Gel propulsion systems have many advantages with respect to high performance, the energy management of liquid propulsion systems, storability, high density impulse, and low leakage of liquid propellants. The atomizati...Gel propulsion systems have many advantages with respect to high performance, the energy management of liquid propulsion systems, storability, high density impulse, and low leakage of liquid propellants. The atomization process provides sufficient contact surface area between the gelled fuel and oxidizer jets. It is important to study how injection characteristics of gelled propellants are related with break-up and spray distribution. The break-up and mixing processes are very important in achieving maximum efficiency and necessitate the careful study of combustion instability. Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the break-up process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. Especially, the break-up processes of the impinging jets at the initial conditions are studied. The break-up process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids which are mixed by ionized water 98.5 wt%, Carbopol 941 0.5wt% or 1.0wt%, and NaOH(concentration 10%) 1.0wt%. For the like-on-like doublet injector, the generation of a liquid sheet at the impinging point of two jets was observed. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Generally, the break-up length decreased due to the increasing Reynolds number. However, surface waves and atomized droplets increased. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. Also, the rim patterns of spray have no disturbances on the spray sheet. As the injection pressure increased, rimless patterns w展开更多
The aluminum-water system is a promising propellant due to high energy and low signal characteristics,and the gel form is easier to store and utilize.In this work,hydrogels of water and aluminum particles were prepare...The aluminum-water system is a promising propellant due to high energy and low signal characteristics,and the gel form is easier to store and utilize.In this work,hydrogels of water and aluminum particles were prepared using the low-molecular-weight gellant agarose.The various physical properties of gel systems,including the water loss rate,phase transition temperature,and centrifugal stability at different gellant and aluminum contents,were examined.Rheological properties were assessed through shear thinning tests,thixotropy tests,strain sweep analysis,and frequency sweep experiments.The microstructure of the gel was obtained through scanning electron microscopy images.The results show that the aluminum-hydrogel network structure is composed of micron-scale aluminum and agarose nanosheets,and the unique micro-nanostructure endows the gel with excellent mechanical strength and thermal stability,which improve with increasing gellant and aluminum contents.Notably,the gel with 2% agarose and 20% aluminum had the best performance;the storage modulus reached 90647 Pa,which was within the linear viscoelastic region,and the maximum withstand pressure was 111.2 kPa,which was 118.8% greater than that of the pure hydrogel.Additionally,the gel demonstrates remarkable shear thinning behavior and can undergo gel-sol transformation upon shearing or heating to exceeding 114℃.展开更多
基金(Grants No. 00040486) was supported by Business for Cooperative R&D between Industry, AcademyResearch Institute funded Korea Small and Medium Business Administration in 2010
文摘Gel propulsion systems have many advantages with respect to high performance, the energy management of liquid propulsion systems, storability, high density impulse, and low leakage of liquid propellants. The atomization process provides sufficient contact surface area between the gelled fuel and oxidizer jets. It is important to study how injection characteristics of gelled propellants are related with break-up and spray distribution. The break-up and mixing processes are very important in achieving maximum efficiency and necessitate the careful study of combustion instability. Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the break-up process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. Especially, the break-up processes of the impinging jets at the initial conditions are studied. The break-up process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids which are mixed by ionized water 98.5 wt%, Carbopol 941 0.5wt% or 1.0wt%, and NaOH(concentration 10%) 1.0wt%. For the like-on-like doublet injector, the generation of a liquid sheet at the impinging point of two jets was observed. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Generally, the break-up length decreased due to the increasing Reynolds number. However, surface waves and atomized droplets increased. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. Also, the rim patterns of spray have no disturbances on the spray sheet. As the injection pressure increased, rimless patterns w
基金supported by the Haihe Laboratory of Sustainable Chemical Transformations.
文摘The aluminum-water system is a promising propellant due to high energy and low signal characteristics,and the gel form is easier to store and utilize.In this work,hydrogels of water and aluminum particles were prepared using the low-molecular-weight gellant agarose.The various physical properties of gel systems,including the water loss rate,phase transition temperature,and centrifugal stability at different gellant and aluminum contents,were examined.Rheological properties were assessed through shear thinning tests,thixotropy tests,strain sweep analysis,and frequency sweep experiments.The microstructure of the gel was obtained through scanning electron microscopy images.The results show that the aluminum-hydrogel network structure is composed of micron-scale aluminum and agarose nanosheets,and the unique micro-nanostructure endows the gel with excellent mechanical strength and thermal stability,which improve with increasing gellant and aluminum contents.Notably,the gel with 2% agarose and 20% aluminum had the best performance;the storage modulus reached 90647 Pa,which was within the linear viscoelastic region,and the maximum withstand pressure was 111.2 kPa,which was 118.8% greater than that of the pure hydrogel.Additionally,the gel demonstrates remarkable shear thinning behavior and can undergo gel-sol transformation upon shearing or heating to exceeding 114℃.
