INDUSTRIAL A N D ENGINEERING CHEMISTRY
278
Vol. 17, No. 3
The Effect of Crank-Case Dilution’ By D. P. Barnard, 4th MASSACHUSETTS INSTITUTE OF TBCHNOLOOY, CAMBRIDGS, MASS.
T
H E data in this paper represent the results of two thesis investigations to determine the extent to which dilution of crank-case oil influences the rate of wear occurring in the automobile engine. Road Tests
These tests were made on the personal cars of members of the Institute staff, which were operated under ordinary service conditions. No attempt was made to control the operation of the machines, as the primary idea was to study the effect of dilution under actual service conditions. Twelve cars were placed on test, but circumstances caused the withdrawal of all but five before complete results could be obtained. A brief description of the cars test,ed is given in Table I. Table I Previous. serLUBRI- vice Car ENGINE CATION Miles REMARKS 6 cylinder overhead valve Splash 26,000 0 cylinder overhead valve Splash 20,000 N e w rings installed prior t o tests 4 cylinder ”F” head Splash 6,000 9,000 4 cylinder overhead valve Splash 4 cylinder “L” head Splash 10,000 Lubricating oil: High-grade “medium” motor oil. Viscosity, approximately: 285 seconds Saybolt a t 100’ F.
Before placing a car on test the crank case was drained, thoroughly flushed out, and refilled with the oil used in the test. After 200 to 300 miles of operation the crank case was again flushed out and refilled with fresh oil. The tests consisted of runs of approximately 500 miles each, during which period samples of the oil were taken every 100 miles for determination of dilution and iron content. All samples were withdrawn immediately after the car had been in service. They were siphoned through the breather tubes with the engine running in order to obtain as representative sampling as possible. Dilution was determined by comparison of the viscosity of the crank-case oil with a curve obtained by viscosity determinations on samples of the original oil artificially diluted with kerosene. The Saybolt Universal viscometer was used a t 38” C. (100” F). The amount of wear occurring in the engine was estimated from determinations of the iron suspended in the various samples of crank-case oil. It was assumed that all of the iron 1 Presented before the Division of Petroleum Chemistry a t the 68th Meeting of the American Chemical Society, Ithaca, N. Y.,September 8 t o 13, 1924.
found in the crank-case oil had been removed from the cylinder walls and rings. No attempt was made to estimate bearing wear. All analyses were made in duplicate or triplicate. On the completion of a 500-mile run the crank case was flushed out and refilled with fresh oil in preparation for the next test run. Dynamometer Tests
The car tests were supplemented by tests on two engines connected to dynamometers. A brief description of the engines tested is given in Table 11. T a b l e I1 Engine 1 2
TYPE 4 cylinder “L” head 8 cylinder “I,” head
Ll;BRIC.4TION
Previ.ous service Hours
Splash Force
300 500
The dynamometer tests consisted of a series of test runs of 7 to 10 hours’ duration in each of which the viscosity waa maintained substantially constant by the frequent addition of fresh oil or kerosene as necessary. I n the tests on Engine 1 the crank case was drained a t the end of each run and the oil thoroughly stirred in an effort to obtain a reliable sample for analysis. In the tests on Engine 2 , the lower half of the crank case was removed after each run and the interior thoroughly cleansed of sediment. This was accomplished rather easily on account of the construction of this engine. The crank-case washings so obtained were thoroughly mixed with the oil before sampling for analysis. As in the car tests, several samples were taken for check analyses. Results
The results of the car tests are given in Figures 1 and 2. Two curves are recorded for each run, showing, respectively, dilution and cylinder wear plotted against mileage. Figures 3 and 4 give the results of the dynamometer tests. For Engine 1 (Figure 3) two curves are given in which the cylinder wear occurring during a 7-hour run is plotted against dilution and lubricant viscosity, respectively. The viscosity-dilution curve a t 38” C . (100’ F.) for the oil used is also recorded in this figure. The load of 6.7 brake horsepower imposed on the engine represents approximately25 per cent of full engine power and is equivalent to that occurring at a car speed of about 25 miles per hour. Similar curves are given in Figure 4 for the tests on Engine 2. The oil used in these
INDUSTRIAL A N D ENGINEERISG CHEMISTRY
March, 1925
tests is identical with that of the car tests, but is different from that used in the tests on Engine 1. As before, the brake Zd
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load of 14 horsepower represents about 25 per cent full power and a car speed in the neighborhood of 25 miles per hour. Discussion
