An efficient long-term storage of cryogenic propellants is a challenge for future space exploration missions. The vapour bubbles formed as a result of boil-off in the tank walls can generate foam structures, which could be hazardous in different operations in orbit. A recently proposed approach to control the dynamics of bubbles is based on the generation of an acoustic field by means of a piezoelectric transducer. This technology needs to be validated at cryogenic temperatures in order to be applicable in space. In this perspective, different piezoelectric elements and matching layer materials have been tested at cryogenic temperatures to assess their performance at such environmental conditions. We consider the use of soft PZT piezoceramics coupled with an epoxy resin as the matching layer. Experimental data reveal that epoxy resin-based acoustic matching layers exhibit a linear increase in the transmittance of the acoustic amplitude at cryogenic conditions. The peak-to-peak amplitude increases as temperature decreases up to a factor of 1.6. This result opens the possibility of generating and transmitting acoustic waves at cryogenic temperatures, which could be used in the recently proposed technology to control the dynamics of vapour bubbles in cryogenic fuel tanks.

中文翻译：

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超声波控制低温燃料箱中气泡的性能评估

低温推进剂的有效长期储存是未来太空探索任务的挑战。由于油箱壁中的沸腾而形成的气泡会产生泡沫结构，这可能会对在轨运行中的不同危险。最近提出的控制气泡动力学的方法是基于借助于压电换能器的声场的产生。为了在太空中应用该技术，需要在低温下对其进行验证。从这个角度出发，已经在低温下测试了不同的压电元件和匹配层材料，以评估其在这种环境条件下的性能。我们考虑使用软质PZT压电陶瓷和环氧树脂作为匹配层。实验数据表明，基于环氧树脂的声匹配层在低温条件下的声振幅透射率呈线性增加。随着温度降低到1.6倍，峰峰值幅度增加。该结果打开了在低温温度下产生和传输声波的可能性，这可以在最近提出的技术中用于控制低温燃料箱中蒸汽泡的动力学。