US3643640A

US3643640A - Low-polluting internal combustion engine wherein exhaust gases are recycled in a controlled pattern

Info

Publication number: US3643640A
Application number: US10906A
Authority: US
Inventors: Bernard J Kraus; Dae Sik Kim
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1970-02-12
Filing date: 1970-02-12
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22
Also published as: US3643425A; GB1314859A

Abstract

A low-pollution internal combustion engine wherein exhaust gas is recycled by control means only when the engine is operating intermediate idle and full throttle subject to the engine not being choked. A particular feature is the introduction of the recycle exhaust gases intermediate, the point of introduction of the fuel and the flapper valve.

Description

Edited States Eatent Kraus et a1.

[ 1 Feb. 22, 1972 [54] LOW-POLLUTENG INTERNAL COMBUSTION ENGINE WHEREIN EXHAUST GASES ARE RECYCLED IN A CONTROLLED PATTERN [72] Inventors: Bernard J. Kraus, Roma-Ostia, Italy; Dae

Sik Kim, Maplewood, NJ.

[73] Assignee: Essa Research and Engineering Company [22] Filed: Feb. 12, 1970 [21] App1. No.: 10,906

[52] U.S.Cl. ..123/l19A [51] Int. Cl ..F02m 25/06 [58] EieldofSearch ..123/119A [56] References Cited UNITED STATES PATENTS 2,154,417 4/1939 Anderson ..l23/l 19 A 2,317,582 4/1943 Bicknell ..l23/119 A 2,421,406 6/1947 Bicknell ....123/l19 A 2,543,194 2/1951 Paris, Jr. ....123/119 A 2,722,927 11/1955 Cornelius... .....l23/119 A 2,969,800 1/1961 Skirvin et a1. .....123/1 19 A 3,139,873 7/1964 Gardner ..l23/119 A 3,204,621 9/1965 Hol1iday...... .....l23/119 A 3,141,447 7/1964 .lernigan ..123/l19 A Primary Examiner-Wende11 E. Burns AtmmeyR. D. Manahan [57] ABSTRACT A low-pollution internal combustion engine wherein exhaust gas is recycled by control means only when the engine is operating intermediate idle and full throttle subject to the engine not being choked. A particular feature is the introduction of the recycle exhaust gases intermediate, the point of introduction of the fuel and the flapper valve.

7 Claims, 3 Drawing Figures LOW-POLLUTING INTERNAL COMBUSTION ENGINE WHEREIN EXHAUST GASES ARE RECYCLED IN A CONTROLLED PATTERN The present invention is concerned with a low polluting internal combustion engine whereby objectionable compounds such as nitrous oxides, carbon monoxide and unburned hydrocarbons are minimized in the exhaust gases. These objectionable compounds are minimized by means whereby exhaust gases are recycled to the engine only when the throttle is intermediate the idle position and the full throttle position and when the engine is not being choked. These objectionable constituents are also greatly minimized by the introduction of a controlled pulsed airstream into the exhaust ports at points adjacent to the exhaust valves when these exhaust valves are open. Furthermore, undesirable overheating of the exhaust manifold under certain conditions is prevented by introducing additional air into the intake manifold when the pressure in the exhaust manifold remains at a predetermined figure for a predetermined duration.

The major gaseous pollutants from automobile engines include unburned hydrocarbon, carbon monoxide and oxides of nitrogen. The first two are results of incomplete combustion of the fuel due either to lack of oxygen or to lack of time required-to complete the combustion reaction. Since the combustion reaction in an engine is contained and the containing wall must be cooled to protect the metal wall, the incomplete combustion is inevitable in the cylinder. Therefore, an afterbuming reaction is required in order to maintain these two pollutants below certain levels. The oxygen for this purpose can'be supplied either by lean operation or by secondary injection of air. The smooth operation of the engine and the fueling of afterbuming not only prefers, but also requires rich operation. When very low levels of these pollutants are desired, it is necessary to inject secondary air.

The oxides of nitrogen are formed in a flame where an efficient combustion reaction is occurring. The high power and high efficiency operation causes higher formation of oxides of nitrogen (N Any method of NO, suppression causes loss of volumetric efficiency of the engine. Rich operation up to 20 percent extra fuel and exhaust recycle up to percent does not drastically affect the desired aspects of the engine operation with respect to power level and fuel efficiency, but does result in about 80 to 90 percent reduction in undesirable NO, formation.

