In this paper,design and optimization technique of slotted tube grain for solid rocket motors has been discussed.In doing so,the design objectives and constraints have been set,geometric parameters identified,performa...In this paper,design and optimization technique of slotted tube grain for solid rocket motors has been discussed.In doing so,the design objectives and constraints have been set,geometric parameters identified,performance prediction parameters calculated,thereafter preliminary designs completed and finally optimal design reached.Geometric model for slotted tube grain configuration has been developed.Average thrust has been taken as the objective function with constraints of burning time,mass of propellant,fixed length and diameter of chamber case.Lumped parameter method has been used for calculating the performance prediction parameters.A set of preliminary designs has been completed and an analysis of these results conducted.Although all the preliminary results fulfill the design requirements in terms of objective function and constraints,however in order to attain the optimal design,Sequential quadratic programming optimization technique has been adopted.As the slotted tube grain geometry is totally dependent upon various independent variables and each of these variables has a bearing on explicit characteristic of grain designing,hence affects of the independent variables on performance parameters have been examined,thus variation laws have been developed.Basing on the variation laws and the analysis of preliminary design results,upper and lower limits have been defined for the independent geometric variables and an initial guess provided for conducting optimization.Results attained exhibits that an optimal result has been attained and the value of objective function has been maximized.All the design constraint limits have also been met while ensuring sound values of volumetric loading fraction,web fraction and neutrality.This methodology of design and optimization of slotted tube grain for solid rocket motors can be used by engineers as a reference guide for actual design and engineering purposes.展开更多
With isopentane as working fluid, the heat transfer performances for corrugated, nodal and horizontal grain tubes are simulated. The structural parameters of the three kinds of tubes are compared with those of the pla...With isopentane as working fluid, the heat transfer performances for corrugated, nodal and horizontal grain tubes are simulated. The structural parameters of the three kinds of tubes are compared with those of the plain tube. The numerical results using computational fluid dynamics are validated with theoretical values. For the corrugated, nodal and horizontal grain tubes, the heat transfer enhancements(HTEs) are 2.31—2.53, 1.18—1.86 and 1.02—1.31 times of those of the plain tube, respectively. However, the improved HTEs are at the expense of pressure losses. The drag coefficients are 6.10—7.09, 2.06—11.03 and 0.53—1.83 higher, respectively. From the viewpoint of comprehensive heat transfer factor, the corrugated tube is recommended for engineering applications, followed by the horizontal grain tube.展开更多
The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on se...The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on seed setting rate. The rice pollen grain started to germinate at 2 min after pollination and the pollen tube penetrated stigma into style in 5-10 min, 30 min later the end of pollen tube reached the bottom of ovary, and only some pollen tubes arrived at embryo sac at 40 min after pollination. Meanwhile, a small amount of callose began to deposit in the pollen tubes, a great deal of callose was observed at 50 min after pollination, whereas the pollen grain began to shrink. The growing rates of pollen tube in the rice stigma, style and ovary were 1500, 5000, and 5400 μm/h, respectively. The seed setting rate was quite low when the stigma was removed at about 10-15 min after pollination, gradually increased when it removed at 20 min to 50 min after pollination, and over 60% when it removed at 50 min after pollination and finally tended to be stable.展开更多
Inwall shot blasting is a method of improving the surface hardness and high temperature oxidation resistance of the S30432 high-pressure boiler tube.The differences on residual stress,sub-grain size,micro-hardness and...Inwall shot blasting is a method of improving the surface hardness and high temperature oxidation resistance of the S30432 high-pressure boiler tube.The differences on residual stress,sub-grain size,micro-hardness and structure between the S30432 inwall shot-blasting tube produced by Baosteel with six technological process parameters and the imported super 304H were studied systematically by contrast test research.It has been demonstrated that the S30432 obtains a higher residual stress,a deeper distributed layer and a better sub-grain size of the inwall field shot-blasting layer;the martensite content of the shot-blasting surface was low;and micro-hardness and structure refinement were better.After 2000 h’ oxidation test under the 650℃/26MPa steam condition,steam oxidation resistance of the Baosteel steel tube shot-blasting surface was higher,the oxide layer was thinner,and was well combined with bulk material.展开更多
