US2696806A - Removal of combustion chamber deposits in spark-ignition engines - Google Patents

Description

United States Patent fiice 2,596,805 Patented Dec. 14, 1954 REMOVAL OF COMBUSTION CHAMBER DEPOSITS IN SPARK-IGNITION ENGINES John Mingle, Jr., Richmond, Califl, assignor to Califorma Research Corporation, San Francisco, Calif a corporation of Delaware No Drawing. Application August 7, 1953, Serial No. 373,051

9 Claims. (Cl. 123-1) This invention relates to a method of purging the combustion chamber of spark-ignition internal combustion engines, and particularly to a method of removing deposits from the internal parts of the combustion chamber Which normally detract from efficient fuel combustion and decrease the power output in the operation of the spark-ignition internal combustion engines.

It is an accepted fact that normal operation of sparkignition engines with conventional lubricating oils and gasoline compositions normally accumulates organic and inorganic deposits within the combustion chamber and upon the moving parts of the engine. These deposits rapidly reduce engine efiiciency and ultimately require complete dismantling of the engine for a cleansing or replacement of fouled engine parts.

Numerous methods have been proposed by which these carbonaceous deposits could be removed without having to resort to a complete dismantling of the engine. These various proposals generally fall within the categories of oxidation, solvent action and mechanical removal. Numerous proposals have been made to inject various solvents into the fuel itself in an attempt to dissolve the deposits during operation of the engine. Other methods involve the introduction of oxidative catalysts and the application of heat to oxidize these deposits. The mechanical and manual methods which include peening and shot-blasting normally require an exposure of the engine parts to effect a removal of the deposits.

While a number of these methods have achieved a certain measure of their objective, namely that of reducing the amount of combustion deposits without requiring a complete dismantling of the engine, none of these methods, with the possible exception of mechanical or manual deposit removal, have removed enough of the combustion deposits to materially improve the performance of the engine and bring the engine efficiency back to its original potential. In the solvent and certain oxidative removal methods whereby the purge process is conducted incidentally to engine operation, all of the proposals continuously stress smooth engine performance without perceptible knocking.

Contrasting the underlying precepts of these previous proposals, it has been found that effective removal of combustion chamber deposits in a spark-ignition engine may be attained with a negligible modification of the mechanical aspects of engine operation by operating the engine for a short period under conditions of auto-ignition. Thus, it has been discovered that by mere substitution for the normal gasoline fuel of an auto-ignitable fuel composition possessing a volatility substantially within the gasoline volatility range and operating the engine thereon under sufficient loading conditions as to cause auto-ignition, effective cleansing and purging of the internal surfaces of the combustion chamber and associated moving parts are obtained. In this type of operation, the,combustion deposits are removed through the exhaust system of the engine and the engine is substantially restored to its potential performance characteristics.

In conducting this purge method, the auto-ignitable fuel composition is preferably introduced into the fuel line of the engine preceding the carburetor as a replacement of the normal gasoline fuel. When operating the engine on the auto-ignitable purge fuel, a sufficient load is applied to the engine either by internal friction and inertia or by external loading such as with a dynamometer to cause the fuel composition to auto-ignite within the combustion chamber of the engine.

The period of auto-ignition operation required to effect a substantial removal of the combustion chamber deposits is variable depending upon the mechanical characteristics of the engine, such as compression ratio, etc., as well as the amount of deposits to be removed. From a practical standpoint, the duration of the purging process is controlled simply by the introduction of a predetermined amount of auto-ignitable fuel.

In the preferred method of conducting the purge process, the spark-ignition engine is disengaged from its external load and a measured quantity of auto-ignitable fuel is introduced into the fuel line entering the carburetor through gravity flow from an overhead receptacle. The engine is started up on the purge fluid and operated under intermittent full-throttle acceleration with internal engine friction and inertia as the only load applied until the combustion deposits are substantially exhausted from the system. Although the number of full-throttle accelerations progressively reduces the amount of combustion chamber deposits, it has been found that approximately 70-80% of the combustion chamber deposits will have been effectively exhausted after about thirty full-throttle openings.