Thus, among the objectionable constituents of exhaust gas are carbon monoxide, unburned hydrocarbons, and oxides of nitrogen which are very undesirable from an air pollution standpoint. Carbon monoxide is harmful for its toxic properties and the oxides of nitrogen are physiologically harmful. Hydrocarbons and oxides of nitrogen are additionally harmful, even though present in very small amounts since they participate in a sequence of photochemical reactions which cause eye irritation, crop-damaging and visibility-reducing smog. These problems become acute in urban areas where local meteorological conditions prevent the normal upward convective movement of ground level air for long time periods.

The present invention greatly reduces these objectionable constituents in a manner that will be more clearly understood by reference to the drawings illustrating adaptations of the same.

FIG. 1 is a diagrammatical sketch of an eight-cylinder internal combustion engine.

FIG. 2 illustrates one pulse-programming means of securing controlled pulsed airflow to the exhaust ports of the respective cylindersl FIG. 3 illustrates the flow rate or shape of pulses to these exhaust ports as a function of time.

Referring specifically to FIG. 1, an internal combustion engine 10 is shown containing an intake manifold 1, an exhaust manifold 2, and eight cylinders, one of which is designated as 3. Inlet ports of the respective cylinders communicating with the intake manifold are not shown but are of conventional design and operation. All cylinders contain conventional exhaust valves and ports, one of which of cylinder 3 is designated as 4. The engine also comprises an air filter 5, an air inlet conduit 6, a choke plate 7, and a flapper valve 8, all of which are conventional. Fuel is introduced into the carburetor 9 by means of line 11, the induction of which is secured by known means. The engine also comprises an exhaust pipe 12 leading into a muffler 13, by which gases are vented to the atmosphere through exhaust conduit 14.

Flapper valve 8 is operated by conventional throttle means not shown. Flapper valve 8, in addition to conventional throttle means has a suitable linkage means 15 which actuates a bleed valve 16 between the. position shown in solid lines (a) and the position shown in dotted lines (b). Bleed valve 16 is in position (a)-when flapper valve 8 is in the idling position while bleed valve 16 is in position (b) when flapper valve 8 is at full throttle.

Bleed valve 16 is at a position intermediate (a) and (b) in a manner to close the opening in line 17 and thus prevent bleeding of atmospheric air when flapper valve 8 is intermediate the idle position and the full throttle position. Under these conditions, when the engine is operating the vacuum in the intake manifold 1 is transmitted through line 18 through line 19 causing control membrane 20 to move upwardly in a manner to open valve 21 by means of linkage 61 and thus permit exhaust gases to recycle from exhaust line 12, through line 22, through valve 21 and be'introduced at a point intermediate the point of fuel injection, line 11, and the flapper valve 8. When line 17 is closed due to bleed valve 16 being in an intermediate position, this will occur and exhaust gases will be recycled.

When flapper valve 8' is open to full throttle, valve 16 will move to position (b) and pennit air to flow or bleed through port 23, flow through line 17' and thereby overcome the tendency or force of the vacuum in the intake manifold to move membrane 20 upwardly. Membrane 20 will move downwardly under the action, for example, of the spring loaded valve 21 which closes and prevents recycle of any exhaust gases. This will close conduit 22 and no recycle of gases will be secured from line 12. On the other hand, when flapper valve 8 is in the idling position of (a),air will flow or bleed through port 24 through line 17 and will also function to close valve 21 in a manner as described. Thus, recycle of exhaust gases is secured only when bleed valvel6 seals off line 17 at a position intermediate (a) and (b), namely between idling and full throttle.

A particular further feature of the present invention is the overriding effect of choke valve 7, even when bleed valve 16 seals off line 17. Choke valve 7 is connected by suitable linkage means 25'soas to open aport 26 in line 27 when the engine is choked. Thus, when theengine is being choked, atmospheric air will flow through port 26, through line 27, and overcome or negate the vacuum pressure from the intake manifold on membrane 20. Thus, membrane 20 is not subject to the suction of the intake manifold and valve 21 will close as described thereby preventing any recycle of exhaust gases. Thus, by the present mechanism-recycle of exhaust gases is secured only intermediate idle throttle and full throttle and when the engine is not being choked.

