Design construction and testing of a small axial flow propeller turbine

Abstract

The possibility of extracting power from water resources in Malta was probably never investigated due to lack of natural lakes and rivers on the island. Furthermore, rainfall in Malta is so infrequent that large water catchments are not feasible. Nowadays, water production on the island is mostly dependent on Reverse Osmosis (R.O.) which is one of the most common commercial methods for separating soluble salts from water. Normally, in such systems, only 33% of the feed water is actually converted to potable water, the rest is being discharged to the sea as brine. Consequently, such a large reject has aroused our interest in investigating the possibility of recovering part of this fluid energy available for use in the R.O. plants. The large flow rates of reject water are normally discharged at low heads and consequently the use of an axial flow propeller turbine seemed adequate for such a situation. This project consisted mainly in designing, constructing and performance testing of a small propeller turbine, the results of which were used in studying the feasibility of installing such a turbine for the existing conditions at the R.O. plants. The context includes considerations of the basic theory involved when treating propeller turbines. The design and manufacture of each of the main features of the turbine are described separately. The results obtained from the tests carried out on the model constructed are given in Chapter 5 followed by the relevant conclusions deducted in relation to the R.O. plant considered. The main handicaps encountered were the lack of time available, lack of financial resources and the scarcity of literature relevant to the subject.