Cavitation evolution and damage by liquid nitrogen in a globe valve

Valves are key components of the safety of fluid transportation systems because of induced disturbance and cavitation damage in them.In this study,a 2D model of a cryogenic globe valve with liquid nitrogen(LN_(2))as working fluid was established by Fluent,and thermal effects were specially considered in the simulation.The validity of the LN_(2) cavitation model was verified by the experimental data of hydrofoil LN_(2) cavitation from earlier studies by NASA.Cavitation characteristics of LN2 in the cryogenic globe valve under three typical working conditions were investigated.The average pressure and pressure pulse at different positions of the wall were further studied to reveal cavitation risks from fatigue and vibration.Results show that with similar valve structure and openings,the pressure pulsation frequencies of LN_(2) are lower than those of water,and the shape and location of the cavitation clouds also show significant differences.For LN_(2) cavitation,an extended period of valve opening at 66% should be avoided since its pressure pulse peak is the largest compared to openings of 33% and 100%,and reaches 5×10^(7) Pa.The opening of 33% should also be monitored because of the large torque caused by the pressure difference between the two sides of the valve baffles.To prevent resonance,a critical state for the valve opening and the connecting pipe length is proposed.These predictions of cryogenic cavitation in the globe valve are helpful for the safe and reliable operation of cryogenic fluid transport systems.

Effect of Cone Angle on the Hydraulic Characteristics of Globe Control Valve

Globe control valve is widely used in chemical, petroleum and hydraulic industries, and its throttling feature is achieved by the adopting of valve plug. However, very limited information is available in literature regarding the influence of valve plug on the internal and external features in globe control valves. Thus the effect of valve plug is studied by CFD and experiment in this paper. It is obtained from external features that the pressure drop between upstream and downstream pressure-sampling position increases exponentially with flow rate. And for small valve opening, the increment of pressure drop decreases with the increase of cone angle（β）. However, with the increase of valve opening, the effect of cone angle diminishes significantly. It is also found that the cone angle has little effect on flow coefficient（Cv） when the valve opening is larger than 70%. But for the cases less than 70%, Cv curve varies from an arc to a straight line. The variation of valve performance is caused by the change of internal flow. The results of internal flow show that cone angle has negligible effect on flow properties for the cases of valve opening larger than 70%. However, when valve opening is smaller than 70%, the pressure drop of orifice decreases with the increase of β, making the reduction in value and scope of the high speed zone around the conical surface of valve plug, and then results in a decreasing intensity of adjacent downstream vortex. Meanwhile, it is concluded from the results that the increase of cone angle will be beneficial for the anti-cavitation and anti-erosion of globe control valve. This paper focuses on the internal and external features of globe control valve that caused by the variation of cone angle, arriving at some results beneficial for the design and usage of globe control valve.