Measured Far-Field Flight Noise of a Counterrotation Turboprop at Cruise Conditions

Abstract

R i c h a r d P. Woodward, I r v i n J . L o e f f l e r , and James H. D i t t m a r N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n Lewis Research Center C l e v e l a n d , O h i o 44135 SUMMARYModern high-speed p r o p e l l e r (advanced t u r b o p r o p ) a i r c r a f t a r e expected t o o p e r a t e on 50 t o 60 p e r c e n t l e s s f u e l t h a n t h e 1980 v i n t a g e t u r b o f a n f l e e t w h i l e a t t h e same t i m e matching t h e f l i g h t speed and performance o f t h o s e a i rc r a f t . C o u n t e r r o t a t i o n t u r b o p r o p engines o f f e r a d d i t i o n a l f u e l s a v i n g sb y means o f upstream p r o p e l l e r s w i r l r e c o v e r y . T h i s paper p r e s e n t s a c o u s t i c s i d el i n e r e s u l t s f o r a f u l l -s c a l e c o u n t e r r o t a t i o n t u r b o p r o p e n g i n e a t c r u i s e c o n d it i o n s . The engine was i n s t a l l e d on a Boeing 727 a i r c r a f t i n p l a c e o f t h e r i g h t -s i d e t u r b o f a n engine. A c o u s t i c d a t a were t a k e n from an i n s t r u m e n t e d2 L e a r j e t chase p l a n e . S i d e l i n e a c o u s t i c r e s u l t s a r e p r e s e n t e d f o r 0.50 and i n a wind t u n n e l a t 0.72 Mach c r u i s e c o n d i t i o n s . The model d a t a were a d j u s t e d t o f l i g h t a c q u i s i t i o n c o n d i t i o n s and were i n g e n e r a l agreement w i t h t h e f l i g h t r e s u l t s .

Nearfield Unsteady Pressures at Cruise Mach Numbers for a Model Scale Counter-rotation Open Rotor

“…Comparisons of model scale acoustic data to the full-scale counter rotating engine flight test in the 1980's were found to be in good agreement. [5] 2.1 Drive Rig • C (200 • F), and can be independently controlled using a feed-back system to drive the rotor speeds independently to more than 8,000 RPM with an accuracy of ± 15 RPM. This drive rig was operated in the late 1980's, and was refurbished in order to correct any detrimental effects of long-term storage.…”

Acoustic Shielding for a Model Scale Counter-rotation Open Rotor

“…Comparisons of model scale acoustic data to the full-scale counter rotating engine flight test in the 1980's were found to be in good agreement. [11] 2.1 Model Description…”

The Acoustic Environment of the NASA Glenn 9- by 15-Foot Low-Speed Wind Tunnel

“…Testing in the 9x15 LSWT has included model turbofans and propellers for both NASA research projects and external customers. 9,10,11 Current turbofan models are powered by the NASA Ultra-High Bypass drive rig. 12 Recent and future turbofan models being evaluated are advanced designs incorporating technologies such as reduced fan tip speeds, increased bypass ratios and advanced acoustic liners.…”