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I . S . V . R . Memorandum No. 311 HELICOPTER ROTOR 3IOISJ$
FIBAL REPORT: PART xr
E X P E R m A L STUDY OF ROTOR NOISE by J.V. Leverton June 1969 HELICOPTER RCITOR ROISE 1st December 1965 t o 30th Novqber 1968 National Aeronau-bics and Space Administration, Research Sponsor: Washingtcn D . C * B.A.S.A. Grant N.G.R. -52-O25-.OO2 Research Contractor: I n s t i t u t e of Sound and Vibration Resea.rchs University of Southmpton.
Contract No. 9634132 Research Personnel: Research staff: J.W. Leverton (Experimental) Until 31st August 1968 EX. Tanna (Theoretical) From 23rd October 1.967 Supervisor : Professor E.J. Richards 3rd September 1967 Until C e L ! . ? o r fey From 4th Sepkniber 1.967 Professor J.P. Jones Associate : This report describes the experimental work carried out on the M.A.S.A. contract during t h e period 1st December 1965 30th November 1968. A review of the theoretical work has already been presented i n reference 1.
I n t h i s report a summary of information presented i n the series of status reports is given, together with results obtained during the last s i x month period of the contract.
The scope of t h i s report i s l h d t e d t o presenking; the experimental data collected and i n i t i a l observations on the results.
Because of a number of contributing factors it has not, i n the t h e available, been possible t o prepare for publication the series of NASA CR reports as originally planned. It is, however, intenc?.ed that the author Will con”cnue preparation of the series of detailed studies, which will be submitted for publication as NASA CR reports i n due course and/or issued as ISVR technical Reports.
The flrst report on blade slap (2) was published last year and a second report, giving the results o f t h e experimental results related t o blade slap, is now i n the f i n a l stages of preparation.
( i i ) LIST OF W H ~ S mKe No.
ii PREPACE List of figures iv 1 1 . INTRoDumIo1p 2 2 . XXPEZ3IMF!lQ'AL RESULTS 4 3. BLADE LOADSlG 4, TORQW EEASUREMEMTS si 6 5 . OBSERVATION ON EXPE.RXEEKi!A.L RESULTS 5 . 1 Rig Results (3-Bladed Rotor) 8 Full Scale Results (l-*Bla(?ed Rotor) 5.2 10 6. ~ I C O P T ~ RESULTS A C ~ O ~ G ~ ~ S 3 . 4 REFERmCES Table 1 to 4
Figure 1 - 16
L i s t of figures 1 . Comparison of sparwise loading calculated using blade element theory and estimated from N.A.C.A. 3688 (method of obtaining empirical correction for calculating blade l i f t ) Cmpax5,son of calculated and rraeaswed blade loading.
2.
Effect of speed on spectrum s b p e at l o w pitch - 2 ' pitch -
3.
3 blades.
4.
Zero pitch. S.P.L. v. Rotor speedo 2 ' pitch S.P.L. v, Rotor speed' 5 .
6. 1st Iiamonic S.P.L. v. Rotor speed 8' Pitch S.P.L. v. Rotor speed 7 .
1000 R.R.P.M. S.P.L. v. Pitch 8.
900 R.R.P.M. S.P.L. v. Pitch 9.
10 tr 500 R.R.P.M. S.P.L. v. Pitch F u l l scale Single Bladed Results.
11.
Rotational Noise -* variation with pitch.
12.
S.P.L. v . Tip Mach Number.
14. Narrow band Analysis of Helicopter Eloise -
Hovering Wessex.
1. IHTRDDUCTIOR A detailed experimental study was made using the I.S.V.R.
rotor hover r i g fitted w i t h 1 t o 4 blades. Data and i n i t i a l observation on some of the results have already been reported i n the Status reports which were issued bi-annually.
Although i n i t i a l l y the main a h was t o study broadband and rotational noise, the discovery of rotational peaks i n the "vortex'* region and the advent of rotational noise theories resulted i n the main emphasis being placed on rotational (discrete frequency) noise To determine the applicability of the trends being found on the I.S.V.R. rotor r i g , a detailed analysis was carried out on a series of f u l l scale single rotor blade recordings obtained by Westland Helicopters Limited. Flight t e s t s have also been re-analysed using a narrowband (2 Hz bandwidth)analyser t o give r e a l helicopter data.
- 1 - 2- ExPEHIMERT!ALREsULTS The main emphasis t o i?a+,e has been on the rotational or discrete frequency noise. Prior t o t h i s report some o f t h e results have been issued i n the regulez series of NASA Status Reports.
1.S.A.V. No. 194 (Status report for period 1st December 1966- 30th Kay 1 9 6 ~ ) ~ contained the following data: 4 bladed ISVR Rotor Rig Results.
l.
2. Single Bladed-Full Scale Results.
3. S R N ~ Propellor Results, I 4 x m s 1 and 2 were pxesented i n graphical and table form, Fjhile item 3 was only given i n graph form. A more comprehensive f o m o f t h e single bladed rotor f u l l scale results i s gresented i n reference 3.
