1、h NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TECHNICAL NOTE 2966 PROPELLER-PERFORMANCE CHARTS FOR TRANSPORT AIRPLANES By Jean Gilman, Jr. Langley Aeronautical Labor at ory Langley Field, Va. Washington July 1953 Provided by IHSNot for ResaleNo reproduction or networking permitted without license fr
2、om IHS-,-,-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TECWTICAL NOTE 2966 PROPELLER-PEFGORE CHARTS FOR TRANSPORT AIRPLANES By Jean Gilman, Jr. SUMMARY The preliminary selection of a propeller bn the basis of cruising and take-off performance for application to transport airplanes at flight Mach num
3、bers up to 0.8 can be accomplished by the use of the charts and methods presented. The charts are of sufficient scope to permit a fairly rapid evaluation of the propeller performance for engine power ratings of 1,000 to 10,000 horsepower. interest of propeller -noise abatement . The method is presen
4、ted primarily in the INTRODUCTION Increasing engine power ratings, together with expanding airport operations and greater concentrations of people near airports, have led to serious complaints in regard to airplane noise. Inasmuch as the air- plane propeller is a major offender as a producer of high
5、 noise levels, a general study of the propeller-noise problem has been undertaken by the National Advisory Committee for Aeronautics. The initial phase of this study concerned quiet propeller operation for the light personal- owner airplane and the results have been presented in references 1 and 2.
6、The propeller-noise investigation has now been extended to include trans- port airplanes having engines with power ratings of 1,000 to 10,000 horse- power. Reference 3 presents methods and charts for estimating propeller noise, and indicates the factors which govern the intensity of the noise. The p
7、resent paper is concerned with the performance of propellers selected on the basis of quiet operation. are intended to be used in conjunction with each other. are charts by means of which the performance of various propeller con- figurations at cruising and take-off conditions can be quickly analyze
8、d. This paper and reference 3 Presented herein It is presupposed that the preliminary airplane design has pro- gressed to the point where the cruising velocity, altitude, and engine power ratings have been determined. It is also presumed that the airplane Provided by IHSNot for ResaleNo reproduction
9、 or networking permitted without license from IHS-,-,-2 NACA TN 2966 weight, the velocity required for take-off, and the lift-drag ratio of the airplane for take-off have been established. With these factors known, the propeller analysis can proceed along the lines suggested in the paper. SYMBOLS AI
10、? activity factor per blade B number of blades b blade width (chord) , ft airplane lift coefficient CL CP power coefficient, P/pnW A CT d Ct ld C D I% h J KS L M thrust coefficient, T/pn2D4 section drag coefficient section lift coefficient design section lift coefficient propeller diameter, ft; drag
11、, lb rotational energy per unit time in slipstream, ft-lb/sec blade section maximum thickness, ft advance ratio, V/nD coefficient for take-off run airplane lift, lb flight Mach nutuber Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 2966 3 MR
12、 N n P P CV R r S S T TO T1 v W X rl rotational tip Mach number propeller rotational speed, rpm propeller rotational speed, rps power, ft-lb/sec power coefficient, P/pv3D* propeller tip radius, ft radius to a blade element, ft wing area, sq ft take-off distance, ft thrust, lb static thrust, lb net s
13、tatic thrust, lb velocity of advance, ft/sec or mph airplane weight, lb power-coefficient adJustment factor fraction of propeller tip radius, efficiency, JC/C or TV/P r/R efficiency of ideal actuator disk basic induced eff iciency induced efficiency profile efficiency c1 ground friction coefficient
14、VO Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4 NACA TN 2966 P air density, slugs/cu ft cf propeller -element solidity, Bb/xDx propeller-element load coefficient OC 2 Subscripts : 0-7R at 0 . 7-radius station D profile drag i induced t take-off
15、DISCUSSION The selection of propellers from performance considerations is a twofold problem. First of all, a reasonable cruising efficiency must be maintained. Secondly, the take-off run must remain within the limi- tations of practical airport runways. The selection of a propeller to meet both cond
16、itions usually involves consideration of a number of pro- pellers in order to arrive at a suitable compromise. A series of pro- peller charts covering ranges of parameters suitable for quiet operation is presented herein and should give fairly rapid estimates of suitable propeller dimensions and the
