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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

TECHNICAL NOTE

C'. I. -T \4, v'-1 ' V( %sls No. 1619 O _o -T, <'

AN EVALUATION OF PROPOSED REFERENCE FUEL 1

SCALES FOR KNOCK RATING

By Henry C. Barnett and Thomas C. Clarke

Flight Propulsion Research Laboratory Cleveland, Ohio

Washington July 1948 NATIONAL ADVISORY CO11MITTEE OR AERONAuTICS

TEI1ICAL NOTE NO. 1619

A1 EVAIAJATION OF PROPOSED REFERCE FrThffJ

SCALES FOR KNOCK RATING

By Henry C. Barnett and Thomas C. Clarke

Proposed reference-fuel scales for measuring th knocking tendencies of aviation fuels were investigated to ascertain possible limitations from consideration of sensitivity to changes of engine operating conditions and consideration of the range of knock- limited performance by which the propoeed scales would extend current rating scales. The investigation was conducted entirely in F-3 and F-4 aviation fuel-rating engines.

It is concluded that the proposed reference-fuel combinations are comparable in temperature sensitivity with typical aviation fuel blends and will extend the range of knock-limited performance of current rating scales by an appreciable amount when used with satisfactory rating engines. On the other hand, difficulties with the occurrence of preiit1on in the F-4 engine and the severity of operating conditions in the F-3 engine indicate that these two engines in present form and under present specified operating conditions are lnadequate for rating aviation fuels having performance numbers in excess of 161.

I1'ITROIXJOTION

For many years the efforts of investigators In the field of fuel research have been directed toward the development of suitable scales for measuring the 1nockIng characteristics of fuels. As a result of these efforts, a number of scales have been studied, but only a few have passed beyond the stage of tentative acceptance. The emphasis in this development has generally been placed upon one objective - that the method permit the assignment of a numerical antiknock value to each fuel and that the rating so determined be reasonably constant regardless of the engine or operating condition used.

The achievement of this objective has been hindered because the many fuels suitable for aviation use vary widely In their 2 NACATNNo. 1619 response to changes in engine conditions and also because the rating scales currently used are unsatisfactory for rating fuels in the high performance range. As a result of these difficulties, attention has been turned in recent years to the problem of establishing a rating scale that will permit determination of ratings for high- performance fuels. An effort has been made in these studies to select reference fuels that will respond to changes in engine conditions in a manner similar to that of service fuels.

On the basis of studies made by the Coordinating Research Council (reference 1), it has been proposed that triptane (2,2,3-triniethylbutane) and n-heptane be adopted as the reference fuels for a new rating scale. Both fuels would contain 3.78 ml TEL per gallon. The studies on which this proposal was based were conducted in F-3 and F-4 fuel rating engines at standard operating conditions. In order to extend the data of the Coordinating Research Council beyond the standard operating conditions used, an investigation of the proposed rating scale over a range of engine conditions was conducted at the NACA Cleve]1and laboratory. The results are compared with those obtained for current rating scales and other proposed scales.

In the NACA investigation reported, the effects of varying engine conditions were simulated by varying inlet-air temperature from 100° to 300° F in the F-4 engine. The combinations of reference fuels investigated were:

(1) Isooctane and n-heptane

(2) Isooctane and tetraethyl lead (0 to 6 mi/gal)

(3) Isooctane.and n-heptane (both containing 3.78 ml. TEL/gal)

(4) Triptane end n-heptane (both containing 3.78 ml TEL/gal)

(5) Triptane and isooctane (both containing 3.78 ml TEL/gal)

In addition to the presentation and discussion of results obtained, a brief history of rating-scale development is included as an indication of the limitations of these scales. A more detailed history is presented in reference 1.

DEVELOPMENT OF Fu:EL-RATING. SCALES

Octane scale. - One of the earliest and the most enduring knock-rating scales Is the familiar octane-number scale proposed NACA TN No. 1619 3

by Edgar in 1927 (reference 2). ThIs scale Is based on two reference fuels, Isooctane (2,2,4-trlmethylpentane) and n-heptane, suggested by Edgar because isooctane knocked less and n-heptane more than any fuels then known. In this system, Isooctane is arbitrarily assigned a rating (octane number) of 100 and n-heptane, a rating of 0. The characteristic shape of curves representing the octane scale Is shown in figure 1 fran data obtained in the F-4 engine;

It can be seen that the octane scale is restricted to the determination of ratings for fuels producing knock-limited power equal to or less than that of isooctane and equal to or greater than that of n-heptane. At the lower end of the scale, the limitation offers no serious obstacle because Interest In fuels with greater knocking tendencies than n-heptane is purely academic. On the other hand, the upper or isooctane end of the scale offers a very serious obstacle inasmuch as many pure hydrocarbons and. commercial blending stocks are known to exceed the knock-limited power output of Isooctane.

In addition to being limited in use to fuels having antiknock values between those of n-heptane and isooctane, the octane scale fails to provide numerical ratings that remain constant from engine to engine or f ran one condition to another. That is, a fuel having an octane number of 80 in one engine may have an octane number of 90 in another engine. Investigation has shown (reference 3), however, that the ratings of paraffinic fuels, with the exception of certain highly branched isomers, tend to remain more nearly constant from engine to engine than do widely different types of hydrocarbons within the range of performance covered by the octane scale. This fact can be attributed to the differences in sensitivities of various fuels to changes of operating conditions. Inasmuch as the rating fuels (Isooctane and. n-heptane) are paraffinic, it would be expected that these fuels would respond to changes in operating conditions in much the same manner as a paraffinic test fuel. If, on the other hand, the test fuel contains large concentrations of aromatic, cycloparaffinic, or olefinic compounds, the response to variations in operating conditions would differ greatly from the behavior of the parat'finic rating fuels.

Lead scale. - When fuels with knock ratings that exceeded the upper limit of the octane scale began to appear in service, it became apparent that the octane scale was no longer adequate for rating aviation fuels; consequently, the search began for a performance scale that would accommodate the high-performance fuels used in modern 4 NACA TN No. 1619

aircraft power plants. In order to meet this problem, it was decided that fuels exceeding the performance of isooctane should be matched against isooctane to which had been added a given amount of tetraethyl lead. (See fig. 2.) The procedure for rating fuels by the lead scale is the same as that used for the octane scale; that is, the knock intensity of the test fuel is determined in a standard engine at standard conditions and the knocking tendencies of blends of isooctane and tetraethyl lead are compared with those of the test fuel until one blend Is found to give a knock intensity equal to that of the test fuel.

