Study On Flow Flied Of Two Local Resistance In Pipe Based On PIV

Particle image velocimetry PIV is a mature and new method of velocity measurement, with no interference to record the whole instantaneous flow field.It not only can provide the whole instantaneous information of flow field, but also the its fluid velocity and direction;and its measuring range is very wide (PIV with TR-PIV system model suitable for measuring the velocity of the flow field within2m/s).Sudden-expansion pipe has important significance in engineering practice and theoretical research,due to sudden expansion of geometric cross section caused vortex flow.Sudden expansion pipe has been widely used in the energy, power, chemical industry, environmental protection department;the phenomenon can be happened in the chemical, pharmaceutical and pipe flow system in the oil industry;it also can be applied to the air circulation tube, dump combustor and liquid jet device,so the flow field measurement for sudden-expansion pipe has great practical value. Gate valve is a very common valve in the oil field, it has a lot of advantages,just like flow resistance is small, the fluid media flow in a straight line when it flow through internal channel.Compared with the globe valve,gate valve spend litter effort than it when opening or closing. Water hammer is not easy to be produced, because of the long closed time;fluid flows on both sides to any direction, and gate valve is easy to be installed, gate on both sides of channel is symmetrical.Gate valve has a short form,its structure is simple,and has been a good manufacturing technology, so its scope of application is wide.But when the gate valve is open partially, the gate is perpendicular to the flow direction of fluid,so it is easy to produce vortex flow on the back of the gate, and this vortex flow will cause erosion and vibration to the gate. If we can show this phenomenon intuitively by some equipments, it will help people have a better understanding of gate valves.In this paper,the flow field which fluid flow through Sudden-expansion pipe and gate valve were given by PIV.Through Tecplot, relevant velocity cloud picture, streamline picture and vortical contour were given,and axial velocity and tangential velocity also were shown by Excel.In the vortical contour we can find, when the mainstream velocity is small, the first formed position of vortex the mainstream velocity is small when the position of the vortex formed first;vortex value is increasing with mainstream velocity;if mainstream velocity is larger a certain value,the vortex will appear in the whole tube, not limited to one position.