Nanofiber-based enrichment device for sampling organic contaminants in vacuum environment

A novel method for sampling and enriching organic volatile contaminants in the vacuum environment combined with qualitative analysis based on the vacuum simulation test is proposed. A nanofiber is used as absorbent to collect the organic volatile contaminants in the vacuum environment and then eluted by methanol. The eluent is analyzed by gas chromatography （ GC ） and gas chromatography-mass spectrometry （GC/MS） to identify the composition of the organic contaminants. The nanofiber is composed of polystyrene and it is prepared by electrospinning. Before being used, the nanofiber is processed by ultrasound in ethanol for 15 min to remove some impurities and dried in an oven at 60 ℃, and then 10 mg of the nanofiber is wrapped in a thermoplastic polyester fabric pocket. The vacuum pump oil and di-iso-decyl phthalate （DIDP） are chosen as absorbates to test the absorbent performance of the nanofiber in the vacuum environment. Experiments are performed under the pressure of 10-4 and 103 Pa, respectively. It is shown that the nanofiber-based enrichment device can be used to adsorb the organic contaminants in the vacuum simulation environment.

Ground-based investigations on phase-moving phenomenon with space sublimation cooling for lunar exploration missions

The lunar surface is a typical vacuum environment,and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission.In addition to the radiator,the sublimator is recommended as one of the promising options for heat rejection.The sublimator makes use of water to freeze and sublimate in a porous medium,rejecting heat to the vacuum environment.The complex heat and mass transfer process involves many physical phenomena such as the freezing and sublimation phase change of water in the porous medium and the movement of the phase-change interface.In this paper,the visualized ground-based experimental approaches of space sublimation cooling were presented to reveal the moving law of threephase point and the growth phenomenon of ice-peak and icicle in microchannels under vacuum conditions.The visualized experiments and results prove that the freezing ice is divided into the porous ice-peak and the transparent icicle.As the sublimation progresses,the phase-change interface moves downward steadily,the length of the ice-peak increases,but the icicle decreases.The visualized experiments of space sublimation cooling in the capillary have guiding significance to reveal the sublimation cooling mechanism of water in the sublimator for lunar exploration missions.

Multi-parameter decoupling and slope tracking control strategy of a large-scale high altitude environment simulation test cabin

A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic control of the temperature–pressure two-parameter and overcome the control difficulties inherent to a large inertia lag link with a complex control system which is composed of turbine refrigeration device, vacuum device and liquid nitrogen cooling device. The system includes multi-parameter decoupling of the cabin itself to avoid equipment damage of air refrigeration turbine caused by improper operation. Based on analysis of the dynamic characteristics and modeling for variations in temperature, pressure and rotation speed, an intelligent controller was implemented that includes decoupling and fuzzy arithmetic combined with an expert PID controller to control test parameters by decoupling and slope tracking control strategy. The control system employed centralized management in an open industrial ethernet architecture with an industrial computer at the core. The simulation and field debugging and running results show that this method can solve the problems of a poor anti-interference performance typical for a conventional PID and overshooting that can readily damage equipment. The steady-state characteristics meet the system requirements.