2342
INDUSTRIAL AND ENGINEERING CHEMISTRY
tween two flat plates, much the same as liquid between two metal plates. This behavior which probably plays a part in the over-all adhesion adds a net resultant to the normal attraction. This behavior would exhibit poor shear resistance and in the usually practiced testing procedure would show up as poor adhesion. I t is reasonable to visualize that excessive polymerization or gelling or other phase changes from the mobile state set up competing forces whose resultant is sufficient to overcome the remaining normal attractive interfacial forces. A general picture is now being developed for all types of adhesion between the various organic systems and substrata. No effort is being made a t this writing to define the explicit physicalchemical nature of the forces that contribute t.n adhesion and its loss.
Vol. 41, No. 10
SUMMARI
This discussion has provided, by virtue of some quantitative data obtained from a new technique in measuring adhesion, an insight into the nature of adhesion. 9 simple statement is proposed on the nature of adhesion. Measured adhesion depends on the presence of a fluid, or quasi fluid, or mobile state a t or near the film-met a 1 interface. LITERATURE CITED
1) Moses, Saul, and mitt. R . K., IND,E m . CHEM.,41, 2334 (1949). K t ; a m v ~ uJuls 0, 1948. Presented before the Division of Painr, VarmaL and Plastics Chernktry at the 114th Meeting of t h e AMERICAKCnmiIr.4i 3 o r I F r I W a - h i n g t o n , D. C.
Antiknock Quality Requirements High Compression Ratio Passenger Car Engines R.
W. SCOTT,
C;. S. TOBIAS. A W
P. L. HAINE3
Standard Oil Development Company. Elizabeth, N . J .
'1'0
determine the antiknock quality requirements of high compression ratio gasoline engines, road antiknock studies employing the Borderline technique ha\ e been conducted on sixteen gasolines varying in composition, octane number, and tetraethyllead content in four cars having engines specifically designed to operate at conipression ratios of 8.0, 8.0, 10.0, and 12.5 to 1, respectively. Similar evaluations were also made in two cars of presentdaj design, one equipped with a 7.5 and the other with a 9.0 to 1 compression ratio engine head. The data indicate that the antiknock quality requirements of the engines in terms of laboratory octane numbers may be generalized as a function of compression ratio varying at sea level from 93 research octane number for 8.0 to 1 compression ratio to 102 research octane number for 12.5 to 1 compression ratio. Furthermore, in high compression ratio engines the research octane number requirement is limiting, and fuels of greater sensitivity apparently can be tolerated as compression ratio is increased.
T
HE, uw oi higher winpression ratio enginea repreaentc a basic means of obtaining improved over-all engine efficiencq in automotive equipment. However, the extent to Rhich the compression ratio of gasoline engines can be increased may be limited hy fuel antiknock quality. In the past, automotive manufacturers have progressively increased cornpression ratio as higher antiknock quality gasolines were made available. Fox example, from 1927 to 1941, the motor octane number of the average regular grade gasoline marketed in the United States increased from the vicinity of 55 to 75. During this samri period the average compression ratio of new automotive engines increased from 4.4 to 6.6 to 1. The utilization of highcr compiesjion ratios to date has been primarily to achieve increased performance, whereas improved mileage has been a somen hat less important consideration. It appears that present-day cars nou have about all the get away and top speed which the public requires or is feasible within the limits of currently designed cars and highways. For the most part then, any future increases in compression ratio will presumably be directed primarily toward an improvement in fuel economy. This seems to be highly desirable, particularly as long &s the higher antiknock qualit) gasolines required to permit this further increase in compresqion