Performance-number scale. - Neither the octane scale nor the lead scale permitted the assignment of a numerical rating indicative of the power output of a fuel, and in an effort to circumvent this difficulty a scale of performance numbers was adopted. The performance scale (fig. 3) represents an approximate average of the knock-limited performance as determined In several different engines at different operating conditions for isooctane containing various amounts of tetraethyl lead. Although empirically determined, this scale has proved useful in expressing fuel ratings and. in correlating performance of fuels in different engines but still doeà not provide an absolute measure of power output.

The performance-number scale does not alter the procedure for rating fuels by use of leaded isooctane (lead scale) but does change the method of reporting the rating. For example, if a test fuel is found to give performance equal to isooctane plus 2.0 in]. TEL per gallon, its rating is reported as 138 performance number. (See fig. 3.)

The performance scale as originally adopted was intended for use only with fuels having ratings above an octane number of L00 by the F-4 method. General acceptance of the scale soon led to expression of F-3 ratings by the same method and later resulted in extension of the scale below a performance number of 100.

Proposed rating scales. - One limitation of the octane scale and the lead scale Is the fact that the service fuels containing an approximately constant amount of tetraethyl lead (3.0 to 4.6 ml/gal) must be matched against unleaded rating fuels or against rating fuels having variable concentrations of lead. This limitation is inherently related to the problem of fuel sensitivity to changes in operating conditions in that tetraethyl lead affects the sensitivity of the fuel to which it is added.

In order to minimize this effect on fuel ratings, investigators in the field have proposed rating sca1e in which the reference fuels

NACA TN No. 1619 5 contain a constant amount of tetraethyl lead in the range of concentrations found in service fuels. Some of these schemes recommend the addition of a third component in the reference fuel blend, such as an aromatic, to produce reference fuels having sensitivities more nearly equal to service fuels.

Reference fuels. - Three reference fuels were used in setting up the Inock-rating scales examined in this investigation: namely, triptane, isboctane (primary), and n-heptane (primary). The inspection properties of the triptane used are presented in table I.

Service fuels. - The following service and service-type fuels were included in this investigation as a means of comparing the merits of the several rating scales:

Nominal performance Fuel grade F-3/F-4

AN-F-26 76/88 AN-F-28 (28-R) 100/130 Special blend number 1 (SB-l) (23 percent benzene 100/140 + 34 percent virgin base stock + 43 percent alkylate + 4 ml TEL/gal) AN-F-33 33-R) 115/145 Special blend number 2 (B-2) (43 percent diisopropyl 120/150 + 12 percent virgin base stock + 45 percent alkylate + 4 ml TEL/gal) Special blend number 3 (SB-3) (34 percent diisopropyl 130/160 + 12.5 percent hot-acid octane -i- 41.5 percent alkylate + 12 percent isopentane + 4 ml TEL/gal) Special blend number 4 (SB-4) (55 percent diisopropyl 135/175 + 8 percent triptane + 29 percent alkylate + 8 percent isopentane + 4 ml TEL/gal) Special blend number 5 (SB-5) (62 percent diisopropyl 140/200 + 19 percent triptane + 11 percent alkylate + 8 percent isopentane + 4 ml TEL/gal) RAFD-52 (45 percent S reference fuel + 45 percent 146/175 dilsopropyl + 10 percent isopentane + 4.6 ml TEL/gal)

RAFD-53 (45 percent S reference fuel + 45 percent 153/192 triptane + 10 percent isopentane + 4.6 ml TEL/gal) ______

6 NACA TN No. 1619

In choosing these particular fuels and blends, an effort was made to cover a wide range of performance numbers both rich and lean. Inspection properties for the foregoing fuels are presented in table II.

APPARATUS AND PROCEDURE

The experimental portion of this investigation was conducted in the F-3 (CRC F-3-544; ASThI D 614) and F-4 (CRC P-4-443) rating engines. The F-3 engine was provided with a barometrically controlled dry-air supply instead of a dehydrating ice tower. The F-4 engine was equipped with a lO6360D piston instead of the standard 1O636OG piston.

In the selection of the correct knock intensity by the F-4 method, audible knocking was accepted as the criterion. The degree of audibility was such that the operator could reproduce the point of knock with reasonable accuracy.

Complete mixture-response curves were obtained for . all reference fuels and service-type blends at inlet-air temperatures of 1000, 1500, 225°, 2500, and 3QQO F in the F-4 engine. All other operating conditions were standard. Tests in the F-3 engine were made at standard conditions.

In order to check the reproducibility of data obtained in the F-4 engine, unleaded S reference fuel was run frequently throughout the investigation at standard conditions.

PRESTATI0N OF DATA

Reproducibility of thet data. - During the 7 months devoted to thi5 investigation, the knock-limited performance of unleaded S reference fuel was determined 27 times in the F-4 engine at standard operating conditions in order to obtain an indication of the reproducibility of the data. The spread in knock-limited indicated mean effective pressures occurring in these tests is shown by the broken lines in figure 4.

For comparison the solid curve representing S reference fuel from the standard F-4 reference fuel framework is included. The deviation of the lower limit of spread from the standard curve is as great as 15 pounds per square Inch at fuel-air ratios of 0.09 and 0.10; however, the exclusion of one of the 27 runs on S reference fuel would move the lower limit upward by 4 to 6 pounds per square inch at fuel-air ratios between 0.085 and 0.112.

NACA TN No. 1619 7

F-4 engine data. - Where possible, complete Imock-limited mixture-response curves were obtaihed in the F-4 engine; however, the analysis of results presented IS restricted to two fuel-air ratios, 0.065 and 0.11. Data at these two fuel-air ratios and different inlet-air temperatures for the five reference-fuel combinations listed in the II'TR0DUCTI0N are presented in fIgures 5 to 9. The points on the curves in these figures are cross-plotted from mixture-response curves and are shown merely as an indication of the reliability of the data.

The data In figure 6(a) for inlet-air temperatures of 225°, 250°, and 300° F are incomplete, which is also true of the data at 2500 F in fIgure 6(b). These omissions occurred because incomplete mixture-response curves were obtained In a few cases. Reruns were not made because it Is believed that the omissions have a negligible effect on the value of this analysis. The data in figures 8 and 9 are also incomplete for reasons that will be sub- sequently given.

From figures 5 to 9 points were taken from the faired curves and replotted as shown In figures 10 to 14 for convenience in assiguing ratings to service-type fuels.

F-3 engine data. - Ratings made by the F-3 method for various reference-fuel blends are presented In table III.

