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LS25-type 1 spin paddle type velocity apparatus is a kind of rivers hydrological instrument, mainly used for testing generally rivers, channels and reservoirs, lakes and section water in the average speed of flow measuring reservation, so as to determine the cross-section of the flow.
the key technical indexes
1. Speed range: V = 0.06 ~ 7.0 m/s
2. Work water depth: general is not more than 24 m;
3. Work water temperature: 0 ~ 40C;
4. Work water quality: fresh water (contain not excessive minerals) or contains the sediment muddy water
5. Continuous work of total time: 8 h;
6. Instrument up turn speed: V0 than 0.05 m/s
7. Check formula of the mean square error: 1.5% or m
8. Blades pitch: 250 mm;
Working principle and calculation method
LS25-type 1 spin paddle type velocity apparatus working principle is: when the role of inductive components into the instrument-blades, blades which produce the rotary motion, the water flow faster, the faster the blades, speed and flow velocity between exist certain function relation, namely V = f (n). Say so, sure water flow, in fact as long as accurate measure instrument blade rotation and corresponding time line. Assume that the critical speed for instrument Vk, experimental results show that the following to speed up Vk V0 between, function is curve form, Vk above is linear relation between them.
Each build instruments verification results, are provided the following graph and the verification of formula: V = bn + a
Type: V-flow (m/s);
N-blades turn rate (speed), equal to the total number of blades turn "n"
And the corresponding speed for the "T" than, namely n = n/T;
B-hydraulic pitch (corresponding to the original standard K), the unit is m;
A constant--instruments (corresponding to the original standard C), sheet is m/s;
B value and a value and blade pitch and supporting system of other factors, such as the friction resistance, so that part of the parts must be careful to use and careful maintenance, it will affect the accuracy of the test to flow velocity.
The determination of flow velocity, in fact, but in a due time velocity measurement instrument by the current impulse of the blades which RPM. Blade rotation of the instrument is converted to electrical impulses contact with institutions signal, via wire transfer to the surface of the part of the instruments to count the calculation. Blades turn every 20 turn, contact agency contact time, count instrument that is a plan to send the signal, the serial number of measurement statistics this letter, and took 20 times, that is the actual flow velocity blades turn number. The RPM record with stop watch the corresponding speed for the "T", and with the last "T" in addition to turn several "N", for a quick spin blades turn rate "N". Finally, the "n" turn rate multiplied by hydraulic pitch "b", and add instruments constant "a", that the measured velocity.
If less than the critical velocity of flow velocity Vk, can be magnified directly on the graph according to spin propeller speed "n" check velocity.
In order to avoid velocity pulse speed achievements influence, therefore, should not be less than 100 general speed lasted seconds, had better be the characteristics of according to each river, through the test, to carry on the analysis, to be sure.