The principal point brought out by the car tests is the practical impossibility of obtaining representative sampling (for iron analyses) of the crank-case oil when the cars are subject t o intermittent service. There is every indication that iron or other solid particles which settle out in the crank case never get back into suspension. This observation agrees with that of Nickinson.2 In some of the test runs, in which the cars stood idle for several days a t a time, actual decreases were noted in the iron content of the oil. A n instance of this is recorded in Figure 1 by the last point of the wear curve for Car 2 . Car 4 gave the most consistent results, in all probability because it was driven steadily and was not subjected to periods of idleness exceeding 12 hours in duration, Since
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would bend upward more sharply. The fact that the curves do not pass through the origin is in all probability due to iron remaining in the oil passages and reservoir. In winter operation of automobiles it is common to experience serious trouble due to corrosion of parts of the engine by acids formed largely by solution of sulfur trioxide in water condensed in the crank case. Such corrosion, however, occurs only to very slight extent when the engine is hot, and is most active during the periods of idleness or “cold running.” Since in every case the data showed a decrease in iron content of the oil when the car had been standing idle, it is not probable that any appreciable amount of corrosion occurred in these tests, This was checked by examining the entire bulk of oil drained from the crank case after each run. I n no instance was more than a very small amount of water present, and it required only a drop or two of dilute alkali to neutralize any faint traces of acidity. Obviously, there was no opportunity for corrosion in the dynamometer tests. A11 the cars were equipped with air-cleaners, which, it was hoped, would remove enough of the grit from the intake air to eliminate the possibility of excessive wear coming from this source. The indications are, however, that the cleaners used were much less efficient than was claimed for them. This is shown by the fact that Run 1 on Car 4 was made prior to installation of the cleaner, Runs 2, 3, and 4 were made with the cleaner installed, and in Run 5 the cleaner was removed. There is little indication of any part played by the cleaner in reducing wear. Cars 1 and 2 were identical with the exception that new piston rings had been installed in Car 2 shortly before the tests mere begun. This is probably responsible in part for the greater wear occurring a t lower dilution than for Car 1. Inasmuch as no two engines are just alike, no comparison between different types can be made. Indeed, the wide variations between the individual runs on Car 4 indicates that variations in operating conditions have a far greater influence on wear than has dilution. The car tests may be summed up as offering no conclusive evidence of increased engine wear caused by ordinary amounts of dilution. It should be noted, however, that with increased precautions to secure correct sampling, there is a decided tendency for the car tests to show increasing wear a t the higher dilutions, The dynamometer tests were made in an effort to eliminate the errors introduced by variations in driving conditions of
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the rate of settling is undoubtedly higher a t increasing dilutions, the curves representing the correct amount of wear 2
Aulomobile Engineer, January, 1924.
the cars. I n the case of Engine 1 (Figure 3) each point represents a run of 7 hours’ duration at a constant dilution. The engine was so constructed that it was impractical to drop the crank case after each run for proper cleansing. However, it
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
was Bushed out several times with fresh oil and the washings were thoroughly mixed with the used oil before sampling for analysis. The laboratory in which the engine tests were run was remarkably clean and free from dust and dirt. These tests indicate an increased rate of wear occurring at dilutions in excess of 15 per cent. The tests on Engine 2 (Figure 4) were conducted in a manner similar t o those on Engine 1 with the exception that the crank case was removed for thorough cleansing after each run, and the tests were of 10 hours’ duration instead of 7 as in the previous runs. The first series of tests indicates a greatly increased rate of wear at about 10 per cent dilution. After this series the engine was opened up for examination, but no evidences of excessive wear were found. The engine was reassembled and a second series of runs made, with the results also indicated in Figure 4. A change was not,ed in the behavior of the engine in that its equilibrium dilution under the existing conditions increased from about 5 per cent for the first series to 9 per cent for 6he second series. The results show a marked increase in wear a t dilutions above 10 per cent. The fact that the same wear was observed a t both 20 and 30 per cent dilutions may be accounted for by the small change
in viscosity for this range.
