HYDRAULIC TURBINES

1 Hydraulics and HYDRAULIC MachinesD r . M . N . S h e s h a P r a k a s h , P r o f e s s o r , J . N . N . Co l l e g e o f E n g i n e e r i n g , S h i m o g a1 HYDRAULIC TURBINESI n t r o d u c t i o n :T h e d e v i c e w h i c h c o n v e r t s h yd r a u l i c e n e r g y i n t o m e c h a n i c a l e n e r g yo rv i c e v e r s a i s k n o w n a sH y d r a u l i c M a c h i n e h e h yd r a u l i c m a c h i n e sw h i c h c o n v e r t h yd r a u l i c e n e r g y i n t o m e c h a n i c a l e n e r g y a r e k n o w n a sT u r b i n e sa n d t h a t c o nv e r t m e c h a n i c a l e n e r g y i n t o h yd r a u l i c e n e r g y i sk n o w n a sP u m p s.

2 F i g . s h o w s a g e n e r a l l a yo u t o f a h yd r o e l e c t r i c p l a n t .Animation as in the PPTHghLHPenstockTurbineTailraceHeadraceH eadRaceTailRaceHgHhLHydraulics and HYDRAULIC MachinesD r . M . N . S h e s h a P r a k a s h , P r o f e s s o r , J . N . N . Co l l e g e o f E n g i n e e r i n g , S h i m o g a2It c o n s i s t s o f t h e f o l l o w i n g :1 .ADa mc o n s t r u c t e d a c r o s s a r i v e r o r a c h a n n e l t o s t o r e w a t e r . T h er e s e r v o i r i s a l s o k n o w n a sH e a d r a c e .2 .Pi p e s o f l a r g e d i a m e t e r c a l l e dP e n s t o c k sw h i c h c a r r y w a t e r u n d e rp r e s s u r e f r o m s t o r a g e r e s e r v o i r t o t h e t u r b i n e s.

3 T h e s e p i p e s a r eu s u a l l y m a d e o f s t e e l o r r e i n f o r c e d c o n c r e t e .3 .T u r b i n e sh a v i n g d i f f e r e n t t yp e s o f v a n e s o r b u c k e t s o r b l a d e sm o u n t e d o n a w h e e lc a l l e d r u n n e r .4 .T a i l r a c ew h i c h i s a c h a n n e l c a r r yi n g w a t e r a w a y f r o m t h e t u r b i n ea f t e r t h e w a t e r h a s w o r k e d o n t h e t u r b i n e s . T h e w a t e r s u r f a c e i n t h et a i l r a c e i s a l s o r e f e r r e d t o a s t a i l r a c e .I m p o r t a n t T e r m s :G r o s s H e a d ( Hg) :It i s t h e v e r t i c a l d i f f e r e n c e be t w e e n h e a d r a c e a n dt a i l r a c e.

4 N e t H e a d : ( H ) :N e t h e a d o r e f f e c t i v e h e a d i s t h e a c t u a l h e a d a v a i l a b l ea t t h e i n l e t o f t h e t o w o r k o n t h e t u r b i n e .H = Hg-hLW h e r ehLi s t h e t o t a l h e a d l o s s d u r i n g t h e t r a n s i t o f w a t e r f r o m t h eh e a d r a c e t o t a i l r a c e w h i c h i s ma i n l y h e a d l o s s d u e t o f r i c t i o n , a n d i sgi v e n b ydgVLfhf242 W h e r efi s t h e c o e f f i c i e n t o f f r i c t i o n o f p e n s t o c k d e p e n d i n g o n t h et yp e o f m a t e r i a l o f p e n s t o c kLi s t h e t o t a l l e n gt h o f p e n s t o c kVi s t h e m e a n f l o w v e l o c i t y o f w a t e r t h r o u gh t h e pe n s t o c kDi s t h e d i a m e t e r o f p e n s t o c k a n dgi s t h e a c c e l e r a t i o n d u e t o g r a v i t yHydraulics and HYDRAULIC MachinesD r.

5 M . N . S h e s h a P r a k a s h , P r o f e s s o r , J . N . N . Co l l e g e o f E n g i n e e r i n g , S h i m o g m T Y P E S O F E F F I C I E N C I E SD e p e n d i n g o n t h e c o n s i d e r a t i o n s o f i n p u t a n d o u t p u t , t h e e f f i c i e n c i e sc a n b e c l a s s i f i e d a s( i )H yd r a u l i c E f f i c i e n c y( i i )M e c h a n i c a l E f f i c i e n c y( i i i )O v e r a l l e f f i c i e n cy( i )H yd r a u l i c E f f i c i e n c y: ( h)It i s t h e r a t i o o f t h e p o w e rd e v e l o p e d b y t h e r u n n e r o f at u r b i n e to the power supplied at the inletof a turbine.

