1、RESEARCH MEMORANDUM A PRELIMINARY EXPERIMENTAL INVESTIGATION OF A SUBMERGED CASCADE INLET By R. Duane Christiani and Lauros M. Randall Arne s Aeronautical Laboratory Moffett Field, Calif. ClASSlFfCATtON CANCELLED NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WASHINGTON March 25, 1949 Copy No. Rd No. A
2、9A24 5 - . ._ . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-OF A SUBMERGED CASCAIlE IKGET By R, lzuase Christiani and Irturs M. Randall An elcperlnaental investigation of a submerged air inlet incor- porating a cascade of airfoils for turning and
3、 dlffusing the entering air is bscribed. The investigation was prelimimry in nature and intended to be a guide for further research on this tspe inlet . Variables asswiated with both mCA- submerged air inlets and airfoil.scade designs were considered. Modifications to the submsrged inlet included ch
4、anges to the ramp plan f om and ramp angle. The casoade variables were: caecaaxis inclination, cascade4lade angle, solidity, and inclination of the aenter line of the duct aft af the casoade of airfoils. For a cascade having a given nwd19r of blades and blade apcirg, increasing the inclination of th
5、e oascade aria from 20* to 40 inoreased the =ximum pressure recovery for a given inclination of the duct center line and diffusion of the intab air. Increasing blades) inoreased the mximum ran-pressure recoveries obtained with large air defleotians and reduced the maximum nm-pessure recoveries obtai
6、ned with mll air deflections. the solidity =ti0 Of the OaSCade from 0 (no babe) t0 2 moo (9 The test results showed that for inlehvelooity ratios less then 1.0 an entranoe mnp with aurved diverging walls provided substantially higher z”pessure recoveries than a ramp with parallel walls. The detz”b1
7、effect upon rabpessure recovery of increasing ramp angle was found to De less for the submerged inlet with a cascade of airfoils thsn previoua research had i39m for the submerged inlet alone. Ramp angle B between 8O and 10 . appeared to be about optirmns from considerations of ram-pressure recovery.
8、 - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 A cascade of airfoils my be employed to defleot an air stream with relatively mll loss of available energy. With proper ge- metrio arrangement, the deflection at? the air stream is also accompnled
9、by a oormiderable decrease in velmity. As prt of the pmgram to study ductrinlet problems, an invest; igation was =de -to dStermLne the feasibility of incorporating a oaeoade of airfoils as an integral part td a fully submrged intab. It was reasoned that,if an efficient ossoade of airfoils were combi
10、ned with an EACA submerged inlet (reference l), the resultant air-induction system would diffuse and defleot the air in a mininnrm of spoe and still give a rea80nabl0 nuwp-essure recmry. The inmetigation discussed here was preliminary in nature and was meant to sem as a guldq for future researoh. On
11、ly the more important variables Crp airfoi1“oaeuade and submerged-inlet design were oonsidered. SYMBOLS a1 arbitrarily defined area of the inlet at station 1 C blade chord, feet (A1 = wt sin a), square feet H total pressure, pounds per square foot AE .total“pressure loss, pounds per squsse foot 2 di
12、stance between the movable duct walls measured along the casoade axis, feet P statio pasure, pounds per square foot Q Qmamlc pressure, POm of cascade axis (fig. 2) MODEL AKD AP!TlE The subnerged cascade inlet was installed on one side rd a model Provided by IHSNot for ResaleNo reproduction or networ
13、king permitted without license from IHS-,-,-4 NACA RM No. A924 of a fuselage. No wing or tail surfaces were included un the model, 7- by lirelocity ratio an envelope of the OUPBE fOr various blade angles represents the maximum value of ?mwcecovery ratio attain, able with the tspe of inlet used for a
14、 given angle of the duct center line. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 To summrize the results of the tests with various modifioakions of the inlet, the envelopes of the urns of msximum -uoverg ratio obtained for the range of angles
15、of the duct oenter line investigated were determined for variours inlet-velmity ratioer. These results are presented in figures 8 to 10. The pobts of bqprny of the envelope cur“ with the aurvBs representing the wriation of lam-recovery ratio wlth angle of ths duct oenter line for constant blade angl
16、es are indioated by the inbrsaotione of the dashed lines with the envelope CUVS. For a given angle of the duct center line, as would be the ease for a norml lmtallatian, It ie evident that the optirmun blade angle varied sumwhat vith inlet velocity ratio. The inlet-velocity ratio for mxlmum rmna-eco
17、very ratio was not established for all modifications of the inlet tested. The range of inlet-velocity ratios investigated was aomidered adequate for this preliminmy investigation; it was limited by the size of -1, tha capacity aP the ctxupressor sumlying the awclliasg air, and the required accuracy
18、of the data. Caeoade Modlf loations As shown by the data of figure 8, Increasing the solidity ratio fram 0 to 0.67 gave higher ram+reoovery ratios for all angles of the duct center line tested, particuhrly far those angles greater than 300. ncreasing the eolidity ratio froan 0.67 to 1.00 generally p
19、rovided a elight increase of nxwreoovery ratio for duot cantesline angles greater than 40. Further inarease of soliaity ratio from 1.00 to 2.00 gave detrimental effeots for emall angles of the duct center line and large inlet-veloafty rat106 but increased the ncovery ratios for the largest angles of
