A Review on the Precise Control of the Liquid Nitrogen Supplying System in Transonic Cryogenic Wind Tunnel

The liquid nitrogen (LN2) supplying system, one of the four key systems of the cryogenic wind tunnel (CWT), is an essential guarantee for the precise control, fast and safe regulation of the wind tunnel's total temperature. Firstly, the technical schemes, advantages and disadvantages of different LN2 supplying systems are discussed and analyzed based on the operation conditions and test requirements of different CWTs. Then, together with the development of the pilot cryogenic transonic wind tunnel (PCTW), the key technologies of the system, including the supplying mode, rapid and accurate regulation of injection pressure, development of large scale cryogenic centrifugal pump, and matching technology between pumps and pipe network, have been summarized and the solutions to the existing issues are given. Finally, a supplying process suitable for large-scale CWT is proposed, which has the ability of independent commissioning, rapid regulation, accurate control of injection pressure and transient response to the wind tunnel's wide range of working conditions. The breakthrough in LN2 supplying system enables China to construct a CWT for the future competitive high Reynolds number aircraft.