Performance analysis of a novel stratospheric airship concept based on gas–liquid phase change

Abstract

This paper presents a new concept of a stratospheric airship with a triple-gasbag configuration to reduce the super pressure caused by the superheat during the day–night station-keeping operation. First, it introduces the concept design of a triple-gasbag airship that can regulate the differential pressure by means of gas–liquid phase change. According to a comparative analysis, ammonia is identified as the optimal working gas for this phase change. To investigate the capability of this method, a steady state model is built. Steady state performance analyses show that a conventional airship cannot effectively reduce the super-pressure caused by the superheat, whereas the triple-gasbag airship is theoretically effective in reducing the super-pressure by over 45% through regulating the volume ratio of ammonia from 10% to 0 at a constant altitude during the diurnal cycle. Considering the rapid increase in the temperature and pressure of gases inside the airship at sunrise, a coupled dynamic model is built, which can describe the transient behavior of the thermodynamic and kinetic parameters of the triple-gasbag airship. Further dynamic analyses demonstrate that even though the gas temperature significantly increases at sunrise, the phase-change method based on appropriate operational planning can also substantially reduce the super-pressure by over 45%. A few problems that require further investigations in the future are discussed.