DISCuSSION OF RESULTS

Cnparisons among various reference scales. - In figure 15, the various reference scales are cnpared at standard F-3 and. F-4 operating conditIons. It is seen in fIgure 15(a) that for F-3 conditions the data for leaded blends of isooctane and. n-heptane fall on a 45-degree line Indicating that the F-3 rating of Iaoocbane containing 3.78 ml TFI per gallon Is equal to that of triptane containing the same quantity of tetraethyl lead. On the other hand, data at F-4 (rich) conditions (fig. 15(b)) show that for equal knock-limited Indicated mean effective pressures more isooctane is required than triptane In leaded blends with n-heptane. Fig- ure 15(b) indicated that between 80 and 84 percent triptane in a blend vith n-heptane (leaded) would be required to equal the upper limit (161) of the current performance scale. 8 NACA TN No. 1619

An additional observation can be made from figure 15; namely that for F-3 conditions the two-component reference-fuel systems with constant tetraethyl-lead concentrations are related by straight lines, whereas at F-4 conditions definite curvature Is obtained.

Unpublished data from the Coordinating Research Council were compared with the NACA data In figure 15 and. the agreement was found to be quite good.

Temperature sensitivity of reference fuels. - As a measure of the temperature sensitivity of the reference-fuel combinations, the slopes of the curves shown in figures 5, 6, 7, 8, and 9 were computed. at an inlet-air temperature of 225° F (standard F-4 conditions) and plotted against the knock-limited indicated mean effective pressures at the same temperature. These plots were made for fuel-air ratios of 0.065 and 0.11 nd are shown in figure 16. A single curve was drawn through each set of points (lean and rich) to Illustrate the variation of temperature sensitivity with knock-limited performance for the various reference-fuel blends • The different portions of the curve determined by individual reference-fuel combinations are also indicated on this figure.

It Is seen in figure 16 that above the upper limit of the current performance-number scale the sensitivity Increase s rapidly as the knock-limited Indicated mean effective pressure Increases. If this trend is generally true for service-type fuels, then It Is apparent from figure 16 that such fuels having high knock limits should be matched against leaded blends of triptane and Isooctane or triptane and n-heptane in order to have reference fuels and service fuels of comparable sensitivity. For lower performance fuels, however, any of the reference scales Indicated would be suitable from sensitivity considerations.

Temperature sensitivity of service-type fuels. - The effects of Inlet-air temperature on the knock-limited performance of 10 service- type fuels were investigated in the F-4 engine. The results are presented in figure 17. In order to compare the temperature sensitivities for the service-type fuels with the sensitivities of the reference fuels, the slopes of the curves (at 225'-' F) were determined from figure 17 and plotted as shown in figure 18. On this sane figure the curves from figure 16 were reproduced.

It is seen In fIgure 18 that the points representing service fuels lie primarily above the curves established for the reference fuels. This divergence Is attributed to the fact that the service fuels are blends containing a number of different components; whereas the reference-fuel blends are composed of only two components. Insofar as a perfect rating scale Is concerned, the ideal condition would be for the service-fuel data to fall directly on the reference-fuel curve.

NACA TN No. 1619 9

Because this situation is Improbable, the next best solution must be for reference-fuel blends and service fuels to have sensitivities of approximately the same magnitude at the seine knock- limited performance levels. The attainment of this characteristic can be approached by the use of either the joint reference scale, leaded triptane-isooctane and leaded isooctane - n-heptane, or by the leaded trlpta.ne - n-heptane scale (f 1g. 18).

In evaluating the merits of a rating scale, however, three factors other than temperature sensitivity must be considered, namely, that the scale

(1) should be a continuous scale

(2) should involve a minimum number of reference fuels

(3) should cover the complete range of knock-limited performance likely to be encountered with a variety of service fuels

In fIgures 16 and 18, it has been shown that both the leaded triptane - n-heptane scale and the joint scale of leaded Isooctane - n-heptane and leaded triptane-isooctane have the last of these characteristics. Only the leaded triptane - n-heptane scale, however, possesses the first two characteristics as vell consequently, this scale appears to be the most practical choice. The problem of availability of reference fuels is obviously important but is beyond the scope of this investigation.

Ratings of service-type fuels. - The 10 service-type fuels were assigned ratings in terms of the five reference scales examined in this investigation. These ratings are given In table IV for standard F-3 conditions and for F-4 conditions at five inlet-air temperatures and two fuel-air ratios. Figures 10 to 14 were used for assignment of the F-4 ratings.

The ratings in table IV were made for the purpose of comparing the constancy of the assigned ratings over a range of conditions established by varying inlet-air temperature. This comparison is presented in figures 19 and 20. On the ordinates of the (b) parts of these figures the scales are discontinuous. This arrangement was chosen inasmuch as the leaded isooctane - n-heptane scale and the leaded triptane-isooctane scales are 'considered for joint use. The broken-line portions of curves in figures 19(b) and 20(b) indicate that such fuels would be matched against different pairs of reference fuels depending upon the operating conditions.

Figures 19 and 20 are included merely to illustrate the constancy of numerical ratings and cannot alone serve as a basis

10 NACA TN No. 1619 for choosing the best reference scale. This statement is based on the fact that the constancy of an assigned rating from one set of operating conditions to another is largely dependent upon the relative sensitivities of reference fuels and test fuels previously discussed.

Limitations of reference scales. - In the preceding discussion, it has been stated that in many cases knock-limited indicated mean effective pressures were not obtained for some of the higher- performance service-type and reference fuels Investigated In the F-4 engine. The attainment of complete data for high-performance fuels was hampered throughout the investigation by the tendency of these fuels to preignite In the F-4 engine. The engine operator at all times obtained as much of the mixture-response curve as possible before the start of preigultIon; however, for some fuels points richer than about 0.08 fuel-air ratio could not be taken. Inasmuch as the peaks. of the curves were not obtained, ratings could not be made in the fuel-air-ratio range characteristic of the standard F-4 rating method.

Prelguition occurred with the high-performance fuels regardless of the condition of the engine and changing the type of spark plug failed to prevent preignitlon.

Preignition was encountered so frequently that earlier unpublished data obtained at this laboratory were examined in order to define the range of Indicated mean effective 'pressure in which preignition is likely to occur in the F-4 engine. The results of this study are presented In figure 21 together with data from the present investigation. Each point on this plot represents the richest point of a mixture-response curve that could be obtained before the occurrence of preignition. It is seen in this figure that with several fuels it was possible to reach preigultion-free performance at Indicated mean effective pressures greater than 400 pounds per square inch; however, a number of fuels preignited at levels below 400 down to about 258 pounds per square inch. In moet cases, the limiting fuel-air ratios were leaner than the fuel- air ratio range in which F-4 ratings are usually made.

