526 



HYDRAULICS AND ITS APPLICATIONS 



Governing of Impulse Wheels The preceding considerations also apply, 



The governing of both turbines is by oil-pressure Servo-motor (relay motor). 



The diagrams Bhow the maximum change of speed with sudden charge or discharge. Observations to the left of each vertical 

 line represent charge in kilowatts ; those to the right, discharge in kilowatts. 



TURBINE. VII TURBINE IX 



Normal 500 fievs per Mm 



ffeacf, ff- 60m 



These are fitted with 

 heavy Fty wheel> 



Fly wheel Moment of Jnertut "* Fly wheel Moment of Inertia 



aD'- 560OO Kam * a I)** 10500 Kfrrr, 2 



Head- H- 147m. 



56000Kgr. 



Cut off Period, 

 at 2150 Kw Load -25 

 Pressure Variation, 18% 



L englh of Supply 

 & K Pipe -WOm 



Dvomteter-'ZOm 



^ 



These hadno 

 separcUeFty-wheet, 



Total 



Moth turbines are governed by oil-pressure Servo-motor. 



Tu rbine X 1 1 Turbine XI II 



The turbine is fitted with auto- The turbine is fitted with jet 



mat.ic pressure regulation. rut-off gear. 



Normal :575 revs, per minute Normal 030 revs, per minute 



Head H = 350 m. Head H = 850 m. 



Fly-wheel moment of inertia Fly-wheel moment of inertia 



g D'-J = 55,000 sq. kg.- m. g D'-J = 13,000 sq. kg.-m. 



Max. pressure variation, 1.8 per Max. pressure variation, 3.9 per 



cent. cent. 



Length of supply -pipe = 925m. Length of supply pipe -2130rn 



= 1.35m. 1.05m. Diameter = 0.5 m. 



FIGS. 252, 253. Governing Tests of Pressure Turbines. 



so far as cases a and b are concerned, to the governing of impulse turbines, 



except where, as in the case 

 of a Pelton wheel fitted with 

 deflecting nozzle, the velo- 

 city of flow through the 

 supply main is maintained 

 uniform for all loads. Al- 

 though in this case inertia 

 effects are not to be feared 

 in the governing of the tur- 

 bine, yet the occasional 

 necessity for quickly shut 

 ting off the supply renders 

 the provision of a relie 

 valve near the lower end o 

 the pipe essential. 



Owing to the absence o 

 any cyclical variation o 

 turning moment in a pres- 



2000 3000 4000 1000 2000 



& Output Kyv Output, 



FIG. 254. Governing Tests of Pelton Wheel. 



3000 



sure turbine, a special flywheel is not usually necessary for clost 

 governing, sufficient flywheel effect in general being obtained from th( 