The 4 Bladed Results quoted i n ISAV Bo. l g & are limited t o % blade passing harmonics; since t h i s date the d&ta havebeen re- examined and the study extended t o cover 12 hamonics. The new data, together with that previously given i n ISAV Bo. 194, Similar results for the 3 bladed is presented i n Table 1.
tests are given i n Table 2.
I n these tables the following notation is used: - Indicates no 'peak' (discrete frequency) detected.
4lT Indicates that it is not a clear peak.
jP 54 Indicates that the peak is less than 10 dB and more than 3 dB above the background (rig) noise.
In addition t o 3 and 4 bladed rotor results, detailed analysis It was originally has been carried out on 1 and 2 blade t e s t s .
intended that these should be included i n %his f i n a l report: unfortunately a number of d i f f i c u l t i e s have arisen which have For t h i s cask doubt on the validity of some of these results.
reason it is considered that they should not be issued u n t i l a further detailed review has been made of the data, and relevant analysis.
1 and 2 blades kests are, Frequencies associated with t h e obviously, lower with the fundamentals being below t h e frequency - 2 - In order, however, range af conven*,iona a~diysid otpipment.
that inf'cma-bion nn t h e effects of the number of blades etc: could be obtained, equipment ~ t h a calibrated frequency response down t o 8 NZ was used. Recordings were made on an FM tape recorder using a special low frequency F . E . T . Cathode Follower and analysis was performed using the Spectral Dynamics a-rzalyser f i t t e d w i t h a 2 Hz f i l t e r . Unfortunately t h i s resolution is not sufficient t o allov a 'peak' on the analysis t o be positively ideatified as being rotational noise. In t h i s coI.Lfext it should be remembered that a large nmber:of 'low frequency' components are produced by the r i g i t s e l f and consequently the rotor noise peaks can only be located by a detailed frequency analysis. In the case of the 1 and 2 bladed results the position is confused by the fact that the r i g (background) noise spectra contains a range of frequencies which coincide with the rotational It appears harmonics when using a 2 Hz f i l t e r Tor analysis.
t h a t 'tape speedup' and then narrowband a n a l p i s w i l l be required t o separate the r i g and rotor noise. This w i l l only be successful however, if the r i g and rotor noise "peaks" occur at slightly different frequencies An i n i t i a l investigation suggests t h i s is t h e case, but it i s not possible t o analyse the results at the present t i m e because the required equipment is not availablie
at the Ism4 It is hoped, however, i n the near future t o use
equipment at Westland Helicopter Limited, Yeovil for t h i s analysis.
On the 3 and 4 bladetests the frequencies are higher and except for a few specificcases the "discretes" do not clash trith any r i g frequencies. I n the 3 b l a a s e r i e s of test the 700 RRFW condition is most affected and f o r t h i s reason the quoted results f o r t h i s condition should ' only be taken as an indication o f t h e Eevels. The remainder of the results are correct, except for the 1 ~ t a f ; i o n outlined previously.
3. BLADELOADIIJG An estimation of the blade and t o t a l rotor loading has been made for all the conditions tested and the results are presented i n the tables 3 and 4 f o r t h e 3 and 4 bladed rotor respectively.
Blade element ( s t r i p momentum) theory w a s used t o calcula%: the 'ideal' spanwise l i f ' t and an allowance for the t i p effect w a s then aade empirically.
Data given for a non twisted rotor i n NACA 3688 (4) was used as a basis for the method. Figure 1
i1lustra;tes the method - the particular case for the 3 bladed
rotor operating a t 6 ' pitch, 500 RRPM i s shown. A factor was applied t o the results obtained using the blade element theory (at the calculation points) t o reduce the value t o the spanwise loading derived from EACA 3688.
Although this method has obvicm limitations it i s considered t o be sufficiently accurate for t h i s particular noise investigation.
A similar estimation was made for the single blade f u l l scale t e s t programme, where actual thrust measurements were available.
Figure 2 shmrs a compazison of the estimated and measured thrust levels. The "theory" tends t o over estimate the measured values i n all cases except the high pitch (15O cuff) and high speed 1 1 ' and 13' pitch s e t t i w .
conditions a t The 5O and 7* cuff measuremerrbs are suspect and it appears t h a t the load c e l l w a s not zeroed before commencement of the t e s t , with the result that the indicator "bottomed" on 500 lbs. I n general, however, the agreement is relatively good, w i t h the biggest error being i n the order of 13$* It is worth noting that if these loadings are convefied, into noise units, (dB's) then the difference between using the e s t h a t e d and mzasured loadings would be extremely s m d l .
- 4 - 4. TGRQUE MEASUREMENTS
me torque absorbed by the rotor for each condition is
presented i n Tables 3 and 4. From direct measurements of horse power of the driver motorr the krorse power necessary t o rotate the r i g without blades is subtracted t o obtain the appropriate I?
rotor H,P.". This has been coaverted i n t o torque f o r convenience.
