Improvement of the method of determining cavitation characteristics of the centrifugal pumps

Cavitation is a process of formation of vapor bubbles within a liquid at low pressure regions. There are strain ten- sions at low-pressure region, which lead to a gap, producing cavitational cavities. These cavities contain vapor bub- bles. When cavities come to a high pressure region, they collapse, leading to a local water hammer which is able to erode the surface of a centrifugal pump. The occurring and the evolution of cavitation in liquids bound to the existence of so called cavitational cores. A physically pure liquid can resist to a strain tension efficiently, however industrial liq- uids always have cavitational cores. The cavitational cores are undissolved gas inclusions. The acceleration of evolu- tion of cavitation depends on free and dissolved gases and thermodynamic properties of liquid as well. Cavitation brings three negative factors to the performance of a centrifugal pump: performance failure - an abrupt decreasing of main parameters; erosion corrosion; low-frequency pulsations that cause the unstable work. Every centrifugal pump goes through cavitational tests for the determination of the cavitation performance. How- ever, the contemporary test methods do not have the required accuracy; moreover, the duration of a test is bigger than the work time of a pump in a rocket engine. The paper has the suggestion of the accelerated method of cavitational tests. To get the results, the new method works without maintaining of the mass flow rate, but with increased pressure-change speed on the pump entrance. For the decreasing of the error, the new method includes automatic measuring system. The authors have determined that the accelerated method with automatic measuring system does not influence the accuracy, but in the same time makes the test process shorter in time and easier to accomplish.