Inasmuch as preignition imposes a very real limit on an F-4 rating scale at a rich fuel-air ratio, the maximum Indicated mean effective pressures that can be obtained with current and proposed reference scales are indicated in figure 21. The difference between scales is about 75 pounds per square inch indicated mean effective pressure, thus the adoption of either reference scale utilizing triptane as one of the components will extend the range In which "direct match" ratings can be made by about 75 pounds per square inch. Even then there will be some fuels (as Indicated by preignition test points in fIg. 21) that cannot be rated in this NACA TN No. 1619 11 range. in fact only three of the five service-type fuels exceeding a performance number of 161 could be rated in the present investigation (shown as solid lines between fuel-air ratios of 0.10 and 0.12 in fIgure 21.) The remaining two fuels having performance numbers over 161 preignited at fuel-air ratios leaner than 0.08. (Indicated on fIg. 21 by El).

CONCLUSIONS

Considering the general implications of the investigation reported herein, it is clear than if F-3 and F-4 engines are to be used as the standard fuel-rating engines, the advantages to be gained by the adoption of new reference-fuel systems utilizing triptane are questionable. It has been shown that the present scale of performance numbers will permit ratings for fuels up to a performance number of 161 in the F-3 engine and that triptane plus 3.78 ml TEL per gallon, which represents the maximum performance of either of the proposed reference-fuel combinations, will permit ratings only up to a performance number of 151. Moreover, in the F-4 engine the tendencies of many high-performance service-type fuels and high- performance reference-fuel blends to prelgnite makes the advantage of extending the range in which ratings can be made in this engine somewhat uncertain.

If, however, it is assumed that new rating engines will be developed in the future to replace the F-3 and F-4 engines, the conclusions in this study may be reduced to pure considerations of the reference fuels. On this basis, the following conclusions are drawn and these conclusions are nceasari1y confined to the conditions used in this investigation:

1. At rich mixtures (F-4 method) the use of the leaded triptane - n-heptane scale or the joint scale, leaded triptane- isooctane and leaded isooctane — n-heptane, will extend the range of performance in which ratings can be made by an indeterminate amount over the range of the current scale of performance numbers.

2. At lean mixtures (F-3 method), the evidence obtained in this investigation indicates that the proposed reference scales would reduce the range of performance that can now be measured on the scale of performance numbers.

3. Either the joint reference scale,' leaded triptane- isooctane and leaded isooctane n-heptane, or the leaded

12 NACA TN No. 1619 triptane - n-beptane scale is satisfactor' from considerations of sensitivity to changes of operating conditions and considerations of the range of knock-limited indicated mean effective pressures to be measured. The leaded triptane - n-heptane scale, however, is more desirable because only two reference fue's are involved and the scale itself is continuous.

Fligit Propulsion Research Laboratory, National Advisory Committee for Aeronautics, Cleveland, Ohio, December 5, 1947.

R.IENCES

1. brooks, Donald B.: Development of Reference Fuel Scales for Knock Rating. SAE Jour. (Trans.), vol. 54, no. 8, Aug. 1946, pp. 394-402.

2. Edgar, Graham: Measurement of Knock Characteristics of Gasoline in Terms of a Standard Fuel. md. and Eng. Chem., vol. 19, no. 1, Jan. 1927, pp. 145-146.

3. Wear, Jerrold D., and Sanders, Newell D.: Experimental Studies of Knock-Limited Blending Characteristics of Aviation Fuels. II - Investigation of Leaded Paraffinic Fuels in an. Air-Cooled Cylinder. NACA TN No. 1374, 1947. NACA TN No. 1619 13

TABLE I - INSPECTION DATA FOR TPIPTANE (2,2, 3-TRIMETHYLBtJTANE)

A.S.T.M. distillation Initial boiling point, °F ...... 172 10 percent evaporated, °F ...... 174 40 percent evaporated, °F ...... 174 50 percent evaporated, °F ...... 174 90 percent evaporated, °F ...... 175 Endpolnt,°F ...... 180 Residue,percent ...... 0.4 Loss,percent ...... 0.6 Copperdishgum, (mg/lOOm].) ...... 1.0 Reid vapor pressure, (lb/sq. in.) ...... 3.0 Freezingpolnt,(°F) ...... -18 Hydrogen-carbon ratio ...... 0.191 Net heat of combustion, (Btu/lb) ...... 19,200 680 1.3896 Refractive index, D' at F ......

14 NACA TN No. 1619

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NACA TN No. 1619 15

TP1BLE III - F-3 RATINGS FOR H RCE-JXL BLFIDS

Composition, percent by volume F-3 Rating ______(a) ______n-Heptane Isooctane Triptane Octane number or Performance isooctane + TEL number 100 0 47 80 20 60 60 40 76.3 54 40 60 85.3 65.5 20 80 .14. 105 0 100 3.78 151.3 80 20 4.0 152.5 60 40 4.0 152.5 40 60 4.0 152.5 20 80 4.4 154.5 o 100 3.6 150.5 80 -20 62 • 60 40 76.8 54.5 40 -60 90.8 • 75.3 20 80 .85 123 aAll blends contained 3.78 ml TEL/gal. 16 NACA TN No. 1619

TABLE IV - F-3 AND F-4 RATINGS OF SERViCE AND SERVICE- Fuel designation Rating F-3 F-4 rating at fuel- F-4 rating at fuel- and nominal scale rating air ratio of 0.065 air ratio of 0.11 grade (a) (b) (c) (c) tr &t -air jperaturj 1000 1500 225° 250° 3000 1000 i 225° 3000 AN-F-26 Imep -134 114 94 88 79 159 163 156 152 145 (76/88) ON 91 95 94 95 95 97 97 98 98 98 98 PN 76 85 82 85 85 90 90 93 93 93 93 LIH 60 72 69 64 61 55 77 80 80 80 78 LTH 60 60 58 56 55 53 65 66 66 66 65 LTI AN-F-28 Imep --180 154 121 111 92 216 214 202 195 180 (100/130) ON ------P11 101 112 110 110 110 109 125 130 127 125 119 LIB 72 86 84 81 78 68 92 93 93 92 89 LTH 72 72 '7]. 68 67 62 75 76 75 75 73 LTI

