A Numerical and Experimental Study of the Time Averaged and Transient Flow Downstream of a Butterfly Valve

This research took the DN50 butterfly valve as the research object and studied the flow situation of butterfly valves with different shafts. The resistance characteristics, flow state, characteristics, and flow instability of butterfly valves with different structures were studied by experiments and numerical simulations. Research shows that the edge of the valve disc occurs flow separation, and the drag of the valve disc fluctuates non-periodically with time. Under different opening degrees, the velocity distribution downstream of the valve varies, and the effect of the shaft on the velocity fluctuation is different. Finally, the unstable region of flow downstream of the valve is determined. This study provides a reference for the use and optimization of butterfly valves.

Effects of Valve Disc on Flow Characteristics Inside a Swing Check Valve During Opening and Closing Processes

The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.

Study of Hydrodynamic Torque of Double Offset Butterfly Valve Disc through Experiment and CFD Analysis

A butterfly valve is commonly used as control device in applications where the inlet velocity is high and the pressure drop required is relatively low. Hydrodynamic torque is a significant design parameter for engineers dealing with control valve design. Predicting the hydrodynamic torque for all opening and closing conditions in rotary valves is of utmost importance. This study sought to compare experimental and simulated computational fluid dynamics (CFD) performance factor and hydrodynamic torque of 150mm double offset butterfly disc for various opening and closing angles in the increments of 100. In general, as the flow rate increases through the valve, greater force is exerted upon the disc by the fluid. These increased dynamic forces require more torque to rotate the disc. The amount of torque required to rotate the disc during operation varies depending on type of fluid flowing through the valve, velocity, shape and position of the disc. Finally a correlation has been established between the experiment and CFD values and valve industry can make use of this data for optimum selection of gear box and actuator.

Preparation of WC/Ni Flexible Cloth Coating by Vacuum Brazing

In this study, one novel WC/Ni flexible cloth coatings were prepared to enhance the abrasion and erosion resistances and meanwhile to accommodate the complicated component surfaces. Neither precipitation of WC particle nor pores or cracks were detected in the coating. The scarification extent of WC particle decreased with the increase in the WC content. With the abrasion mechanism of three body abrasive wear, the WC/Ni coating with 59.8 wt.% WC (WC/Ni-59.8 wt.%) showed the best abrasion resistance with the wear rate of 0.3% of 304 stainless steel. At 30° of impact angle, the WC/Ni-59.8 wt. % exhibited a superior erosion resistance to that of WC coating developed by high velocity oxygen fuel (HVOF). The application potential of WC/Ni flexible cloth coating for the commercial components was testified by developing the coating on a ball valve disc.

Improving of operating properties of the gas distributing mechanism of internal combustion engine

Reducing the heat load of the valve mechanism of the gas distribution system is an urgent task. This is due to the need to reduce the risks of deformation of the working surface of the valve disc and, as a consequence, to increase the resource of the gas distribution mechanism. The paper proposes a valve mechanism design with the possibility of supplying the coolant to the combustion chamber through the valve cavity. The data from the preliminary study showed the effectiveness of the coolant supply. When comparing the temperature indicators in the test points under study, a decrease in the valve temperature by 0,72–25 % was revealed.

Structural design and parameter optimization on a waste valve for hydraulic ram pumps

Hydraulic ram pump is an automatic water-lifting machinery, which converts the low-head potential energy of a large volume of water into a small high-head potential energy through the periodic open and close of waste valve and delivery valve. The pump would run inefficiently or even fail if the valves are poorly designed. In this paper, a novel and reliable waste valve of lift-check-valve structure has been developed. The sealing mode integrating soft and rigid sealing rings, the equation for the valve disc thickness and the equation for the flow passage in terms of the diffuser length, the larger radius and the smaller radius, are presented to guide future design. Major factors influencing the hydraulic performance, including the flow passage, valve opening and valve clack mass, are discussed with model experiments and numerical simulations. The optimized configuration for a 100-mm hydraulic ram pump includes a curved diffuser, 25–30-mm valve opening and 1.2-kg valve clack mass. The proposed waste valve can decrease the head loss coefficient of the system by 45%, achieve relatively higher working efficiency, and lift the largest water when the delivery head is lower than 30 m.

Comparison of Swing and Tilting Check Valves Flowing Compressible Fluids

Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum Mach number under small valve openings, the dynamic opening time, and the hydrodynamic moment acting on the valve disc are chosen to evaluate the difference between the two types of check valves. Results show that the maximum Mach number increases with the decrease in the valve opening and the increase in the mass flow rate, and the Mach number and the pressure difference in the tilting check valve are higher. In the swing check valve, the hydrodynamic moment is higher and the valve opening time is shorter. Furthermore, the valve disc is more stable for the swing check valve, and there is a periodical oscillation of the valve disc in the tilting check valve under a small mass flow rate.