滑动索膜结构超压气球设计与形状修正

Design and shape correction of super-pressure balloon with sliding cable membrane structure

摘要:

在探空科学超压气球设计时,通过在囊体表面布设加强筋的方式,可有效提高超压气球的抗压能力. 为解决带有加强筋的超压气球在高“纬度”位置处膜面与加强筋的纵向应变差值较大问题,提出了一种滑动索膜结构超压气球的设计方案.该方案采用与囊体相对滑动的绳索代替与囊体固连的加强筋,更有利膜面应力传递.为了使囊体上应力沿环向分布更均匀,先在理论上进行了索膜结构膜面平衡形状分析,再根据分析中囊体膜面经、纬向曲率半径值与气球抗压能力的关系,采用一种对单幅囊体截面曲线进行椭圆修正的方法设计滑动索膜结构超压气球囊体.最后,以16幅膜面、直径为4 m的正球形超压气球为例,用有限元软件Abaqus建立了浮空状态超压气球的有限元模型对设计外形及修正外形进行验证,并分析了摩擦系数对索、膜匹配性的影响. 结果表明:按该方案设计,气球承压极限值在一定范围内随在赤道截面绳索径向收紧量dl的增大而增大；且经过修正设计后的超压气球,膜面应力分布更均匀,能承更高超压量；另外,索、膜间摩擦系数仅仅在较小值范围内会影响气球受力分布,其值的减小能相应降低绳索应力.

Abstract:

When designing a scientific super-pressure balloon, the capability of a balloon to withstand pressure can be effectively improved by arranging tendons on the surface of the balloon. To solve the problem of the large difference of longitudinal strain between the balloons membrane and tendons at the high “latitude” position, a design scheme of a sliding cable membrane structure was propased. First, the sliding cables on the balloon was used to replace the tendons sealed to the menbrane, which is more advantageous for the stress transmission on membrane. Then, in order to make the stress on the membrane evenly distributed in the circumferential direction, the equilibrium shape analysis of the membrane of the cable membrane structure was carried out. According to the relationship between the radius of the meridional and the latitudinal curvature of the balloon membrane and the capability of the balloon to withstand pressure, an elliptical correction method was adopted to design a super-pressure balloon with sliding cable membrane structure to make the membrane stress more evenly distributed along the circumferential direction, thus further improving its capability to withstand pressure. Finally, taking a super-pressure balloon with sixteen bulges as an example, whose original shape is spherical with a diameter of four meters, the finite element model of the floating state super-pressure balloon was established by the software Abaqus for numerical simulation. Numerical results show that the pressure bearing capacity of the balloon increased with increasing radial tightening amount dl of the equatorial section rope, the modified super-pressure balloon could withstand higher pressure, and the stress distribution was more uniform on membrane. When the cable and the film were relatively smooth, the reduction of the friction coefficient could reduce the rope stress.