The accuracy is considered t o be good, except f o r the low speed/ low pitch setting cases where the power absorbed is small and it i s extremely difficulty t o read the relevant meters accurately.
Using blade elmant theory it i s possible t o e s t h a t e the torque i n a similar manner t o l i f % . In t h i s case the agreement is not expected t o be as good since it no not knc3.m how t o account the drag component at any pitch for the 'drag tern'* Ideally A stutiy of measured H.P. shows, angle i s simply a constant C D o however that it incresses at a more rapid rate than can be the contribution of the lift term. It has been accounted for by follows shown experimentally by many investigations that i n fact C D o the fom: where C is the value at zero pitch (lift), a the "effective" Elomin This explains the difference angle of attack and x and y constants.
Since, howsver, between the measurements and predicted values t h e solution for CDo may be even more complex then given above, measured values of "torque'i are used i n any c a l c a a t i o n and torque The trends quoted have been o3tained from direct measurements.
calculated values have not been included in this report since %hey are only of academic interest.
- 5 - 5. OBSERVATIONS ON M p F s I m A L RESULTS It has proved impracticabl-e t o decide on a general graphical Thus rather then presenting f o m t for presenting t h e results.
a large number of figures, graphs a r e included trhich shmr particular trends cf interest. Although t h e results shown are for specific cases, a l l t h e data have been reviawed to verify that t h e observations are general. Cross reference i s also nade between t h e ISVR model results and f u l l scale measurements.
Details on t h e microphone layout r e l a t i v e t o t h e model r i g It i s worth noting have been given previously ( I S A V No. 194).
t h a t t h e main microphone vas mounted 1 0 ' below t h e rotor disc and 3 diameters away.
To date i s has not been possible t o compare t h e results with any theory except steady state Gutin calculations, since although detailed theoretical mode9s a r e available, aerogdnmic data i s lacking w i t h t h e result t h a t they cannot be applied t o any particular congigurat ion.
For convenience t h e folloiing discussion i s limited t o t h e results obtained from the 3 bladed rotor tests. A study of t h e data presented i n t h e tables will shokr+ however t h a t t h e 'four bladed rotor' results also f o l l o v t h e same trends.
If a detailed examination i s made of t h e three bladed results it w i l l be observed at some speeds, particularly 600 and 700 RRPM, that at the high pitch setting ( b o and above) an increase occurs i n some of the hammics which is completely out of keeping with the other harmonics. The increases are at the 3rd, 6th and 9th harmonics. The origin of t h i s effect is not kno~m, but it is thought that it could be the result of a 'flapping mode' resonance.
I. Simons i n some of h i s aerodynamic studies carried out using t h e same rotor found similar effects vken studying blade loadings, Since these "peaks" do not follow t h e trends associated with t h e other r e s u l t s they are not considered i n t h e following discussions.
In studying t h e results it t r i l l be observed t h a t there is considerable s c a t t e r i n t h e levels quoted, except for t h e fundamental This order of scatter is, hovever, common on lover hsxluonics.
- 6 - the type of model tests carried out during the investigation.
For t h i s reason it is often necessaryto cnnsider the general trend rather than compare specific results.
5.1 gig Results (3-Bladed Rotor) A t zero and low pitch the fundamental frequency component r i s e s at a much more rapid rate, relative t o t i p velocity, than the higher harmonics. Figure 3 plots SPL vs Harmonic f o r a range of higher t i p speeds at 2 ' pitch. It w i l l be observed that the a mean amplitude while higher harmonics are '*scatteredsfabout the fundamental increases directly with rotor speed above 6/700 RRPM, The results for Oo and 2 ' pitch are plotted as a function of rotor RRPM i n Figures 4 and 5 respectively. It w i l l be noted t h a t there is not sufficient data available at 0 ' pitch t o d r a w
different trends - it i s clear however f r o m g t h e results
presented that the 0 ' and 2 ' cases are very similar and thus Oo and 2O pitch c m generally be discussed together. The main difference between the two conditions is t h a t 0 pitch the second harmonic appears t o follow the sane trends as the fundamental, while a t 2 ' pitch the second harmonic follows the trend of the other higher harmonics.
The gGutin' prediction f o r the fundamental at low pitch, where the torque t e r n dominates, shows an increase according t o l a w . As expected ( V ' + 4 since drag a V2). It %Jill be observed that the fmdamental increase at a higher r a t e than given by ?Gutin' at rotor speeds above 600 RRF% with the e-erimental increase being i n the order of V I 8 (54 aB/doubling of speed), The higher harmonics on the other hand appear t o fluctuate around a mean as shown on Figure 5. There is, however, an indication of a 'drop off' of level w i t h increasing harmonic number t h i s is also shown in Figure 3.
The effect of pitch on the fundamental in terms of r o t o r speed is i l l u s t r a t e d i n Figure 6. A%ove 600 RRPM, the majority of results skox the same trend although the 6O pitch condition tends t o suggest a higher r i s e rate. Power limitations of the r i g prevented results being obtained at high pitch settingslhigh speed.