The purge fluid is a fuel composition which is susceptible to auto-ignition under the conditions of operation obtainable in the spark-ignition engine, and possesses a volatility substantially within the gasoline volatility range. It has now been determined that for effective deposit removal, coupled with practical application in the conventional spark-ignition engines, the auto-ignitable purge fluid should possess an A. S. T. M. octane number at least 35 octane numbers lower than the equilibrium octane requirement (EOR) of the engine to be purged as determined by the conventional test procedure identified as CRC designation E-l-748. As previously indicated, the combustion chamber deposits gradually accumulate in service with corresponding increase in octane requirement of the engine until the octane requirement reaches a substantial equilibrium which, in the case of normal automotive engine operation, is attained in about 2000 to 3000 miles of driving.

Although, directionally, the lower the octane number and, correspondingly, the higher the cetane number of the purge fluid, the greater the eificiency in deposit removal over a given period of auto-ignition engine operation, certain practical limits are dictated in the case of the more recent high-compression, high-octane requirement engines. In certain of these high output engines, the differential between initial and equilibrium octane requirement is comparatively small, and, for a comparable purge efficiency, allow the use of a higher octane number auto-ignitable purge fluid. It has been found preferable in engines having an EOR above to employ an auto-ignitable p'urge fluid having an octane number between about 35 to 60 octane numbers below the EOR of the engine. In the case of engines having an EOR less than 90, it is preferable, for maximum purge efficiency, to employ an auto-ignitable purge fluid whose octane number is at least 50 octane numbers lower than the EOR of the engine.

In order to obtain the maximum effect of this purge method, particularly for application in spark-ignition engines with compression ratios of 5.5 :1 and above, 1t has been discovered that the auto-ignitable purge fluid should possess an A. S. T. M. octane number below about 30 and an A. S. T. M. cetane number above about 45. Auto-ignitable fuels satisfying this octane-cetane number balance include the low octane, straight chain hydrocarbons and the high cetane, oxygen-containing chemicals conventionally recognized as cetane-improving agents, as well as blends thereof in varying proportions, provided the final composition possesses a volatility substantially within the gasoline volatility range. When referring to A. S. T. M. octane numbers and A. S. T. M. cetane numbers throughout the specification and claims, it is to be understood that reference is made to octane numbers measured by A. S. T. M. D357-48 and cetane numbers as measured by A. S. T. M. D6l3-48T.

Suitable hydrocarbon fuels which may be used per se or in various blends thereof are the predominantly straight chain hydrocarbons boiling within the gasoline boiling range, such as n-heptane, n-octane, Z-methylheptane, 3- methylheptane, 4-methylheptane, n-nonane, Z-methyl octane, 3-n1ethyl octane, 4-methyl octane, 2,6-dirnethylheptane, l-octene, n-propylcyclopentane, n-propylcyclohexane, and certain selected natural and straight run gasoline stocks. In addition to the hydrocarbon fuels and preferably complementing the higher octane stocks, a group of chemical compounds falling within the recognized classification of oxygen-containing cetane-improving agents may be employed in the auto-ignitable purge fluid. These compounds, which possess a high cetane value, are normally used in additive amounts to up ade the cetane number of diesel fuel oil stocks and characteristically promote precombustion vapor phase oxidation. The principal components of this category of compounds are the organic ethers, peroxides, and nitrate esters, of which the following compounds and materials are typical: methyl isopropyl ether, methyl sec. butyl ether, din-propyl ether, di-n-butyl ether, di-isoarnyl ether, diethoxyacetone, diethyl formaldehyde, 1,2-propyiene glycol diethyl ether, glycerol tri(ethoxyethyl) ether, py-