i'itic) c u i be made available ac a price ahich will enable the cai owncar to travel more miles for his dollar. .4s cited by Ketterinp ' d ) , an improvement of as much as 40% in miles per gallon mal be realized by raising the compression ratio of an engine from 6.5 t o 12.5 to 1. It has been estimated that an improvement of only l C c in fuel economy (miles per gallon) would result in a yaving of approximately 7.0 gallons of gasoline annually per passenger car, since the average car cowumes 714 gallons of gasolinc in traveling about 10,000 miles per year a t 14.0 mile5 per gallon. Thus, on a nationwide basis with 31,000,000 passenger cars in use, a 1% saving in fuel would reduce gasoline COII.umption by 217,000,000 gallons per year and would result in H saving of about $49,000,000 per year in gasoline cost to the public n-suming a retail price of 22.5 cents per gallon for gasoline. To determine the fuel antiknock quality which will be required by high compression ratio passenger car engines, sixteen expeririiental fuels were evaluated at the General Motors proving ground in four General Motors cars specifically designed to operate a t high compression ratio. These tests were made in cooperation with the Research Laboratories Division of General Uotors Corporation who performed the road antiknock evalualion3 of these fuels in the four cars. In addition, these sanie fuels c're evaluated in the Elizabeth, K.J., area by the Standard Oil Dr-velopment Company in two cars of present-day design hut rquipprd n i t h high compre-sion ratio engine cylinder head5
DESCRIPTION OF FUELS, C4KS, i Y D rES'I METHOD5
I'hr histpen evperimental fuels evaluated for antiknock perrorniancix in the six cars were of varying composition, laboraton octane number and, to some extent, tetraethyllead conteni Pertinent laboratory inspection data on these fuels, which art designated by the numbers 1 through 16, are presented in Table I. The antiknock quality of the fuels studied covered a range o? roughly 79 to 102 by the motor method and of 90 to 100 by the research method. Fuels 1 through 6 were pure hydrocarbon blends, whereas the remaining 10 fuels were high octane number gasolines representative of possible future rommercid production Qr products of typical refinery processes. Four of the six cars employed were powered by engines specifically designed to operate a t high compression ratio. These arc designated as cars A, B, C, and D with compression ratios of 8.0, 8.0, 10.0, and 12.5 to 1, respectively. The additional cars designated as E and F, were of present-day design equipped. respectively, with a 7.5 and 9.0 to 1 compression ratio engine wljnrlrr hi3ad. Thp distributor spark advance with increasing
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1949
T4BLE
INSPECTIONS I. LABORATORY 3
2
I
Fuel No. Octane No. Motor method CFR-research Sensitivity
ON M O T O R
4
2343
FUELS TESTED I 3 HIGHCOMPRESSIOS R.4TIO ENGINES 6
7
x
4
10
101.7
84.2 13.8
87 5 95.5 8 0
83.0 95.5 12.5
79.0
98.0
5
12
13
82.7 98.4
7Y.W 90.0
11.0
s3.7 94.4 10.7
88.5
15.7
100 0 11.5
87 I 100 4 13 3
11
15
14
85.5 98.8 13.3
91.3 100,o 8.7
87.5 92.2 9 9 . 1 99 2 11.6 7.0
87.9 99.3 11.4
97.5 -4.2
TEL, ml./gallon
Si1 50,o
Si1 19.6
Si1 Nil
Si1 Si1
Yil Xi1
3.0 Nil
3.0 39.6
3 1 25.3
3.1 91,s
Nil 2.2
Si1 103.1
0.4 89.8
2.9 35 4
1.5 38.5
2 5
Bromine S o . (cg. Hr: 1011 m1.i
Estimated YColefins Estimated % aromatics
50 0
20 0
0
0
0 0
52
!0 .I
61
100 0
31
IS
23 9
0
a0
0 83
13
32 13
35 13
36 20
Reid vapor pressure. Ib z q . in. A.S.T.11. Distillation. F. Temp. for 107, evaporation Temp. for 5 0 r r fLvaporation Temp. for SOL, *-vaporation
1.9
1.F.
1.3
I .i
11.6
1.2
6.0
$.ti
4.8
0.9
4.3
9.0
9.Q
9.7
6 6
210 211 212
210 210 210
'19 223 226
11Cl
275
146 208
174 116 257
156 219 333
245
194
317 323
207 207 208
133 199
13'2 201 289
131 232 358
2 16
4.S.T.X.I. breakdown,.minutes General Motor. gum 1 me. '1 no ml.)
