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Advantages of V-cone flowmeter
l Short straight tube needed by installation: only 0-3D of straight tube in the front and 0~1D straight tube in the rear.
V-cone flow sensor adopting the throttling pattern of “internal wall gradually shrinkage” can force the regions with high flow velocity to be shrinkage and close to the pipe wall when fluids flow through the spaces between V-cone and internal wall of the pipe, so that the flow velocity is homogenized smoothly. The process of “homogenization of flow velocity”can be seen from the following schematic diagram.
That why V-cone flow sensor has the function homogenizing the flow velocity is determined by the throttling pattern of “internal wall gradually shrinkage” adopted in it, and it is also determined by structure and shape of V-cone. Because V-cone has such a function of “self commutating function of homogenizing flow velocity”, it only needs very short straight tube in the front and rear when V-cone flowmeter is adopted to measure flow quantity. The experimental results showed that only maximum 3D (front) and 1D (rear) of straight tube in the front and rear of V-cone flowmeter are needed for V-cone flowmeter. This not only solves the defect of conventional differential pressure flowmeters such as orifice plate flowmeter such as very long straight tube in the front and rear of flowmeter, but also has shorter straight tube than non differential pressure flowmeters such as electromagnetic flowmeter and vortex flowmeter. Following table shows requirements of various kinds of flowmeters on straight tube in the front and rear in installation:
Straight tube in the front (D is the internal diameter of pipe) | Straight tube in the rear (D is the internal diameter of pipe) | |
Electromagnetic flowmeter | 5D | 3D |
Vortex flowmeter | 10D | 5D |
Ultrasonic vortex flowmeter | 10D | 5D |
Annubar / verabar flowmeter | 20D | 10D |
Orifice plate flowmeter | 10D | 5D |
Positive displacement (PD) flowmeter | none | none |
Mass flowmeter | none | none |
Ultrasonic flowmeter | none | none |
V-cone flowmeter | 3D | 1D |
High precision 0.5%, good repeatability 0.1% and wide ratio of range 10:1
As the throttling pattern of “internal wall gradually shrinkage” is adopted in V-cone flow sensor, the static pressure generated at the downstream is signal with high frequency and low amplitude (turbulence), but not signal with low frequency and high amplitude generated by conventional differential pressure flowmeters such as orifice plate. It is shown as the following diagram (schematic diagram for fluctuation of negative pressure):
V-cone flowmeter 10:1 |
Orifice plate 3:1 |
Time
This makes that differential pressure P measured by differential pressure transmitter is very stable signal with low noise. If it is under the background of large noise, differential pressure transmitter can not measure the pressure signal with low pressure and small flow quantity.
Experimental results showed that at the low pressure side, the differential pressure transmitter of V-cone flowmeter can measure pressure whose resolution is better than 2.5mm water column, so that very large ratio of range and repeatability can be obtained when only one differential pressure transmitter is used.
Large amounts of experimental data showed that shape of angle of V-cone which are designed and fabricated precisely (very critical) can make flow velocity to be “homogenized” possibly (it is the main reason for generation stable signal with low noise of high frequency and low amplitude), and it can make that the precise grade of V-cone flowmeter (a differential pressure transmitter whose precision grade is 0.2 is equipped) is better than 0.5%, repeatability is better than 0.1% and ratio of range reaches up to 15:1 (this can be realized only when different structures are adopted for V-cone flow sensor with different diameter). These advantages possessed by V-cone flowmeter overcome defects of conventional differential pressure flowmeter such as low precision grade, bad repeatability, narrow ratio of range and unstable signals.
V-cone flowmeter