A t the higher pitch s e t t i n g the higher noise harmonics also follow the trend set by the fundamental, particularly at rotational speeds above 600 R R P K T h i s is i l l u s t r a t e d i n Figure 7.
The relationship between the noise and lift /torque also appears interesting. A t high t i p speeds the fundmental, and t o some extent the second harmonic, renains constant v i t h increase i n pitch (which produce an increase i n both torque and lift).
The high harmonics on the other b i d increase quite rapidly w i t h pitch. Figures 8 and 9 i l l u s t r a t e these effects. A% the low speeds the fundamer,tal and a l l the harmonics agpear t o follow the s a m e trends w i t h pitch as i l l u s t r a t e d i n Figure 1 0 for the 500 RRPM case.
5&2 Full Scale Results (1-Bladed Rotor) The fundamental on the single bladed f u l l scale t e s t s (3) was found t o agree well wi_th t h e trends predicted using the 'Gutin' rehtionship. Figure 11 show a comparison of the 'Gutin' and measured values. It w i l l be noted that the 'Gutin' theory overestimated the values i n all cases with t h e main difference occuring at the low pitch settings. Part of the discrepancy could be due t o the choice of effective radius f o r t h e Gutin cahulations (0,8 x t i p radius).
appear t o be The high harmonics, on t h e okher hand, do correlated with either %l?rwC, or torque and are prnct.ically independent c f these panmeters as i l l u s t r a t e d In Figme 12.
It will be observedthat the increase on t h e 9th harmcmic is In 2 dB. Harmonics up t o the 15th also Oollow t h i s trecd, terms of velocitJr the harmonics appear t o follow the sene general trends as shown i n Figure 13.
'Profile drags oy thickness effects seem t o be the only parameter which could explain these results. 1% i s of interest
- 8 -
t o note that results presented earlier f o r the ISVR rig shm the fundamental and 2nd harmonic t o bs practically constant i n level, as pitch was increased at the h:gher rotor rotational speed (1000 RRPM - 418 ftlsec t i p speed).
In the case of the three-bladed results the fundamental follows the same trends as the 2nd/3rd harmonics of single blade tests. In t h i s case there w a s no correlation with the 'Gutin' value except at the high pitch settings. The reason for t h e difference i n the trends of the fundamentalfor the two tests is not known, but it is of interest t o note t h a t the 3rd harmonic for the single bladed tests i s of the same form as the 1st harmonic for t h e three bladed tests ( i + e e at t h e same mI3 number).
Although it is not definite, i-t does appear from %lies3 reszlts that there i s another mechanism i n addition t o the 'fluctuating load mechanism' involved i n r o t o r noise generation, Alternatively it could be that the flucthiating blade loads are completely independent steady thrust and torque on t h e rotor. It is difficulty, however t o understand the velocity trends (Figurel3) i f latter reason i s used t o explain t h e results.
6. HELICOPTER RESULTS Considerable date, on +,he mise proiluced by real helicopters has been collected and asalysed over the three years of the contract.
Although t h e majj.ority of t h i s could not be used f o r detailed studies it has provided invaluable back up material. Much of the data is, however, not of direct interest t o the investigation outlined i n t h i s report and f o r t h i s reason helicopter results have only aspects of helicopter rotor noise.
been used t o i l l u s t r a t e various Some of t h i s data has already been presented i n previous status reports and it seems fair t o sbate t h a t the first results discrete components that c89. occur showing the large number of i n the region traditionally taken as being *broadband' were This Ciscovery, of course, helped produced at the ISVR i n 1965.
t o stimulate many of the theoretical studies outlined i n reference 1 .
It i s now a w e l l established fact that rotational noise harmonics (discrete frequencies ) occur i n the broadband (vortex) noise region e For t h i s reason it would appear that some authors have considered discrete frequency noise t o be the most important fromthe point of view of the 'overall noise' level i n a l l cases.
It is clear, however, from experimental results that broadband noise of very significant levels is produced by some rotor configmation.. In t h i s section of the reporb an attempt is made t o i l l u s t r a t e the relative importance of these two main types of rotor noise.
/ It w a s known from tests on the fST?i single rotor r i g t h a t broad- band noise, free fron discrete components, could be obtained provided the turbulence and/or the re-circulation around the rotor was small.
Unfortunately t h i s could only be o'btained i n the laboratory w i t h low l i k t conditions.
Since it 17as desirable t o know if these 'peaks' also occured ii the broadband *= vortex region when t h e l i f t on the blade was high, a carefully controlled test vas carried out using a I?essex helicopter. Recordings of' the Wessex hovering at an altitude of 40 ft. and 200 ft. from the microphone, were made i n normal wind conditions (wind speed aboub 8 knots) and again with a vew lo^ wind speed enviroment (less than 2 knots). The narrow band analysis results are s301m i n Figure 14;trace ( a ) shows a typical
- 10 -
1 . 5 % aarrow bar,& analyeis while (b) and ( c ) are 2 Hz bandwidth
analyses of the 'less than 2 knot' and '8 knot' wind conditions respectively. It w i l l be noted there are many discrete components i n the l i g h t wind case, trace c, and t h a t the 'broadband' noise i s Further test practically the same level for both conditions.
results have shown that 'wind' is not the controlling parameter, arid that the use of different helicopters and/or p i l o t s produces the same order of differences i n the spectrum. The two results reproduced do however tend t o show the minkurn and maximum discrete frequency noise content i n the broadband region, for t h i s particular helicopter under normal operation conditions.
