Liquid nitrogen cooling cryogenic cutting is one of the most effective means to realize green machining of titanium alloy and other difficult-to-machine materials.In order to realize the preferred nozzle structure for the temperature-velocity control of the low-temperature nitrogen jet process,numerical simulation combined with experimental research was used to analyze the influence of the conical straight nozzle inlet diameter D,outlet diameter d,contraction angle α0,and the length-to-diameter ratio l/d on the temperature-velocity distribution of the outlet jet field.The results show that the existence of a core structure field makes the velocity and temperature consistent with that of the nozzle exit,and the magnitudes of velocity decay and temperature rise outside the core structure field decrease with the increase of the exit diameter d.Under the experimental conditions,when d increases from 2.0 mm to 4.0 mm,the jet velocity decay amplitude decreases from 386.3 m/s to 40.1 m/s,and the jet temperature rise amplitude decreases from 92.7 K to 41.1 K.The core area length of the jet velocity sn1 and the core area length of the jet temperature sn2 are positively correlated with d linearly,and the rate of change of sn1 is 1.4 times as much as that of sn2.d and l/d have effects on the exit axial jet velocity,with the effect of d being more significant.As d increases from 2.0 mm to 4.0 mm,um decreases by 74.9%.As the length-to-diameter ratio l/d increases from 1 to 4,um increases by 3.2%.It is indicated that decreasing d and increasing l/d can increase the exit jet velocity.
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