Ultrasonic flow measurement technology because of its unique advantages, namely without direct contact measurement medium, no broken tube;
Measurement process has nothing to do with the fluid pressure, temperature, velocity, no mechanical damage, no pressure loss, in the industrial production flow measurement firmly occupy one seat, and with the constant improvement of the research and development technology, the measurement of adaptability and accuracy are increased year by year, has now become one of the hot flow meter
on the market selection.
In this paper to remove water supply system in generating set cold flow monitoring for the use of ultrasonic flowmeter
Generator can produce a lot of heat in the process of work, at present are generally USES the built-in circulating water cooling system for cooling, because the heat generated by the generator set to work is very big, so the generator stator winding of power generation equipment damage caused by blocked waterborne major accidents happen frequently, huge economic loss.
In order to ensure the safe, economic and stable operation of power generation equipment, issued by the state grid company (
No. 589, 'to prevent power production major accident of 25 key requirements in stressed the generator maintenance, the stator line bar water flow test must be conducted.
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Before, in order to determine whether the amount of water in the cooling system to keep the system Settings of the scope of the right, need to pass in the overhaul of the unit, the artificial tear open the insulation of the generator water diversion pipe and sink pipe to take over the head, using the measuring cup, measure water flow per unit time.
But this method of measurement of disadvantage is obvious, because we need to open the generator end dozens of root water diversion pipe insulation, time-consuming, will seriously affect the repair time limit for a project.
And because the handbag to the original good insulation to open the parcel again, and again, damage to the sealing and insulation of things also happen from time to tome, cause new accidents.
After using ultrasonic flowmeter, all the problems solved, this is thanks to the ultrasonic flow measurement with unique advantages, because do not need to open the insulation of the water diversion pipe to be tested, no mechanical damage, no pressure loss, outside the tube is out of touch with current body measurement;
During generator overhaul measuring the same conditions and the normal operation of various insulation of chilled water diversion pipe, malathion reflect actual flow pipe.
A, 1 ultrasonic flowmeter measurement principle.
1 time difference method principle of time difference method the principle of measuring fluid flow is shown in figure 1.
It USES sound waves in the fluid with the fluid flow in a different direction and different velocity of propagation, the characteristics of measuring its page flow propagation time t1 and countercurrent propagation time difference of t2, so as to calculate the speed of the fluid flow and flow rate.
A static fluid velocity for c, and fluid flow velocity for & nu;
A1, A2, a group of transducer is installed on both sides of the pipe, two transducer for axial distance d, its connection with the pipe canal axis installation Angle, the distance of the transducer for L.
Fired from A1 to A2 downstream, acoustic travel time t1 as follows: 1.
2 resolution and detection principle of ultrasonic ultrasonic propagation in the liquid, the pipe material, wall thickness, diameter and the influence of the fluid, when transmitted from one side of pipe to the other side, signal attenuation, inevitably occur deformation.
At the same time, the scene of the electrical noise, electromagnetic interference and interference signals, such as ultrasonic signal received by the transducer ultrasonic flowmeter, together in this way, accurately distinguish and detect ultrasonic signal becomes the key technology of ultrasonic flowmeter.
General ultrasonic flowmeter using sound waves to detect large peak sound wave signals and to track the flow measurement.
Upon initial ultrasonic flowmeter, ultrasonic flowmeter based on fluid velocity of sound in the received signal is given from the transducer of reference, if the reference with the sound waves in the fluid velocity is close to the current temperatures (
Such as sound velocity in 20 ℃ under the pure water is about 1480 m/s, and 50 ℃ under water in the sound velocity of about 1530 m/s)
Transducer to accept, said this is correct, the ultrasonic signal;
If a far cry from a reference value and the actual sound velocity, the transducer receives signals may be interference requires manual input the actual sound velocity, the re-initialization, near the transducer in a 2 l/c time interval search ultrasonic signal.
Actually proved that when the ultrasonic wave is given reference sound velocity in close proximity to the actual sound velocity, can achieve stable point measured data quickly, high precision.
Second, the technical features of generator stator and cold water flow measurement QFSS - to Shanghai steam turbine factory production
Type 2 pairs in the cold water unit as an example, the stator coil end water diversion pipe insulation structure as shown in figure 2.
This generator can be seen from the figure 2, a total of 48 root stator coil insulation water diversion pipe and 12 generator stator insulation lead water diversion pipe.
That each of the 48 stator coil insulation water diversion pipe and the corresponding upper wire rod and the lower bar connection, its serial number to join the upper bar slot Numbers are consistent;
12 generator stator insulation lead water diversion tube number to join the stator lead don't agree.
Can be seen from the figure 2, in the space of a week about 2 m diameter distribution of the water diversion pipe insulation to 60, smaller interval between tube and tube, pipe straight part mostly short, the 12 elements of the stator wire insulation water diversion pipe, in particular, is almost entirely bending state, which bring some difficulties to the ultrasonic flow measurement.
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