Due to the problems of fossil fuel exhaustion and environmental pollution, the use of hydrogen fuel has been increasing gradually, so there is also need of commercialization of hydrogen fuel cell vehicle. In order to increase its fuel efficiency, light-weightning and structural design, which are to optimize thickness and shape of the pressure vessel (end closure and boss) and winding angle of composite, have been required. This study has carried out as follows to obtain structural safety of hydrogen pressure vessel (type 4) under working pressure (700 bar). Plastic liner was designed using dome shape with isotensoid curve and spherical shape not to slip in the dome region while filament winding. After calculating the initial thickness of composite by netting theory, the composite thickness in both cylinder and dome parts to satisfy structural safety were obtained by FEM, changing the thicknesses calculated from theory. Also, optimal design of aluminium boss shape was performed using the response surface method to achieve light-weightning and increase of inner capacity. Based on the above results, structural safety of the optimal hydrogen pressure vessel (type 4) with the composite layer and boss shape finally determined was verified through FEA.
The helical grooved seal, which is a non-contact sealing device using the viscosity of the fluid, prevents leakage by reducing fluid pressure according to the shapes of the rotor and stator. It has been widely adopted to turbomachinery because no wear deliveries high efficiency, unlike to the existing contact sealing device. In this study, parametric study was performed by CFD analysis, considering helical grooved seal shape: ratio of groove width and land width (w ratio ), helical angle (β) and groove depth (d). Based on the leakage characteristics analyzed through CFD results, improved seal shape of the helical grooved seal to reduce leakage was suggested. Analysis model of helical-grooved seal Geometry and analysis conditionsVariation of cavity between rotor and stator causes throttling and pressure drop, so difference between the inlet pressure and outlet pressure of the seal reduces leakage, which means the helical grooved seal shape mainly influences on the flow characteristic and leakage amount. Parametric study was performed considering the design parameters relating to helical grooved
Non-circular gears can maintain rotational motions of general gears and implement all varying rotational motions of the cam. They adjust the angular velocity of driven gear according to operating conditions and make precise changes in angular motion. The design of non-circular gears has not been sufficiently studied because of their particularity and complex design methods unlike spur gears. In the gutting section of the Squid Belly Opening and Gutting Machine (SBOGM), spur gears generate rotational impact due to constant angular velocities, causing noise and equipment damage; so, efficiency should be improved by varying sectional angular velocity. Therefore, we derived pitch curves by selecting angular velocity ratio considering operating environments, and the tooth profile was designed by calculating module for each section according to radius through theorical analysis for precise expression of angular velocity ratio. To confirm reliability of design, angular velocity ratio and structural safety of designed non-circular gears were verified using, commercial software, ‘DAFUL 2020 R1′.
The liner of a CNG pressure vessel is manufactured by a DDI (deep drawing and ironing) process for the cylinder part, which is a continuous process that includes a drawing process to reduce the diameter of the billet and a subsequent ironing process to reduce the thickness of the billet. A tractrix die used in the 1st deep drawing allows the blank to flow smoothly by decreasing the punch load and radial tensile stress occurring in the workpiece. It also increases the draw ratio compared to conventional dies, but it causes forming defects. In this study, a shape coefficient (Sc) is proposed for the tractrix die using the blank diameter (D0), inflow diameter of the workpiece (di), and inflow angle of the workpiece ($$\theta$$ θ ) for design of the tractrix die. The effects of the thickness and inflow angle of the workpiece on wrinkling and folding were investigated through FEA. Also, a discriminant is proposed for the relative radial stress ($$\tilde{\sigma }$$ σ ~ ) generated during the deep drawing process using the tractirx die and used to predict fracture. Based on the results, the blank thickness, the draw ratio, and the inflow of the workpiece angle in the 1st deep drawing process are suggested, and the number of operations in the DDI process was reduced from 6 to 4. This improves the productivity and reduces the manufacturing cost.
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