Numerical Analysis Of The Effect Of The Nozzle On The Ejector Performance

The consumption of energy is rather huge in our country, energy saving and environmental protection issues is the primary research in today’s society. Ejector as a industrial equipment which is simple and has high working efficiency so that it has been widely used in metallurgy, oil chemical industry, light industry, textile, construction, refrigeration, industrial thermal and other fields. The fundamental characteristic of the ejector is increasing the pressure of the fluid mechanical energy without direct consumption, the structure of the ejector compares with the mechanical pressure equipment is simple and reliable, the effect of energy saving is more remarkable. Supersonic nozzle is a core component in ejector which converts the pressure energy of the working fluid to speed energy. Therefore, optimization design of the nozzle is an important measure to improve the performance of ejector.This paper based on the Sokolov ejector design theory, through reasonable assumption and according to structural design formula of ejector, the author establishes a physical model for ejector which is working with refrigerant R134a. The author carries out numerical simulation of two-dimensional flow field of ejector internal by using Fluent software in the designed condition. Analysing the influence by some factors like turbulence model, the discrete format and so on to obtain grid convergence of the solution. At the same time obtaining the distribution regularities of pressure field, velocity field and temperature field.In order to investigate the influence on the performance of ejector nozzle, this paper studied the different thermal parameters (working fluid pressure) and structure parameters (nozzle exit to throat area ratio and the axial size) of nozzle. The simulation results show that ejection coefficient increases with the the working fluid pressure increases when it is lower than 3.2MPa in nozzle, ejection coefficient decreases with the working fluid pressure increases when it is higher than 3.2MPa. The suitable range of the working fluid pressure in nozzle is 3.2MPa-3.6MPa. The ejection coefficient reaches the maximum when the nozzle area ratio is 2.51, the ejector can not work normally when the nozzle area ratio is 1.61,1.73 and 2.29. So ejector have best performance when the nozzle area ratio remains in the range of 2.14～2.51. The ejection coefficient has not changed much when the ratio of convergent section and outlet diameter in the nozzle between 1.05-2.11 and the ratio of diffusion length and outlet diameter between 0.84～1.89. So the influence of axial size on the performance of ejector is very small in a certain range.