Study On The Condensation Flow Field In The Sonic Nozzle And Heat Effect Temperature Field Of Nozzle Wall

The sonic nozzle is one of the most common flow sensors and has been used in micro flow measurement.But there are also many problems to be explored due to the effect of nozzle structure,machining precision,Reynolds number,heat transfer in nozzle wall and humidity of medium on the flow rate.Aiming at researching the vapor condensation and fluid-solid coupling heat effect caused by gas expansion and cooling,the characteristic of the condensation flow field and heat effect temperature filed of nozzle wall were researched in this paper.The main work and results are shown below.For condensation flow field,a non-equilibrium condensation model with a k-εviscous solver for the moist air supersonic flow was built and validated by the experimental data of time-averaged pressure distribution.For the steady condensation flow characteristic,it was found that with the humidity,temperature and carrier gas increasing,the condensation onset moved upstream.The increase of humidity and temperature and decrease of the carrier gas pressure would enhance the relative condensation intensity.The entropy due to phase change reached the maximum at condensation onset and the entropy due to viscous and heat conduction were distributed in the boundary layer.Then the self-excited oscillation characteristic of unsteady condensation flow was researched.To measure the high-frequency pressure fluctuation signal,the micro probe-transducer system was designed by B-T(Bergh-Tijdeman)model.The pressure fluctuation frequency and intensity of self-excited oscillation were analyzed under different inlet conditions combining experimental data and physical simulation model.Importantly,a new semi-empirical relation of dimensionless frequency was acquired by dimensionless analysis identified,of which average error is reduced to 5.51%.At last,the nonstationary of the pressure fluctuation was explored based on the continuous wavelet transform.For the heat effect temperature field of nozzle wall,a nozzle wall temperature field reconstruction algorithm was put forward based on the kriging interpolation and differential equation of heat conduction.The verification result showed that the algorithm can solve the problem of ‘buphthalmos’ and unsmooth isotherm with good accuracy.Then a sonic nozzle transient temperature field reconstruction and visualization system was built of which the controller is DSP(digital signal processor).The temperature of nozzle wall was obtained and the cloud pictures of temperature field were reconstructed by experiment.The experiment result showed that the decrease of inlet pressure and nozzle throat diameter would cause the position of lowest temperature moved upstream.For the same nozzle,the transient temperature decreased with time and the lowest temperature point dropped the fastest with unchanged position.The above characteristics were closely related to the shock wave position of the flow field.