Experimental and numerical studies on self-excited periodic oscillation of vapor condensation in a sonic nozzle

The unsteady nozzle flow induced by vapor condensation has many different self-excited periodic oscillation modes and affects flow field and mass flow-rate of sonic nozzle. A detailed discussion of thermal choking and oscillation frequencies of this unsteady flow was carried out. To investigate these different oscillation modes, an experimental sensor for measuring inlet humidity/temperature, and monitoring pressure oscillation was built. A numerical model for condensation process in sonic nozzle was established and validated by experimental data of moist nitrogen reported by Wyslouzil and Lamanna. The output of measurement sensor for nozzle flow of moist air agreed with the results of this numerical model. At last, four different oscillation modes caused by vapor condensation were explored. The rules of frequencies and amplitudes of pressure signals for these oscillation modes were discussed in detail. All results can promote the study on the effect of vapor condensation on accurate metering of sonic nozzle.