Preparation Of High Performance Oxygen Permeable Membrane For Oxygen Enriched Combustion Of Engine

The oxygen-enriched combustion technology is of great significance to the energy-saving and emission-reduction of engine.The membrane-based oxygen enrichment technology is one of the best ways to the oxygen-enriched combustion.However,the membranes developed currently are difficult to meet the requirements of the combustion,cause its low air permeation and poor mechanical property.In this paper,the modifications of cross-linking and doping were made to the lower molecular weight vinyl silicone to obtain a more available membrane.A membrane with high oxygen-enriching property was achieved,the oxygen concentration of which was similar to the commercial membranes,and the air permeability was 10 times to the unmodified silicon membrane.In this paper,the self-made vinyl silicone was used as material,the polymethylhydrosiloxane was used as crosslinking agent to prepare the crosslinking modified coating.The influence of the feed ratios,reaction time,curing temperature and curing time,the molecular weight of the support membrane and the operating vacuum on the oxygen-enriching properties of the new membranes were investigated respectively.The results showed that the feed ratios of 2~6,reaction time of 1h~3h,curing temperature of 60℃~110℃,curing time of 2h and molecular weight of 2W were more beneficial to the oxygen-enriching properties of membranes.The Box-Behnkn of the design-expert was used to design the optimization tests to optimize the feed ratio,reaction time,curing temperature and curing time.A model with high confidence level was obtained,and predicted optimized condition for the oxygen-enriched membrane preparation.Membrane with air permeability of4696.33 barrer and oxygen enriched concentration of 28.68% was obtained under the predicted conditions.The oxygen-enrich property was similar to the predicted value.The mechanical properties of the membranes prepared in this experiments were weaker rhan the commercial polysulfone membrane,however,colud meet the requirements of general module.By the way of organic/inorganic doping,membranes with nano-SiO2 were prepared with small excesses of polymethylhydrosiloxane.Of the membrane,nano-SiO2 was connected with the silicon by covalently association.The influence of the addictive of nano-SiO2 on the oxygen-enrich property was investigated.And a membrane with oxygen enriched concentration of 29.76%,air permeability of 5801.46 barrer was made with the addictive of 19wt% of nano-SiO2,which was 1105.13 barrer higher than the air permeation without nano-SiO2 addictive,and 1.08% higher than the oxygen concentration without nano-SiO2 addictive.Results of mechanical performance showed that the tensile strength decreased with the increasement of Si O2 addictive.A spiral-membrane module of 3m2 was made with the membrane above.The influences of the pressure,air temperature and air intake on the performance of module were investigated.The results showed that the oxygen enriched concentration was over 29.01% and the air permeability was over 5m3/h when operating pressure was above 0.086 MPa.The recovery rate was 8.3%~25% and the oxygen enriched concentration was 24.38%~29.01% when the intake flow was 20~60m3/h.The temperature of the intake should be controlled within 20~40℃ to prevent the module from destroying.The module kept stable in the 300 min performance tests,which is desirable to apply in the combustion tests of engine.