VoI. 17, No.3 This is shown by the plot of wear
vs. viscosity in the second part of Figure 4. Conclusions
1-Road tests under ordinary conditions in which wear is estimated from oil analysis, although indicating increased wear with dilution, are inconclusive because of settling of the metallic particles. 2-Liability to increased wear caused by excessive amounts of suspended matter is considerably lessened by this settling. 3-As shown by the dynamometer tests, rate of wear increases with dilution. Furthermore, rate of wear increases much more rapidly than dilution and, above a dilution of 10 or 15 per cent, percentage increase in wear is much greater than the percentage dilution. Acknowledgment
The writer wishes to express his appreciation to C. W. Stose and E. R. Barnard, whose theses furnished the data given in this paper, to B. A. Fides and H. M. Meyers of the Institute staff for their invaluable assistance, and to the Standard Oil Company of New Jersey for their generosity in supplying the oils used in the tests.
A New Type of Silica Gel’ By Harry N. Holmes and J. Arthur Anderson OBERLIN COLLEGE,OBERLIN,OHIO
A method is described for the preparation of silica gels of different degrees of porosity. Some of the gels so prepared are much more adsorbent for certain substances than are any gels previously known. For example, addition of a dilute solution of ferric chloride to a dilute solution of sodium silicate yields a gel or gelatinous precipitate composed of a n intimate mixture (formed in the act of precipitation) of hydrated ferric oxide with hydrated silicon dioxide. Previous custom has called for washing out by-product salts while gels are rather soft. In this paper it is pointed out that is it far better to dry gels to a rigid structure before washing in order to prevent collapse of capillary walls. T o secure still greater porosity the hydrated ferric oxide is removed from the ferric oxide-silica mixture by
soaking the dried product in dilute hydrochloric acid. Soluble ferric chloride is washed out leaving a chalkwhite hydrated silica. When this is dried and activated it contains all the capillaries expected from removal of water and, in addition, a network of larger capillaries due to the removal of ferric oxide. In the preparation of such gels nickel chloride, or other salts, may be substituted for the ferric chloride. Owing to the presence of coarser capillaries a “gel from iron” was able to decolorize completely a sample of Lima crude oil, whereas ordinary silica gel could not do so. Furthermore, the “gel from iron” was decidedly more effective in removing objectionable sulfur compounds from Lima crude than was ordinary silica gel.
AN Bemmelen2 observed in 1897 that dried silicic acid improved the methods of drying silicic acid (to “activate” adsorbs various vapors and gases and even removes it), and studied its use in the separation and recovery of vasome material from solution. Marcus3records the use pors and gases. Wilson and Parsons dried and activated a of silica gel as an adsorbent in taking up undesirable constitu- precipitate of ferric hydroxide, obtaining a good adsorbent ents from gases and liquids. Patrick4and his a ~ s o c i a t e s ~ ~gel. ~~~~* Since hydrated silica and hydrated ferric oxide represented 1 Presented under the title “The Preparation of Highly Adsorbent Gels.” acids and bases, i t was thought that an intimate mixture of before Section 2-Colloids, of the Division of Physical and Inorganic Chemthe two might be interesting as an adsorbent. The writers istry a t t h e 65th Meeting of the American Chemical Society, New Haven, Conn., April 2 t o 7, 1923. Received October 23, 1924. secured this intimate mixture by adding a solution of ferric 2 Z . anorg. Chem., 13,296 (1897). chloride to a solution of sodium silicate. The gelatinous * British Patents 17,873 (August 5 , 1911); 25,220 (February 5, 1912); precipitate was probably not ferric silicate, for hydrolysis of German Patents 263,388 (June 13, 1912); 268,057 (March 26. 1912); 279,such a salt must be practically complete. An X-ray study of 075 (February 20, 1914); 283,882 (March 8, 1913); French Patent 465,569 (December 1, 1913). the dried gel9 failed to indicate any crystalline structure. 4 Inaugural Dissertation, Gottingen, 1914. This evidence, however, is not conclusive. 6 McGavack and Patrick, J . A m . Chem. Soc., 41, 946 (1920). Although this work was begun with a mixed gel of hydrated Davidheiser and Patrick, I b i d . , 44, 1 (1922). silica-hydrated ferric oxide, i t turned out to be merely the 7 Miller, Chem. Met. Eng., 23, 1155 (1920). 8 U. S. Patent 1,297,724 (March 18, 1919); 1,335,348 (March 30, 1920); introduction to an improved method of making an unusually British Patent 136,543 (December 6, 1919); 137,284 (December 24, 1919); porous silica gel.
V
159,508 (February 26, 1921); Canadian Patent 200,912 (June 15, 1920); 217,365 (March 28, 1922).
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Made by Wheeler Davey of the General Electric Company.