SB-i Imep -184 148 104 95 83 231 225 212 207 193 (100/140) ON 99.3 -99 99 100 P11 98 114 107 97 97 100 154 136 134 135 128 LIII 71 87 83 72. 67 59 95 95 95 95 95 LTH 71 73 69 61 59 56 '78 78 77 77 75 LTI AN-F-33 Ime--229 178 137 126 107 ---- 229 222 218 205 (115/145) ON PN 115 138 126 120 121 122 ---- 138 140 140 137 LIII 77 95 91 89 87 81 ---- 96 97 97 95 LTH 77 80 76 75 72 70 ---- 79 79 78 77 LTI SB-2 Inie--277 212 145 131 109 260 257 249 244 23]. (120/150) ON P11 121 157 148 125 125 124 148 152 155 155 152 LIH 79 ---- 99 91. 89 83 99 LTH 79 -75 74 70 LTI 7 ----- 2 5 5 1 ai 0 , knock-limited indicated mean effective pressure; ON, octane number; P11, performance number; Liii, blend of isooctane and n-heptane containing 3.78 ml TEL/gal; LTH, blend of triptane and n-heptane containing 3.78 ml TEL/gal; LTI, blend of triptane and isooctane containIng 3.78 ml TEL/gal. bOctane numbers and performance numbers obtained by the standard F-3 rating procedure. Ratings in terms of other scales estimated from figure 15(a). °Knock-limited imep obtained from faired curves in figure 17. Ratings made from figures 10 to 14.

LI N AC A TN No. 1619 I 7

.s V

TYPE FUELS IN TERMS OF SEVERAL REFERENCE-FUEL COMBINATIONS uel desiiation Rating F-3 F-4 rating at fuel- F-4 rating at fuel- and nominal scale rating air ratio of 0.065 air ratio of 0.11 grade (a) (b) (c) (c) Inlet-air temperature °F Inlet-air temperature s 01. ______I5 r 300 300° SB-3 Imep -292 235 162 143 118 270 270 265 258 235 (130/160) ON P1.1 134 156 147 139 135 152 159 -155 LIII 86 --99 95 90 LTH 86 --79 77 74 LTI 16 9 --4 11 14 13 4 SB-4 Imep --262 189 165 126 -298 286 261 (135/175) ON PN 141 -160 146 LIH 91 -95 LTH 91 -77 LTI -24 15 9 ----. -29 26 23 SB-5 Imep -267 195 173 133 -299 (140/200) ON P1.1 143 -155 LIH 92 -100 LTh 92 -80 ______LTI -27 20 16 2 -44 RAFD-52 Imep -247 205 188 137 -287 279 262 (146/175) ON PN 147 160 LIII 96 LTH 96 LTI -15 29 31 6 -24 23 23 RAFD-53 Imep -246 189 147 -312 (153/192) ON PN 147 LIII 96 LTH 96 ______LTI -32 16 -50

18 NACA TN No. 1619

Fuel-air ratio 170 ).11 160

150

1140

130

S /_

110 .0& 100 -IE •g 90 4.3 S-s E

'-4 80

0 70

20 0 20 140 60 o 100 Octane number Figure 1. - Curve representing octane scale determined on F-If engine at standard condi-tions.

NACA TN No. 1619 19

Fuel-air 260 ratio ).11 250 -

214.0 --_

230 - -- __7 -- 220 ____L--

. 210

C. 'I) 200 •0 190 a) -A-- E io 'ri a> .065 '-I E 170 _

--- C) 160 0 150 _/ _ 1140

130 -1 --

120

110 iiiiiiiii_

100 1.0 2.0 3.0 14.0 5.0 6.0 TEL, mi/gal isooctane Figure 2. - Curve representing lead scale determined on F-14 engine at standard conditions.

20 NACA TN No. 1619

160

•0

J140

120

I boll 0 1.0 2.0 3.0 Ll.O .o 6.0 TEL, mi/gal Isooctane Figure 3 . - Performance-number scale.

NACA TN No. 1619 21

______U _

i6o -4

0 CA ______•AUUUUM .-

1110 0. --4 - -U.-

4-.

-4 120 -4I 0 U-... ______0

100

__ _ • ____

.05 .06 .07 .0 .09 .10 .11 .12 Fuel—air ratio Figure 4-. - Reproducibility of engine results obtained with S reference fuel in F-11- rating engine at standard operating conditions.

22 NACA TN No. 1619

160 150 Iii- lleo • ___ _ --

130

'4 0' _-- a.

100

-4

30 -- - •

100 110 10 220 260 300 Inlet-air temperature, °F (a) Fuel-air ratio, 0.065.

Figure - Knock-limited performance of unleaded blends of isooctane and n-heptane5 . at various inlet-air temperatures in F- engine. All oonI'ttons other than inlet-air temperature were standard.

NACATN No. 1619 23

190

-- 1g0 .1 __- _I

170

160

150

1140

130

; 120 q4 I __ 110 I!

100

go U __ U.. ______'I - -

20 114.0 io 220 260. 300 Inlet-air temperature, OF (b) Fuel-air ratio, 0.11. Figure 5. - Concluded. Knock-limited performance of unleaded blends of is000tane and n-heptane at various inlet-air temperatures in.)'-4. engine. AU conditions other than inlet-air temperature were standard.

24 NACA TN No. 1619

27O

260 0

250

20 C

230

220 TEL 210 (mi/gal)-

.1 o6 c 200 - — —\- — — — C 44.5 — 0 3.7S 1.2S 190 _ - v.5 0. a) N . 10

a, 170 S

160 -- C) 0 S 150 \

114.0

130 120 ----:z-ç-\--- 110 ______

100

90 Isooctane so ______100 10 150 220 260 300 Inlet-air temperature, °F - (a) Fe1-air ratio, 0.065. Figure 6. - Knock-limited performance of isooctane containing various concentrations of tetraethyl lead at several inlet-air temperatures in F-Il. engine. All conditions other than inlet-air temperature were standard.

NACA TN No. 1619 25

29 C ______-- ______TEL __ -- (ml/ga].) 28C - o6 a k.5 I -.- 0 3.78 27c 1.28 - zz - .5 ---0 26C - ______0 250 • _____D 9 211.0

:230

220 ---

210

200

0 190 V --

V •- 180

170

16o - - --

S Is000tane 150 1 00 iko 1() 29fl - Inlet-air temperature, °F (b) Fuel-air ratio, 0.11. Figure 6. - Concluded. Knock-limited performance of isooctane containing various concentrations of tetraethyl lead at several Inlet-air temperatures in F-11 engine. All conditions other than inlet-air temperature were standard. 26 NACA TN No. 1619

270

260

250

21.0 •uiuiu

._;. 230 •I!IU.0 UR

220 If: : 210 - - 200 UR•••R .

190

o .R...RU.R....R.. U)

r4 auaauusaa•uuuu•

16c RRR.....RU....RR E 150 '...IRR.URRRRRRR 114.0 •MRRRUIRURRIRRR • 13C C) 12C lic 4URRRRRERUUUURUR

1OC

9C ..RUU.IUURR..R

Sc IURRRRRRRR

7C 'UURRUURRRR 6c

50 ______14.0RRUUUURMNEtiva. ______100 1140 10 220 EbO 300 Inlet-air temperature, °F (a) Fuel-air ratio, 0.065.