This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent d...This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.展开更多
文摘In this paper,design and optimization technique of slotted tube grain for solid rocket motors has been discussed.In doing so,the design objectives and constraints have been set,geometric parameters identified,performance prediction parameters calculated,thereafter preliminary designs completed and finally optimal design reached.Geometric model for slotted tube grain configuration has been developed.Average thrust has been taken as the objective function with constraints of burning time,mass of propellant,fixed length and diameter of chamber case.Lumped parameter method has been used for calculating the performance prediction parameters.A set of preliminary designs has been completed and an analysis of these results conducted.Although all the preliminary results fulfill the design requirements in terms of objective function and constraints,however in order to attain the optimal design,Sequential quadratic programming optimization technique has been adopted.As the slotted tube grain geometry is totally dependent upon various independent variables and each of these variables has a bearing on explicit characteristic of grain designing,hence affects of the independent variables on performance parameters have been examined,thus variation laws have been developed.Basing on the variation laws and the analysis of preliminary design results,upper and lower limits have been defined for the independent geometric variables and an initial guess provided for conducting optimization.Results attained exhibits that an optimal result has been attained and the value of objective function has been maximized.All the design constraint limits have also been met while ensuring sound values of volumetric loading fraction,web fraction and neutrality.This methodology of design and optimization of slotted tube grain for solid rocket motors can be used by engineers as a reference guide for actual design and engineering purposes.
基金Supported by the National High Technology Research and Development Program of China("863"Program,No.2012AA053001)
文摘With isopentane as working fluid, the heat transfer performances for corrugated, nodal and horizontal grain tubes are simulated. The structural parameters of the three kinds of tubes are compared with those of the plain tube. The numerical results using computational fluid dynamics are validated with theoretical values. For the corrugated, nodal and horizontal grain tubes, the heat transfer enhancements(HTEs) are 2.31—2.53, 1.18—1.86 and 1.02—1.31 times of those of the plain tube, respectively. However, the improved HTEs are at the expense of pressure losses. The drag coefficients are 6.10—7.09, 2.06—11.03 and 0.53—1.83 higher, respectively. From the viewpoint of comprehensive heat transfer factor, the corrugated tube is recommended for engineering applications, followed by the horizontal grain tube.
基金the National Natural Science Foundation of China (Grants Nos. 30070454 and 30471045)
文摘The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on seed setting rate. The rice pollen grain started to germinate at 2 min after pollination and the pollen tube penetrated stigma into style in 5-10 min, 30 min later the end of pollen tube reached the bottom of ovary, and only some pollen tubes arrived at embryo sac at 40 min after pollination. Meanwhile, a small amount of callose began to deposit in the pollen tubes, a great deal of callose was observed at 50 min after pollination, whereas the pollen grain began to shrink. The growing rates of pollen tube in the rice stigma, style and ovary were 1500, 5000, and 5400 μm/h, respectively. The seed setting rate was quite low when the stigma was removed at about 10-15 min after pollination, gradually increased when it removed at 20 min to 50 min after pollination, and over 60% when it removed at 50 min after pollination and finally tended to be stable.
文摘Inwall shot blasting is a method of improving the surface hardness and high temperature oxidation resistance of the S30432 high-pressure boiler tube.The differences on residual stress,sub-grain size,micro-hardness and structure between the S30432 inwall shot-blasting tube produced by Baosteel with six technological process parameters and the imported super 304H were studied systematically by contrast test research.It has been demonstrated that the S30432 obtains a higher residual stress,a deeper distributed layer and a better sub-grain size of the inwall field shot-blasting layer;the martensite content of the shot-blasting surface was low;and micro-hardness and structure refinement were better.After 2000 h’ oxidation test under the 650℃/26MPa steam condition,steam oxidation resistance of the Baosteel steel tube shot-blasting surface was higher,the oxide layer was thinner,and was well combined with bulk material.
文摘This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.
