| Airflow field in melt blowing is a transient temperature field formed by a collision of jet. This paperproposed:(1) a dynamic measurement technique in transient temperature field which is first time used to conductexperimental study of spatial dynamic behavior on airflow field in melt blowing.(2) a method to establish dynamiccharacteristic model and divide feature regions during the spatial evolution which is also used to analyze the effectof change of initial nozzle’s conditions on airflow field in melt blowing.This paper studied the experimental techniques:(1) the synchronous measurement of temperature andvelocity should be made in the variable temperature field measurement, the key of which lies in that velocitycalibration coefficient under corresponding temperature must be brought in the calculation of velocity.(2) A/Dboard must be used and not cleared when data acquisition for long time is made using DANTEC hot wireanemometer.(3) in the analysis of data of variable temperature flow field, calibrated coefficient of variabletemperature must be brought in.This article studies spatial dynamics behavior of airflow field in melt blowing (1) Different shape ofnozzle flow field: Studies show that, in all kinds of incoming flow temperature working condition, the stretchingand compression region on the flow direction of rectangle and oval nozzle is longer than of square and roundnozzle. It indicates that fiber can be stretched more in spatial domain, and appears earlier on shaping the flow fieldimpact dynamics before shaping turbulent region. The spatial variation gradient of stretching and compressionregion on the airflow velocity of rectangle and square nozzle is better than of oval and round nozzle, and collisionturbulent region is also longer.(2) Different angles of nozzle: Studies show that when slot angle of nozzle reaches10°, it is easier to appear stretching region on melt blowing, and the appearing region is always in the front ofturbulent region. The spatial variation gradient of stretching and compression region, shaping from airflow of therectangle and square nozzle reaching10°slot angle, is the best. Only rectangular and oval-shaped of30°anglespout could form stretch zone at a high inlet fluid temperature. For the flow pulsation turbulence of rectangular andoval-shaped spout angle of30°, its tendency changed relatively slow.(3) Different inlet fluid temperatures andvelocities: It was found that the higher inlet fluid temperature was, the more easily stretch zone of flow field wasformed. Meanwhile, the higher inlet fluid temperature was, the smaller influence of the attenuation by inlet fluidvelocity. In a high inlet fluid temperature condition, the temperature within stretch zone of rectangular spout wasthe minimum attenuation. The more the inlet fluid flow, the greater the turbulent region. However, the turbulence inthe measured space was little attenuation. Numerous regional characteristics of melt blowing flow field in the spatial evolution have occurred in theturbulent region. In most cases, spanwise turbulence field of airflow field in melt blowing was earlier generated inspace position than flow turbulence field. And the length of spanwise turbulence field was greater than the length ofthe flow turbulent region. In all conditions, the position to the nozzle of spanwise velocity turbulence to reach peakwas closer than flow rate turbulence to reach peak. |
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