17、 associated performance. The discussion begins with a presentation of charts which are used in selecting propellers for the cruising condition. Then follows a consideration of the factors affecting the take-off run. the discussion, charts for obtaining the thrust for calculating the take-off run are
18、 presented. To complete Perf0rmanc.e in Cruising Condition The selection of a propeller to satisfy the requirements of the cruising condition is accomplished through the use of four charts. ure 1 is a composite plot, conveniently arranged to show the interrela- tionship of the major propeller design
19、 variables, which gives the basic induced efficiency T. (The construction of this chart is explained in appendix A.) Figure 2 is an adjustment chart to account for various numbers of propeller blades. Figure 3 is an adjustment chart to be used when needed to accommodate dual-rotating propellers. Fig
20、ure 4 gives the Fig- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 2966 5 profile efficiency, and thus accounts for blade profile drag. all efficiency is simply the product of the induced efficiency and the profile efficiency. The over- The
21、 procedure for using figure 1 is indicated by the axrows in the figure. tion at an altitude of 25,000 feet with 400 miles per hour as the air- plane cruising velocity (M = 0.54). The propeller is to be operated at a relatively low tip speed (say 700 feet per second) in an effort to obtain a low prop
22、eller-noise level. The combination of airplane forwad speed (587 feet per second) and the tip speed just cited gives an advance ratio V/nD of 2.64. The arrows in figure 1 show that a trial diameter of 16 feet leads to a total activity factor of about 600. induced efficiency is about 91 percent. The
23、example shown involves a 3,800-horsepower engine for opera- The basic In working the problem in figure 1, the assumption has been made that the approximate required engine horsepower has been established. By a trial-and-error process, however, the application of the results in figure 1 could be exte
24、nded to the problem of estimating the required engine horsepower, provided that the drag horsepower (airplane velocity multiplied by airplane drag) has been established. Choice of number of blades and associated adjustment factor.- The basic induced efficiency of the propeller is subject to an adjus
25、tment which is dependent on the advance ratio, the total activity factor, and the number of blades, as shown in figure 2. The choice of the number of blades would ordinarily be governed by the obvious desirability of using blades of standazd design that are available from the various pro- peller man
26、ufacturers. varying from about 80 to .approximately 150. total activity factor obtained from figure 1 by vmious numbers of blades gives required blade activity factors for the cruising condition. Such blades generally have activity factors A simple division of the The activity factor as obtained fro
27、m figure 1 need not be exactly matched. The curves of figure 1 for total activity factor are based on gropellers of optimum load distribution having the lift coefficient at the 0.n station equal to 0.5. This is a desirable value, at least for flight Mach numbers up to about 0.8, but actually this li
28、ft coefficient can vary from about 0.4 to about 0.6 without undue harm to the propeller efficiency. Inasmuch as the induced efficiency is in reality a function of the product of the total activity factor and the operating lift coef- ficient, it is sufficient to match the total activity factor from f
29、ig- ure 1 within approximately 20 percent. The total activity factor for the example indicated by the arrows in figure 1 is about 600. four blades having an activity factor of 150 each, for which figure 2 gives an adjustment value The propeller configuration might consist of Aqi = -0.018, or it migh
30、t consist of six blades Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 I?ACA m 2966 having an activity factor of 100 each, for which Aqi = 0. eight blades having an activity factor of 75 each would result in a pos- itive Aqi adjustment but might l
31、ead to structurally undesirable blades. A choice of In any event, the adjusted induced efficiency is given by Thus, in the example, the induced efficiency of the four-blade propeller is 0.892, and that of the six-blade propeller is 0.91. Adjustment for dual rotation.- An examination of the lower rig
32、ht- hand corner of figure 1 shows that rather low values of at the higher values of V/nD and total activity factor. Figure 3 is a plot of the quantity Er/P against J at various constant values of total activity factor and blade number. energy loss due to rotation of the slipstream. Experience has sh
33、own that about 60 percent of this loss is recoverable through the use of dual- rotating propellers. Thus, the adjusted induced efficiency for a dual- rotating propeller is qi axe obtained This quantity is the fractional qi = Ti + AT, + 0.6 P In the example of figure 1 a six-blade dual-rotating prope
