Cavitation treatment of water from a wastewater treatment plant

Hydrodynamic cavitation damages the apparatus by intensive cavitational erosion of the elements in a hydro system. Being acquainted with the mechanisms of effect, hydrodynamic cavitation can be used to intensify technological processes in different industrial areas. The aim of the present work is to investigate the possibilities using hydrodynamic cavitation for wastewater treatment from an urban treatment plant. To intensify the purifying process series of trials, at different levels of intensity of the electrical field in the zone of cavitation, were performed. Additionally presented, the electrical field assists in forcing the process of silver ions separation with the purpose of microbiological purification of the flowing water. Here we present the results of experimental studies conducted at various times and electrical fields intensity. These trials substantiate the idea of the microbiological purification of wastewaters via hydrodynamic cavitation and represent a huge range of opportunities for applying this method in various industrial fields. The basic criterion that supports our statement is the enormous drop of the microbe number by increasing the cavitation treatment time.

Cavitation research results of hydroturbine impeller blades and their analysis

Cavitation erosion affects the hydropower plants operation mode, destroys the surface of water-conducting way, affects the efficiency coefficient as well as the turbine output. The most common damage is observed on water-conducting ways having poor streamline shape, various ledges, irregularities along the water flow. Disruptive cavitations are formed initially on the rotation axes of vortexes, and the caverns of disruptive cavitation develop with the period subordinating the Strouhal Law. One of the methods of cavitational erosion field studies is the method of obtaining high-speed cavitational erosion of metal plates, which has low resistance to cavitation mechanical effects. It provides an opportunity to determine erosion degree and intensity at different modes of hydropower plants operation. The paper demonstrates the results of studying the cavitational erosion process of hydroturbine impeller blades of Zhiguli Hydroelectric Station (HS). Cavitation tests are conducted for three operating modes. Technological peculiarities are also described. The paper presents results of turbine blades of Unit 5 for three operation modes. The destruction areas of impeller blades peripheral edges are visualized. The study provides the results of field and laboratory cavitation tests of hydroturbine elements that serve as recommendations for repairing and restoration of damaged hydroelectric units of Zhiguli HS.

Destruction Mechanism of ZnAl4 as Cast Alloy Subjected to Cavitational Erosion Using Different Laboratory Stands

The main reason of a cavitational destruction is the mechanical action of cavitation pulses onto the material’s surface. The course of cavitation destruction process is very complex and depends on the physicochemical and structural features of a material. A resistance to cavitation destruction of the material increases with the increase of its mechanical strength, fatigue resistance as well as hardness. Nevertheless, the effect of structural features on the material’s cavitational resistance has been not fully clarified. In the present paper, the cavitation destruction of ZnAl4 as cast alloy was investigated on three laboratory stands: vibration, jet-impact and flow stands. The destruction mechanism of ZnAl4 as cast alloy subjected to cavitational erosion using various laboratory stands is shown in the present paper.

The Effect of Aluminum Content on the Microstructure and Cavitation Wear of Feal Intermetallic Alloys

Intermetallic-based alloys (so called intermetallics) of the Fe-Al binary system are modern construction materials, which in recent decades have found application in many branches of the power, chemical and automotive industries. High resistance of FeAl based alloys to cavitational erosion results first of all from their high hardness in the as-cast state, large compressive stresses in the material, as well as homogeneous structure. In the present paper, the effect of aluminum content on the microstructure, texture and strain implemented upon cavitation wear of FeAl intermetallic alloys, have been analyzed by field emission gun scanning electron microscopy (FEG SEM) and electron backscatter diffraction (EBSD) analysis. Obtained results of structural characterization indicates that with increasing aluminium content effects of orientation randomization (weakening of <100>//ND casting texture), grain refinement and rising of mechanical strenght (and so cavitational resistance) take place.

Cavitation Erosion Resistance of Alloys Used in Cathodic Protection of Hulls of Ships

Seawater is an aggressive environment which causes the necessity of using corrosion protection of hulls of ships. Cathodic protection is an effective prevention method which has been applied in this area for many years. In this method, potential of the ship’s hull is reduced by using galvanic anodes (so-called protectors), which are additionally exposed to cavitation erosion. Results of cavitation erosion resistance investigation of alloys commonly used in cathodic protection of hulls of ships, are presented in this paper. The tests were carried out on the three, most often applied materials which are zinc, aluminium and magnesium alloys. The investigated samples were subjected to cavitation conditions in a jet-impact laboratory stand. Destruction mechanism of the surface layer affected by working liquid was described. The highest cavitational erosion resistance among all studied alloys was exhibited by AlMg alloy.