rogallol trimethyl ether, di-isopropyl polyethylene oxide,

diethyl Carbitol, benzoyl peroxide, benzyl peroxide, peroxided decahydronaphthalene, diethyl peroxide, mesityl oxide peroxide, trimolecular acetone peroxide, di(tert. butyl) peroxide, cyclohexyl' hydroperoxide, alkyl hydroperoxides, prepared in accordance with Patents 2,317,968 and 2,365,220, dialkyl peroxides, prepared in accordance with Patents 2,521,698, 2,522,015, and 2,522,016, amyl nitrate, ethyl nitrate, etc.

In preparing a suitable purge fluid to meet the requisite octane-octane number balance and volatility, one or more cetane-improving agents may be blended together and used per se, or in combination with a comparatively high octane gasoline stock. Although the cetane-improvii agents satisfying the volatility requirements may be used per se, it is preferable to blend these agents with a hydrocarbon fuel stock to obtain better starting characteristics in the purge fluid. When using octane-improving agents in the compounding of the purge fluid, the octane number of the base gasoline stock may materially exceed 30.

The composition of the purge fluid is susceptible to considerable variation within the foregoing specifications and is dependent to a great extent upon availability and economics of suitable blending stocks and chemical. components. Some of the individual cetane-improving agents, such as the hi h molecular weight peroxides and hydroperoxides obtained from the oxidation of kerosene stocks, etc., are not sufficiently volat le to allow satisfactory carburetion for introduction to the engine. These materials may be modified by bending with more volatile cetaneimproving agents, such as ethyl ether. and/or compounding with the more volatie hydrocarbon stocks, such as n-heptane. As an illustration of effective blends of cetaneimproving agents in hydrocarbon stocks, desirable autoignition fluids are obtained by incorporating 20-50% by weight of ethyl ether in n-heptane and 3-10% amyl nitrate in n-heptane.

In automotive spark-ignition engines. the improvements in engine operation obtained by removal of combustion de osits in accordance with the subiect process h ve been effectively illustrated by a series of comprehensive tests wherein the degree of deposit remov l and efiiciency of the purge method was defined by differences in octane requirement of the engine. In determining these improvements, the automotive engine was subjected to a standard road octane requirement test conducted in accordance with the procedure outlined in CRC designation E1748 entitled, Research Technique for Determination of Octane Number Requirements of Vehicles on the Road, both before and after subjecting the automotive engine to the present purging method. This test is conducted on a series of reference fuels and ascertains the octane number of the fuel required for incipient knocking of the engine over a standard road course within the normal speed range of the vehicle.

Test results on a series of automobiles of conventional make and contemporary manufacture with the subject purge method employing representative purge fluids within the foregoing specifications have resulted in decreases in octane requirement varying from 2 to 18 octane numbers, depending upon the type of engine and service history of the engine. In addition to the octane requirement decrease obtained, it was found that acceleration times L were consistently improved and represented an average power increase of about 4% on 21 test cars.

The following examples serve as an illustration of a number of methods of applying the subject purging process with certain specific auto-ignitable purge fluids. It is to be understood that these examples are not to be construed as a limitation of the invention, either with respect to urge fluid composition or the method of applying the foregoing purge process.

Example I The octane requirement of a 1941 De Soto sedan, with an odometer reading of 34,585 miles was determined on the road in accordance with standard procedure outlined in CRC E1748, using primary reference fuels. In order to obtain the octane requirement, the fuel line of the engine was disconnected at the suction side of the fuel pump and a special inch line run into the cab of the car where the reference fuels were carried. With the timing checked at the standard spark advance for a 1941 De Soto, the test procedure was conducted and the octane requirement determined to be 86. The time required to traverse a measured test course on a hill starting at 20 M. P. H. was 13.4, and a check at 13.0 seconds.

