The leaflet vibration phenomenon in bileaflet mechanical heart valves (BMHVs) can cause complications such as hemolysis, leaflet damage, and valve fracture. One of the main reasons for leaflet vibration is the unsteady blood flow pressure pulsation induced by turbulent flow instabilities. In this study, we performed numerical simulations of unsteady flow through a BMHV and observed pressure pulsation characteristics under different flow rates and leaflet fully opening angle conditions. The pressure pulsation coefficient and the low-Reynolds k-ω model in CFD (Computational Fluid Dynamics) software were employed to solve these problems. Results showed that the level of pressure pulsation was highly influenced by velocity distribution, and that the higher coefficient of pressure pulsation was associated with the lower flow velocity along the main flow direction. The influence of pressure pulsation near the trailing edges was much larger than the data obtained near the leading edges of the leaflets. In addition, considering the level of pressure pulsation and the flow uniformity, the recommended setting of leaflet fully opening angle was about 80°.
Aiming at the leakage problem on the top of gate valve, the finite element method is used to analyze the gate valves seal face and body, as well as the distributing laws of the stress, deformation and seal pressure are obtained. The shutter is simplified as the circular plate simply supported on the whole circle, and the gate valve is optimized according to the relevant formula to meet sealing requirement. The results show that: the combination of the numerical simulation and theoretical calculation, not only the more accurate theoretical basis for the optimization of the large diameter gate valve can be provided, but also the time of the development and design can be shorten greatly.
In order to promote the localization of critical valve in ultra-supercritical thermal power generating unit, a two-stage superheated electrical steam trap was designed and developed. Its structure and operation principle was introduced. Three-dimensional numerical simulation of the internal turbulent fluid field was performed by using Fluent of computational fluid dynamics software. The results show that the superposed design of associated reaction with multiaperture equalizer and guide sleeve was adopted in the two-stage superheated steam trap. The internal flow field become more uniform, local maximum velocity reached 37.2m/s. The brush erosion of valve seat is reduced and the service life is increased. Success rate of the first sample's trial-manufacture is greatly improved by using CFD simulation experiment in the process of design. Development cycle is shortened and the cost is reduced, which can provide a reference for two-stage superheated steam trap design.
In order to promote the technical progress of pressure reducing valve in nature gas transport system, a high pressure pilot operated axial-flow pressure reducing valve was designed and developed. The three-dimensional modeling of the natural gas pressure reducing valve internal flow passage was found by using Solidworks software. Import the flow channel model into meshing in CFD software based on the internal flow channel geometry and flow characteristics. The ideal gas compressible fluid model of natural gas and improved RNG k-Epsilon model were used to solve the pressure and velocity distribution as well as other flow related parameters of the natural gas pilot operated pressure reducing valve. The flow fields of the pressure reducing valve with different valve plug shape were analyzed. Changes of valve plug shape were made to improve the performance of the valve.
Aiming at the lack of research for key parameters of the cage-type trim of sleeve-type steam trap, the numerical simulation calculation was carried out for the cavitation flow in valve, the influences of orifice types, orifice diameter, guide sleeve types on cavitation were researched. The distribution of pressure, velocity and vapor volume fraction on flow field were got for different sleeve parameters. The results show that using multi-stage sleeve, and decreasing the orifice diameter properly can suppress the occurrence and development of cavitation, and the double orifices structure sleeve is more favorable to anti-cavitation, the gap sleeve is superior to the guide sleeve. It can provide certain references for the research of anti-cavitation and multi-stage depressurization valves.
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