6 Since the power supplied is HYDRAULIC ,and the probable loss is betweenthe striking jet and vaneit is rightlycalled HYDRAULIC is the Runner Power and is the Water Power(ii)Mechanical Efficiency: ( m)It is the ratio of the power available at the shaft to the power developed by therunner of a turbine. This depends on the slips and other mechanical problems thatwill create a loss of energy between the runneri n t h e a n n u l a r a r e a b e t w e e nt h e n o z z l e a n d s p e a r , t h e a m o u n t o f w a t e r r e d u c e s a s t h e s p e a r i sp u s h e d f o r w a r d a n d v i c e-v e r s a.

7 A n d s h a f t w h i c h i s p u r e l y m e c h a n i c a l a n d h e n c e m e c h a n i c a le ff i c i e n c S . P . i s t h e S h a f t P o w e r( 0 2 )( i i i )O v e r a l l E f f i c i e n c y: ( )It i s t h e r a t i o o f t h e p o w e r a v a i l a b l e a t t h e s h a f t t o t h e p o w e rs u p p l i e d a t t h e i n l e t o f a t u r b i n e . A s t h i s c o v e r s o v e r a l l p r o b l e m s o fl o s s e s i n e n e r g y, i t i s k n o w n a s o v e r a l l e f f i c i e n cy. T h i s d e p e n d s o nb o t h t h e h yd r a u l i c l o s s e s a n d t h e s l i p s a n d o t h e r m e c h a n i c a l p r o b l e m sInlet of turbineTurbine h ( 0 1 )Hydraulics and HYDRAULIC MachinesD r.

8 M . N . S h e s h a P r a k a s h , P r o f e s s o r , J . N . N . Co l l e g e o f E n g i n e e r i n g , S h i m o g t h a t w i l l c r e a t e a l o s s o f e n e r g y b e t w e e n t h e j e t p o w e r s u p p l i e d a n dt h e p o w e r g e n e r a t e d a t t h e s h a f t a v a i l a b l e f o r c o u p l i n g o f t h eg e n e r a t o r .( 0 3 )F r o m E q s 1 , 2 an d 3 , w e h a v e = hx mC l a s s i f i c a t i o n o f T u r b i n e sT h eh yd r a u l i c t u r b i n e s c a n b e c l a s s i f i e d b a s e d o n t yp e o f e n e r g y a tt h e i n l e t , d i r e c t i o n o f f l o w t h r o u gh t h e v a n e s , h e a d a v a i l a b l e a t t h ei n l e t , d i s c h a r g e t h r o u gh t h e v a n e s a n d s p e c i f i c s p e e d.

9 T h e y c a n bea r r a n g e d a s p e r t h e f o l l o w i n g t a b l e :TurbineType ofenergyHeadDischargeDirectionof flowSpecificSpeedNameTypePeltonWheelImpu lseKineticHighHead >250m to1000mLowTangentialto runnerLow<35 Single jet35 60 Multiple jetFrancisTurbineReactionTurbineKinetic +PressureMedium60 m to150 mMediumRadial flowMedium60 to 300 Mixed FlowKaplanTurbineLow< 30 mHighAxial FlowHigh300 to 1000A s c a n b e s e e n f r o m t h e a b o v e t a b l e , a n y s p e c i f i c t yp e c a n b ee x p l a in e d b y s u i t a b l e c o n s t r u c t i o n o f s e n t e n c e s b y s e l e c t i n g t h e o t h e ri t e m s i n t h e t a b l e a l o n g t h e r o w.

10 Hydraulics and HYDRAULIC MachinesD r . M . N . S h e s h a P r a k a s h , P r o f e s s o r , J . N . N . Co l l e g e o f E n g i n e e r i n g , S h i m o g a5 PenstockNozzleWheelSpearP E LTO N W HE E L O R T UR BINEP e l t o n w h e e l , n a m e d a f t e r a n e m i n e n t e n gi n e e r , i s a n i m p u l s e t u r b i n ew h e r e i n t h e f l o w i s t a n g e n t i a l t o t h e r u n n e r a n d t h e a v a i l a b l ee n e r g ya t t h e e n t r a n c e i s c o m p l e t e l y k i n e t i c e n e r g y. F u r t h e r , i t i s p r e f e r r e da t a v e r y h i gh h e a d a n d l o w d i s c h a r g e s w i t h l o w s p e c i f i c s p e e d s.