. The latterremains closed until the engine warms up 'sufficiently to actuate thermal switch 23, thus breaking the circuit. This deenergizes the solenoid 20 so that its associated linkage 26 permits valve '19 to open. Thermal switch 23, a bimetallic type of 'unit, is adjusted to be actuated at approximately the temperature at which butterfly valve 15 starts to close, thus preventing any appreciable restriction of air flow t0 the engine. Timer switch 22, preferably a 6 or 12 volt element, breaks the circuit after a predetermined interval of time, say 10 minutes after start-up, regardless of the condition of switch 23. If timer switch 22 is eliminated, the operation of valve 19 depends entirely on the operation of thermal switch 23.

As illustrated in Figure 4, the desiccant container 12 can be attached to exhaust manifold 11 by a clamp 30 and bolts 31 and 32. In this modification, the inner .wall 33 of the desiccant container 12 is spaced from ex- 7 the desiccant being required to remove moisture at a rate sufficient to maintain the relative humidity of the entering air below about 60 per cent as long as the temperature of the air is below 60 F.

Several factors must be correlated in order to render this device operative. One of these is the selection of the desiccant. Deliquescent salts suchas calcium chloride, potassium chloride, and lithium chloride are impractical in the present invention because they tend to liquefy when hydrated, causing the individual particles to soften and stick together. If sufficiently hydrated they are converted to a corrosive solution. These desiccants cannot be regenerated. The preferred desiccants here are adsorbents of the type exemplified by silica gel and activated alumina; these retain their physical form when hydrated and can be readily regenerated by heating.

- Another consideration is the rate of water adsorption by the desiccant. volume of desiccant is required. It has been determined, however, based on silica gel, that the volume of desiccant required is not excessive. For example, a 250 cubic inch engine has a displacement of 181 C. F. M. at 2500 R. P. M. This would be a medium-sized auto engine operating at 3040 M. P. H. AS Shown by Ahlberg, Industial and Engineering Chemistry, p. 990 (1949), a one inch thick bed of silica gel '1 foot square removesenough water vapor to lower the per cent relative humidity of 47 F. air from 67 to at a rate offlow of 178 C. ,F. M. for 10 minutes. Activated alumina is somewhat inferior to silica gel on this score since it requires a thicker bed and lower air flow rate.

Another factor bearing on the quantity of desiccant required concerns the pressure dropthrough thedesiccant bed. The bed must .be large enough to minimize the pressure drop. It has been determined, based on the method of Chilton and Colburn, Industrial and Engineering Chemistry, p. 913 (1931'), that 181 C. F. M. of air will flow through a 1 foot diameter, one inch thick 'bed of silica gel with a pressure drop of less than 1' inchofwater. Themaximum allowable pressure drop through thedesicant con ma e sh sh -abqut 1 i ch f me -..I:I, .th 9 the tie cs nt sontainer neednot beexcessive. I Y

If the rate is too slow, an unduly large r Both of the above determinations are based on the displacement of the engine. The actual flow will vary from about 10 C. F. M. at idling to over 250 C. F. M. at road speeds. During the time when cold stalling probl ms are greatest, the air will-be approximately 25-30 C. F. M.

A third factor concerns the quantity of 'heat available for regeneration of the desiccant. Silica gel can be reactivatedby contacting with air at 300-350 F., and its adsorbing power is not greatly decreased after beingsubjected to high temperatures. For example, U. S. 1,297,- 724 states that properly prepared gel is not injured by heating to 700 C. (1292 F.). With the exhaust nanifold temperatures in the range of 800-1400 F., it is obvious that sufiicient heat is available to reactivate the gel without damaging it.

Another factor concerns whether the desiccant might begin regenerating and rejecting moisture to the air before the carburetor is warm enough to prevent the formation of ice. Generally little or no icing occurs if the temperature of the inlet air is above 60 F. or if therelative humidity is below 60 per cent. As shown by Ahlberg, Figure 3 (supra), silica gel has considerable adsorption capacity at 104 F. Thus the adsorptive capacity of the 'silica gel is more vthan enough to remove moisture under operating conditions, since severe trouble is not encountered until the air is cooler than 60 F. and has a relative humidity above 60 per cent.

The foregoing specification in intended to be illustrative, not limiting, since obviously numerous modifications could be made in a desiccatingsystem of this type. For example, a set of shutters could be provided for air intake '13 to operate in lieu of or in combination with butterfly 17. This would prevent surface saturation of the desiccant while the engine is idle.

I claim:

1.,In combination, a gas engine having a carburetor provided with an air-intake, and means in said air-intake for dehydrating the incoming air.

