## Friday, November 27, 2009

### Modification of the Hydraulic system in existing Hydram System

Introduction : As we know that the principle of working of hydram is based on change in impulse momentum which is able to lift small quantity of water to relatively higher head using available energy of flowing water at lower head with larger quantity of water. However, the hydram is not getting success up to the optimum potential due to its operational and maintenance problems. Jerk due to up and down of the valve leads to high vibration and frequent breakage of joints / seal and valve itself. This problem can be avoided by replacing snifting box to turbine system and centrifugal pump having pump characteristics of low discharge and high head which can be mounted on the same shaft of the turbine. Part of the excess water from the tails race of the turbine can be stored in a small sump-well in which suction pipe of the centrifugal pump can be lowered.

Principle of the modified hydram is as under :

Power generated by the turbine with available discharge, Q and head, H would be

P = w Q H ηt (1)

Where,

w = Unit weight of water

ηt= Efficiency of turbine

Similarly the power required by the pump to lift discharge, q up to height of h would be

P = w x q x h / ηp (2)

Where,

w = Unit weight of water

h = head of water to be lifted

ηp= Efficiency of pump

From equation (1) and (2) it is observed that P would be same, neglecting minor losses.

P = w x Q x H x ηt = w q h / ηp

(q/Q) x (h/H) = ηt x ηp

(q/Q) x (h/H) = η (3)

Where,

η = Combined efficiency of turbine and pump

i.e. product of the ratio of discharges and ratio of heads would be constant and equal to the combined efficiency of the turbine and pump. The reduction of discharge from Q to q would enable to increase in head from H to h according to principle of conservation of energy if neglect the all losses and product would be equal 1. But in practical, due to energy losses at various stages the product of the above ratios would always less than 1 which will equal to η.

Conclusion and action to be taken : The techno-economic feasibility of the system based on above principle needs to be explored.This will provide a low cost lift irrigation system especially for hilly region for irrigation as well as water supply system and also save huge cost of energy involved for lifting water by two/three stage rising mains from Khad and Nallah having sufficient discharge.