A further feature of the present invention is the use'of programmedpulsed airstream which is introduced into the system by means of a pump 30 or equivalentmeans which air enters from the atmosphere through line 31. This air flows through line 32, through line '33 toga pulse-programming assembly means 40 suitably connected to the crankshaft by timing belt or gear .assemblymeans-4l. The particular programming assembly means 40 illustrated comprises a plurality of outlets or ports, one'ofwhich is designated as'42. Outlet 42 is in communication'to exhaust port4 of cylinder'3-by means of conduit 43. The number of outlets or ports on programming device 40 programming device 40 is opened substantially concurrently The particular programming device 40 is illustrated in FIG.-

2 wherein a rotatingplate 44 contains a control port 45. Plate 44 is rotated by shaft 46 driven by assembly 41, preferably timed by the camshaft. As shown in FIG. 2, port 42 communicating with port 4 by means of line 43, is in full open communication with port 45 in rotating plate 44. Thus, the airflow rate to port 4 is full and is approximately position (c) of FIG. 3. Port 45 of plate 44 is of a sufficient diameter so that when port 42 is half closed by the rotating plate, port 45 will be in a position permitting flow of air through adjacent port 47 which port will communicate by suitable similar means to an exhaust port of the next cylinder. In essence, the control means 40 is designed to have a continuous flow of air from the interior of means 40 substantially equivalent to the flow of air volume when port 45 is in full communication with port 42.

A further feature of the present invention is that it is very desirable that the exhaust manifold 2 be operated at a relatively high temperature, namely in the range of about l,500 to about 1,800 F. The conversion rate of carbon monoxide to carbon dioxide drops sharply below l,500 F thus it is desira' ble to maintain the reactor or exhaust manifold temperature above this value. Although high reactor temperatures are generally desired for high rate of conversion and thus lower final pollutant level, two practical aspects limit the upper temperature to about 1,800 F. These are working temperatures of available reactor materials and the extent of richness or excess fuel which can be afforded to heat the exhaust to this temperature level and subsequently be wasted.

These temperatures are secured by a number of 'means, as for example, by insulation. The exhaust manifold in essence becomes a reactor at these temperatures for the substantial complete fuel conversion of unburned hydrocarbons and carbon monoxide to innocuous materials. However, if the engine should be operating for a substantial length of time, at high power levels, the temperature in the exhaust manifold or reactor 2 will tend to build up with the possibility of burning out the element. Under these conditions, pressure will build up in exhaust pipe 12. In accordance with the present invention, this pressure is transmitted by suitable means through conduit 50 to a control membrane 51 which actuates to open or close by suitable linkage 62 a control valve 52 positioned in line 53. As the pressure builds up on membrane control 51, this will open valve 52 permitting air to flow through line 32, through line 53 through valve 52 into the intake manifold l in a manner to lean the carbureted mixture entering the intake manifold from the carburetor. This will reduce the temperature and at a predetermined level and at a predetermined pressure will allow spring or otherwise actuated valve 52 to close.

Thus, suppression of unburned hydrocarbons and carbon monoxide is carried out in an exhaust manifold reactor. For a V-8 engine, two reactors are used. As heretofore pointed out, the proper operation of the reactors, high temperatures in the range of about l,500 to about 1,800 F. are required. The function of the secondary programmed pulsed air is to ensure the mixing of the secondary air and the rich exhaust before they enter into the exhaust reactors. This further ensures the effective utilization of the whole reactor volume, uniform optimum mixture ratio, high mixture temperature, and the minimum excess secondary air. Thus, the programmed pulsed air injection is essential when very low pollutant levels are desired.

The presence of excess fuel and the resulting reducing gases in a rich engine operation tend to capture and minimize the oxygen needed for the formation of NO, The partial recycling of exhaust gas suppresses the peak flame temperature. Both of these methods tend to suppress the N formation. The combination of these two methods do not affect the operation of engine and their effect are near additive.

It has been known in the art that the amount of exhaust recirculation should be a constant fraction of the engine air intake. This is usually accomplished by the use of complex recycle valves which are generally not reliable. The usual method of injection is into the intake manifold. The present invention involves introduction of the recycle at a point before the throttle plate but after the fuel inlet. Since the pressures at these points are always near ambient, no special control valves are required to proportion the exhaust stream for recycle. Contrarily in the usual means of injection into the intake manifold, a special and complex valve must function to maintain proportionalrecycle against the widely varying pressure difference between exhaust and intake.

From the drawing it is evident that substantially atmospheric pressure exists in the carburetor at the point of introduction of the recycle gases. Thus, the A P from the point of withdrawal of the exhaust recycle gases through the recycle line to the carburetor is equivalent to the A P from the point of withdrawal of the recycle gases through the exhaust muffler to the atmosphere. Thus, the ratio of the flow resistance through the recycle line to the flow resistance through the muffler will determine the ratio of gases recycled to the gases emitted into the atmosphere through the muffler. By controlling the ratio of the respective flow resistances, the ratio of gases recycled is readily controlled.