14401
14401-
306
1440+
a4
14401-
194
180
301
1440t
195
1 .s
1.3
1.9
0.3
11.40.2
6.3
I 5
0.2
5 6
3.tt
2 0
Gravits--. ' .1,P.I.
68.6
70.5
36,9 57.k
43.9
58.i
ti5A
60.Y
41 3
162 ,,?I
60 1
sn
212 214
71.i
engiiit speed ustd uii all of the cars &-as normal i n that relationb between spark advance, engine speed, maximum torque, and maximum power conformed to current automotive practices. Currently tTvo common laboratory methods are in use for evaluating the antiknock performance of motor gasolinesnamely, the research and motor methods. -1cornparkon of the pertinent conditions employed in these procedures is summarized in Table 11, whereas a drfailed descripriori of thP two methods may be found in ( 1 ) . Table I1 shoT$s that the research octane number rating is obtained under what, are generally- considered as relatively mild opwating conditions- namrlv. a mixture trmperature of about
296
91 3 12.3
276
315
229 331
291
40 !I
140 306 990
100* F,a1 600 engine r.p.ni, nith a hxed ,park advance oi 18The motor method octane number, which is determined untlpi more severe conditions involving a mivture temperaturr of 300" F. at 900 engine r.p.m. is usually numerically lower than the corresponding research octant, numher obtained on the same fuP1
The spiead between the reararch and mol or octane numbers which may exist is illustrated in Table I11 for several gasoline stocks made by representative current refinery procesws Throughout this paper the term "-r.nsitiritv' will be used t o dc-
96 94
92 90 88 66 84
82
Ia
EP
LIBOllilTOR"
76-
'\
Tit,
ON
78-
nnrwc*au& FUEL12 F J E L 13
*>
7 9 0 0 4 L .
900 94.4
a'
'
e.9
I
E N G INE SPEED - R PVi
Figure 2.
Fuel Antiknock Performance and Car Octane Requirement
Car B, 8 : l compression ratio: Detroit area
11s0'0.9scTEL.)
109
150+0.3ss.TEL.)
102
I ~
4
I
I
100 98 96
94
ecI
I
acc
1200
16w
zoco
ENGIkE SPEE?
Figure 3.
2400
2am
1 3200
- RPM
Fuel Antiknock Performance and Car Octane Requirement
Car C. 1O:l cornpression ratio: Detroit area
ENGINE S P E E C - R P M
Figure 4.
Fuel Antiknock Performance and Car Octant. Requirement Car D. 12.5:l comprcr-inn area: Detroit area
2344
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 10
ciote the diffprence between the research rating and the motor Air method rating of a fuel. Mixture bngine Spark I n general, the paraffin typr Temp.. Speed. Setting Compresaion Referenrc Method Ensne OF. R.P.N. RTnCa Ratio Fuelh y d r o c a r b o n s whihit little Research Single cylinder l O O b Constant a t 600 Constant a t 13 sensitivity, with Talues rangMotor Single cylinder 300 Constant a t 900 l - a r i e d , with rom- 1 Varied t o obtain Secondary, [calipression ratio r denired knock brated in terilip ing from 0 t o about 3 units f r o m 1:J t o 26 intensity of primary cvhile the aromatic and olefinic standards) * Before top dead center. type hydrocarbons have scnsi, ? Temperatures not controlled, agurouimate. tivities ranging from about 12 to 16 units. The naphthenir T.4BLE 111. UNLEADEDLABORATORY OCTANE R 1 T I S G S OF hydrocarbons are generally oi REPRESENTATIVE REFINERY STOCKS intcrniediate sensitivit>-. The trend toward the pioductior~ Sensitivity, Research Motor Research 0.S. of motor gasolines of higher sensitivity as the general octant Stock 0.x. 0,s. 3Iinus Motor O.N. number level is increased is illustrated by comparing thr Straight-run naphtha 69 66 3 antiknock quality of housi~hrandgasolines marketed in 1'339 Thermal naphtha 83 73 10 Catalytically cracked n a p h t