Spray Characteristics of Non-Circular Nozzle in Air-Assisted Injection System

In order to analyze the spray characteristics of non-circular nozzle holes based on the air-assisted spray system, the spray characteristics of circular and non-circular nozzles were studied under the pressure of 0.2-0.6 MPa and the spray volume of 1000-5000 mL/h. Elliptical nozzle and triangular nozzle are classified as non-circular geometries. The spray cone angle was measured by processing the spray image captured by a CCD camera. The measured spray cone angles of the circular nozzles were analyzed, and the axis switching phenomenon of minor plane of elliptical nozzle was found during the test. Among the three shapes of nozzles, the elliptical nozzle had the largest spray cone angle, and the triangular nozzle had the smallest. The velocity field obtained depended on the PIV system. The results show that for axial velocity, elliptical orifice spray has greater kinetic energy and smaller droplet size under the same working parameters. Compared with the circular and elliptical nozzles, triangular orifice reached maximum spray velocity the fastest, but its velocity decay was the fastest. For radial velocity, away from the axis, the spray velocity of the elliptical orifice was less affected by the injection parameters, and the velocity was less than that of circular orifice and triangle orifice. Increasing air pressure will weaken radial propagation. The increase of liquid spraying rate had no remarkable effect on the increase of spraying rate. The results of particle size analysis show that the particle size of the non-circular orifice is reduced compared with that of the circular orifice, which promotes the breakup of droplets to a certain extent and enhances the atomization effect.

Theoretical performance simulation of a high pressure agro-forestry swirl nozzle

Equations of dynamic systems in droplet distribution at high pressure and boundary value flows in the swirl chamber of a swirl nozzle were used in conjunction with momentum equations of forces on moving curved vanes to develop mathematical models.A computer program in C++language was developed and used to simulate the effect of some flow and geometric parameters,including flow rate,pressure and swirl chamber diameter,on the spray performance of a high pressure agro-forestry swirl nozzle.Each of the three performance parameters of axial flow rate,spray cone angle and output discharge(or performance)coefficient were studied as a function of any two combinations of the nozzle supply pressure,exit orifice diameter and swirl chamber diameter.The study established that the spray cone angle of the discharge flow pattern varied from the minimum value of 40°for a swirl chamber diameter of 90 mm to 220°for 40 mm as the exit orifice diameter varied from the minimum value of 0.5 mm to 4.0 mm.The simulated nozzle output discharge coefficient could be varied from 0.98,when the nozzle supply pressure was 400 kPa to the minimum value of 0.001 at any of the other six simulated nozzle supply pressure values of 200,250,300,350,450 and 500 kPa by varying the exit orifice diameter from 0.5 mm to 4.0 mm.The pattern of variation of the simulated nozzle discharge coefficient values were similar to those obtained by measurement during the validation exercise in the laboratory although their sensitivities to the independent variables were different.The results indicated that the range of nozzle discharge coefficient of 0.80 to 0.98 required for a well designed high pressure agro-forestry swirl nozzle has been simulated.With the successful development of the C++computer program,a useful tool that will cut down on the rigor encountered and time spent by nozzle designers and evaluators during nozzle development process has been developed in the study.

Effect of nozzle inlet parameters on the dry granulation atomization process of Si_(3)N_(4) ceramic bearing balls

In this paper,the atomization characteristics of Si3N4 ceramic dry granulation affect the performance of Si3N4 ceramic bearing balls.In order to improve the dry granulation characteristics and the comprehensive performance of Si3N4 ceramic bearing balls,the atomization mechanism of the spinning nozzle used for Si3N4 dry granulation was studied in detail.The interaction between air and binder in the pressure-swirl nozzle is analyzed based on VOF method,the modified realizable k−εturbulence model is used to simulate the flow field inside and outside the pressure-swirl nozzle,the effects of nozzle inlet parameters including the number of tangential inlets and the deflection angle of tangential inlets on the binder volume fraction,velocity distribution and pressure distribution are analyzed.The results show that when the number of tangential inlets increases from 1 to 4,the swirl strength of gas–liquid two-phase in the nozzle increases,the mean diameter of air core increases from 1.51 mm to 2.01 mm,and the spray cone angle increases from 18.5◦to 26.4◦.Besides,when the deflection angle of tangential inlet increases from 0◦to 15◦,the swirl strength of gas–liquid two-phase in the nozzle with the deflection angle of tangential inlet of 10◦is the largest,and the mean diameter of air core and spray cone angle is 3.04 mm and 30.7◦,respectively.Based on the atomization experiment platform of the electric control fuel system,the mean diameter of air core and spray cone angle are measured,the micromorphology of Si3N4 particles is observed,which verifies the correctness of numerical simulation.When the Si3N4 particles are prepared by dry granulation,taking the atomization performance of nozzle into consideration,the pressure-swirl nozzle with 4 tangential inlets and 10◦deflection angle should be selected.