Experimental investigation of spontaneously condensed nitrogen droplets in a Laval nozzle

Jiaxin Hou, Xueli Li, Wang Zeng, Junlong Xie and Jianye Chen

Energy, 2025, vol. 335, issue C

Abstract: Cryogenic wind tunnels (CWT) achieve ground-based experimental conditions for transonic flight by effectively utilizing cryogenic energy. These facilities play a key role in enhancing flight safety and improving energy efficiency. The use of spontaneously condensed nitrogen droplets as tracer particles in CWTs offers significant potential for non-intrusive flow measurements. The effective use of nitrogen droplets can enable high-fidelity measurements, enhance thermal management, and optimize cryogenic energy use. However, the droplet formation properties and the distribution characteristics have not been clarified. This study aims to obtain the parameter variations during the formation and analyze the distribution characteristics of the droplets through a visualization-based experimental approach. Accordingly, a cryogenic supersonic nitrogen condensation visualization platform integrating a cryogenic nitrogen supply system, a Laval nozzle condensation visualization device, a buffer and backpressure control system and a data acquisition system was developed. Spontaneously condensed droplets were captured at the Wilson point. Spatial analysis reveals that the droplet size distribution is predominantly uniform, with 87.2 % of the droplets ranging from 1.8 to 2.5 μm. This uniformity offers advantages for using the droplets as tracer particles in CWT. The droplet concentration reaches 109 m−3 under certain conditions. A strong positive correlation is observed between droplet quantity and inlet pressure; higher pressures lead to more pronounced condensation. The results provide an experimental basis for the application of spontaneously condensed nitrogen droplets in non-intrusive flow field measurement techniques.

Keywords: Laval nozzle; Flow visualization; Spontaneous condensation; Nitrogen droplet (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:335:y:2025:i:c:s0360544225040046

DOI: 10.1016/j.energy.2025.138362

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