In administering the purge treatment, the engine was stopped and the fuel line disconnected at the carburetor. 8 ounces of an auto-ignitable purge fluid, consisting of a blend of 30% ethyl ether in a straight run Michigan gasoline stock possessing an A. S. T. M. octane number of 23, was introduced into the fuel line preceding the carburetor from a separate container. The engine was started and as soon as the gasoline in the carburetor was consumed, which was evidenced by initial knocking, the throttle was alternately opened and closed. The engine was operated in this manner, namely, open throttle for accelerations to about 2500 R. P. M. and closed throttle until the engine slowed down to an idling speed of about 450 R. P. M. with no external load applied, for 37 throttle openings, of which 32 were at maximum knock intensity. This treatment required about two minutes.

The fuel system was then returned to its original position for conducting the octane requirement without adjusting the ignition system or the timing. The octane requirement after the purge process was determined as 74, and the corresponding acceleration times over the same course dropped to 12.4 and 12.7 seconds. The removal of combustion chamber deposits by this purge method resulted in a lowering of the octane requirement of 12 numbers, and a power increase, as represented by the decrease in acceleration times, of 5.2%.

Example 11 The procedure as outlined in the previous example was conducted on a 1946 Dodge pick-up truck. The initial octane requirement was determined as 70, and the accheck 14.1 seconds; and on the south course 17.2 check 14.9 check 14.1 seconds. The application of the purge method resulted in a decrease in octane requirement of 11 numbers, and a power increase of 9.6%.

Example III The purge method was applied to a stationary L-head CPR engine. In this test combustion chamber deposits were built up by operating the engine on commercial gasoline and lubricating oil for a period of 265 hours, corresponding to about 5000 miles of automotive engine operation. The equilibrium octane requirement of the engine was then determined by supplying the engine successively with reference fuel blends until the rating level knock was observed. Commercial diethyl ether was carbureted to the engine for 15 minutes at normal fuel-air ratio. The engine operating conditions were as follows: 900 R. P. M., 6.8 to 1 compression ratio, F. jacket coolant temperature, 75 'F. intake manifold temperature, 4 B. T. C. ignition timing, full throttle. The engine operated immediately under conditions of auto-ignition upon admitting the ether into the manifold. Auto-ignition was evidenced by characteristic sound, key-01f ignition, and observation of the diagram on an oscilloscope. After 15 minutes of operation on the diethyl ether, the octane requirement of the engine was determined in the same manner as previously stated. The octane requirement of the engine immediately prior to application of the purge process was 81. After 15 minutes of operation under auto-ignit on conditions on the diethyl ether purge fluid, the octane requirement was reduced to 45. The clean engine octane requirement was established to be 33.

Example IV In this test, the purge method was applied to a 1950 Buick sedan which had been operated for 3521 miles on commercial fuel and lubricating oil. The initial octane requirement of the engine was determmed as outlined in Example I and found to be 88. Contrasting the procedures of Examples I with II, wherein the purge method was employed under no-load conditions, in this test the purge fluid was applied to the engine under conditions of external load or under road operation.

The purge fluid was composed of n-heptane compounded with 20% by weight of concentrated dialkyl peroxides, in which the alkyl groups averaged about C10. The cetane-improving agent was obtained by acid treating a peroxidized kerosene stock within the bo1l1ng range of about 300-370" F. as described in U. S. Patents 2,521,698, 2,522,015 and 2,522,016. After this purge fluid was admitted to the carburetor, five fullthrottle accelerations from -60 M. P. H. were made with keyoif ignition. There was good acceleration and good engine operation on the first two accelerations. On the third, acceleration from 2030 M. P. H was sluggish. On the fourth, there was one cylinder misfirmg, and on the fifth there was no ditference in acceleration w1th ignition key on or off. After five accelerations over the test course, the engine was switched to the primary reference fuels to determine the octane requirement. The octane requirement was determined to be 8 3.

