Influence of Diesel Nozzle Geometry on Cavitation Using Eulerian Multi-Fluid Method

Dependent on automatically generated unstructured grids, a comprehensive computational fluid dynamics(CFD)numerical simulation is performed to analyze the influence of nozzle geometry on the internal flow characteristics of a multi-hole diesel injector with the multi-phase flow model based on Eulerian multi-fluid method.The diesel components in nozzle are considered as two continuous phases, diesel liquid and diesel vapor respectively.Considering that both of them are fully coupled and interpenetrated, sepa...

Effect of nozzle geometry on pressure drop in submerged gas injection

Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths. Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter and on the modified Froude number with the hydraulic diameter of the nozzle do as characteristic length.

The Acoustic Performance of 3D Printed Multiple Jet Nozzles with DifferentConfigurations

This work investigated multiple jet nozzles with various geometrical shape,number of exits,and material on reducing noise radiated from jet flows.Nozzles are categorized in two groups with few and many exit numbers,each with various exit shapes,slot and circular,and geometry.Firstly,nozzles are designed and then fabricated by a 3D printer,Form Labs,Form2USA,with polymeric resin.Also,the nozzle with the most noise reduction made of stainless steel.Noise and air thrust were measured at three air pressure gauges,3,5,7 BAR and directions from nozzle apex,30°,90°,135°.Nozzles with slot exit shape made of both plastic and stainless steel revealed the most noise reduction among all nozzles with few exit numbers,nearly 11–14 dB(A)and 11.5–15 dB(A),respectively.On average,slotted nozzle noise reduction was nearly 5–6 dB(A)more than finned nozzle.However,nozzles with more exit numbers,finned and finned-central exit,illustrated much more noise reduction than nozzles with few exit numbers,by almost 16–18 dB(A),they represented similar sound.All tested nozzles and open pipe demonstrated equal air thrust at each pressure gauges.The nozzles with slotted exit shape,either plastic or stainless steel,can provide reasonable noise reduction in comparison to other configuration with few exit numbers.In contrast,nozzles with more exit numbers demonstrated the most noise reduction.

Cold model on bubble growth and detachment in bottom blowing process

The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography and digital image processing. For these configurations, the experiments reveal that the bubble growth consists of a petal-like stage, an expansion stage and a detachment stage. The petal-like shape is qualitatively described through the captured images, while the non-spherical bubbles are analyzed by the aspect ratio. The bubble size at the detachment is quantified by the maximum caliper distance and the bubble equivalent diameter. Considering the dependence on the opening ratio, different prediction models for the ratio of maximum caliper distance to hydraulic diameter of the nozzle outlet and the dimensionless bubble diameter are established. The comparative analysis results show that the proposed prediction model can accurately predict the bubble detachment size under the condition of multi-hole nozzles.