CFD-Based Physical Failure Modeling of Direct-Drive Electro-Hydraulic Servo Valve Spool and Sleeve

Abstract

Direct-drive electro-hydraulic servo valves are used extensively in aerospace, military and control applications, but little research has been conducted on their service life and physical failure wear. Based on computational fluid dynamics, the main failure forms of direct-drive electro-hydraulic servo valves are explored using their continuous phase flow and discrete phase motion characteristics, and then combined with the theory of erosion for calculation. A mathematical model of the direct-drive electro-hydraulic servo valve is established by using Solidworks software, and then imported into Fluent simulation software to establish its physical failure model and carry out simulation. Finally, the physical failure form of the direct drive electro-hydraulic servo valve is verified by the simulation results, and the performance degradation law is summarized. The results show that temperature, differential pressure, solid particle diameter and concentration, and opening degree all have an impact on the erosion and wear of direct-drive electro-hydraulic servo valves, in which differential pressure and solid particle diameter have a relatively large impact, and the servo valve must avoid working in the range of high differential pressure and solid particle diameter of 20-40 um as far as possible. This also provides further theoretical support and experimental guidance for the industrial application and life prediction of electro-hydraulic servo valves.

Keywords: CFD; direct-drive servo valve; erosion and wear; fluent simulation; physical failure model.

Figure 1

Overall work flow chart.

Figure 2

Servo valve zero position state.

Figure 3

Spool moves to the left; left inlet port opens.

Figure 4

Spool moves to the right; right-hand inlet opens.

Figure 5

Simulated flow field model of spool valve sleeve: (a) Spool valve sleeve flow field model; (b) Flow field meshing model.

Figure 6

Valve port flow velocity analysis: (a) 0.1 mm; (b) 0.2 mm; (c) 0.3 mm; (d) 0.4 mm; (e) 0.5 mm.

Figure 7

Effect of opening on erosion rate: (a) 0.1 mm; (b) 0.2 mm; (c) 0.3 mm; (d) 0.4 mm; (e) 0.5 mm; (f) variation of maximum erosion rate with increasing opening.

Figure 8

Effect of oil temperature on erosion rates: (a) 20 °C; (b) 40 °C; (c) 60 °C; (d) 80 °C; (e) 100 °C; (f) 120 °C; (g) graph of erosion rate as a function of temperature.

Figure 8

Effect of oil temperature on erosion rates: (a) 20 °C; (b) 40 °C; (c) 60 °C; (d) 80 °C; (e) 100 °C; (f) 120 °C; (g) graph of erosion rate as a function of temperature.

Figure 9

Effect of particle concentration on erosion rates: (a) original particle concentration; (b) 2 times particle concentration; (c) 4× particle concentration; (d) 8× particle concentration; (e) 16× particle concentration; (f) 32× particle concentration; (g) variation of maximum erosion rate with increasing particle concentration.

Figure 9

Effect of particle concentration on erosion rates: (a) original particle concentration; (b) 2 times particle concentration; (c) 4× particle concentration; (d) 8× particle concentration; (e) 16× particle concentration; (f) 32× particle concentration; (g) variation of maximum erosion rate with increasing particle concentration.

Figure 10

Effect of particle diameter on erosion rate: (a) 5 um; (b) 10 um; (c) 20 um; (d) 35 um; (e) 55 um; (f) 100 um; (g) variation of maximum erosion rate with increasing particle diameter.

Figure 11

Effect of different pressure differentials on erosion wear: (a) 2 MPa; (b) 4 MPa; (c) 6 MPa; (d) 8 MPa; (e) 10 MPa; (f) 12 MPa; (g) 14 MPa; (h) curve of maximum erosion rate as a function of differential pressure.

Figure 11

Effect of different pressure differentials on erosion wear: (a) 2 MPa; (b) 4 MPa; (c) 6 MPa; (d) 8 MPa; (e) 10 MPa; (f) 12 MPa; (g) 14 MPa; (h) curve of maximum erosion rate as a function of differential pressure.