Zhenlong Fang

Effects of area discontinuity at nozzle inlet on the characteristics of self-resonating cavitating waterjet

The current research on self-resonating cavitating waterjet(SRCW) mainly focuses on the generation mechanism and structure optimization. Researches relating to the influences of disturbances at nozzle inlet on the characteristics of the jet are rarely available. In order to further improve the performance of SRCW, effects of area discontinuity(enlargement and contraction) are experimentally investigated using three organ-pipe nozzles. Axial pressure oscillation peak and amplitude as well as aggressive erosion intensity of the jet are used to evaluate the effects. The results reveal that area enlargement and contraction affect the peak differently, depending on the inlet pressure, nozzle geometry, and standoff distance; while area contraction always improves the amplitude regardless of these factors. At inlet pressures of 10 MPa and 20 MPa, area discontinuity improves the peak at almost all the testing standoff distances, while this only happens at smaller standoff distances with the inlet pressure increased to 30 MPa. The capability of area discontinuity for improving the amplitude is enhancing with increasing inlet pressure. Moreover, the cavitation erosion ability of the jet can be largely enhanced around the optimum standoff distance, depending on the type of area discontinuity and nozzle geometry. A preliminary analysis of the influence of area discontinuity on the disturbance waves in the flow is also performed. The proposed research provides a new method for effectively enhancing the performance of SRCW.

Numerical and experimental investigation on flow field characteristics of organ pipe nozzle

As a new technology that is developed rapidly in recent decades, water jet technology is widely applied in coal, petroleum, chemical industry, aviation, construction, etc. Self-resonant cavitating jet, by playing cavitation, is capable of great destruction. As a typical kind of self-resonant cavitating nozzle, organ pipe nozzle has its special application. In this paper, the flow field of organ pipe nozzle was numerical simulated. Nozzles with different structures were manufactured according to simulation results; their performances were tested on different driving pressure under the condition of submerging. The results showed that working pressure, cavity length and cavity diameter had influence on the characteristics of organ pipe nozzle and it exited optimum parameters.

The influence of collapse wall on self-excited oscillation pulsed jet nozzle performance

The self-excited oscillation pulsed jet (SOPJ) is widely used owing to its simple structure and good separation of pressure source and system. The structure of nozzle is one of the main factors that influence the performance of the SOPJ nozzle. Upper collapse wall and lower collapse wall is important to the formation and transmission of eddy in oscillation cavity. In this paper, the influence of collapse wall on SOPJ nozzle was analyzed by numerical simulation. The LES algorithm was used to simulate the flow of different combinations of collapse wall. The result showed that when both collapse walls are of the same type, the SOPJ nozzle will have a good performance; the influence of upper collapse wall is more obvious than lower one; model of two-semi-circle upper collapse wall is the first choice when we design SOPJ nozzle.

Numerical investigation on high-pressure convergent nozzle by comparative and statistical analysis method

Water jet is a kind of technology which is using nozzle structure to transform high pressure water into high velocity water jet beam. For high velocity water flow into low velocity water flow, it is extremely complicated because of the existence of velocity gradient. In this paper, convergent nozzle structure is chosen as simulation prototype and investigational region is selected as the water jet flow can fully develop, the mesh scheme of investigational region is structured mesh and numerical simulation results is independent with the grid number, various kinds of turbulence model are employed. Combining theory, experimental data and different kinds of turbulence models computational results of the velocity distribution and flow pattern, we can figure out that k-epsilon realizable turbulent model is more suitable than any other kinds of turbulent simulation models for simulation water jet. It is useful for the application of CFD technology in water jet field and helpful for understanding the interior filed of water jet flow, at the same time, this work can also provide reference for further investigation and discussion about using turbulent model to simulate water jet flow.