| Landing gear is an important bearing part of the aircraft,which can provide support for the aircraft in the process of take-off,landing and taxiing,and ensure the safe and stable taxiing of the aircraft on the ground.As the main buffer part of the landing gear,the buffer can effectively absorb the impact energy in the process of aircraft take-off,landing and taxiing,and convert it into heat energy to dissipate.With the application of more and more small aircraft in agriculture,military,rescue and other fields,in order to make it suitable for all kinds of complex and changeable runway environment,and reduce the impact load and vibration of aircraft during landing and taxiing.It is necessary to further improve the design of landing gear buffer of small aircraft.Thus a kind of hydro pneumatic spring buffer is designed to meet the needs of small aircraft taking off and landing on complex and changeable runway.This paper designs a kind of oil-gas spring buffer suitable for small aircraft strut main landing gear according to the design criteria of landing gear buffer,combining the design method of compression spring,gas working characteristics and oil-liquid damping characteristics.According to the design method of the cylinder spiral compression spring,the damping stiffness,spring pitch and helix angle of the cylinder spiral compression spring are calculated.According to the working principle of oil-gas buffer,the structure of the buffer is designed.With the aircraft landing and landing,the buffer will continue to compress and extend.Which will lead to the changes of the flow characteristics,pressure and temperature of each part of the internal cavity.Which will affect the flow rate,sealing and heat transfer characteristics of the internal oil.In order to study the stability of the buffer,firstly,the oil and gas cavity model of the buffer is established by Catia software,and the simulation test and calculation are carried out by using Fluent software.The four factors,such as the velocity of oil inlet,the length of the damping hole,the pore diameter and the inverted angle size are taken as the research variables.The influence of the variable size on the pressure and flow characteristics of the oil and gas cavity is obtained by simulation.Secondly,in order to improve the sealing performance of the upper air cavity of the buffer.The tenon sealing face flange structure is adopted for the sealing connection between the upper end cover and the outer cylinder of the buffer,and the three-dimensional model of the tenon sealing face flange of the upper end of the buffer is established.According to the design method of ASME code for flange seal.It is calculated that when the internal pressure of oil and gas cavity is 1.2MPa and 2.4MPa.The bolt pretightening force required for sealing is 1515 N and3520 N respectively.ANSYS Workbench software is used for simulation calculation,and the radial deformation,strain,stress of the flange structure with mortise sealing face and the contact pressure distribution characteristics of each contact surface of the sealing gasket are obtained under the combined action of two kinds of internal pressure and bolt preload.Finally,based on the theory of heat transfer,the steady-state temperature field of each part of the outer cylinder and the transient temperature change characteristics of each part of the outer cylinder when the lower end of the outer cylinder and the oil cavity are heated are obtained by simulation.The research contents of this paper can provide a new idea for the design of landing gear shock absorber of small aircraft,and provide a simulation test method for improving the internal pressure and oil flow in the oil and gas chamber.The research and analysis of the structural design of the tenon sealing flange at the upper end of the shock absorber and the temperature distribution of the outer cylinder when heated can provide effective guidance for the design of improving the sealing and heat dissipation of the shock absorber. |
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