Copyright 1983 by ASME NEGATIVE INCIDENCE FLOW OVER A TURBINE ROTOR BLADE

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1 THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 345 E. 47 St., New York, N.Y GT-23 ^+ The Society shll not be responsible for sttements or opinions dvnced in ppers or in G discussion t meetings of the Society or of its Divisions or Sections, or printed in its publictions. Discussion is printed only if the pper is published in n ASME Journl. Sl Relesed for generl publiction upon presenttion. Full credit should be given to ASME, the Technicl Division, nd the uthor(s). Ppers re vilble from ASME for nine months fter the meeting. Printed in USA. Copyright 983 by ASME NEGATIVE INCIDENCE FLOW OVER A TURBINE ROTOR BLADE H. Dvid Joslyn, Reserch Engineer Robert P. Dring, Mnger, Gs Turbine Technology United Technologies Reserch Center Est Hrtford, CT 68 ABSTRACT The opertion of vrible cycle gs turbines t negtive incidence cn result in highly three dimensionl seprted flows on the turbine rotor pressure surfce. These flows cn impct both performnce nd durbility. The present progrm ws conducted to experimentlly study the behvior of surfce flow on lrge scle xil flow turbine rotor with incidence vrying up to nd including negtive incidence seprtion. Fullspn pressure distributions nd surfce flow visuliztion were cquired over rnge of incidence. The dt indicte tht t lrge negtive incidence, pressure surfce seprtion occurred nd extended to 6 percent chord t midspn. These seprted flows were simulted t midspn by pplying potentil flow theory to mtch the mesured pressure distributions. NOMENCLATURE B, Airfoil xil chord C Absolute flow speed Cp Pressure coefficient: (P Tl -P)/(PTl-P2) P Sttic pressure PTReltive totl pressure: (p + _, W2) r Rdius U Wheel speed W Reltive flow speed x Axil distnce Reltive flow ngle P Density Subscripts Rotor inlet 2 Rotor exit x Axil m Midspn INTRODUCTION Component durbility (life) is vitl concern to the gs turbine designer. The opertion of dvnced high pressure turbine irfoils (rotor bldes) t negtive incidence in vrible cycle engines cn result in conditions tht could drsticlly shorten their life expectncy. Wlker nd Mrklnd (Ref. ) hve shown tht for turbine cscde with ttched boundry lyers, incresed negtive incidence resulted in n increse in pressure surfce het trnsfer due to the boundry lyer trnsitioning from lminr to turbulent flow. Opertion t negtive incidence leding to pressure surfce seprtion would be expected to result in locl increses in het trnsfer coefficients to pproximtely twice tht of the ttched turbulent boundry lyer vlues (Ref. 2). It hs lso been shoen (Refs. 3 nd 4) tht strong rdil outflows cn be present on the pressure surfce of turbine rotor blde. The results (Ref. 3) indicted tht ny film coolnt injected from the forwrd 3 percent of xil chord of the pressure surfce would not rech the triling edge region s typicl throughflow design clcultion might ssume. Under conditions of negtive incidence seprtion, more drmtic mldistribution of pressure surfce coolnt nd possible coolnt "blowoff" might be expected to occur. This sitution could led to loclized metl distress on the irfoil nd significntly reduced rotor blde durbility (life expectncy). Presently, due to the hostile therml environment Downloded From: on /3/29 Terms of Use:

2 nd size limittions in ctul engine test rigs, there is little informtion vilble to guide the designer s to the nture of the surfce flow over turbine rotor blde t negtive incidence. To provide some insight into this re, the present study ws performed to experimentlly determine the nture of the surfce flow over lrge scle xil flow turbine rotor operting up to nd including negtive incidence seprtion. The onset, size nd surfce flow chrcteristics of the seprted region were determined with surfce flow visuliztion nd mesured fullspn rotor pressure distribuions. The onset of seprtion t midspn ws predicted using the two dimensionl boundry lyer clcultion, ABLE (Ref. 5). The size of the seprted region ws