Integrative design of nozzle,cavity and pressure recovery system

The 3-dimensional numerical simulation of nozzle and diffuser for COIL system is performed.Several nozzle and diffuser designs are compared and analzed.The gasdynamic process from cavity inlet till diffuser outlet is computated.The sufficient mixing of primary and secondary flows in cavity can be reached by means of aiding tab,which is 0.77 cm×0.254 cm.The computational model of diffuser is the 1/4 construction,of which the input cross-section is 30 mm×60 mm.After keeping the same cross-section size till the length is 500 mm,the diffuser is continued with the same width and 4° divergent angle in height till the length is 700 mm.The final output area size of diffuser is 79 mm×60 mm.The input(output of cavity) gas condition of diffuser is air with Mach number of 3.2,static pressure of 1 232 Pa and temperature of 110 K.The output condition is total pressure of 13 300 Pa and total temperature of 300 K.The results show that the output static pressure is more than 10 times high as the input one and this diffuser has very good pressure recovery capability.On the other hand,the total pressure decreases till 1/4.5(from 60 648 Pa till 13 300 Pa),which can lessen the ejector's working load then.Using the high static pressure cavity design can at least remove one stage of ejector in order to miniaturize the whole system.