h r 95 81 14 with those niarketed in 1948. During this period the research Polymer 97 83 14 Aviation alkylate 95 92 3 oct,ane number increas:d from about 78 to 85, while the sensiiivity increased from 6 to 8 units. Furthermoro, i r i 1048 tlit companion preiiiium grad( gasoline of 90 icseaich octane number shoiwd a sensitivity of about 10 units. It is cxpccted that this trend toxvvard incrcasing sensitivity n i t h increasing octane number level will continue, berause c a t a l v t i c cracking and polymerization, hotli of which producc. fuels of high sensitivity, !\ill probably be employed to an increasing degree in the production of high ocatanp quality motor gasolincas. Fuel a n t i k n o c k performance a n d engine 32 octane rcquirementb \\ere obtained on the road over the speed range fromabout Figure 7. Relation between Research Oc800 to 3000 r.p.m. by a tane Number and Low Speed Road hntiBorderline type of test knock Performance .I completc description of Car C, 1 0 : l compresnion ratio: speed 1601) r.p.m. the Bordcrlinc tctcr m-ocedure may hc found in ( 2 ) . The advantage of the Borderline method ovvr other conventional road test mcxrhodh is ilSOt0 3 cc T E L I that the octane rating of a fuel and engine octane requirtlmcnt can be established over the entire speed range. I n this type of test the colirentional automatic spark advaiici niechanisiii is rendered iiiopi~rativi and the spark setting ih controlled manilally by the test car operator. Deteriiiinations are msdc tluriiig a full Throttle level road acct~1c~r:~tior~ over the speed range previo\id:, i r i dicated. I n the cssc of CRTS A , 13. C'. n i i d D, a constant Icnork iiitoiiait>1 of trace knock TVRS niniiitairirtl I t h r o u g h o u t t h e accc,l(-ratioti by I I 86 90 94 I I I niariually maneuvering the igni503 IO00 I500 ZOOC 2500 L ~ B O R ~ T O RUOTOR V METHOD O C T 4 h t NUURER tion timiiig. A variation of this ENGIhE S"EED - R P M Figure 8. Relation hetween llIotor technique was used with cars E 3Iethod Octane Number and High Speed Figure 6. Fuel Antiknock Performand F: n-ith repeated accelerations Road Antiknock Performance ance and Car Octane Requirement a wrirx of knock-dir-out, spced9 Car C, 10: 1 rornpresdon ratio; speed 2800 r.p.m. C a r F, 9.0:l compression ratio; sea level
TABLE 11. PERTINEST TESTCOSDITIOSS OF RE=.E~RCH AXD XOTOR METHODS
"r-----
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1949
TABLEIv.
quirenients of both 8 to 1 compression ratio cars, A and B, but failed to do so a t lolv speed, being deficient by about 1 octane number for the Detroit area. The addition of 2.5 ml. of tetraethyllead per gallon to fuel 12 improved the laboratory antiknock performance of this fuel by 4 to 5 octane numbers, as may be seen bi- comparing fuels 12 and 13 in Table I. Figures 1 and 2 show also that a similar improvement in the road antiknock rating waF effected by the addition of lead to fuel 12 so that fuel 13 was mow than satisfactory in both of these cars throughout the speed range The 10 to 1 compression ratio car, C, was satisfied complrt,ely h!fuels 14 and 15 as shon-n in Figure 3. These fuels had research
OCTASE r T l I B E R CORRECTIOS FOR ELEV.4TION
Research Octane S u m b e r Level
Porrection t o Sea Level i r o m Detroit Area
100 90
+l.0 +2.0
80
+3.0
2345
various ignition settings were obtained over the speed range. I n either case, a relation between ignition timing and rngine speed necessary to maintain trace knock intensity is es