Following this test cycle, the purge fluid was again admitted to the carburetor, and five passes of the test course were made, with several full-throttle accelerations per pass. Again the octane requirement was determined and found to be 82. At the completion of the test, the cylinder head of the engine was removed and the combustion chamber inspected and found to be exceptionally clean, with no deposits. There was a small amount of powder on the exhaust valves and the spark plugs were undamaged.

The engine was disassembled and the exhaust valves and entire combustion chamber surfaces were manually cleaned by scraping and wire brushing. The octane number of the cleaned engine was determined and found to be 80.

Example V The purge process as outlined in Example I was conducted on a 1953 Cadillac which had been operated for 4072 miles on commercial fuel and lubricating oil. The octane requirement of the engine as determmed in accordance with CRC E1-748 was 93. The purge treatment, employing as the auto-ignitable purge fluid 35% iso-octane in normal heptane, was administered and 30 full-throttle no-load accelerations were applied. At the conclusion of the treatment, the octane requirement was determined to be 91.

In order to determine the effectiveness of the purge process, the engine was dismantled and mechanlcally cleaned. The octane requirement of the mechanicallycleaned engine was found to be 90, indicating an octane requirement increase for the period of operation of 3 octane numbers, 2 of which were removed by a s ngle purge treatment with a 35 octane number purge fluid.

Example VI In ascertaining the eifect of octane number level in the auto-ignitable purge fluid, the following experiment was conducted on a 1953 Buick which had been operated on conventional fuel for 4174 miles.

The octane requirement of the engine after this period of operation was determined to be 91 and a purge treatmentwas administered similar to thepreceding example employing as the purge fluid a mixture of 60% iso-octane in normal heptane. At the conclusion of the treatment, namely, after 30 no-load full-throttle openings, the octane requirement of the engine was determined to be /2, indicating no significant reduction in the combustion chamber deposits. The engine was again purged in a similar manner employing 35% iso-octane in normal heptane as the purge fluid. At the conclusion of this treatment, the octane requirement of the engine was determined to be 87 /2, whereas the engine in a mechanically-cleaned condition hadan octane requirement of 86.

Example VII A further comparison of the effectiveness of the subject process, particularly with respect to engines of low octane requirement increase, was conducted on a 1950 Buick whose engine had an equilibrium octane requirement of 85. On level road acceleration tests from 2060 M. P. H. in high gear, the acceleration times averaged 12.6 seconds. This engine was subjected to the conventional purge treatment with a 60 octane number purge fluid. At the conclusion of this treatment, the octane requirement of the engine remained at 85, indicating no effect upon the combustion chamber deposits and the acceleration times averaged 12.5 seconds.

In a second purge treatment, a 45 octane number purge fluid was employed resulting in a drop in octane requirement of the engine to 83 with a corresponding reduction in acceleration times to 12.0, indicating a 5% power increase. The octane requirement of this engine in a mechanically-cleaned condition was determined to be 82.

Similarly, a 1950 Buick having an equilibrium octane requirement of 89 was purged with a 30 octane number purge fluid to an 86 octane requirement with a substantially clean engine octane requirement of 85.

This application is a continuation-in-part of my application, Serial No. 203,220, filed December 28, 1950, entitled Removal of Combustion Chamber Deposits in Spark Ignition Engines," and now abandoned.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A method of removing combustion chamber deposits in a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine as the sole fuel an auto-ignitable fuel composition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M. octane number at least 35 octane numbers lower than the equilibrium octane requirement of said engine, and operating said engine with said fuel composition under loading conditions sufiicient to cause auto-ignition until the exhaust system is noticeably free of the purged combustion chamber deposits.

2. A method of removing combustion chamber deposits in a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine an auto-ignitable fuel composition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M. octane number at least 35 octane numbers lower than the equilibrium octane requirement of said engine, and operating said engine with said auto-ignitable fuel composition in the absence of external load under intermittent fullthrottle acceleration until the exhaust system is noticeably free of the purged combustion chamber deposits.

