Theoretical performance of turbojet engine for light subsonic aircraft

e l s t a t i c c o n d i t i o n s w a s c a l c u l a t e d u s i n g component maps e s t i m a t e d by L e w i s component s p e c i a l i s t s .A t n o m i n a l c r u i s e c o n d i t i o n s , t h r u s t i s 346 pounds (1540 N) and s p e c i f i c f u e l consumption i s 1 .2 5 pounds f u e l p e r hour p e r pound o f t h r u s t (0.127 kg/(hr) (N)).Compressor p r e s s u r e r a t i o i s f o u r w h i l e t u r b i n e i n l e t t e m p e r a t u r e i s 1560' R (867O K).A minimum s p e c i f i c f u e l consumption of 1 . 1 5 pounds f u e l p e r h o u r p e r pound t h r u s t (0,117 kg/(hr) (N)) i s o b t a i n e d a t 75 p e r c e n t r a t e d t h r u s t and a t u r b i n e i n l e t t e m p e r a t u r e o f 1330O R (739' K).A t 25 p e r c e n t r a t e d t h r u s t , s p e c i f i c f u e l consumption i s 1 .5 9 pounds f u e l p e r hour p e r pound t h r u s t (0.1625 kg/ ( h r ) (N)) .With t h e d e s i g n v a l u e o f e x h a u s t n o z z l e a r e a , t h e e q u i l i b r i u m o p e r a t i n g l i n e f o r s e a -l e v e l s t a t i c c o n d i t i o n s i n t e r s e c t s t h e e s t imated compressor s u r g e l i n e a t 72 p e r c e n t r o t a t i o n a l s p e e d .Thus, some form o f v a r i a b l e geometry i s r e q u i r e d t o o b t a i n s u r g e margin below t h i s s p e e d .When compressor e x i t b l e e d was used, a d e q u a t e s u r g e margin was o b t a i n e d ; b u t v e r y h i g h v a l u e s o f t u r b i n e i n l e t t e m p e r a t u r e were r e q u i r e d (2300' R' (1278' K ) ) a t a t h r u s t s e t t i n g o f 6 p e r c e n t o f maximum s e a -l e v e l t h r u s t ) .