Figure 7. - Knock-limited performance of leaded blends of isooctane and n-heptane at various inlet-air temperatures in F-14 engine. All condTtion8 other than inlet-air temperature were standard.

NACA TN No. 1619 27

27c

26(

25(

23C

22C

-I 21C uQr, cOO •1

190 0. lC

•g 170 4.3 U..... -i. 160 '-I U. 150 0 4 1O

130

120

110

100

70 ______

6o lou iso O b0 300 Inlet-air temperature, °F (b) Fuel-air ratio, 0.11. Figure 7. - Concluded. Knock-limited performance of leaded blends of isooctane and n-heptane at various inlet-air temperatures in F- engine. All cnditions other than inlet-air temperature were standard. NACA TN No. 1619

230

220 Triptane n-Heptane iiii (percent by volume) 210 o 80 20 0 60 4.0 200 - - 40 60 v 20 80 1QO 190 -- - (AU blends contain 180

170 -

U) -

150 E N rd 140 - a) 4.3 130 120 - -- 110 ------100 - - 90

50 EEEEEn-Heptane 40 100 14.0 180 220 2b0 300 Inlet-air temperature, °F (a) Fuel-air ratIo, 0.065. Figure 8. - Knock-limited performance of leaded blends of triptane and n-heptane at varIous inlet-air temperatures in F-4 engine. All condi.- tions other than inlet-air temperature were standard. NACA TN No. 1619 29

250

211.0

230

220

210 Triptane n-Heptane (percent by volume) 200 0 20 60 110 190 Uo 60 - v 20 -- - 100 -' lo 0' (All blends contain 3.7 ml TEL/gal) ;f 170

160

a) - 4..

-;I 111.0 -- . 0 0 130 --_--

120

110 -

100 -

70 IiEII - n-Heptane 111.0 - igo 220 .2b0 300 Inlet-air temperature., °F (b) Fuel-air ratio, 0.11. Figure . - Concluded. Knock-limited performance of leaded blends of triptane and n-heptane at various inlet-air temperatures in F-4 engine. All conditions other than inlet-air temperature were standard. 30 NACA TN No. 1619

300

290

• 2go

270 _ _ -.ff ______'I,

260 • •

250

• 211.0

230

.0 220 •_N.._____

210

200

190 U._'.11 -- 0 10

170

160 _ _ 'U _ __

150

i11•o

130 100 ILIU J.öU UU Inlet-air temperature, °F (a) Fuel-air ratio, 0.065.

Figure 9. - Knock-limited performance of leaded blends of triptane and isooctane at various inlet-air temperatures in F-11 engine. All conditions other than inlet-air temperature were standard.

NACA TN No. 1619 31

_ _ IIHHITriptane Isooctane (percent by volume)

o 60. £1.0 o 1.O 60 G 20 100 (All blends contain 3.7 ml TEL/gal)

• 311C

33 C ------

- 320

310

300 ______N a • 290 p a 20 -I ____z_ 1 270 __ 0 ______N 260 ------___ 250

2110

____ 2 30 ______Is000tane 100 140 10 220 260 oo - Inlet-air temperature, °F (b) Fuel-air ratio, 0.11. Figure 9 . - Concluded. Knock-limited perform.nce of lea&ed blends of triptane and isooctnne at various inlet-air temperatures in F_L1. engine. All conditions other than inlet-air temperaturewere fitandard.

32 NACA TN No. 1619

160

150 1

111.0 _ II _

130 120 ____WA_ 'I . 110 ___ •ri _ •0 r4 100 ______vji_ Q) E 4 90

-74 70 _____

b 60

11.0

2C • II. .1. iI• Isooctane in blend with n-heptane, percent (a) Fuel-air ratio, 0.065. Figure 10. - Rating curves for octane number determined in F-k engine. NACA TN No. 1619 33.

190

150

170

160 .Ii

150

114.0 _____"A_

• 130 ______'/1

0' u-I - 120 ____ 1)1/I 0 ,-1 0. 110 ______IL- _ a)

100

70 _____ VAA

14.0

20 • f. ftie Isooctane in blend with n-heptane, percent (b) Fuel-air ratio, 0.11. Figure 10. - Concluded.. Rating curves for octane number determined in F-14 engine. 34 NACA TN No. 1619

290 Inlet—air ;emperature, °F 20 ------27ó _7_ -- 260 -- L-- -- 150 250

- ___z 20 / V 230 - -- 7__ - 220 ___L_7____

210 .1 -- -- 200 •0 -1- - 7-- 190 _L

-.4 10 _z-

170

160

150

1I.0

130

120

110

100

TEL, mi/gal isooctane (a) Fuel—air ratio, 0.065. Figure 11. -: Rating curves in terms of leaded isooctne determined in F-4 engine.

NACA TN No. 1619 35

Inlet-air mperature, °F 29 C

I Iioo 2SC

1501 ? 7C

26C

• 25C

300] 2110

•0 '-4 230

220 a) 210

200 0

190

170

16o

150 0 1 2 3 4. 5 6 TEL, mi/gal isooctane (b) Fuel-air ratio, 0.11. Figure 11. - Concluded. Rating curves in terms of leaded isooctane determined in F-4 engine. 36 NACA TN No. 1619

230

220 --

210

200 i1

190 _ •ii__

iso ______111___ 170 'ii 160

'- 150 __ -- i,1vj a, . i10 -- --yAwl

a, 130

'-4 120 _ __ VAVA _ 0 0 110 _ _WM

100

6o .5° • ______0 20 l.0 60 So iOO Isooctane in blend with n-heptane, peroent (a) Fuel-air ratIo, 0.065. Figure 12. - Rating curves in terms of leaded isooctane blended with leaded n-heptane determined In F_Il. engine.

NACA TN No. 1619 35

Inlet-air ______;emperature, °F 29 C

? 7C

26C 7_

25C

c 20 __/ y u / / _ _ • 230 ____ / i Z 0. //7.____ 220 a) / 210

200 0

190

170

1 6o

150 0 1 2 3 Z. 5 6 TEL, mi/gal isooctane (b) Fuel-air ratio, 0.11. Figure 11. - Concluded. Rating curves in terms of leaded isooctane determined in F-Il- engine.

