• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.607-616
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• 2019

Free body diagram analysis is done for key parts of pilot stage of LLV (Load Limit Valve) which is used to protect overload for static structural test of aerospace flight vehicle. It is shown through the analysis that diameter ratio($D_2)^{ten}/D_2)^{comp}$) of two poppets in a pilot stage must be equal to piston area ratio($A_{comp}/A_{ten}$) of a hydraulic actuator for making a poppet open consistently at constant force applied by an actuator. The result of the analysis is verified by measuring geometries of the poppets in the four different LLVs which are corresponding to four actuators with different capacity and have been used after being imported in this laboratory. Results of "Adjuster resolution tests" with two different pilot stages show the max. deviation of Fi(actuator force in instant of opening poppet) from average Fi obtained for each turn of adjuster is 0.3KN and max. deviation of the Fi normalized by average Fi of each turn of adjuster is 3.7%. From the results, it is verified that the two pilot stages with same poppet diameter ratio make a poppet consistently open at Fis within ${\pm}3.7%$ deviation from the average Fi. The deviation is shown to be caused from frictional force of O-ring in the poppet. Additionally, design factors for poppet spring and adjuster, which are also key parts of the pilot stage, are distinguished and procedure for deciding the factors are also shown in this study.

• Journal of Hydrogen and New Energy
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• v.34 no.1
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• pp.17-25
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• 2023

The purpose of this study was to propose a design that shows optimal performance by changing the geometry of the internal flow path of the receptacle in order to prevent the decrease in flow rate and differential pressure performance due to the application of the receptacle in the hydrogen charging system. To achieve this, 3D computational fluid dynamics simulation was performed for the receptacle, according to the geometry of the flow path inside the receptacle. The pressure results at the inlet and outlet were measured the same as both of N and H₂ in the experiment, and the flow rate of H₂ was 3.75 times higher than that of N₂. In addition, since the flow performance of the receptacle improved under conditions where the flow path was widened, it was confirmed that reducing the diameter of the poppet and the width of the guide are advantageous for improving performance.