T h i s clearly illustrates the effect of small scale turbulence the occurrence of discrete frequencies i n the broadband region.
a n d This does not imply that the rotational noise conponents are more important t o the overall noise level for the condition shown i n trace (c), since if the energy is computed f o r a wide frequency range it w i l l be greater from the 'broadband' than the discrete component s .
It is wo&h noting that a 1.5% or 10 Hz analysis of t h e two
conditions gives practically identical spectrum shapes , w i t h the
Thus if a semi-narrow '8 knot case' having slightly higher levels.
band analyser is used t o measure broadband noise t h e maximum level + This could detected could be due t o the discrete components, explain the apparent anomalies i n the 'broadband velocity laws' ifnich have been found on certain helj.copters.
O n other rotor configurations rotational noise will dominate A number of both the overall level and the narrow band spectrum.
examples are illusLrated i n the narrow band analysis results repro- ducted i n Figure 15. Txzce (a) is for a hovercraft propeller operating at mcderate thrust, trace (b) shows the results from a Bell Helicpker i n f l i g h t , and t r a c e ( c ) is an analysis of oce of' the All t h e recordings were taken at angles i n the ISVR test rigs.
range 105/120° from the direction of thrust and it is clear that i n each case the 'overall levelst aye dependent on the rotational It is also of interest t o observe the large noise components.
nw-ber of rotational components that can be detected on the
- 11 -
latter two traces. From the results on Figures 14 and 15 it is obvious that either rotational (discrete frequency) or broadband noise can dominate the overall noise level, and i n many cases the two types of noise can be equally hportant.
In discussing rotational and broadband noise, it should be remembered that the results do not h p l y that the two categories of noise are produced by separate mechanisms. Experimentally, howeir-r, it is necessary a t the present t i m e t o consider the two ty-pes separately since they appear t o follow different trends and t h e r i e s are not sufficiently developed t o a l l o w the ' t o t a l noise' concept t o be used.
An extensive study has been made of experimental data available, t o determine i f the rotational noise spectra follow any generd pattern. According t o theoretical considerations the results should be studied as a function of 'mB1 and not i n terms of blade passing harmonics m. To date, however, the majority of results available are for 3 and 4 bladed rotors and it has only been possible t o correlate t h e results relative t o the fundmental frequency (first blade passing harmonic).
Although The envelope of the results is presented in Figure 16.
t h e envelope applies i n general t o rnultibladed rotors operating at moderate t i p speeds, some results for a f u l l s i z e single bladed rotor (3) show a similar pattern. A comparison has also been made between the Gutin 1st harmonic Value, at an angle of 1l0/l2o0 from the direction of thrust, and measured levels of the fundmental. Good agreement was found t o occur provided the thrust was large compared t o t h e torque force, as i n n o d operating conditions.
- 3 2 - ACKNOWLEDGEXENTS The author wishes t o express his sincere thanks t o the two supervisors l i s t e d below for t h i e r help and guidance throughaut the investigation. The supervisors izre Professor E . J . Richards, now Vice-chancellor, University of Technology, Loughborough, formally Director of I n s t i t u t e of Sound and Vibration Research (Period 1st December 1946- September 1967 ) .
&. C . L . Morfey (Period Septeaber 1967 t o date).
The author muld also like t o thank the following: 1. N.A.S.A. for financial supgort of t h i s investigation.
2. Westland Helicopter Limited, Yeovil, for making freely available f i l l scsle test ma f l i g h t data and i n particular Mr. O . L . L . F i t z w i l l i a s , a i e f Fngineer (Research), for his help and interest shown i n the work.
The following helicopter manufacturers f o r supplying data 3.
i n the tape form9 an various helicopters.
Bell Helicopter Company, Fort Worth, Texas.
(a) (b) Boeing-Vertol, Morton, Pa.
Sikorsky Aircraft Company, Stratford, Conn, ( c ) References.
1. B.K. Tanna I.S.V.R. Memorandum No. 283.
Helicopter Rotor noise Final Report : Part 1 March 1969.
2 . J . F J . Leverton Ilelicoptes Noise - Blade Slop.
Part 1: Redew and Theoretical Study NASA CR-1221. October 1968 3. J . I ? . Leverton Helicopter Rotor Noise R.E. Couser Single Bladed Rotor Results.
ISAV Memo. No. 169, June 1967.
4. JeP. R O b b O t t Static Thrust Measurements of the Aerodynamic Loading on a Helicopter Rot or Blade.
EACA Tech, Note 3688 - July '56.
TABLE 1 3 -Bladed Botor ISVR R i g
f
HARMONIC ORDEB dB PITCH RRPM 8 LII?
