Instruments for measuring the water velocity of bodies of water such as rivers, lakes, and channels. There are three types of mechanical, electrical and ultrasonic testing. The mechanical type is mainly based on a rotor type, and has a propeller type and a rotary cup type flow meter. Electrometric type electromagnetic flow meter. Ultrasonic time difference method and Doppler flow meter.
The flow meter is generally suitable for measuring the average flow rate during a fixed period of time. The current flow rate can be measured by a magnetic current meter or a multi-turn rotor-type flow meter. It can also be used as a speed measurement by the ship method. The speed range of the instrument is generally 0.03 to 5.00 m/s, and the applicable water depth is generally 0.2 to 20 meters. In 1790, R. Waltmann made a rotor-type flow meter for flow rate measurement. The rotary cup type and propeller type flow meter manufactured and manufactured in China from the 1950s to the 1960s have the characteristics of good waterproof and sand-proof performance. The development direction of the flow meter is non-rotor electrical measurement technology, optical technology, ultrasonic technology and telemetry technology. Propeller-type flow meter consists of three parts: propeller, frame, and tail. Rotating propellers are equipped with signal contacts, bearing shafts, etc. China's "25-1 type" propeller flow meter shaft system has a winding labyrinth structure, the interior is filled with light oil, has good water and sand performance, can be high Flow rate and use in sandy rivers. Propeller-type flowmeters, rotary cup-type flowmeters and rotary-blade-type flowmeters are all rotor-type flowmeters. The principle of operation is basically the same. They use water flow to force the rotor to rotate, and the flow velocity is derived based on the rotation speed. The formula is:
Flow meter
In the formula, υ is the flow velocity; N is the total number of revolutions in the time period; t is the time period duration; c is a constant, which reflects the friction resistance when the rotor rotates; K value depends on the pitch of the blade or the cup type. The K and c values ​​are verified in a special tank. At low speeds, due to the large influence of c-values, the velocity formula is a function of a curve, and the above formula is no longer used.
The number of revolutions is shown by a counter. The simplest counters are small lights, bells, and transistor sounders. For every 20 rotations of the propeller, the switch is turned on once, the light flashes or sounds, manual counting, stopwatch timing, and more complete electric counter, electronic counter, timing counter, and direct reading flow rate monitor, these counters can be used There are many signal flowmeters for every rotation of the propeller, which can improve the accuracy of speed measurement.
The principle of the electromagnetic flow meter is to use the water flow as a conductor to cut magnetic lines in a certain magnetic field, ie, to generate an electromotive force whose voltage is proportional to the flow velocity. The instrument has no rotor, has a smooth appearance, a small volume, and low power consumption. There are excitation coils in the body cavity, and a pair of electrodes are connected to the water body in a direction perpendicular to the magnetic force lines. When the water flows on the surface, a slight voltage signal is generated on the electrode, which is transmitted to the counter by the wire, and the flow rate can be directly displayed through circuit processing such as amplification and analog-to-digital conversion.
The principle of ultrasonic speedometer is shown in the figure. The transducer is placed on a certain depth of water on both sides of the river bank, in a diagonal direction. The period of time that A point sends a sound pulse to point B is t 1 , whereas the time period that point A sends from point B is t 2 because of the flow velocity. In the presence of water, the speed of sound is reduced in the direction of the water, and the water is increased. The time difference is Δt = t 1 -t 2 , and the flow rate υ has a linear function with Δt. With the microsecond timing circuit, the average flow velocity on the AB line segment can be directly displayed after processing and calculation.
Aluminum brazing sheet is one of Trumony strong product.Brazing sheet is a special technology which we use hot rolling technology to roll different layer of aluminum together.Such as 4343/3003/4343 or 4045/3003/4045 or 4343/3003/7072.Outside layer 4343 will be melt under lower degree than 3003.So through brazing furnace,outside layer of 4343 will melt and 3003 can be welded together with attached material.
While 7072 is corrosion resistant purpose for longer shelf life of the Aluminum Sheet.
Using of the aluminum brazing sheet is saving the adhesive reagent which is now using more and more in different industry.Trumony Aluminum Limited,your best choice of aluminum brazing sheet
Brazing Sheet,3003 Aluminum Sheet,Clad Aluminum Sheet,Aluminium Brazing Sheet
Trumony Aluminum Limited , https://www.szaluminumcoil.com