Experimental And Flow Field Simulation Study Of Supercritical Carbon Dioxide Spray Dyeing

With the development of green environmental awareness,the textile and dyeing industry has higher and higher requirements for clean production,and the new water-free dyeing technology has attracted more and more attention.The supercritical carbon dioxide(SC-CO2)dyeing technology is expected to become a new direction of the textile industry because it uses CO2 to replace water to avoid water pollution.In this paper,the mechanism and classification of SC-CO2 dyeing and the research progress of SC-CO2 spray dyeing technology are summarized.As the equipment for realizing the spray dyeing technology,SC-CO2 dyeing sprayer lacks in-depth research on the key issues such as the change rule of leakage,flow field distribution in the spray dyeing area,spray dyeing feasibility and the dyeing effect,and the optimization of the structure of the spray dyeing area.In order to study the above issues,an SC-CO2 experimental dyeing sprayer was developed,which was divided into spray dyeing area,reflux area,labyrinth sealing area and discharge area.The labyrinth sealing area and discharge area were the main areas for reducing leakage,the spray dyeing area was the main area for fabric dyeing and the reflux area was the main area for fluid recovery.First of all,based on SC-CO2 experimental dyeing sprayer,the leakage analysis was carried out,the mechanism of labyrinth sealing area and discharge area acting together to reduce leakage was clarified,and the influence of single factors such as discharge outlet pressure,labyrinth seal area inlet pressure,inlet temperature and seal clearance on leakage were analyzed by simulation.The actual leakage was detected by means of experiment,and the accuracy of the leakage simulation was verified by comparing with the experimental data.Mathematical model of each influencing factor and leakage rate was established by uniform design,and the interaction of various factors on leakage was studied.Secondly,the influence of reflux outlet pressure,inlet pressure,inlet temperature and two kinds of experimental spray plate structures on the flow field in the spray dyeing area was revealed by simulation.It was found that the lower the pressure at the reflux outlet,the more obvious the edge effect in the spray dyeing area was;The fabric surface pressure and temperature could be changed by adjusting the inlet pressure and temperature;The two spray plate structures had little influence on the flow field;the flow field in the spray dyeing area could ensure the dyeing condition,the dyeing flow field was uniform and the throttling effect had little influence.An ideal point evaluation function was established based on Minkowski function.The closer the inlet pressure was to 20MPa and the closer the inlet temperature was to 393K,the deeper the dyeing effect could be obtained.Thirdly,the influence of process conditions and two kinds of experimental spray plate structures on actual dyeing effect was studied,the change rule and mechanism of dyeing depth of dyed fabric were analyzed,and the apparent morphology,color fastness,penetration,chemical structure,crystallization and mechanical properties of dyed fabric were analyzed.The results indicated that the spray dyeing effect of the fabric was good,and the fabric quality had not changed significantly.The accuracy of the flow field simulation was verified by comparing the measured temperature of the fabric surface and the actual spray dyeing effect with the simulation results.Finally,the structure of the spray dyeing area was optimized.Firstly,the influence of the orifice shape,the orifice diameter,the distance between the orifice and the fabric,the orifice spacing and the orifice arrangement on the uniformity of the spray dyeing area,the spray dyeing low efficiency area and the throttling effect were studied by single factor analysis.Then,optimization functions with homogeneity of flow field,extreme difference of flow field along orifice axis,diameter-distance ratio and ratio of spray dyeing inefficient zone as optimization objectives were established,and each optimization objective function was weighted by the method of Entropy Weight.The single-objective optimization function of the structure of the spray dyeing area was obtained,and the optimal structure parameters were finally determined by solving the function.This paper provides some theoretical guidance for the research of spray dyeing technology and helps for the development of water-free dyeing technology.