Study On Condensation In Sonic Nozzles Base On Parameter Adjustment In The Standard Nozzle Device

Sonic nozzle is widely used in many industrial process such as measurement,aerospace and energy,because of its simple structure and stable performance.When the nozzle satisfies the critical conditions,the fluid's velocity in throat will reach the local sonic velocity.At this time the vapor or moist gas will condense because of temperature drops.And this phenomenon will influence the measurement accuracy of sonic nozzle seriously.This supersonic vapor condensation flow is complicated.The existing theoretical model can not accurately analyze its phenomenon essence roundly.And there are lack of comprehensive experimental research.In this paper,the phenomenon of condensation flow is the core of study.Aimed at those complex changes of condensation and the self-excited oscillation phenomenon in sonic nozzle,a quantitative experimental study based on the existing qualitative theoretical analysis has been carried out.Then,the related regularity characteristic have been summarized.Around the core of this study,the main work and results in this paper are as follows:Through the analysis of basic principle and characteristic about the condensation flow phenomenon in sonic nozzle,clarified the experiment study target of condensation flow phenomenon.The hardware and performance index of the regulating system are determined based on the standard positive nozzle device of Tianjin University.In view of the regulate target of pressure,temperature and humidity,a multi-parameter adjustable experimental condensation apparatus was set up.According to the separation of strong and weak electrical,the hardware design of control system was completed,based on the structure design of apparatus.Designed a PLC fuzzy controller to adjust the parameter,and used MCGS software to design the monitor system.This adjustable apparatus is operated normally,and it can realize the parameters adjustment of fluid medium such as pressure,temperature and humidity,which can support the experimental study of the condensation phenomenon in sonic nozzle.Constructed a pressure distribution acquisition device and designed two sonic nozzles with different structure,in order to obtain the pressure jumps caused by condensation.Through these devices,the condensation phenomenon in sonic nozzle was caught accurately.By a lot of experiments and numerical simulation,according to the characteristic of steady and unsteady self-oscillation flow of condensation,the timeaveraged pressure and transient pressure were obtained to summarize the regularity of condensation combine with semi-empirical formula.The regularity shows that the condensation phenomenon in sonic nozzle is heavily influenced by the temperature,pressure and humidity of flow.The location of condensation moves forward and the intensity increase with the increase of temperature and humidity.Meanwhile,the location of condensation moves forward with the increase of the pressure while the intensity is weaken.The frequency of self-oscillation is positively correlate with the humidity and temperature,while it is negatively correlate with the pressure.And the amplitude of self-oscillation is positively correlate with the pressure,temperature and humidity.