20、 the duct center line investisted. It is apparent from theee data that the soiLidity ratio for nmximum mapressure recovery inoreased with inoreasing angle of the duct center line . For a fixed blade chord, the optimum solidity ratio should increase with air defleotion up to the point where the press
21、ure loseres provided by the inoreasing rimer of blades offeet the increased turning effloiemy. The optlnrum solidity ratio was Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-RllCA RM Ro. A9224 9 not established for ths larger air deflections by the
22、conditions tested. Cascaaxis amles.- The envelope curves of the lnaximum ra+ recovery ratios obtained with cascade-axis angles of 20, 30, and 40 are shown in figure 9. The data were obtained with the ranp havfng parallel walls and a cascade solidity ratio of 1.0. As the engle of the cascade axis inc
23、reased from 20 to bo, the entrance width-tdpth ratio .decreased from 2.05 to 1.09 and the raslp angle increased frm 7.90 to 13.7O because of the mechanic8 of the model. It was found in reference 1 that variations of entrance width-tc+ depth ratio within this range had only a -11 effect on -recovery
24、mtio for a submerged inlet with pmllel ramp walls. As will be shown later, variation of ramp eagle within the range encountered hd only a -11 effect. The results presented in figure 9 indicate that for a given angle of the duct oenter line the mxirmrm mn-pressure recoveries increased with increasing
25、 angle of the uascade axis, For an angle of the duct center line of 4oo and an idet-mlocity mtio of 0.6, increasing the angle OP the cascade axis from 20 to bo increased the mxirmrm ram-recover;g ratio fran 0.50 to 0.65. The ratios of the velocity of the air aft of the cascade to that of the free-st
26、rearm air for these two conditions were 0.24 and 0.39, respectively. For constant values of inlet-velocity ratio and angle of the duct center line the aamunt that the air was diffused in pssing through the cascade decreased as the cascade-axis angle increased. This reduc- tion of diffusion at the hi
27、gher cascade-axis aqles would provi.de a smaller pressure rise aoross the cascade and should reduce the pressure losses . To provide a more equitable comparison for a given engine installation, results which illustzate the effect of cascade-axis angle on the mximum mxa-pressure recoveries obtained f
28、or a given diffusion have been tabulated. For a ratio of the velocity aft of the cascade to free-sixeam velocitr V2/T0 of 0.3 and an angle of the duct center line of kOo, the following results were obtained: Maximum ram- cp recovery ratio VJV 200 60 .46 400 .58 56 30 0.52 0.76 Provided by IHSNot for
29、 ResaleNo reproduction or networking permitted without license from IHS-,-,-10 SFmilar results were obtained for other diffusione and angles of the duct center line. It is noted that the largest angles of the casoads axis tested provided the Mast ram-recovery ratios. Submerged-Entmace Modif iwtions
30、Two important design prameters which affect the aerodynamic cha.racteriatio8 of 8Ub11rged-typ air inleta are ramp plan form and raslp angle, as has been indioated in reference 1. The effects of these two geometzical changes on the oharaoteristics of a submerged inlet utilizing a oascade of airPoils
31、were imstigated. A solidity ratio of 1.0 and a oascade-axis angle of 20 were ohoeen for the i8titiDfI. Pasn, Dlan form.- Previous research on submerged inlets has shown tbat at the lower Inle-L-velOcity ratios curved divergent ra;mp walla effected substantial gains in -pressure recovery over that at
32、tainable with parallel ramp Wll8. Figure 10 shm this cha?xcixr- istio to be true also for a cascade inlet. For an angle of the duot center line of 4-00 and an ir The angle8 of the duct center line teated, however, did not cover a all casoade blade angles and emp angles. The maxim mnqreseure recoveri
33、es attainable for any angle of the duct center line, there- fore, were not aeoertainad. Test results are presented in figures = and 12, however, for three blade angle0 and the test angles of the duct center line that met nearly represented those for mxirmun ram-pressure recovery. The results are giv
34、en as the variation of rmweoovery ratio with inlet-velocity ratio far ramp anglee of 7.9O, 9.7Ot E.oO, and 13.0 for the InJ-et with Fuel ranrg (fig. U) and the inlet with curved divergent ramp W +, 20“; q LO; A X9p Iv P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-u, 0 (No b/odes/ .90 .BO 8S.70 /O 20 30 40 50 60 Ang/e of dud cent6f/neJ yJ deg u, LOO .a 0 10 20 30 40 50 60 Ang/e d duct center /ineJy, deg . P, 2.00 /O 20 30 40 50 60 Angle of duct center /ineJyJ deg
36、 Figure 8. - Variafion of maximum rom -recovery rafio wifh angh of duct cenfer line for four so/idify ratios wifh para/e/ ramp wa/s. +, 2 0: p, Z9: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26 gjgo a 50 f .6O f! .40 *300 /O PO 30 40 50 60 P e A
37、ngle of duct center line,y, deg 90 60 .m .60 30 .40 300 IO 20 30 40 50 60 Angle of pr lo, . . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. 1. 0 .60 so e! t 6 .40 .30 lniet-velocity ratio, Y 15.0 ,$*O -70 F .60 P e k ,50 P p: Q 6 -40 0 .P .4 .6 .8 LO i.2 1.4 Intet-ve/ocity ratio, V& I figure 12. - The effect of mmp angle on the variatim of ram-recovery ratio &it inlet-uelocity mto for. the ramp with curved divergent w/k +,2q L7,f.o. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