simulted nlyticlly using the mesured irfoil pressure distribution s input to n inviscid, two dimensionl, finite re clcultion (Ref. 6). The results of this study show tht t lrge negtive incidence, extensive pressure surfce seprtion occurs. The seprted region is fullspn nd extended up to 6 percent xil chord t midspn for the mximum negtive incidence tested. The surfce flows re nerly rdilly outwrd in the seprted region. These rdil flows would hve definite dverse impct on the effectiveness of ny pressure surfce cooling scheme. EXPERIMENTAL FACILITY The United Technologies Reserch Center (UTRC) Lrge Scle Rottion Rig No. I (LSRR-I) is 5 feet (.52 meters) in dimeter. The.8 hub/tip rtio turbine model normlly hs three rows of irfoils: first vne, first blde nd second vne. For the present study, the second vne row ws removed. The xil spcing (x/b x ) between the first vne nd first blde ws.65. Both irfoils hve spect rtios (spn/ xil chord) of pproximtely unity. The irfoil chords re pproximtely five times engine scle. The lrge scle hs the dvntge of giving Reynolds numbers which re typicl of high pressure turbines t nominl model running conditions of 4 rpm nd test section verge xil flow velocity of 75 ft/sec (23 m/s). Vrition of (C x /Um ) nd hence rotor inlet ngle ws chieved by vrying the rotor speed. The motivtion for this pproch ws to hold the irfoil Reynolds numbers (bsed on exit velocity) constnt t ll test conditions. The vrious bsolute nd reltive flow ngles nd the irfoils tht produce them re lso typicl of current high pressure turbine stges. A more detiled description of the turbine model cn be found in Refs. 3, 4 nd 7. DISCUSSION The root, midspn nd tip contours of the rotor blde re shown in Fig.. The irfoil xil chord ws constnt with spn. The leding edge ws lened in the direction of wheel speed nd the triling edge ws lened pproximtely the sme mount in the opposite direction. The nominl tip Fig.. Rotor Geometry (X/B x ) BE ROOT clernce ws.4 percent of the rotor spn. The inlet flow ngle, l, nd the chnge in incidence, i, from the design vlue re defined in Fig.. MIDSPAN The running conditions, tht is, the vlues of (C x /Um ) t which the flow visuliztion nd pressure distributions were to be cquired were estblished s follows. At the nominl design flow coefficient (C x /Um =.78), the reltive inlet flow ngle t midspn ws deduced from the mesured rotor midspn pressure distribution by compring mesured nd computed (Ref. 6) potentil flow results. This process hs been described previously (Refs. 3, 4 nd 8). The deduced rotor exit flow ngle used in Refs. 3, 4 nd 8 of 25.5 ws found to lso give excellent results in the present study. At the nominl design flow coefficient reltive inlet flow ngle t midspn of 4 ws deduced. The rotor inlet flow ngle t midspn ws then clculted s function of (C x /Um ) ssuming tht the gp verged first vne exit bsolute velocity ws invrint with wheel speed. Vlues of (C x /Um ) were selected which would provide steps in the midspn reltive inlet flow ngle (elm) from 35 to 85. In ll cses, C x ws the model inlet (St. of Fig., Ref. 7) verge xil velocity. Experimentl Results With the test conditions estblished fullspn flow visuliztion ws crried out t ech selected rotor midspn inlet flow ngle. The flow visuliztion technique ws the sme s tht employed in Refs. 3 nd 4. In brief, it consisted of flowing smll mount of mmoni out of the rotor pressure tps. The mmoni cused blue streks to pper on Ozlid pper which hd been glued to the surfce of the irfoil. The results for ll inlet flow ngles hve been reported in Ref. 9 nd results for the design inlet flow ngle, 5l m = 4, hve lso been included in Ref. (Fig. ). TIP Downloded From: on /3/29 Terms of Use:

