Taking a vehicle carbon fiber fully-wound hydrogen storage cylinder as the research object,based on the ANSYS workbench platform,the difference of the cylinder structure layer and the uneven distribution of temperature load are fully considered,and the fluid-thermal-solid coupling numerical simulation and analysis are carried out.The specific method is to firstly carry out 3D numerical simulation of the gas flow field inside the cylinder during the fast filling process to study the law of temperature rise,then load the flow field calculation results into the cylinder structural layer for steady-state thermal analysis,and finally load both the flow field and thermal analysis results into the cylinder structural layer for structural static analysis.The results show that the maximum temperature of the cylinder and the maximum stress on the carbon fiber composite layer appear at the connection between the end head and the cylinder when the filling is finished.The thermal stress caused by the temperature load is small compared with the mechanical stress caused by the internal pressure.The difference between the mechanical stress and the coupling stress is not large,and the mechanical stress on the carbon fiber composite layer is slightly smaller than the coupling stress,while the thermal stress caused by the temperature load on the aluminum alloy liner layer is partly offset by the mechanical stress due to the large expansion coefficient,making the coupling stress smaller than the mechanical stress.
In order to solve the problems of low dust removal efficiency and excessive particle concentration at the fan discharge port due to the irrational design of the gravity settling chamber,the flow field analysis and structural optimization design of the gravity settling chamber of a certain type of road sweeper was carried out.Firstly,FLUENT was used to simulate the internal flow field characteristics of the settling chamber and the movement of dust particles inside the chamber,and the single-factor effects of the key structural parameters of the settling chamber(angle of the dust shield,width of the dust baffle plate,and the distance of the inlet duct outlet from the top of the chamber)on the settling performance(velocity at the bottom of the chamber,velocity at the front of the outlet,and the along-travel pressure drop)were investigated.Based on Box-Behnken design and regression analysis,a multi-objective response surface optimization of the gravity settling chamber was carried out,and the optimal structural parameters of the gravity settling chamber were obtained.Finally,based on the DPM particle phase model,it was verified that the optimized gravity settling chamber had a better settling effect for dust particles with an equivalent particle size above 0.5 mm.
Based on the plasma fluid theory,the effects of high-frequency source frequency in dual frequency capacitive coupling discharge on the various particles'density and plasma parameters of argon oxygen mixture discharge plasma at atmospheric pressure were studied.We simulate the discharge in different high-frequency source frequencies and have achieved the one-dimensional space-time distribution of the various particles'density,electron temperature,electric field and other parameters,and a better understanding of the influence of high-frequency source frequency on plasma characteristics in dual frequency discharge.The results show that when the discharge voltage is fixed,the electron density increases with the increase of the high-frequency source frequency;The electron temperature,electric field and potential have a downward trend;The density of various argon ions and sub argon atoms increases with the increase of high-frequency source frequency;With the increase of high-frequency source frequency,the density of various oxygen ions increases,the density of oxygen atoms decreases first and then increases,and the metastable density of oxygen molecules increases first and then decreases.Electronic pressure heating,electronic ohmic heating,electronic heating and energy loss are gradually increased due to the influence of high-frequency source frequency.In addition,the effective current density and effective power density generally increase with the increase of high-frequency source frequency.
In order to address the mechanism of leakage rate variation for similar channel-type positive pressure standard leak holes under different operating conditions,a mathematical model was established by filling the channel-type leak holes with porous foam metal.Numerical simulations were conducted to analyze the impact of different operating conditions on the leakage rate of the channel-type positive pressure standard leak holes,and the velocity field distribution inside the foam metal was also provided.The results show that under constant air source pressure,compared with Air,He and D2,H2 has the largest leak rate,and the leak rate of the leak hole increases with the increase of air source pressure.Under the condition of constant pore diameter or porosity,the leakage rate of channel type positive pressure standard leak increases with the increase of pore diameter or porosity,and decreases with the increase of channel type positive pressure standard leak length.Nonlinear change of porosity can effectively improve and control the leakage rate.This study provides valuable reference significance for the production and development of positive pressure standard leaks,leak detection in metrology,and optimizing and designing sealing system performance by controlling leakage rates.
Cryostat is a device that utilizes refrigeration technology to provide and maintain a stable low-temperature environment.It is widely used in the fields of magnetic resonance systems,superconductivity,cryogenic spectroscopy,large scientific devices,and other low temperature tests in the laboratory.The dominant technologies to obtain low temperatures are refrigerants and cryogenic cooling.However,due to the limited cooling capacity of passive cooling,experimental cryostats still predominantly rely on refrigerant and active cooling.This paper presents several common experimental cryostat structures based on cryogenic liquid and active refrigeration,discusses the development of cryostats and associated issues,and analyzes the solutions adopted by leading products in the market.Additionally,the paper also outlines the progress of domestic cryostats and their related technologies,including a self-developed cryogenic thin film resistance test instrument.Finally,the paper provides a brief outlook on the research prospects for cryostats.This study offers technical references for domestic peers/colleagues within the field.