1 2 3 4 5 6 7 8 g i o n 1 2 I 1
O0 - 52% 47* 40* 43* 45" 47* E 45% 50" 44" 44" 68
51 48% 44% 42% E 45* 45" 42" 5 40% 40 40% 69
46 47" 4435 46" 38% 4435 44" 44* 41 5 42% 40* 69
600 48 35* 46* 44* 44" 44 46s 40 42" 42% 42* 43" 71
49 4.6" 469 44" a* 46* 43% 42* 46" 46" 44% 44% 74
61 51 43* 46% 46% 48* 44" 46% 45% 43* 44* 43* 75
-
71 56 44 48" 44% 46% 44" 45% 44* 44* 47 78
-
78 62 45* 47 E 48 k6+3 46% E 44 46 46 84
2 " 4 O goo 73 70 57 60 58 54 58 55 50 52 48 48 82 1001) 79 67 61 62 67 65 62 60 60 57 57 55 84 TABLE 1 contd.
6 '
300 - 47% 53* 46% 46% 47% 46" 0 47" 53% - 44* 69
400 - 45% 548 46" 48" 54" 48" 48* - 51" 51" 47% 71
500 53 64 56 61 53 47* 56% 50 52 49 48 47 73 57 52 60 57 52% 56* 53% 54 53 52 57 54 75 703 57 64 61 65 64 58 58 57 57 57 56 55 78
800 66 68
62 62 63 64 57 63 60 58 57 56 81 900 74 74 69 70 69 65 68 67 62 6 1 4 61 G o 84
8' 300 - 39% 38% 37" 40% 3 40" 38* 37% 41" - 36% 70
42* 55 48 53 48" 52 39" 40 37 42" 38% 72 400 =- 500 57 66 64 62 51 54 55 52 55 52 47 53% T4 600 58 56 65 6 1 5 1 1 61 57 58 59 57 58% 56* 78 71 76 70 66 62 64 59 62 58 59* 60% 83 700 61 77 76 79 74 75 76 80 73 70 72% 70% 8b 800 77
- -
- 43" 48" 47* 45 48 47* 46" 45* 50% - 45% 69
loo 300
- 42% 52% 50% 57 51 52 52% 51 50 50 52 75
500 60 61 62 60 52% 53 54 54 56 56 49 52 76 600 74 61 55 63 57 58 58 60 55 54 80 62 59 72 67 68 E2 64 58 61 59 60 58 84 700 64 71
49s 55JE 47" 48" 52 48% 49% 47" 51% 45.- 45% 69
1 2 O 300 -
400 - 46% 5i5* 49* 47 57 52% 53 Fs 48" 5 75
500 59 70 65 64 54 55% 60 56 59 59 57 58 80 59 73 67 62 66 65 63 64 64 60 60% 83 600 64 -8 -+ 56 51 48" 50% 5 0 " 50 48" 51 47 48 69
300 - 48
400 - 47 58 56 59 52 57 56 55 54 55 52 76
59 70 62 65 59 58 60 59 60 56 57% 81
--I Note 46 indicates that it is not a clear peak -* indicates no peak
* peak is not 10 d9 above background level
AU l e v e l s are d~ rel. 0.002 DYNES/&
m m 2
4 - Bladed Tests -1 ISVR Rig
IiBRElOMIC ORDER dB dB.A PITCH RRPM LIB 1 2 3 4 5 6 7 8 9 i o 1 1 1 2
-
300 48 5 7 5 45 47 60 48 - 50 55 50 42 67
400 - - e w - - - 46 - 46 47 47 69 63.5
500 - 463 - - 48 44 46 48 50 50 50 49 71 67.5
600 46 - 49 - 48 48 52 52 51 55 54 52 75 71*5
700 52; - L, L= 49 50 53 54 56 54 56 - 2 77 75.5
800 65; 60 - 49 52 56 56 58 59 50 - 81 79
900 73 53 - 54 57 58 58 57 - - - - 85 83
1000 73 60 56 58 58 59 59 - - - - 87 85.5
57 0 - Lm . . 7 - Y
2 ' 300
69 66.5 - 58 52
e - .> - 4 8 - - -
70 66.75 53 -
483 =a . z = ,
- 53 44 45 - 49 - - -= 70.5 67
53 - 55 - 52 45 48 51 51 47 45 45 71.5 68.5
- 60
-
53 c - 53
700 58 52 57 51 52 lc8 74
71.5 65 59 57 58 58 59 59 56 51 53 56 53 77 7s 61 66 64 733 63 58 61 56 59 59 57 52 900 81 77.5
1000 67 7 1 66 65 63 67 61 61 57 3 7 83 80
713 70 .=A
48 -= * 43 45 - 71-72 65.5 4O 300 - - 52; -
400 67 =- - 57 48 54 46 47 48 48 45 43 71 65.5
-
500 - 623 59 - =- 38 37 34 36 33 33 32 71.5 67.5
600 59 59 65 59 56 60 57 58 52 54 51 49 75 700 5
700 - 69 62 62 63 61 63 61 55 54 514 78.5 74
800 71 65 67 66 68 68 62 61 58 60 59 - 81 77
300 763 72 68 67 64 69 64 61 - - - -- 84.5 80
1000 7 76 72 75 71 71 70 67 67 64 64 63 88 82 TABLE 2 contd.
