| The pneumatic liquid diaphragm valve is the core component of integrated circuit wet-cleaning and etch equipment,the opening and closing response is rapid.It is responsible for controlling the opening and closing of the fluid flow and the size of the outlet dose.Due to the constraints of raw material supply,relatively low processing level of PTFE plastic parts and unstable structural performance,China’s independent research and development of pneumatic liquid diaphragm valves for integrated circuits is difficult.The internal structure of diaphragm valves for integrated circuits is variable,the flow field is more complex,and the long-term existence of cavitation can lead to the spalling of materials on the inner wall of the diaphragm valve,which can pollute the downstream chip manufacturing process and cause irreparable damage.For example,particle contamination in the process of film growth and deposition will produce defects such as pinholes,microporous,and microcracks;particle contamination in the later stages of device fabrication will cause short circuits between different wires.Meanwhile,the flow resistance characteristics and internal flow field characteristics of diaphragm valves are the main properties of the product.Therefore,it is of great theoretical significance and practical value to analyze and study the flow resistance characteristics,internal flow field characteristics,and cavitation characteristics of the diaphragm valve at the later stage of structural design.By analyzing the results of the calculations and making local structural improvements to address the problems identified,it is also of positive guidance for the determination of the structural design of the later diaphragm valve product.At present,foreign mainstream diaphragm valve manufacturers produce roof-type diaphragm valves,fluid does not pass easily through the ridge when flowing through it,so the flow coefficient is not high.According to market customer feedback and simulation analysis,it was found that the front of the flow channel is prone to the existence of dead zones,which can easily lead to the accumulation of particle contamination after the valve is closed.In order to improve this problem,a pneumatic diaphragm valve with 90° piping structure was designed independently,and the simulation model and experimental platform of the diaphragm valve were built to study its fluid characteristics.The main research works of the paper are as follows:(1)The processing and preparation technology of its PTFE plastic parts of the diaphragm valve was experimentally studied.In response to the problems of the diaphragm valve after the initial assembly,the spring with a different modulus of elasticity was replaced,the stem was structurally improved and reworked,and the realizability of the diaphragm valve working principle was verified by actual testing after reassembly.The diaphragm valve experimental platform was built,and the outlet volume flow magnitude of the diaphragm valve under different operating conditions were compared with the simulation results,and good agreement was found to verify the accuracy of the numerical model.(2)Based on the theory of computational fluid dynamics,a diaphragm valve steadystate flow field simulation model was established.The influence of inlet pressure on the outlet volume flow rate at different opening degrees was analyzed based on linear fitting,and it was found that the outlet volume flow rate of the diaphragm valve has a very high linear correlation with the inlet pressure.The relationship between the flow coefficient and the flow resistance coefficient of the diaphragm valve with the opening degree was analyzed,and it was found that the diaphragm valve is fast-opening flow characteristics,the increase of valve opening induces the logarithmic increase of the flow coefficient and the inverse-proportional decrease of the resistance coefficient,and there is an unobvious change after the valve opening of 1.8 mm.When the inlet pressure was certain,by analyzing the pressure cloud,velocity cloud,and flow trace cloud of the central section of the flow channel at different opening degrees,it was found that the severe change of flow velocity and pressure occurs at the gap between the valve core and valve seat,where the flow velocity surges and the pressure gradient is large.The spool was susceptible to a large fluid scour and a continuous backflow at the top of the spool.(3)The diaphragm valve cavitation model was established and the cavitation characteristics inside the diaphragm valve were qualitatively analyzed using a combination of theory and simulation.Analyzing the gas phase volume fraction clouds at different operating conditions showed that the diaphragm valve did not suffer from cavitation at 0.2MPa inlet pressure.At higher inlet pressures,the seat and spool bottoms were most susceptible to cavitation damage,a finding that echoes previous studies of flow field characteristics,and that cavitation rupture caused an increase in local turbulent kinetic energy intensity.By quantifying the effect of inlet pressure and opening on the maximum gas phase volume fraction and total product number of the gas phase in the diaphragm valve,it was found that the cavitation intensity in the diaphragm valve increases with increasing inlet pressure and decreases with increasing valve opening.(4)To address the problem of cavitation damage at the bottom of the spool,the shape of the bottom of the spool was optimized,a flat bottom spool structure and a curved spool structure were proposed,provided that the cut-off capacity remains unchanged.Based on the Realizable k-epsilon model and the cavitation model of Mixture multiphase flow,the flow and cavitation characteristics of the diaphragm valve with different spool configurations were investigated numerically in the full three-dimensional fluid domain,and it is found that the flat bottom spool has better cavitation resistance while maintaining the good flow characteristics of the initial trapezoidal spool.In particular,the maximum gas phase volume fraction was reduced by 30%. |
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