36 NACA TN No. 1619

24.0

230

220

210 ______ri_

200 ______ii

190 ______•ii__

l0 _ 'MI

170 -- -- Ii. _

160 ______"4-

r4 150 ______.,1vj

a) . 10

a) 130

120 ______•WIffA__ C) 0 - 110 _____-,A

100 ____ •WAU

l. I .f• .I. Isooctane in blend with n-heptane, percent (a) Fuel-air ratio, 0.065. Figure 12. - Rating curves in terms of leaded is000tane blended with leaded n-heptane determined in F-1 engine.

NACA TN No. 1619 37

0 In

—I

C) 0 0 :14

0 20 Ll.O 60 80 100 Isooctane in blend with n-heptane, percent (b) Fuel-air ratio, 0.11. Figure 12. — Concluded. Rating curvee in terms of leaded isooctane blended with leaded n-heptane determined in F- engine.

38 NACA TN No. I69

'5U - - - - - i&;- Inlet-air emperature, °F 20 - - - - -

------

1 .90 --- - -

1 - - -.

1 .70 ------) 225 .-i - - 1 - -/- C. / 250 .' 1 50--- - - '-I

1)1 -I

Wi 3C------

E .1 Hi 2o_____7 gb1en;flain 0 0 1

1 ::iiii

90--

6c- - .- - -

5C- - - --

40 ______0 20 1.0 6o Triptane in blend with n-heptane, percent (a) Fuel-air ratio, 0.065. Figure 13. - Rating curves in terms of leaded triptane blended with leaded ri-heptane determined in F-k engine. NACA TN No. 1619 39

2 5CJ - -______Inlet-air 100 ;emperature, o 2l-c ) ------I - / 150 23 )------h------II 250 22

20(

19C All blends contain 3.7 ml.TEL/gal 1c

C. 17C

c;: 160 0)

d 150 0)

i4o

130

120

110

100

70 -

6o ) 20 11.0 60 Triptane in blend with n-heptane, percent (b) Fuel-air ratio, 0.11. Figure 13. - Concluded. Rating curves in terms of leaded triptane blended with leaded n-heptane determined in F-J4 engine.

NACA TN No. 1619

300 Inlet-air temperature,

290 I F 20

270

260

250

230 225 • 220 p. a, 210 a) 200 250

190

10 I All blends contain I I /1 A' I I 3.7 ml TEL/gal I I 170

160

150

1110

1 fl '0 20 60 Triptane in blend with isooctane, percent (a), Fuel-air ratio, 0.065. Figure 1I4.- - Rating curves in terms of leaded •triptane biende with leaded 1.sooctane determined in F-k engine.

NACA TN No. 1619 41

Inlet-air temperature, °F 3L.0 300

330 25)

320 . /250 -4 a 310

rI 300

a) . 290 a)

-4 -4 / All b1endontajn

, 270 C) 0 4 260

250

240

230

220 20 11j Triptane in blend with isooctane, percent (b) Fuel-air ratio, 0.11.

Figure 111. - Concluded. Rating curves in terms of' leaded triptane blen4e4 with leaded is000tane determined in F-4 engine. 42 NACA TN No. 1619

160

/ 111.0

120

/formance numbei 100

0) _ 7 / C)

80 77/ / __ C) a) Octane num7 . ______

a) c-i , 7 ___ _ _ 6o -z______7L ' / Isooctane blended with n-heptane 3.7 ml TEL/gaiT 1-o

__ / ______

20 2 __/—______/ ______20 4-0 6o 100 friptane in blend with n-heptane, percent (blends contain 3.7 'ml TEL/gal) (a) F-3 engine at standard conditions. Figure 15. — Relations among various rating scales. NACA TN No. 1619 43

1 6c

111.0

12C /fo er

1OC

r-4

C) U) Octane number --,-

C) a:: 6o ______Isooctane blended wi.th n-heptane (3.7g ml TEL/gaiT - - /

1l.

[II 20 o . 6o o Triptane in blend with n-heptane, percent (Blends contain 3.7 ml TEL/gal) (b) FL1. engine at standard conditions; fuel-air ratio, 0.11. Figure 15. - Concluded. Relations among various rating scales.

44 NACA TN No. 1619

-1.2 - - 0 ON-octane number - - - - 0 PN - performance number F -1.1 - LIH - blends of isooctane and - - - n-heptane containing 3.78 ml '1EL/ga1 -1.0 -- LTH - blends of triptane and - - n-heptane containing 3.78 ml EL/ga1 rI - v LTI - blends of triptane and - - isooctane containing 3.78 ml r.. TEL/gal 0ic: - c'JC\1 LTI /

42 -

-.6

- . -PM /1 LTH

-- oN-7--LIH -- 4-- F.: .2 -w______0 0 0 120 ibO 200 20 20 Knock-limited irnep at 225° F, lb/sq in. (a) Fuel-air ratio, 0.065. Figure 16. - Variation of temperature sensitivity with knock-limited performance in F-14. engine for various reference fuel blends.

NACA TN No. 1619 I 45

-.3'

-.3; _ 111111

j,.. -.3' _'Jig' C •.-' III-

-.2i _WA Ii -71 V

inn I: : -. U -I ______-. U •m • C

-u_--iuwsi____ E

-.0

-. O1 _rna.I.. _ _ NLIflI __

0 50 100 150 200 20 30O 350 Knock-limited ifnep at 225° F, lb/sq in. (b) Fuel-air ratio, 0.11. Figure 16. - Concluded. Variation of temperature sensitivity with knock-limited performance in F-u engine for various reference fuel blends.

46 NACA TN No. 1619

.44 • ______

• .

• •I S • I, I A V S S I .5

S SI 300 4 S I . I

260

' 220 I'_____ p4 Q) 200

4-I 160 C) 0

120 I.. __

100

6o 100 1'lO 10 220 260 300 Inlet-air temperature, °F (a) Fuel-air ratio, 0.065. Figure 17. - Knock-limited performance of service-type fuels at various inlet-air temperatures In F-4 engine. All conditions other than inlet-air temperature were standard.

NACA TN No. 1619 47

3 2C

31C • . • I. • 30C • II I A

____ V • • 29C

2C . •

26C ______:, . 25C

,-i 21k

230 -- ___

+Q) 22C H

2lC 'U

20C 19C U.. 17c

i6c U.-. 15C • __ 111.0 -______100 1L1.0 10 220 260 300 Inlet-air temperature, °F (b) Fuel-air ratio, 0.11. - Figure 17. - Concluded. Knock-limited performance of service-type fuels at various inlet-air temperatures in F- il. engine. All conditions other than inlet-air temperature were standard.

