Simulation of effect of nozzle parameters on supercritical hydrothermal combustion characteristics
The role of reactor nozzle is to maintain the stability of the hydrothermal flame in a complex flow field.A computational fluid dynamics model of the supercritical hydrothermal combustion process of methanol in an internally preheated transpiration wall reactor(IPTWR)was developed,and the effects of material thermophysical properties and structural parameters of the nozzle on the feed mixing characteristics and flame structure were analyzed.The results show that the improvement of the heat transfer characteristics of the nozzle material makes the hydrothermal flame move toward high temperature and wide area;the diameter of the oxygen-assisted heat mixing section decreases from 18 mm to 14 mm,the peak axial temperature of the reactor increases from 954.84 K to 981.60 K,and the flame position moves toward the distal end;with the decrease of the indentation depth of the nozzle,the hydrothermal flame is gradually converged toward the nozzle outlet,which is manifested as a phenomenon of flame contraction.In this nozzle structure parameter range,the short oxygen-assisted heat mixing flow path with small diameter helps the hydrothermal flame temperature increase and gathering stabilization.Theoretical guidance is provided for the nozzle design of the internal preheated transpiration wall reactor.
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