3. A method of removing combustion chamber deposits in a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine an auto-ignitable fuel composition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M. octane number at least 35 octane numbers lower than the equilibrium octane requirement of said engine, and operating said engine with said auto-ignitable fuel composition in the absence of external load under intermittent fullthrottle acceleration for at least 30 throttle openings.

4. A method of removing combustion chamber deposits m a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine as the sole fuel an auto-ignitable fuel composition possessing an A. S. T. M. octane number below 30 and an A. S. T. M. cetane number above 45, which fuel possesses a volatility substantially within the gasoline volatility range, and operating said engine with said fuel composition under loading conditions sufficient to cause auto-ignition.

5. A method of removing combustion chamber deposits in a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine an auto-ignitable fuel composition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M. octane number below 30 and an A. S. T. M. cetane number above 45, and operating said engine with said fuel composition in the absence of external load under intermittent full-throttle acceleration.

6. A method of removing combustion chamber deposits in a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine an auto-ignitable fuel composition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M.

octane number below 30 and an A. S. T. M. cetane numposition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M. octane number below 30 and an A. S. T. M. cetane number above 45, and comprising a petroleum distillate fraction of low octane number in combination with at least one organic vapor phase oxidation promoter selected from the group consisting of organic nitrates, organic peroxides, and organic ethers capable of materially improving the cetane number of said petroleum distillate fraction, and operating said engine with said fuel composition in the absence of external load under intermittent full-throttle acceleration.

8. A method of removing combustion chamber deposits in a spark-ignition internal combustion engine which comprises introducing into the fuel line preceding the carburetor of said engine an auto-ignitable fuel composition whose volatility is substantially within the gasoline volatility range and possessing an A. S. T. M. octane number below 30 and an A. S. T. M. cetane number above 45, and comprising a petroleum distillate fraction of low octane number in combination with at least one organic vapor phase oxidation promoter selected from the group consisting of organic nitrates, organic peroxides, and organic ethers capable of materially improving the cetane number of said petroleum distillate fraction, and operating said engine with said fuel composition in the absence of external load under intermittent full-throttle acceleration conditions for at least 30 accelerations.

9. A method of removing combustion chamber deposits in a spark ignition internal combustion engine which comprises substituting for the normal gasoline fuel and introducing into the fuel line preceding the carburetor an auto-ignitable fuel composition possessing an A. S. T. M. octane substantially below said normal gasoline fuel and a substantially positive A. S. T. M. octane number, said auto-ignitable fuel composition further possessing a volatility substantially, within the gasoline volatility range, and operating said engine with said autoignitable fuel composition in the absence of external load under intermittent full-throttle acceleration until the exhaust system is noticeably free of the purged combustion chamber deposits.

No references cited.

Claims (1)

1. A METHOD OR REMOVING COMBUSTION CHAMBER DEPOSITS IN A SPARK-IGNITION INTERNAL COMBUSTION ENGINE WHICH COMPRISES INTRODUCING INTO THE FUEL LINE PRECEDING THE CARBURETOR OF SAID ENGINE AS THE SOLE FUEL AN AUTO-IGNITABLE FUEL COMPOSITION WHOSE VOLATILITY IS SUBSTANTIALLY WITHIN THE GASOLINE VOLATILITY RANGE AND POSSESSING AN A.S.T.M. OCTANE NUMBER AT LEAST 35 OCTANE NUMBERS LOWER THAN THE EQUILIBRIUM OCTANE REQUIREMENT OF SAID ENGINE, AND OPERATING SAID ENGINE WITH SAID FUEL COMPOSITION UNDER LOADING CONDITIONS SUFFICIENT TO CAUSE AUTO-IGNITION UNTIL THE EXHAUST SYSTEM IS NOTICEABLY FREE OF THE PURGED COMBUSTION CHAMBER DEPOSITS.