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Axial-flow pump is a kind of high RPM (500 ~ 1200) vane pump, the large flow low head, flow around 0.1 ~ 50 m ³ / SEC range, is less than 25 meters; Most in 4 ~ 15 meters. Fluid flow in the form of rotor blade, produce along the axial movement of the wheelset. And beca use it leaves like propeller, so they are called propeller pump.deep grove ball bearing
In axial-flow pump, the flow of the water like in spiral movement on the surface, that is, on the one hand, along the axis, on the other hand also follow the impeller rotation.
From the impeller which with the rotation of the tangential velocity flow, if direct access to pipe, is this part of the rotational kinetic energy was completely lost. Therefore, needs to eliminate the rotary motion of the liquid, and the kinetic energy of it can transform for pressure, reach the purpose of improve the efficiency of the pump, so with guide vane.
The number of guide vane generally more than the number of the impeller blades a or less. Number and number of impeller blades and than turn, lower than RPM axial-flow pump (ns = 500 ~ 600), leaf number Z = 5 ~ 6; Than RPM axial-flow pump (ns = 800 ~ 900), leaf number Z = 4; H igh RPM axial-flow pump (ns > 1000), 3 or 2 pieces of Z. For the adjustable axial-flow pump impeller (namely blade can turn), Z > 4 will turn institutions difficulties. Guide vane import side and the distance between the impeller outlet side also to have certain requirements, general is 0.1 D, D for guide vane diameter; If the distance is too small, and reliable operation is not stable, if the distance is too big, and increases the hydraulic loss.
Axial-flow pump head of theory, the formula and the centrifugal pump is very similar, but considering the axial-flow pump outlet and inlet circumferential velocity is same, so there are:
H-infinity = u2 (v2u - v1u)/g
If there is no swirl impeller entrance, on the type for h-infinity = u2v2u/g
Theory of flow for: QT = vF
Type v - liquid in leaves of axial speed, m/s;
F - liquid at the exit of the cross-sectional area, m ².machine b earing
And reliable work, also can produce cavitation phenomenon. Work is in the back of the blade pressure is reduced to below the water, the saturated pressure, liquid starts to bubble evaporation; Bubbles along the flow into the high pressure area, pressure rapid contraction, hydraulic impact, and the blade surface cause serious erosion damage. When bubbles area further expand, blade back will be fully covered by bubbles, the bubbles of destroy not leaves, but behind the blade, so the blade is eroding effect, but as a result of the bubbles blocked the passage between the blade, so the pump flow rate, pressure, efficiency, etc, and generate noise and vibration, damage to the pump work properly.