-
583 46 47 48 76 66.5 400 57 48 57 52 46 49 44 638 62 500 66 60 63 65 75 68.5 60 58 55 53 54 56
600 - 63 68 67 64 65
65 62 62 60 53 54 79 72
68 Q 63 61 60 - 8 1 76
700 672 76 72 65 67 65
800 - - 84.5 79
75& 69 75 70 71 74 71 65
-= -
- - 87 82.5
900 79s 80 74 73 68 70 72
- =* --
46 428 45 48 45 43 47 70.5 68
-
- - 41 -
44 -
400 65 43 - 46 75 68.5
500 578 57 49 66 55 55 52 53 52 50 48 5 0 76 70 600 66 68 73 69 68 61 6 1 63 62 60 57 53 79 73.5 69 68 68 66 65 64 63 62 62 83 700 68 78;. 78 77.5 7 1 7 1 68 67 68 66 60 86 81.5 Boo 66 62 59 61 57
300 52 47 476 47 - 48 - -- 47 44 45 71.5 66
400 75. - - 55 56 - 50 50 53 52 $1 52 77-82 68.5
500 68; 62 - 6 1 58 60 58 57 57 52 52 - 77-78 70
600 68 67 65 66 65 60 60 63 59 57 54 5 1 8 1 73 700 68 79s 73 64 67 66 64 63 65 60 62 60 85.5 77
- - -
493 45 42 44 46 69 64 300 53 47 51 47
49 - 77-73 68
53 55 54 53 52 51 52 51 400 75i 543 54 80 72 653 63 62 60 58 58 57 58 54 55 500 74 67 67 66 60 63 66 61 61 57 53 83 75.5 600 65 65
300 57 493 483 - - 49 53 5 1 46 - - -= 70-72 61.5
400 75 - 62 59 - 56 56 56 -- =- -* 79 68.5
500 73 66 67 67 66 65 62 6 1 3- 60 E - 82 76* 5
I
Npte 48 indicates that it is not a clear peak
... indicates no peak
All levels are dl3 rel. 0.0002 DYNES/C!M TABLE 3 TORQUE LIFT T * A L H.P.
’ITCH RRPM BLADE LIxiT.1bs 1b.ft.
02506 0 . 1 5 O0 300 400 0.28 e 04517 0.49 .0667U 600 e 08665 0*75 12187 1.17 .15158 800 1.63 2.23 18739 1000 24221 3.1 1.71 ,174 .03206 2O 300 0.57 a 284 e 04617 400 1.02 3.06 .06978 1.58 4.76 500 * 507 600 2.28 6.84 .83a 09965 1.2 .12587 3.27 700 9.4 16058 800 4.05 12.15 1.72 5.14 15.42 2.39 20339 e 24221 1000 6.34 19.02 3.1 4.2 .192 . o ~ t 0 6 1.4 bo 300 06917 400 387 2.5 7.5 10178 3*88 u e 7 0 69 16.3 1.1 ,13865 600 5-62.
17187 ‘700 8,03 22.9 1- 57 22158 800 2.28 9.93 29.79 12.6 37.8 3.16 * 27739 1000 46.56 4.29 .34621 15 52 TABLE 3 contd.
2 . 4 4 .274 .06106 6 * 300 7.32 4 0 0 13 * 0 0 e 603 .11617 4 . 3 6 2 0 . 2 2 .16978 6.74 1.03 600 29.22 ,20365 9.74 1.55 2 . 3 1 .26487 700 13.91 3 ? . 5 1 7 . 2 5 1 . 6 800 3 . 3 3 e 3 3 6 5 8 21.8 65.4 4 . 8 9 .44539 .425 .io506 8 O 300 3 . 5 3 10*59 1 8 . 5 a 14817 400 6.32 3'25 9 . 8 1 1 . 4 4 2328 500 29.43 600 42.45 2.23 14 41 . 3 0 3 6 5 1 4 . 1 .581 .15106 loo 300 4 . 7 1 . 1 8 ,24217 400 8 . 4 1 25 23 2 . 0 6 ,34078 13.05 3 9 . 1 5 5 0 0 600 18.81 5 6 . 4 3 3 . 2 7 .45465 .22406 17.7 .831 12O 300 5 . 9 600 2 3 . 6 70.8 4.91 .69465 21 24 1.03 ,28206 14O 300 7.08 TORQUE LIFT H . P .
'ITCH mplvl BLADE LIFT.& 1b.f-t.
