Studies on simple and restricted orifice surgre tanks

Abstract

This thesis deals with certain basic experimental studies conducted on the phenomenon of mass oscillations in restricted orifice surge tanks. Simple surge tanks were also studied, they being considered an extreme case of restricted orifice surge tanks. The studies were made to find out the effect of the steady discharge through the penstock, the size of the orifice and the size of the surge tank on the mass oscillation. The experiments were restricted to the cases of sudden full load rejection and instantaneous full load acceptance. The regulation, in the latter case, was for constant gate. The present thesis comprises of two parts. The first part is a brief review of existing literature on various aspects of the problem of mass oscillations in surge tanks, while the second exclusively deals with the investigations carried out by the author. Part I consists of four chapters. Chapter 1 is an introduction to the phenomena of water hammer and mass oscillations. It contains also a brief historical review of the development of various types of surge tanks. Chapter 2 is mainly devoted to the theory of mass oscillations in surge tanks. The exact solutions are given wherever they exist and certain approximate methods of solution are also indicated. The practical methods of detailed and exact analysis for any general surge tank problem are briefly described. In Chapter 3, the principles of dynamical similitude as applied to surge tanks are described. The scale ratios for various conditions are developed. The scale effects observed by various investigators are indicated. Chapter 4 deals with the problem of stability as applied to various types of surge tanks. The results of the investigations of various research workers are broadly summarised. Part II of the thesis comprises of four chapters. Chapter 5 describes the objectives of the experimental investigations reported, the details of the experimental set-up and the experimental procedure. In Chapter 6, the various results obtained from the experiments are presented in the form of tables and curves. The chapter is devoted to a detailed discussion of the results. In Chapter 7 the results obtained, for some cases of experiment, by calculation with the approximate methods proposed by Calame and Gaden, Paynter, and Taylor et al are compared with those observed on the hydraulic model. Chapter 8 briefly summarises the effects of the steady discharge through the turbines (Q?), diameter of the orifice (d?) and the diameter of the surge tank (D?) on (i) the magnitudes of the extreme surges, (ii) the values of time required for the extreme surges to be attained, (iii) the periods of oscillation and on (iv) the damping rates. Based on the comparison made in Chapter 7, recommendations have been made regarding the particular approximate method that can be usefully adopted for the calculation of the various factors involved in the analysis of a surge tank problem.