When recycling exhaust gases between idle and full throttle, the precise limitations will depend upon various operating conditions including the particular engine design. While an off-on type of recycle may be employed, it is preferred to have a gradual increase and decrease of the quantity of exhaust gases recycled between idle throttle and full throttle. This is secured by the particular apparatus illustrated. Under these conditions, at maximum recycle flow, about 10 to 15 percent by volume of exhaust gases are recycled based upon the total volume of gases introduced into the intake manifold. Generally speaking, exhaust gases will not be recycled when the throttle is opened only about 0 to 10 percent of full throttle and when the throttle is open, about to percent of full throttle. Thus, gases will be recycled only when the throttle is open-in the range from about 10 to 90 percent.

The quantity of air introduced into the intake manifold in order to lean the mixture generally is in the range from about 10 to 20 percent by volume based upon the total volume of gases introduced into the intake manifold. The amount of secondary air introduced to the exhaust ports is in the range of about 10 to 30 percent by volume based on total volume of gases exhausted from the cylinder.

What is claimed is:

1. Process for operating an internal combustion engine in a manner to reduce pollutants ejected into the atmosphere which comprises recycling a portion of exhaust gases to the region between the point of introduction of the fuel and the throttle plate, said gases being recycled only intermediate idle throttle and full throttle and not when the engine is choked, the proportion of said recycled gas is to the fresh charge being essentially constant.

2. Process as defined by claim 1 wherein said gases are recycled only between 10 percent full throttle and 90 percent full throttle.

3. Process as defined by claim 1 wherein the amount of exhaust gases recycled is in the range of 10 to 15 percent by volume of the total gases to the intake system.

4. Exhaust gas recycle control assembly designed to be affixed to a conventional internal combustion engine which comprises: l a first conduit communicating with the exhaust gas manifold and the area between the throttle plate and the fuel intake point; (2) a first valve in said first conduit; (3) a second conduit communicating with the intake manifold of said engine and with (4) a first valve control means adapted to open and close said first valve as a function of pressure by means of 5) a first linkage means; (6) a third conduit communicating with said first valve control means and the atmosphere; (7) a second valve adapted to close said third conduit from the atmosphere; (8) a second linkage means affixed to the throttle plate of said engine and to said second valve, said second linkage means functioning to move said second valve and to close said third conduit to the atmosphere when said throttle plate is intermediate idle throttle and full throttle, and to open said third conduit to the atmosphere when said throttle plate is at about idle throttle or about full throttle, whereby when said throttle is intermediate idle throttle and fullthrottle, a vacuum pressure during engine operation will be exerted to said first valve control means in a manner to open said first valve permitting recycle of exhaust gases, and whereby when said throttle plate is at about idle throttle or about full throttle said second valve will permit communication from said first valve control means to the atmosphere negating said vacuum pressure and said first valve control means will close said first valve preventing recycle of exhaust gases.

5. Assembly as defined by claim 4 wherein said first-valve control means comprises (9) a membrane element attached by said first linkage to control the opening and closing of said first valve.

6. Assembly as defined by claim 5 wherein (10) a third linkage is attached to the choke valve of said engine in a manner to provide communication of said first valve control means with the atmosphere when said engine is being choked whereby said first valve control means will function to close said first valve and prevent recycle of exhaust gases.

7. Assembly as defined by claim 4 wherein the flow resistance through the said first conduit is adjusted with respect to the flow resistance through the muffler in a manner to secure the desired ratio of gases recycled with respect to the total exhaust gases.

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Claims

4. Exhaust gas recycle control assembly designed to be affixed to a conventional internal combustion engine which comprises: (1) a first conduit communicating with the exhaust gas manifold and the area between the throttle plate and the fuel intake point; (2) a first valve in said first conduit; (3) a second conduit communicating with the intake manifold of said engine and with (4) a first valve control means adapted to open and close said first valve as a function of pressure by means of (5) a first linkage means; (6) a third conduit communicating with said first valve control means and the atmosphere; (7) a second valve adapted to close said third conduit from the atmosphere; (8) a second linkage means affixed to the throttle plate of said engine and to said second valve, said second linkage means functioning to move said second valve and to close said third conduit to the atmosphere when said throttle plate is intermediate idle throttle and full throttle, and to open said third conduit to the atmosphere when said throttle plate is at about idle throttle or about full throttle, whereby when said throttle is intermediate idle throttle and full throttle, a vacuum pressure during engine operation will be exerted to said first valve control means in a manner to open said first valve permitting recycle of exhaust gases, and whereby when said throttle plate is at about idle throttle or about full throttle said second valve will permit communication from said first valve control means to the atmosphere negating said vacuum pressure and said first valve control means will close said first valve preventing recycle of exhaust gases.

5. Assembly as defined by claim 4 wherein said first valve control means comprises (9) a membrane element attached by said first linkage to control the opening and closing of said first valve.