.03306 O0 300 0,175 400 0 382 .06917 0 . 6 8 .io078 .12665 600 1 . 0 1 1 . 6 ,17887 ,22058 800 2.23 3.22 29039 zoo0 4 . 3 8 0.42 1.68 0.183 03506 2O 300 0 . 7 6 3.04 0 362 ,06517 1 . 1 8 4.72 0.647 0 O g 5 U 13165 600 1 . 6 9 6.76 1 . 0 3 8 2.44 I . 608 9.35 a7987 12 04 2.26 ,22458 800 3.01 3 . 8 2 15.28 3.37 28533 4.46 36621 1 0 0 0 1 8 . 8 4*7 1 ' 2 1 4 . 8 4 .228 ,05273 4 O 300 8-64 .483 .09217 400 2 . 1 6 1 3 . 4 4 -855 0 1 3 2 7 7 3 . 3 6 5 0 0 600 4 . 8 5 19.4 1 . 4 3 ,18865 6 . 9 4 2.12 . 2 1 r 4 8 7 2 6 . 5 3.02 .so858 eo0 34.3 4 8 . 5 9 1 0 . 8 4 3 . 2 4 . 4 40739 TABLE 4 con%,d.
8.64 2.16 0.357 .08706 6' 300 0.748 .lSU7 400 3.86 3.5'44.
1.33 .21778 23.92 500 5.98 8.62 2.11 * 28965 600 34.48 3.22 .38487 12.98 700 47.5 4.71 A9658 800 61.08 15-23' 1-9.40 6.92 * 65639 77.6 0.544 .14106 3.18 12.72 8 ' 30 22.72 1.05 214.17 400 5.68 8.82 35.28 1.977 .33278 600 12.7 50.8 3.23 -45565 0.723 .lgTO6 4.24 16* 96 loo 300 1.47 .31217 400 30.36 7.59 46.88 2.76 .47178 11.72 4.69 .67165 600 67.8 16.95 24,3 92.0 7.69 .95287 1.405 -39706 5.98 23 92 l 2 O 300 95 0 44 6.97 1.0076 600 23.86 1.36 2.61106 26.32 14O 300 6.53
' 0 . 5 1 2 3 4 4.5
tip cutf Rotor radius (ft.)
Comparison of spanwise loading calcuhated using blade element Fig.1 theory and estimated from N.A.C.A 3688 (method of obtaining empirical correction for calculating blade lift).
(Case iliustrated: 3blades - 60pitch - 600r.r.pm)
..
Blade Loading Weston rig 1 Whirlwind blade 4 000 2 000 vi n .-.
e .t
.-
-I k .
/-
C atcula te d '+ve' and '-v% cornpone 150.
A-
of Lift at Scuff .
1 - # I I s n 1 i UO 160 / . 180 20 0 220 240 260 Rotor ( r r p m ) speed Fig. 2. Comparison of calculated and measured blade loading.
I I I 1 I I I I 1 I & 0 0 Q 0 - h cp v) U Q)
'la's
., -0 C b N tQ ro . .
*
m ..
.
m E
z
1 a's
-4-J fz In
>
i Y .I n Q: w- vi L or - W u
.-
-7 Y c Qt
c
E
L W u j Q ri, m
i i
' 1 a 'S
i 3
CI Ln U . .
c
c
Q, E ' 3 .
' 7 ' d ' S h 5c a : vi Fig..€3. 1000 RRRM.
0 2 i
900 R.R.F?M.
Fig. 9.
4 e 0 2
9. SPL. v P i t c h
. .
i
a : m- .
0 .
N c I %- ' 7 ' d ' S .
I sss BLADE - 'WESTON' TOWER - I= HARMONIC s' P 1 TCH 6 0 so 4 0 3 0 140 149 180 2 0 0 230 260 RR.P.M.
7 0 I 3" PI T C H I I / I 6 0
m -
-U
2 5 0
n
4 0 140 160 I80 2 0 0 23 0 R. R.P. M 6 0 . - 23 0
7 0 .-
6 0 - -
I / I , i 5' 7 O 9O ' I t 0 1 3 O I 5 CUFF PITCH
Full scale single bladed results
Fig.11.
r 230 RRPM.
3Wessex blades 1st harmonic
3rd.' O- -3
1 S55 blade
-c -+-- - - +- -c- Is.+-/ / ,'
A d - / 2nd. / i
+- -
- o - - - o $= e - - - -
n: / Ji
1st ,'
I , + ' 9th.
,,-y-- - j p - / -Y- ---v Y - / 7" 9" 1 1 " 13" is9 wx.
7 O 9" 11° 13" S55 5" Cuff pitch angle Fig.12. Rotational m i s e variation with pitch.
I I I I 0.37 0 . 4 3 0.48 0.53 0.59 0.64 Tip maeh num S P L v Tip m a c h number' Fig . 1 3 .
. .
I- LL r\l I I - J I--* LL rf v ! L !
m >- _-I z n Z m e us Z w L?
l-4 -I 0, a >- I- 0 0 0 L n r - rr!
,W3/3NACI 1000'0 '13tI BCI - 13A31 3tILnES3ad ClNnOS 0- m
K
u ! !
l-4 C l-4 b "N I I
5i
In L u .
w
a
e
M
B
CL
s
a
4 p '
N u , 'n VI A N