Flow Field Analysis On High Pressure Abrasive Water Jet Cutting Nozzle And Optimization On Parameters Of Nozzle

The quality of dynamic capability of jet filed of high pressure abrasive water jet cutting nozzle is immediately influenced by its inside shape. It is a difficulty for scholars around the world to design a nozzle with good construction parameters. Analyzing the characteristic of flow field of five nozzles and discussing which nozzle will be the fittest for premixed or after-mixed and optimizing parameters of nozzle construction is very value.Firstly, five kinds of nozzle molds are discussed in this thesis. Secondly, the control equations and closed equations of single-phase and liquid-solid two-phase are completed. The attention is paid to Hybrid Finite Analytic Method (HFAM). And then, the Semi-Implicit Method for Pressure-Linked Equation and Velocity-Linked Equation for HFAM standard equation in cylindrical axial symmetric coordinate system on the computational plane are discussed in detail. The result of dissertation as following: The length of the beeline segment of transition segment directly influence the distance of jet core and the concentrated characteristic. General speaking, for the range of downstream distances considered, the results indicate that a jet is characterized by an initial rapid decay of the axial velocity at the jet centre while the cross-sectional flow evolves towards a top-hat profile downstream, and the velocity of jet centre is the most quickly. In the condition of single-phase, the nozzle with the interior shape, which has constriction segment,transition segment and diffuseness segment, has a better jet-characteristic. It is in the constriction segment and transition segment with round arc that there is better jet-characteristic. This kind of nozzle is fitter for being after-mixed water jet cutting nozzle in the high pressure abrasive water jet cutting head. In the condition of liquid-solid two-phase, the conventional nozzle with taper-beeline shape has a better dynamic characteristic, and the concentrated characteristic of it is better, and the radial velocity is lower. This kind of nozzle is fitter for being premixed water jet cutting nozzle in the high pressure abrasive water jet cutting head.Lastly, Taguchi is used to design and analyse the parameters of nozzles, and to establish orthogonal array L18 and L9 respectively to optimize the construction parameters of nozzles which is suited for premixed and after-mixed cutting nozzles.