Keywords: high pressure; gas valve; down power 1 Overview Attitude control of the missile need to control the gas jet flow and ejection position, the gas valve as a core component installed in the solid engine at different locations to achieve this goal. In order to achieve the corresponding mass flow, the pressure in the combustion chamber is very large, 11MPa-12MPa, while the temperature reaches 800 ℃, due to the structural space requirements, the valve needs to be designed in the space of φ50mm, the driving device is also a valve The size of the space, so the design must consider the high temperature and pressure seals and valve miniaturization and low power.
Small high-pressure gas valve in the design for the difficulties encountered one by one to analyze and solve the final low-power motor-driven valve to complete the continuous gas regulation.
2 main problems Missile trajectory control engine gas valve needs to meet the overall requirements, due to the bomb on the battery power and size is limited, so with the valve drive motor power can not be too large. The decomposition of contradictions, the final problem is mainly reflected in the following two aspects.
2.1 Gas valve structure The maximum mass flow through the gas valve can not be reduced, which makes the pressure of the combustion chamber and the valve diameter can not be reduced. High temperature gas mixed with dust, dust resistance of the valve is strong, the ability to choose a strong anti-dust cone valve form, the valve driving force is great, while the system has a higher valve speed requirements, resulting in an option Reducer with large reduction ratio. This series of difficulties makes gas valve structure design has become a key point to reduce the valve driving force.
2.2 high temperature and high pressure seal the gas through the valve medium is high temperature and pressure with dust gas, the dynamic sealing of the valve core is a design difficulty. First of all, the rubber seals and packing usually used for dynamic sealing can not be used in the condition of high temperature and high pressure. Secondly, the soft metal seal requires high processing precision, easy adhesion under high temperature and the like, and excessive dust may enter Leading to seal failure, and finally, the sealing pressure can not be too large, can not increase the driving force of the valve too much. These reasons make the sealing problem of the valve core a design difficulty.
3 solutions 3.1 to reduce the structural design of the valve drive torque Various restrictions make the method to reduce the valve torque can only focus on the gas valve structure itself, the small gas valve is still resistant to dust with a strong cone valve form, in order to reduce the spool imbalance forces, the gas introduced into the top of the valve body, balancing the pressure of the upper and lower die, to reduce the driving force of the valve, a specific configuration as shown in FIG.
As can be seen from Figure 1, under the action of static pressure, the force at the lower end of the valve spool and the force at the upper end of the valve spool are balanced with each other, so that the valve spool only needs to overcome the frictional force of the seal. When the valve spool moves, Of the dynamic pressure and the back end of the spool static pressure is not equal, and the specific pressure difference using fluid simulation analysis, fluid simulation also need to calculate the maximum mass flow valve used to test whether the new structure to meet the overall requirements.
Set the gas inlet pressure is 11.5MPa, the outlet pressure is standard atmospheric pressure (0.1MPa), the gas medium temperature is 800 ℃, ignoring the dust which is considered as the ideal gas, the gas in the valve body supersonic part Solver using implicit density solution. The two nozzles of the gas valve are symmetrically distributed. Only one of the nozzles is selected for the flow field analysis to simulate the flow field of a single nozzle. The pressure field of a section of the analyzed flow field is shown in Figure 2.
Flow field simulation can get the maximum mass flow valve 1.95kg / s, to meet the requirements, the maximum valve opening when the maximum dynamic pressure spool front, then the front of the spool pressure 4015.43N, and the back of the valve core gas flow rate Very low, can be considered as static pressure, calculate the back pressure of the valve spool is 3948.51N, which found that the unbalance force of the spool front and rear ends up to 66.92N, significantly lower than the original 4015.43N, The premise of mass flow, significantly reducing the power of the drive motor.
3.2 Structure design of high temperature and pressure seal Sealing between the valve body and the valve body involves not only the sealing gas itself, but also the valve driving force. Sealing structure design should take into account both the high-pressure sealing and high temperature deformation of the valve driving force.
The direct sealing form of the valve core and the valve body is the piston seal, and the piston seal needs to be designed in detail. As shown in FIG. 3, the sealing ring assembly consists of two open metal rings and a broken graphite ring, The seal assembly seals between the valve plug and body. The sealing process is as follows: the two open metal rings are directly pressed against the high-pressure gas to the middle and the graphite ring is beveled at the broken place; the graphite ring can be distracted to open and contact the valve body for sealing; meanwhile, if the valve body is deformed by heat The graphite ring can also adapt to the deformation of the valve body. That is to say, the high-pressure seal is completed and the high-temperature deformation can be endured without greatly increasing the driving force of the valve.
4 Conclusion Through the above analysis, in view of the demand for small gas valve power reduction, the design of a new valve structure, the simulation shows that the valve core driving force significantly reduced, while the sealing form has been improved to adapt to the design of high temperature and pressure Situation, to meet the design requirements. ■
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