3 At ll inlet flow ngles between 35 nd 55, the flow visuliztion on the pressure surfce indicted ttched flow with strong rdil deflection towrd the tip. It ws demonstrted by Dring nd Joslyn (Ref. 4) tht these pressure surfce flow ptterns were not result of tip lekge. When the tip clernce ws reduced from.4 to. percent spn the flow pttern ws the sme except in the immedite vicinity of the tip. It hs been shown (Ref. ) tht these rdil deflections on the pressure surfce cn be ttributed to the reltive eddy" present in the blde-to-blde flow. This rdil outflow on the pressure surfce is shown in Fig. 2 t blm = 55 (just prior to the onset of fullspn pressure surfce seprtion). Little chnge ws observed in the nture of the pressure surfce limiting stremlines s b lm ws incresed from 35 to 55 s long s the boundry lyer remined ttched. However, t midspn inlet ngle of 65 the pressure surfce boundry lyer ws seprted t the leding edge nd over the entire spn (Fig. 3). The surfce flow within the seprtion bubble ws generlly rdilly outwrd. Rettchment occurred t loctions vrying from bout 2 percent xil chord t the root to 6 percent xil chord t the tip. At the lrgest inlet flow ngle exmined (bi n = 85 ) the rettchment loction vried from 5 percent xil chord t the root to 7 percent t the tip (Fig. 4). Before continuing with the discussion of the effect of negtive incidence on the rotor pressure surfce flow, the flow visuliztion results on the suction surfce nd the tip will be briefly discussed. As seen in Fig. 4, t l m = 85, the suction surfce ws free of boundry lyer seprtion nd ws very two dimensionl until influenced by the hub nd RADIAL OUT-FLOW Fig. 2. Rotor Pressure Surfce Flow Visuliztion Prior to Fullspn Seprtion (bl m = 55 ) tip endwll secondry flow. It ws found tht the suction surfce limiting stremlines chnged little with inlet ngle from 35 to 85 (Ref. 9). However, the greter flow ccelertion (convergence) in the rotor chnnel t 85 cused some reduction in the spnwise extent of the endwll secondry flow cells nd n incresed region of nerly two dimensionl flow bout midspn. As shown in Ref. (Fig. ), A Ttnr ha Ark IT Fig. 3. Rotor Pressure Surfce Flow Visuliztion After Onset of Fullspn Seprtion (l m = 65 ) t the design inlet flow ngle (el m = 4 ), the lekge flow on the blde tip ws from pressure surfce to suction surfce t ll loctions. However, the tip lekge flow chnged drmticlly s result of the incresed inlet ngle. At slm = 85 there ws flow from the suction surfce onto the tip of the irfoil nd then returning to the suction surfce (Fig. 4). This reversl in the tip flow ws result of the severe leding edge overspeed occurring on the pressure surfce t lrge negtive incidence. In the nlysis of the fullspn rotor pressure distributions both the inlet reltive totl pressure nd the inlet reltive flow ngle hd to be deduced. Where seprtion did not occur (el m < 55 ), the inlet reltive totl pressure ws deduced from the rotor pressure surfce sttic pressure t 24 percent xil chord. For cses where seprtion occurred, the inlet reltive totl pressure ws deduced from sttic pressure mesurements ner the stgntion point. The spnwise distribution of inlet reltive totl pressure corresponded very closely to uniform rotry pressure (PT,rot = P + 2p (W 2- U 2 ). The vrition of PT,rot with rotor incidence corresponded very closely to wht one would expect if the sttor exit gp verged bsolute velocity vector (Fig. 6, Ref. 7) ws invrint with rotor speed. Inlet flow ngles were deduced t six dditionl spnwise loctions t 5l m of 4. The spnwise distribution t the other vlues of, lri were bsed on the ssumption tht t ech rdil loction the first vne exit gp verged bsolute velocity vector, C, ws invrint with rotor speed. The results re shown in Fig. 5. Note tht the rnge of ngle vrition increses considerbly with spn. In ll cses constnt rotor exit ngle of 25.5 ws found to give best greement in mtching the mesured blde pressure distribution. As mentioned bove, this ws consistent with erlier experience (Refs. 3, 4 nd 8) with this rotor. The mesured (symbol) midspn pressure distributions nd those predicted (line) using the clcu- Downloded From: on /3/29 Terms of Use:

4 3( 2 i' Id, I L iil L _I.I I, i:u cm ) SUCTION SURFACE AND TIP 9' RADIAL -- OUT-FLOW b) PRESSURE SURFACE AND TIP 3m 85 Fig. 4. Rotor Pressure nd Suction Surfce Flow Visuliztion with Mssive Seprtion ltion of Ref. 6 re shown in Fig. 6 for inlet flow ngle vritions from,35 to 85. At 35 the flow on the suction surfce decelerted from the leding edge overspeed ll the wy to the triling edge. On the pressure surfce, however, the flow ccelerted from the leding edge stgntion point to the triling edge. At 4 much of the suction surfce t midspn hd only very smll pressure grdient. At inlet ngles from 45 to 85 the suction surfce flow ccelerted smoothly to the throt t bout 6 percent chord) nd then decelerted to the triling edge. On the pressure surfce there ws wek overspeed t 45 which incresed in depth s the inlet ngle ws incresed. It ws known from the flow visuliztion results (Figs. 2 nd 3) tht fullspn pressure surfce seprtion first ppered between 55 nd 65. At 65 there ws no cler indiction of seprtion evident in the mesured midspn 3 ' ' 5 SPAN (%) Fig. 5. Rotor Spnwise Vrition of Reltive Inlet Flow Angle pressure distribution. However, the impct of seprtion on the mesured pressure distribution could be seen clerly t inlet flow ngles of 75 nd 85 where the predicted (inviscid) pressure surfce leding edge overspeed nd recompression were not in good greement with the mesured dt. The mesured nd computed pressure surfce results cme together t the loction where the rettchment ws seen to occur, e.g., t 6 percent chord t 85 (Figs. 4 nd 6). Finlly, s could be seen from the mesured nd predicted results, the stgntion point moved from loction t bout 5 percent xil chord on the pressure surfce t 35, round towrd the suction surfce to loction t percent xil chord t 85. This would be n importnt considertion in the design of ny rotor leding edge cooling scheme. 4 Downloded From: on /3/29 Terms of Use:

5 pim not clerly evident in the mesured pressure distribution until long fter seprtion hs ctully occurred (el m > 65 ). From 87.5 percent spn to percent spn, the pressure surfce leding edge overspeed predicted by the two dimensionl nlysis is not evident in the dt. I- N - The fullspn nture of the rotor pressure distribution prior to seprtion (el m in the rnge 35 4 to 55 ) hs been reported in Ref. 9. The fullspn (DESIGN) dt t design conditions (lm = 4 ) is reported in Ref. (Fig. 7) nd will be summrized briefly s follows. The greement between the mesured nd computed results ws excellent from 2.5 percent spn out to 87.5 percent spn on both the suction 45 nd pressure surfce. The strong three dimensionl flow due to the hub nd tip secondry flow ppered to hve no significnt effect on the pressure distributions t these spn loctions. As pointed out in Ref. 4, the rdil flow on the pressure surfce hd little effect on the pressure distribution becuse the rdil component ws smll reltive to the 55 totl flow speed nd the totl dynmic pressure itself ws very smll there. Close to the hub t 6.25 percent spn there ws considerble unloding on the suction surfce reltive to the computed results. A very similr effect ws observed by Lngston, et l. (Ref. ) in turbine cscde 65 experiment of similr geometry. At 98 percent spn there ws lrge deprture from the computed results. The freestrem velocities ner the pressure surfce were much higher due to the close proximity of the tip corner. The velocities ner the suction 75 surfce ft of the throt were lso much higher thn predicted. This ws probbly result of the combined influences of the tip lekge nd the tip secondry flow. (XIBx) Fig. 6. Rotor Midspn Pressure Distributions, lm = 35 to 85 The fullspn nture of the rotor pressure surfce distribution is illustrted in Figs. 7 nd 8. Ech figure contins the mesured nd computed pressure distributions from 6.25 percent to 98. percent spn. Although surfce flow visuliztion (Fig. 3) showed fullspn pressure surfce seprtion t slm = 65, the greement between the mesured nd computed results ws in excellent greement in the midspn region between 2.5 percent out to 75. percent spn. The comprison of the mesured midspn pressure distribution with the computed pressure distribution to determine the onset of fullspn seprtion would hve been very misleding in this cse