# Effects of the Damping Parameters on the Opening and Closing Characteristics of Vent Valves
## 4 Conclusions  
Vent valves open and close by a two-stage pressure type pneumatic system and control. The main role of the vent valve is to prevent surges in aircraft engines. The influence of different damping parameters in the valve on the characteristics of the control valve was obtained by the method of parametric simulation through the establishment of the vent  
Figure 15: Opening and closing characteristics of valve under different nozzle diameters of middle shell: (**a**) The variation law of middle bearing pressure with time; (**b**) Control of the change in cavity pressure with time; (**c**) The variation law of piston displacement with time; (**d**) The variation of piston displacement with pressure in control chamber.  
-valve model. The results show that the damping parameters had a great influence on the control characteristics of the valve, and the conclusions are as follows:  
1. In the process of using the vent valve, there was a pressure mutation point in the middle support pressure and the pressure in the control chamber, which made the piston chamber pressure change rapidly and made the vent valve open and close with good rapidness.
2. The damping parameters will affect the control performance of the vent valve, among which \(Z_{1}\) and T\({}_{1}\) are the main components. With the increase in \(Z_{1}\), the middle pressure of the support will increase in advance, and the rate will increase rapidly after a turning point. The increase in the diameter \(Z_{1}\) can reduce the pressure surge point of the piston chamber. There will be serious instability in the closing process of the vent valve when \(Z_{1}\) is too large. The piston chamber needs a lot of pressure to complete the opening and closing action when \(Z_{1}\) is too small. The recommended size of \(Z_{1}\) is between 0.1 mm and 1.0 mm. The increase in T\({}_{1}\) will increase the time for the middle support pressure to reach the control pressure and increase the piston chamber to the transition point of the control pressure. The best recommended diameter for the middle nozzle of the support is 2.8 mm, and a control performance within 1.0-5.0 mm is also acceptable.
3. \(Z_{2}\) and \(Z_{3}\) are distributed before and after the steady flow plate and have little influence on the opening and closing characteristics of the vent valve, and the influence law is the same. With the decrease in the diameter of the damping hole, the piston chamber reaches the control pressure time lag, which is not conducive to the effective control of the valve opening and closing. According to the simulation results, the diameter of the damping hole of the front throttle plate should be greater than 0.4 mm. The increase in T\({}_{2}\) will make the valve unstable during the opening process, and a T\({}_{2}\) value that is too small will cause a pre-pressure in the piston chamber. The recommended diameter for T\({}_{2}\) is from 2.5 mm to 6.0 mm.  
Conceptualization, J.Z.; methodology, J.Z. and W.Y.; software, L.P. and Z.G.; validation, J.Z., Y.S. and Y.L.; formal analysis, Y.L.; investigation, Z.G.; resources, Y.S., L.P. and Z.G.; data curation, W.Y.; writing--original draft preparation, J.Z. and W.Y.; writing--review and editing, J.Z., W.Y. and Y.L.; visualization, Y.S., L.P. and Z.G.; supervision, J.Z.; project administration, J.Z.; funding acquisition, J.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (NSFC) (grant numbers 51890881 and 52005429).  
Not applicable.  
The authors declare no conflict of interest.