34、ller would have an over-all induced.efficiency of 0.946 as compared witn 0.910 for the six-blade single-rotating propeller. The results of reference 3 show that a dual-rotating propeller is noisier than a single-rotating propeller at a given power loading, pro- peller tip speed, diameter, and number
35、 of blades. Thus, for a given sound-intensity level, the dual-rotating propeller would require a lower tip speed than would the single-rotating propeller. Adjustment for propeller blade drag.- Figure 4 is a plot of esti- mated profile efficiency as a function of flight Mach number with J = - v IiD a
36、s parameter. ratio distribution as shown in figure 5. peller efficiency is given by the product The curves correspond to a propeller having a thickness- The approximate over-all pro- for either single- or dual-rotating propellers. Provided by IHSNot for ResaleNo reproduction or networking permitted
37、without license from IHS-,-,-NACA TN 2966 7 For the sample problem indicated by the arrows in figure 1, where the conditions of the problem resulted in an advance ratio of 2.64 and a flight Mach nuniber of 0.54, the corresponding value of from fig- ure 4 is 0.96. Thus the over-all efficiency q of th
38、e four-blade con- figuration would be Tiq0 = 0.856. The over-all efficiency of the six- blade configuration would be 0.874 for single rotation or 0.908 for dual rotation. qo SummaSy outline of propeller selection procedure for cruising con- dition.- The foregoing discussion maybe summarized by the f
39、ollowing step-by-step procedure : 1. For the given cruising velocity, altitude, and shaft horsepower, choose a desired value of rotational tip speed gnD. Calculate V/nD from the equation 2. From figure 1, ob-sin the basic inLxed efficiency the total activity factor for various propeller diameters. T
40、i and 3. Select a suitable number of blades for each case and use fig- ure 2 to obtain the appropriate adjustment Av,. Compute qi from the equation 4. If dual rotation appears desirable, obtain the quantity q/P from figure 3 and compute qi from T - qi -k Aqi + 0.6 Er - P 5. For the required flight M
41、ach number and the trial value of V/nD, obtain yo from figure 4. Compute q from the equation Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a Performance in Take-Off NACA m 2966 Factors governing take-off run.- A discussion of the factors affecting
42、the take-off run is given in reference 4. It is pointed out that the major factors affecting the take-off run, aside from such fac- tors as pilot technique, engine power variations, and presence or absence of wind, are weight of the plane, ground friction, air drag, and varia- tion of thrust during
43、the take-off run. variation of thrust, which will be seen later to be a reasonable assump- tion, Diehl, in reference 4, obtained a simplified formula for the take- off run. By assuming a straight-line In the notation of the present paper, the formula is: where and where Ks is a function of the ratio
44、 A plot of Ks given herein as figure 6. against this ratio is reproduced from reference 4 and is Evaluation of the take-off run in a calm requires the value of static thrust and the value of thrust at take-off velocity; the other quantities in the take-off formula are presumed to be known. Before pr
45、oceeding to methods for estimating these thrusts, typical values of p and D/L will be cited. Reference 4 gives the value of p for hard-surfaced runways as 0.02, which would be typical of normal comer- cia1 airports, and gives a range of values of p. for other types of runways. value of in calculatin
46、g the take-off run. Now that partially deflected flaps are comonly used in the take-off, the use of such a value in making In this reference the suggestion is made that the maximum L/D for the airplane can be used with satisfactory accuracy Provided by IHSNot for ResaleNo reproduction or networking
47、permitted without license from IHS-,-,-NACA m 2966 9 the calculation does not seem advisable. The value of L/D at take-off velocity for modern transport airplanes with flaps partially deflected is shown by some unpublished NACA data to be about 8 or 9. Charts for determination of thrust for take-off
48、 run.- A convenient Figure 8 is an aux- chart for estimating the thrust for the take-off run is given in fig- ure 7. iliary chart (also reproduced from ref. 5) used to account for varia- tions in activity factor. Figure 7 shows the ratio CT/cp2/ as a function of the quantity parameter. The quantity
49、C is obtained from This chart is reproduced from reference 5. / 1/3 with the power coefficient C as PX J Cp PX where X is a function of total activity factor as shown in figure 8. In order to obtain the static thrust To it is necessary first to calculate Cp fromthe formula P cp = - pnb5 where P power, and then to calculat