since the impct of the seprtion is 85 As lm incresed from 65 to 85, the effects of the negtive incidence stll on the pressure surfce leding edge overspeed predicted by the inviscid nlysis ws not evident in the dt. Rther, the pressure surfce dt exhibited region of reltively constnt pressure indictive of flow seprtion extending bck to bout 6 percent xil chord t midspn. The more extreme nture of the leding edge overspeed predicted t the tip reltive to tht predicted t the root ws due to the much lrger incidence vrition t the tip reltive to tht t the hub (Fig. 5). It is interesting to note tht s the inlet ngle incresed (nd lso the rotor convergence rtio) the greement between the mesured nd computed results on the suction surfce ner the hub (t 6.25 percent spn) ws slightly improved. At 85 the re of poorest greement on the suction surfce ws t the tip (98 percent spn) nd ft of the throt. Anlyticl Results A two dimensionl boundry lyer clcultion ws performed for ll vlues of sl m to predict the onset of seprtion on the blde pressure surfce t midspn. The computer progrm ABLE (Ref. 5) ws used to clculte the pressure surfce boundry lyer properties from the blde leding edge stgntion point Downloded From: on /3/29 Terms of Use:

6 SPAN (%) SPAN (%) 6.25 C F- & d_ I I U I- 5 U (X/B X ) (X/Bx) Fig. 7. Rotor Fullspn Pressure Distributions, lm = 65 to the point of seprtion or to the blde triling edge, whichever occurred first. Results (blde surfce velocity) obtined from the inviscid clcultions (Fig. 6) tht provided the best greement with the mesured blde surfce pressure distributions were used s input to ABLE in lieu of the ctul mesured dt for severl resons. First, the density of the mesured dt ner the blde pressure surfce leding edge nd the predicted overspeed/recompression region ws reltively sprse. Since the boundry lyer clcultion is sensitive to dt density, the inviscid results were judged to be the best choice. Second, since slight locl inccurcies in the mesured pressure distributions could result in lrge errors in the clculted boundry lyer ccelertion pr- Fig. 8. Rotor Fullspn Pressure Distributions, Flm = 85 meter, the use of the inviscid nlysis ws gin judged to be the prudent choice. Also, since the ctul flow ws three dimensionl nd the boundry lyer clcultion is two dimensionl it ws more pproprite to use the predicted velocity distributions from the two dimensionl inviscid code. The clcultions were mde ssuming tht the flow ws ) lminr nd 2) fully turbulent from the leding edge stgntion point. The folowing results were obtined. For l m from 35 to 45 the boundry lyer clcultion indicted tht the pressure surfce boundry lyer would not seprte except for the lminr clcultion t i,l m of 45. The boundry lyer clcultions (lminr nd turbulent) for lm 6 Downloded From: on /3/29 Terms of Use:

7 from 55 to 85 ll indicted pressure surfce seprtion. The lminr nd turbulent clcultions predicted tht the seprtion point (x/b x ) would move forwrd towrd the leding edge (x/b x from percent xil chord to 7 percent xil chord nd 3 percent to percent xil chord, respectively) s 5l m ws incresed from 55 to 85. In generl, the predicted onset of seprtion ws in greement with the flow visuliztion results. However, t Ulm = 55, the boundry lyer clcultions predicted seprtion to occur for both the lminr nd fully turbulent cses, wheres the flow visuliztion results indicted tht the pressure surfce flow ws ttched. An explntion for this hs to do with the plcement of the Ozlid pper used for flow visuliztion. For Fl m from 65 to 85 the predicted seprtion loction (x/b x ) ws upstrem of the leding edge of the Ozlid pper used for flow visuliztion. At hl m of 55, the predicted seprtion loction ws pproximtely 5 percent xil chord downstrem of the leding edge of the Ozlid pper. It is therefore believed tht the leding edge of the pper my hve intercted with the boundry lyer in such wy s to prevent seprtion. Therefore, t Ll m = 55, positioning the Ozlid pper leding edge t loction further downstrem (x/b x predicted seprtion loction) my