2. In combination, an internal combustion engine having a carburetor provided with a conduit for the admission of air thereto, a quantityof desiccant in said conduit to dehydrate the incoming air, and means for admitting 'air into said carburetor so as to by-pass said desiccant.

3. In combination, an internal combustion engine equipped with a fuel-air carburetor, a conduit communieating-with said carburetor for admission of air thereto, a desiccant within said conduit to dehydrate the air entering the carburetor, and means for regeneratingsaid desiccant.

4. In combination, an internal combustion engine pro.- vided witha carburetor and exhaust manifold, a first conduit communicating with said carburetor for the admission of air thereto, a valve in the outer end of said conduit, a second conduit branching from said first com duit at a point between said valve and carburetor, .arvalve in said second conduit, and a quantity of desiccant in said second conduit todehydrate the air passing them through, the position of said valves determining whether air enters the conduit only through said first or second conduit or through both.

5. Apparatus of claim 4 wherein the desiccant is -posi-' tioned in heat exchange relationship with the exhaust manifold .so as, to permit thermal. regeneration of the desiccant.

6. In combination, an internal combustion engine provided with a carburetor and an exhaust manifold, a first conduit communicating with said carburetor for the admission .of air thereto, a valve in said conduit, a-second conduit .branching from said first conduit at a point between said valve and carburetor, a portion ofsaid second conduit being adjacent said manifold, a quantity of desire- Qantin said second conduit positioned inheat exchange relationship -,with' said. manifold, whereby the manifold heat is made available for regeneration of tlie desiccant,

thermally responsive means positioned in heat exchange relationship with the engine and mechanically connected to said valves, whereby the position of the latter is regulated according tothe engine temperature.

7. Apparatus of claim 6 wherein the thermally responsive means comprises a pair of coil springs, a housing covering each spring and attached directly to the engine housing, and a mechanical linkage from each spring to the valve it controls, said linkage being actuated by the thermal expansion or contraction of the spring.

8. In an internal combustion engine having a carburetor with air and fuel inlet means and an exhaust manifold, said engine being subject to cold stalling due to formation of ice in the carburetor, in combination, a first conduit communicating with said carburetor for the admission of air thereto, a first throttle valve in said conduit, a second conduit opening into said first conduit at a point between the carburetor and said throttle valve, a second throttle valve in said second conduit, a quantity of desiccant in said second conduit to dehydrate the air passing therethrough, a temperature sensing element on said engine, a direct mechanical linkage between said element and said second throttle valve to control the position of the latter in accordance with the engine temperature, and electrically operated control means for controlling the position of said first throttle valve.

9. Apparatus of claim 8 wherein the control means comprises an electrical circuit which includes the dashboard ignition switch, a timer switch, a solenoid, a thermal switch, and a source of direct current, said circuit being completed by turning on the ignition switch and being broken by the operation of the timer or the thermal switch, and a direct mechanical linkage between said solenoid and said first throttle valve, said linkage being designed to maintain said valve in a closed position when the solenoid is energized and in the open position when the solenoid is deenergized.

10. Apparatus of claim 8 wherein the control means comprises an electrical circuit and mechanical means actuated thereby, said circuit including the dashboard ignition switch, a source of direct current, a thermal switch, and a solenoid, and the means actuated thereby comprising a mechanical linkage between said solenoid and said first throttle valve, the arrangement being such that when the engine is cold the closing of the ignition switch completes the circuit so that the solenoid operates to close said valve, whereby air entering the carburetor must pass through the desiccant, and when the engine is warm the thermal switch opens so as to break the circuit, thus deenergizing the solenoid and allowing said valve to open, whereby air drawn to the carburetor may by-pass said desiccant.

11. An internal combustion engine having a carburetor, a first and second conduit for the admission of air thereto, a first and second throttle valve in the respective conduits, an exhaust manifold, a desiccant container in said first conduit positioned in heat exchange relationship with the exhaust manifold, a quantity of desiccant in said container, and means controlling the position of each throttle valve, said means operating to close said second throttle valve and to open the first while the engine is warming up and to close the first and open the second when the engine has passed the warm-up stage, whereby incoming air is forced through the desiccant during the warm-up stage and by-passes the desiccant during the subsequent operation.

12. Apparatus of claim 11 wherein the means controlling each throttle valve comprises a temperature sensitive element in heat-exchange relation with the engine and having a direct mechanical linkage to the throttle valve, each temperature sensitive element operating only one valve and the two being coordinated so that one valve is closed as the other is opened.

13. Apparatus of claim 12 wherein the temperature sensitive element comprises a coil spring mounted in heat exchange relationship with the engine and attached at one end to said mechanical linkage, the latter being actuated by the elongation or contraction of the spring with changes in engine temperature, said actuation causing a resultant change in the position of the valve controlled by said linkage.

No references cited.

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