# Research on Performance Prediction Model of Impeller-Type Breather
## 5 Conclusions  
In this research, orthogonal test design was used in calculation of the operating condition. The RNG model and the DPM model were coupled to calculate the selected operating conditions. By  
Figure 8: Ventilation resistance. (**a**) Ventilation rate; (**b**) rotating speed; (**c**) temperature.  
Figure 7: Separation efficiency. (**a**) Ventilation rate; (**b**) rotating speed; (**c**) temperature.  
analyzing the results, the significance of various influencing factors and the optimal levels were shown. Based on the dimensional analysis, a dimensionless group equation in general form was established by combining comprehensive separation efficiency, breather separation efficiency, and ventilation resistance. Also, through the least squares method, the performance prediction model of the breather was obtained considering five operating conditions and six structural parameters. Through the research in this paper, the following conclusions are drawn:  
1. The significance of the influential factors affecting the separation of impeller-type breathers and their optimal levels were determined. Among all the operating conditions, rotating speed has the largest influence on separation efficiency, followed by ventilation rate and average inlet particle size. Temperature and oil/gas ratio have relatively little influence. The optimal levels were C\({}_{5}\)B\({}_{1}\)A\({}_{5}\)D\({}_{1}\)E\({}_{2}\). Among all the structural factors, number of blades has the largest influence, followed by external diameter of the blades and thickness of the breather. Blade angle and diameter of vent hole have little influence. The optimal level shows as F\({}_{5}\)H\({}_{1}\)J\({}_{1}\)G\({}_{4}\)I\({}_{4}\)K\({}_{2}\).
2. The significance of the factors affecting the resistance characteristics of the impeller-type breather and their optimal levels were determined. Among all operating condition factors, ventilation rate has the largest influence on ventilation resistance, while temperature, rotating speed, inlet particle average diameter, and gas/oil ratio have little influence. Their optimal levels were B\({}_{1}\)D\({}_{2}\)C\({}_{1}\)A\({}_{1}\)E\({}_{3}\). Among all the structural factors, diameter of the vents has a greater influence, while the other factors, such as number of blades, blades angle, thickness, and the external diameters of the blades, all have a small influence. The optimal levels were K\({}_{5}\)F\({}_{2}\)I\({}_{1}\)J\({}_{4}\)H\({}_{2}\)G\({}_{3}\).
3. The performance prediction model of an impeller-type breather was established. The comprehensive separation efficiency has a mean error of 0.97%, while the ventilation resistance has a mean error of 11.73%. The calculation values and the experimental values share the same trend change, which indicate that the prediction model can be implemented in theoretical calculation of comprehensive separation efficiency, ventilation separation efficiency, and ventilation resistance, providing good references for evaluation and design of an impeller-type breather.  
Conceptualization, X.Z. and W.Z.; Data curation, L.Q.; Formal analysis, M.L.; Writing - original draft, X.Z.  
This research received no external funding.  
The authors declare no conflicts of interest.