# Impacts of Micro-Deviations of Aperture on the Characteristics of Collision Atomization Field
## 6 Conclusions  
The influence of the small geometric deviation of impinging nozzle caused by machining error on internal flow field and atomization field characteristics of impinging injector has been experimentally investigated by using small-diameter transparent nozzles fabricated with slight differences in their structural parameters. The tested colliding nozzles used in the experiment have been measured by a self-developed ultra-high-precision three-dimensional micro-displacement measurement system to study the influence of micro-deviation more accurately for the first time. This paper focuses on the analysis of the  
Figure 14: The relationship between the atomization cone angle and colliding aperture and jet pressure.  
nozzle diameter deviation impact that appears most often on the internal flow field and atomization field. The conclusions of this investigation are summarized as follows:  
1. For the impinging nozzle with a diameter of 1 mm and a length diameter ratio of 4, the injection pressures corresponding to the initial cavitation and flip states are 0.3 MPa and 0.8 MPa.
2. In the initial stage of cavitation, the changes in the SMD and cone angle are especially obvious. When the nozzle with the diameter of 1 mm has a 5% deviation, the maximum changes in the SMD and atomization cone angle can reach 30 \(\upmu\)m and 18\({}^{\circ}\). With increasing injection pressure, the decrease in SMD and the increase in the atomization cone angle reach the maximum 23 \(\upmu\)m and 30\({}^{\circ}\). The change in the two tends to be smooth, where SMD tends to 245-255 \(\upmu\)m and the atomization cone angle tends to 52-60\({}^{\circ}\).
3. When the injection pressure is high enough (0.8 MPa) and the air core reaches a certain length, a narrow flow will be formed in the orifice. In this state, the state of the flow field in the impinging nozzle, the SMD of the atomization field and the change in the atomization angle will become very small and almost reach the steady state. For the impinging nozzle with a diameter of 1 mm, the SMD is stable at 251 \(\upmu\)m and the atomization cone angle is stable at 58\({}^{\circ}\).
4. In addition, the increase in injection pressure will also increase the corresponding atomization cone angle of the same pair of nozzles, and finally the atomization cone angle tends to be stable, gradually approaching and not exceeding the collision angle of the two nozzles. When the impingement angle is 60\({}^{\circ}\), the atomization angle of the nozzle with 1 mm aperture is close to 60\({}^{\circ}\), and the nozzle with a 5% diameter deviation has a maximum stable atomization cone angle of 59.5\({}^{\circ}\) and a minimum of 52.3\({}^{\circ}\).
5. The diameter deviation of the orifice is studied in this paper. In subsequent work, the influence of other orifice structure deviations or liquid properties on the performance of the atomization field can be considered. Additionally, related findings can be extended beyond the range of experiments to give the mathematical approximation of obtained data.  
Conceptualization, Y.M. and H.W.; methodology, Y.M.; software, Y.M.; validation, Y.M., H.W. and J.C.; formal analysis, Y.M.; investigation, Y.M.; resources, J.C.; data curation, Y.M.; writing--original draft preparation, Y.M.; writing--review and editing, Y.M.; visualization, Y.M.; supervision, H.W.; project administration, J.T.; funding acquisition, J.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Outstanding Youth Project of Natural Science Foundation of Heilongjiang Province, Grant JQ2019E002.  
Not applicable.  
All data are presented in this article in the form of figures and tables.  
The authors declare no conflict of interest.