48 NACA TN No. 1619

. 0

I _ 11 .-4 L. 0 _____ N,,_ 0 -. '-I

__ --

0 120 160 200 2L$O Knock-limited imep at 2250 F, lb/eq in. (a) Fuel-air ratio, 0.065. Figure ].B. - Comparison between tezperature aensitivitlee of reference- fue]. blends and service-type fuels in ?-I engine.

NACA TN NO. 1619 49

-S 36

-. 311. ______U

-.32 -- __ -U U

4-' -.22

-.20

43 -á

43 - -.

I -ol

-.12

El 0 43 VII

i :::

-; .011.

.02

50 100 150 200 250 300 Knock-lirnited imep at 225° F, lb/sq in. (b) Fuel-air ratio, 0.11. Figure 1g . - Concluded. Comparison between temperature sensitivities of reference-fuel blends and eervioe-type fuels in F- LI- engine.

50 NACA TN No. 1619

160 --

150 N ______\______

14O --\ --_ _ 130 a> - -,= = C a) 120 E 0 a> p4 110 - Q— - - -

Nominal grade ______100 ----

10 __ __ 100/111.0 -- ___ 115/11.5 V 120/150 90 v 130/160

so 100 10 160 220 260 300 Inlet-air temperature, °F (a) Performance-number scale. Figure 19. - Effect of inlet-air temperature on lean (fuel-air ratio, 0.065) antiknock ratings assigned from different fuel-rating scales. All conditions other than inlet-air temperature were standard F-11. conditions.

NACA TN No. 1619 51

30 _ _ II __ +343 04) 04) __•1 _ __ 2o • ____ '-I •0 10 - __ e 10 - __ _ 43 ,e -I 100

4) 90 _- 43 - - _ 4)43

14) do 'z 80 • r- : _ •L - _ _

, 60

50 ______100 140 180 220 260 300 -____ Inlet-air temperature, op (b) Leaded isooctane -. n-heptane and leaded triptane- isooctane scales. Figure 19. - Continued. Effect of inlet-air temperature on lean (fuel-air ratio, 0.065) antiknock ratings assigned from different fuel-rating scales. All conditions other than inlet-air temperature were standard F4 conditions.

52 NACA TN No. 1619

Nominal grade

___-- ______-- o 76/SS o 100/130 o 100/1'l.O -- 115/1ll-5 v . 120/150 ______v 130/160

1) - -__ ___ -

4-34.3 VQ) .C) L!i Ja)

4-' - -1---

6o c: ---. ,0 QE

G, O C N- 50 (0.

.•1

100 14.0 10 220 260 300 Inlet-air temperature, 0? (c) Leaded triptane - n-heptane scale. Figure 19. - Concluded. Effect of inlet-air temperature on lean (fuel-air ratio, 0.065) antiknock ratings assigned from different fuel-rating scales. All conditions other than inlet-air temperature were standard F-Il- conditions.

NACA TNNo. 1619

30 __ _ n ___

434

00 00

2o --- - • ____ _ II 10 U.- - -- SUL__ .•15 0 __. __

-I 100 ____ _ Ii-

0 90 --____- - Is I0 p. • ___ L : __ _•.ui UI__

I II -

:: ______50 ______100 11-O 180 220 260 300 Inlet-air temperature, 0p (b) Leaded isooctane - n-heptane and leaded triptane- isooctane scales. Figure 19. - Continued. Effect of inlet-air temperature on lean (fuel-air ratio, 0.065) antiknock ratings assigned from different fuel-rating scales. All conditions other than inlet-air temperature were standard F-4 conditions.

52 - NACA TN No. 1619

Nominal grade - ______--- 0 76/ 100/130 0 100/111.0 115/111.5 V 120/150 ____ V 130/160

- W p -

4-) 4) 0-c: Q)) 70 - _ _ - ,CC) I4

p. 4-' ------

jD 6o

-4E G C N- 50 c0.

Z1.O - __ -- __ 100 10 10 220 2b0 300 Inlet-air temperature, °F (c) Leaded triptane - n-heptane scale. rigure i.). - uoncluaecl. rrect or inlet-air temperature on lean (fuel-air ratio, 0.065) antiknock ratings assigned from different fuel-rating scales. All conditions other than inlet-air temperature were standard F-11. conditions. (

NACA TN No. 1619 53

__v- , P 15

1( - - Ii-. --_- _ _

13 C a) E

12C

0 Nominal grade a) 110 0 76/ o 100/130 ______100/111.0 A 115/111.5 V 120/150 ______P 130/160 100

0— -0-- 90

ii 1LD 1S0 220 2An znn Inlet-air temperature, OF (a) Perf ormance_number scale. Figure 20. - Effect of inlet-air temperature on rich (fuel-air ratio, 0.11) antiknock ratings essigned from different fuel-rating ca1es. All conditions other than inlet-air temperature were Conditions. standard FL1.

54 MACA TN No. 1619

O 30 0 430 ii 00o4

.c: -20 43

0.4 0 .- 10 .4 • F.- 'C' 43 p. U. _ u__i.. _ 100. 43 - - I! 90

.4 F—.4 C) 0 0 0.-. go __ 430 00 _U___U._ 043 p. 1-4 .00 70_ 100 l0 10 220 260 300 Inlet-air temperature, °F (b) Leaded isooctane - n-heptarie and leaded triptane- isooctane scales. Figure 20. - Continued. Erfect of inlet-air temperature on rich (fuel-air ratio, 0.11) antiknock ratings assigned from different fuel-rating scales. All conditions other than inlet-air temperature were standard F- conditions.

NACA TN No. 1619 55

Nominal grade

o o 100/130 o 100/11k) 115/]M5

_ 4------b------0-- -_- - _ s— -e - kIQ)

_o- - - —0— - -- -

Jo l4.0 io 220 2h0 Inlet-air temperature, °F (c) Leaded triptane - n-heptane scale. Figure 20. - Concluded. Effect of inlet-air temperature on rich (fuel- air ratio, 0.11) antiknock ratings assigned from different fuel- rating scales. All conditions other than inlet-air temperature were standard F-14- conditions.

56 NACA TN No. 1619

_ __ 1410 N .___iIw :_11MhuhhhhhhlU L4QØ t1r1hhhh1 390 - 380 ______370 I ___ 360

350

.3o

330 • ___ . 320 ___•_ a _ ____ . 310 43 300 _ g _ I _ 290

280 270 __ _Nt.', _ 260 II1I 250 ______I - I - 240

230

220 .06 .07 .08 .09 .10 .11 .12 Fuel-air ratio

Figure 21. - Maximum knock-limited mean effective pressures that can be obtained for various- fuels by F- rating method without encountering preignition.