hve resulted in flow pttern exhibiting seprted flow unlike the results of Fig. 3. The powerful impct tht negtive incidence seprtion could hve on the rotor pressure distribution t Hl m = 85 ws seen in the midspn dt in Fig. 6 nd in the fullspn dt in Fig. 8. The pressure surfce seprtion bubble hd its origin in the inbility of the boundry lyer to negotite the severe recompression of the leding edge overspeed. The seprtion resulted in reduction in the depth of the overspeed (from Cp of.3 to.6) compred to the inviscid clcultion (Figs. 6 nd 8) nd gretly incresed the distnce over which recompression occurred. At midspn the bubble ws seen to close t bout 6 percent chord in both the flow visuliztion (Fig. 4) nd in the pressure distribution (Figs. 6 nd 8). In n ttempt to estimte the size of the seprtion bubble t midspn nd t 85 two pproches were explored: () simulting the bubble by chnging the irfoil pressure surfce contour nd (2) simulting the bubble by mss ddition nd removl long the pressure surfce. The results re illustrted in Figs. 9 nd. The ctul irfoil contour nd the hypotheticl contour used to simulte the pressure surfce bubble re shown in Fig. 9. The hypotheticl contour ws rrived t by djusting the pressure surfce contour until greement ws obtined with the mesured surfce sttic pressure dt. The hypotheticl contour provided n excellent mtch between the mesured nd computed results long the entire pressure surfce nd lso long the suction surfce. The incresed blockge due to the bubble cused higher velocities (lower pressure) not only on the pressure surfce but lso on the suction surfce (Fig. 6). There ws feture of this comprison which, AIRFOIL CONTO HYPOTHETICAL CONTOUR ---SURFACE BLOWING Fig. 9. Potentil Flow Simultion of Seprted Flow Using Hypotheticl Contour nd Surfce Blowing t Fl m = 85 however, ws not totlly defensible. The mesured dt nd the computed results for the ctul contour represented pressures long the ctul contour (Fig. 6). For the hypotheticl contour the computed results represented pressures long the bubble displcement surfce (i.e., on the hypotheticl contour) which were not necessrily the sme s those on the ctul contour. In the second pproch to simulting the size nd shpe of the seprtion bubble distribution of the norml velocity component ws specified long the pressure surfce. Here gin the distribution of norml velocity ws djusted until close greement hd been obtined with the mesured pressure dt. The distribution of positive nd negtive norml velocity ws specified in such wy tht there ws no net ddition of mss to the flow. The mesured results nd the computed results both with nd without blowing on the pressure surfce re shown in Fig.. Also shown is the distribution of norml velocity (WN-Wl). The results re much the sme s for the hypotheticl contour except tht in the present cse both the mesured nd computed results re on the ctul irfoil contour. The pressure distribution in the fluid long the dividing stremline (short dshed lines of Fig. 9) between the fluid in the seprtion bubble nd the minstrem flow over it is lso shown in Fig.. As cn be seen the differe;ce between the pressure on the surfce nd long this dividing stremline is substntil. As shown in Fig. 9, the dividing stremline is similr to the hypotheticl contour but locl differences here lso re substntil. CONCLUSIONS Experimentl dt nd nlyticl results for n xil flow turbine rotor hve been presented which provide detiled informtion on the fullspn nture of the flow over the rotor with prticulr ttention given to negtive incidence seprtion. Specific conclusions derived from the results re summrized Downloded From: on /3/29 Terms of Use:

8 N H N U -.5 z 3.5 WITHOUT BLOWING. ^. - - ON THE AIRFOIL WITH --- ON THE BUBBLE BLOWING.n.5 / / X/BX Fig.. Potentil Flow Simultion of Seprted Flow Using Surfce Blowing - Pressure nd Norml Velocity Distributions t 2l m = 85 s follows.. Fullspn negtive incidence stll occurred on the pressure surfce bove midspn inlet flow ngle of 55 nd grew in extent to 6 percent of xil chord t 85. This would hve very strong impct on film coolnt coverge which coupled with n increse in locl het trnsfer rtes, could result in reduced turbine blde life. 2. Prior to negtive incidence stll, the rotor pressure distributions were in excellent greement with two dimensionl potentil flow theory from 2.5 percent spn to 87.5 percent spn. 3. The mesured rotor pressure distributions did not clerly indicte the onset of seprtion t n ngle of 65 lthough fullspn seprtion ws very evident in the surfce flow visuliztion. From this one would conclude tht mesured pressure distributions re reltively insensitive indiction of the onset of seprtion. 4. The predicted onset of fullspn pressure surfce seprtion ws in fir greement ith the flow visuliztion results. 5. The effect of lrge negtive incidence seprtion on the rotor pressure distribution t midspn ws simulted both by mtching the computed nd mesured pressure distributions for ) hypotheticl irfoil, tht is, one with its pressure surfce contour thickened to simulte the seprtion bubble, nd 2) n irfoil with pressure surfce distribution of blowing nd suction to simulte the seprtion bubble. 6. The rotor suction surfce ws influenced by the hub nd tip secondry flow but mjor portion of it ws covered by ttched, nerly two-dimensionl boundry lyer flow. Evidence of the secondry flow t the root ws seen in the pressure distribution t 6.25 percent spn nd evidence of the secondry flow nd the lekge flow t the tip ws seen in the pressure distribution t 98 percent spn. 7. At lrge negtive incidence, due to the strong leding edge overspeed, tip lekge flow pssed from the suction surfce onto the tip. In summry, negtive incidence opertion of high pressure turbine bldes cn result in extensive fullspn pressure surfce seprtion. Although this three dimensionl mechnism is beyond the scope of the current nlyticl techniques, knowledge of its existence nd impct on turbine pressure surfce flow cn begin to provide guidnce to the turbine designer. ACKNOWLEDGMENTS The work reported herein ws performed under the direction of Dr. Kervyn Mch (APL/POTC), project engineer, Contrct Number F The uthors re indebted to mny people for the successful completion of the progrm nd in prticulr to Dr. Joseph R. Cspr for his inclusion of mss ddition in the blde-to-blde potentil flow nlysis. REFERENCES. Wlker, L. A. nd E. Mrklnd: Het Trnsfer to Turbine Blding in the Presence of Secondry Flow, Int. Journl of Het nd Mss Trnsfer, Vol. 8, pp Ot, T. nd N. Kon: Het Trnsfer in the Seprted nd Rettched Flow on Blunt Flt Plte, ASME Journl of Het Trnsfer, pp , November Dring, R. P., M. F. Blir, nd H. D. Joslyn: An Experimentl Investigtion of Film Cooling on Turbine Rotor Blde, Trns. ASME, Journ. Eng. for Power, Vol. 2, No., Jnury 98, pp Dring, R. P. nd H. D. Joslyn: Mesurements of Turbine Rotor Blde Flows, Trns. ASME, Journ. Eng. for Power, Vol. 3, No. 2, April 98, pp Crter, J. E., D. E. Edwrds nd M. J. Werle: Coordinte Trnsformtion for Lminr nd Turbulent Boundry Lyers, AIAA Journl, Vol. 2, No. 2, Februry 982, pp Cspr, J. R., D. E. Hobbs nd R. L. Dvis: Clcultion of Two-Dimensionl Potentil Cscde Flow Using Finite Are Methods, AIAA Journl, Vol. 8, No., Jnury 98, pp Joslyn, H. D., R. P. Dring nd. P. Shrm: Unstedy Three-Dimensionl Turbine Aerodynmics, ASME Pper No. 82-GT-6, April Dring, R. P., H. D. Joslyn, L. W. Hrdin nd J. H. Wgner: Turbine Rotor-Sttor Interction, ASME Pper No. 82-GT-3, April Dring, R. P., H. D. Joslyn, L. W. Hrdin nd J. H. Wgner: Reserch on Turbine Rotor Sttor Interction nd Rotor Negtive Incidence Stll, AFWAL-TR- 8-24, Components Brnch (POTC), Turbine Engine Division (POT), Aero Propulsion Lbortory, Wright Aeronuticl Lbortories, Wright-Ptterson Air Force Bse, OH.. Dring, R. P. nd H. D. Joslyn: The Reltive Eddy in Axil Turbine Rotor Pssges, to be presented t the 983 ASME Gs Turbine Conference.. Lngston, L. S., M. L. Nice nd R. M. Hooper: Three-Dimensionl Flow Within Turbine Cscde Pssge, ASME Jour. Eng. for Power, Vol. 99, No., Jnury 977, pp Downloded From: on /3/29 Terms of Use: