Summary: this paper describes the use of ultra-high-pressure aerodynamic pressure reduction valvesRationaleMain structureDesign calculationsAnd the test, and the structural characteristics of the valve were analysed。
Keyword: super-high-pressure aerodynamic pressure reduction valve
Introduction
The ultra-high-pressure gas pressure reduction valve is an important component of the aerobic brake system. Because of the small viscosity of the gases, their ease of leakage and the high pressure of system work, the input pressure of the valves is 11-13 mpa and the high output pressure is 7 mpa, the sealing and durability of the valves is a prominent problem. The ultra-high-pressure aerodynamic pressure reduction valves described here break through the traditional structure [1] and optimized the design of the critical zero, component, so that the valves are free of leakage at high pressure and other performances meet the requirements for use。
2. Rationale
The operation of the ultra-high-pressure aerodynamic pressure reduction valve is shown in figure 1. When the pressure does not work externally, the gas from the gas source enters the lower gas chamber of the valve from the input port, the entry valve presses the entry valve with the pressure and re-entry spring, and the valves export the non-gas output. When the pressure is subject to external force f, the pressure moves down the head and contacts the exhaust valve with the vent door by balancing springs to compress the double spring spring 1, so that the vent is isolated from the atmosphere, the pressure continues to move down, tops into the valve, and the air is compressed from the channel controlled by the entry valve into the executive cylinder behind the valve. As the pressure of the cylinder increases, the opening of the entry valve decreases until the entry valve is closed when the flow-export pressure p2 is balanced with the effect of the pressure on the head. When the external force is removed, the entry valve is closed upwards with the force of pressure and double spring 2. At the same time, the head and exhaust valves are repositioned by the force of the compound spring 1 and the exhaust pressure, opening the vent, and the gas from the original output is discharged into the atmosphere by the exhaust valve through the silencer。
Figure 1
Now look at the state of the exhaust valve when it's in a balanced position. Ignoring the gravity and friction of the head, exhaust valves, etc., the equation for resonance of the exhaust valves is:
F=p1a1+p2 (a2-a1)+fs+ff(1)
In form: fs - the sum of the resilience of the double springs
Ff - friction of seals
A1 and a2 - the effective pressure area of the vent, respectively
A1=d12-d012/4
A2 = beryllium (d22-d022)/4
D - the diameter of the vent valve door
D01 - the lower diameter of the top pole
D02 - upper diameter of the pole。
By form (1), the output pressure of the valves p2 is proportional to the effect of the pressure on the head (see figure 4)。
3. Design and calculation
The design of ultra-high-pressure aerodynamic pressure reduction valves is typically based on the choice of the structure pattern of the valves based on the given design parameters and working conditions, followed by the selection and calculation of the structural parameters。
The parameters usually given are: gas source pressure, valve * large output pressure, ventilation, * large manipulation power and itinerary. Designed and calculated are: selected structural patterns, determination of the structural dimensions of valves based on aerodynamic capacity and working pressure, design of balancing springs based on itinerary and manipulation。
The structure of the valves is designed to focus on the sealed structure of the entrance valves, the exhaust valves and the walker because of the small viscosity of the gas and the high working pressure and ease of leakage. The structure of the valves is shown in figure 1。
(1) calculation of ventilation capacity
A valve's ability to vent is the inflating and exhausting time of the valve in the event of a given source pressure, the valve output pressure, the volume of the performing component cylinder and the post-valve pipe。
The ability to vent depends on the size of the vents. The valves are short-lived during inflating and venting, and we ignore the effects of heat exchange, i. E. Insulation and insulation. In addition, according to the working pressure of the valve, the valve is pumped in and out at the sound speed. Thus, the effective area of the valve's gas intake channel aa is calculated downward [2]:
In form: v - total inflatable volume
K - heat ratio, insulation inflating, k = 1. 4
T - temperature of air, t = 293. 15 k of standard air
T1 - inflating time
R - gas constant, r = 287. 1n*m/kg/k
P1 - valve input port pressure
P2 - valve export pressure
P20 - pressure in the cylinder before inflating。
A1 = aa
Based on structure (see figures 1 and 2)
Axle distance (openness) between the entrance valve and the valve seat, based on equal area
Hc≥(d12-d012)/(4d1) (4)
The effective area of the vent is calculated on a lower basis
Where: t2 - exhaust time
P20 - initial exhaust pressure in the cylinder
Pa - external pressure。
Other symbols have the same meaning (3)。
Air vent diameter (see figures 1 and 2)
Axial distance of the vent door to the valve seat (openness)
H2≥(d22-d022)/(4d)(7)
(2) calculation of the diameter of the vent valve
The pressure accuracy of the valve is directly affected by the size of the exhaust valve seat d, as known by its working principles. If the diameter of the valve is large, the pressure adjustment precision is high, and vice versa, the pressure adjustment accuracy is low. However, the diameter of the exhaust valve is limited by manipulation. Emission valve door diameter (see figure 3 (b))
In form: fmax - a given * great manipulation。
The diameter of the vent valve is as high as possible, subject to the fulfilment of the manipulative power values。
(3) design of enter, exhaust valves
The design of the entrance, exhaust valves consists mainly of structural patterns, material selection and geometric dimension determination. Valves are structured using metal-packed rubber valves (so-called metal-packed rubber valves are directly sulphide on the metal skeleton). It takes advantage of the high elasticity of rubber materials and the low pressure of seals, enabling valves to function well as compensatory functions in the course of their work; it also takes advantage of the strength and intensity of metal materials. Valve processing is a good process and low cost。
The selection of rubber material is based mainly on its mechanical performance and the working temperature of the valve。
The thickness of the sulfide rubber is selected according to the height of the valve seat surfaceh and the rubber compression is appropriate (20-25 per cent)。
Copper is appropriate for metal skeletons entering and venting valves because of their good integration with rubber。
(4) design of enter, exhaust valve seating
The side of the valve is in direct contact with the rubber face of the valve, deforming the film during work, sealing and having a significant impact on the valve's lifetime. The surface structure of the valve is shown in figure 2 (where: figure 2 (a) is the entrance valve and figure 2 (b) is the exhaust valve). The height h in the figure is the valve side and r the seal face. R is small, the valve is sensitive; r is large and the valve has a long life. R is better valued in the range of 0. 3 to 0. 5, after optimal design. The roughness of the face of the valve also affects the sealing and lifetime of the valve, and the roughness of ra should not be greater than 0. 4 m
Figure 2b shows support. It's used to limit the excessive transformation of the film and to protect it。
(5) design of a balanced spring
Based on the analysis of the valve performance, the balance spring, like the diameter of the vent door, directly influences the pressure accuracy of the valve. The smaller the impregnated spring, the better the repressure accuracy of the valve. But it's too small, the spring is too long. It is restricted by the given itinerary and should be designed for spring strength according to the given parameters:
K=fmax/(h1+h2) (9)
S springs are designed with their rigidity, resilience and itinerary. The rigidity of the two double springs can be designed to be identical and less than that of the balance spring。
Test
To test the performance of the valve, the rationale for the design of the test system is shown in figure 3。
The output pressure of the valves is related to manipulation as shown in figure 4. Figure 5 shows the filling (winding) of the valves under the condition that the gas tank volume is 2l and the pressure is entered at 11mpa, which is rapidly applied (delegated) on the head. After testing and application, valves are technically capable of meeting requirements and some indicators exceed the same product. It also has characteristics such as simple structure, compactness, small size, light weight, long life and good maintenance。
Figure 2
Figure 3
Figure 4 p2 relationship to f
Figure 5
