1The working principle of Turbine Flowmeter

Principle of the turbine flowmeter shown in Figure 3-1. Pipe in a turbine placed center, bearing support from both ends. When the fluid through the pipeline, the impact of turbine blades, the turbines have driven torque so that the vortex Round to overcome friction torque and fluid resistance moment and have a rotation. In a certain flow of the viscosity of a fluid medium, the turbine rotating angular velocity and fluid flow in direct proportion. Therefore, fluid flow through the turbine rotating angular velocity Have to be calculated by the fluid flow through the pipeline.

Speed through the turbines installed in the chassis, the sensor coils to detect. Turbine blade when cutting from within the shell of the permanent magnets have a magnetic line, sensing coil will result in changes in the magnetic flux. Sensing coil will be detected Periodic changes in the magnetic flux to the signal sent to pre-amplifier, the signal amplification, plastic, with a velocity proportional to the pulse signal, converted into units and Flow Totalizer circuit receive and display the accumulated value of traffic at the same time will also pulse Into the frequency current conversion circuit, pulse signals into analog amount of current, then instructed the instantaneous flow value.

Turbine Flowmeter box with the overall principle as shown in Figure 3-2.

2Construction of Turbine Flowmeter

Fluid from the chassis of the inflow of imports. Stent will be through a sleeve for the fixed in the central axis, the turbine installed in the bearings on. Turbine on the lower reaches of the stent is equipped with a radiation-shaped rectifier board to guide the fluid from the , To avoid the fluid spin and change the role of the turbine blade angle. Turbine at the top of the chassis equipped with external sensor coils, receiving signals changes in flux.

Here are the main components

(1)Turbine

Magnetic stainless steel turbine by the material, with spiral-shaped leaves. Leaf number of changes under different diameter, 2-24 range. In order to make the turbine velocity a very good response, the quality requirements as small as possible.

Structural parameters of the turbine blades to the general requirements: Leaves inclination 10 -15 (gas), 30 -45 (liquid); leaves overlap P for 1-1.2; leaves and the gap between the inner shell for the 0.5 - 1mm.

(2)Bearing

Turbine bearings sliding with the general use of carbide bearings for good wear resistance.

As fluid through the turbines at the turbine will generate a axial thrust so that the uranium for the torque increases the friction and speed up uranium for wear, in order to eliminate axial force, to be taken in the structure of water balance, the principle of this method As shown in Figure 3-3. Turbine because of the DH in diameter slightly smaller than the diameter before and after stent Ds, therefore, in the turbine section of the flow to expand, reduce the flow rate, fluid pressure to increase P, P this will be the pressure Offset by a part of the role of axial thrust.

Figure 3-3 Principle of hydraulic balance

(3)Preamplifier

Preamplifier by the magnetic induction converters and enlarge shaping circuit composed of two parts, the diagram shown in Figure 3-4.

Magnetic converters the general reluctance of domestic style, from its permanent magnet and the coil winding external components. When the fluid through the irony round of the rotation, the leaves are in the permanent magnet at the bottom of the smallest reluctance, the two leaves gaps in Magnets at the bottom of the greatest reluctance, the turbine trip to the constantly changing magnetic circuit of magnetic flux, so that the coil changes in the potential of sensors, zoom into the plastic circuit, a pulse.

Output pulse frequency and the flow through the flowmeter proportional to the ratio for the K factor

K 31

Type in the f - Turbine Flowmeter output pulse frequency;

qv - through the traffic flow meter.

The ratio is also known as the coefficient of turbine flowmeter instrument factor.

Figure 3-4 Turbine Flowmeter principle of pre-amplifier

(4)Signal reception and display

Signal reception and display within the correction factor, Adder and frequency converters and other electrical components, and its role will be pre-amplifier is sent to the pulse signal converted into cumulative flow and the instantaneous flow and display.