Experiment And Numerical Studies On The Atomization Of A Pressure Atomizer

The atomization characteristic of the nozzle is directly related to the efficiency and stability of the combustion. The pressure atomizer is widely used because of simple structure and reliable operation. Domestic and foreign scholars research the influence of the geometry and working parameters on the atomization performance by experiments. With computing technology improvement, numerical simulation is playing a more and more important role in revealing the atomization physical processes. However, the atomization Mechanism is not unified understanding because of the complexity of the atomization process of the nozzle.In this paper, theoretical analysis, numerical simulation and experimental technologies were used for the study of the spray characteristics of the typical pressure atomizer. For the better modeling studies, machining a larger quartz nozzle and establish a visualization system hydrostatic test, practical pressure atomizer and the corresponding experimental system were studied at the same time. Focus on the internal and external flow field of the nozzle by two-dimensional and three-dimensional numerical simulation.The atomization of the pressure atomizer is analyzed theoretically by the simplified model theory and dimensional analysis. The complete mathematical relationship between the characteristic parameters A, flow coefficient and hollow of the cyclone center of the simplified model is obtained by theoretical derivation. The atomization process of the pressure atomizer was related to the geometric parameters A and Re number by dimensional analysis, which to make up for the weakness of the theoretical analysis on the simplified model that nozzle atomization characteristics was not related to the flow rate and viscosity. The flow coefficient of different characteristic parameters A under different pressure was calculated by the experimental result, fitting flow coefficient function on the characteristic parameters o A and Re, and fitting the correction flow coefficient expression based on theoretical and experimental flow coefficient.The flow field in the enlarged quartz model nozzle and the atomization characteristics was researched by experiment and numerical simulation. We observed the internal and external flow field of the visual nozzle and the non-steady-state dynamic response at the starting and shutting moment, and observed the internal hollow column formation in the nozzle. Based on the experimental results, the diameter was smaller in the hollow column under low pressure, as the pressure increases, the hollow column become larger, which is conformed to the Theoretical analysis. We observed the dynamic characteristics of the liquid film of the export, with the ejection pressure increasing, the Perturbation Frequency accelerated, the breakup distance decreases, the surface wave perturbations becomes larger, the performance of the atomization becomes better. We calculated the size of the spray cone angle, flow field structure and velocity distribution of the nozzle through VOF two-dimensional numerical simulation. Numerical simulation reveals the vortex vessel of the internal and external flow field, and the shape of the hollow columns of the swirl chamber accords with the experiment, the spray cone angle is larger than the experiment result, but the regularity is basically the same.Experiment and three-dimensional numerical simulation was done for a small practical pressure atomizer. The experimental study on the atomization characteristics of the pressure atomizer obtained atomized particle size and spray cone angle under the different pressure. Numerical simulation recorded the dynamic process of the change from the start to the stability, capturing process of the hollow conical liquid film is formed, the process is the fuel liquid column-liquid film packet-wavy flow-banded rupture-stabilize atomizing. The Numerical Simulation derived that the hollow vortex exits near the exit of nozzle, the spray cone angle derived from the results is relatively closed to experiment. Numerical simulation of different exit ramp expansion angle of the spray cone angle and analyzed. The influence of different exit expansion angle to the spray cone angle was simulated of and analyzed.The nozzle flow coefficient and film thickness were compared by three ways experiment, numerical simulation and theoretical calculated, the calculated and experimental values of the flow coefficient decreases with increasing pressure, theoretical calculations and numerical simulation exits the error compared to the experimental results are, but exits the same variation trend.The atomization of pressure atomizer is a complex physical process. Experimental study of this paper, especially the experimental results of the model nozzle provides basic data for the further theoretical study. The theoretical analysis and numerical simulation results can also provide reference for the nozzle design.