是以一个同轴安装在测量管内的尖圆锥体为节流件的新型差压式流量测量装置。 The V-shaped cone flowmeter is a new type of differential pressure flow measurement device with a conical cone mounted in the measuring tube as a throttle. It is a new type of throttling device based on the measuring principle of venturi and combining the advantages of classic venturi, annular orifice plate and wear-resistant orifice plate.
First, the measurement principle
V-cone flowmeter is a differential pressure type flowmeter which is a combination of V-cone sensor and differential pressure transmitter. It can accurately measure various media in a wide Reynolds number (8 × 103≤Re≤5 × 107). flow. Its measurement theory is that because the actual fluid is viscous, it is not an ideal fluid. When it flows in the pipeline, it has two flow states, laminar and turbulent, on the premise of fully developing the flow in the pipe. According to the principle of conserving energy of continuous flowing fluid and the Bernhard's equation: For a fluid flowing in a laminar state, its velocity distribution is a parabola symmetrical about the centerline of the pipe. The flow velocity distribution of a fluid flowing in a flow state is an exponential surface with the pipe centerline as a symmetry. The pressure drop of a fluid through a certain pipe is proportional to the square of the flow rate.
The V-cone sensor is a V-cone that is coaxial with the centerline of the pipe in the measuring tube. The measuring tube and V-cone of the sensor are designed and precision machined. When the fluid flows through the V-cone in the measuring tube, the flow pattern locally re-forms before the V-cone, the flow velocity increases, the static pressure decreases, and a pressure difference ΔP occurs before and after the V-cone. The high pressure (static pressure) PH is measured at the upstream pipe wall (before the fluid shrinks), and the pressure opening is taken at the central axis of the V-face downstream end face to obtain the low pressure PL (static pressure), as shown in the figure below:
Among them: β-equivalent diameter ratio ρ-density under fluid conditions
D——Inner diameter of the pipe K——K factor (related to the form of the throttle (fluid beam shrinkage coefficient), diameter ratio, pressure taking method, Reynolds number, and pipe roughness, etc.) Cross-section diameter ε——gas expansion coefficient (for incompressible liquid, ε = 1) qv——volume flow
1. Accuracy level: ± 0.5% (differential pressure flow transmitter accuracy should be higher than 0.2 level, including 0.2 level), (β: 0.45 ～ 0.85, when β <0.55, range ratio 4: 1, accuracy level: ≤ 0.30)
2. Repeatability: 0.1%
3. Working pressure: 0 ～ 40MPa (There are multiple pressure levels to choose from)
4. Working temperature: -40-850 ° C
5. Ambient temperature: -40-65 ° C
6. Requirement for installing straight pipe section: front 0-3D straight pipe, rear 0-1D straight pipe section
7, wide range ratio: usually 10: 1, choose appropriate parameters can reach 50: 1
8, small pressure loss: the same β value, the pressure loss is the orifice plate 1/3-1/5
9. Caliber: 15mm ～ 2000mm
10. Applicable medium: V-cone flow sensor is widely used in the measurement of fluid flow in municipal, electric power, chemical, petrochemical, metallurgical, food processing and other industries. It is suitable for almost all gas and liquid media.
可以成功测量的流体 V cone flowmeter can measure fluids successfully
1. Gas gas: coke oven gas, blast furnace gas, city gas Natural gas: Including natural gas with a moisture content of more than 5% Various hydrocarbon gases: Alkanes, alkenes and other gases Corrosive gases such as nitrogen: Wet chloride gas and other air: Including water, dust-containing air, compressed air and other flue gases: Flue gases emitted from various boilers and heating furnaces
2. Steam saturated steam, superheated steam
3． Liquid oils: crude oil, fuel oil, aqueous emulsified oil, diesel and other water: raw water, drinking water, production water, sewage and other aqueous solutions: acids, alkalis, saline solutions and other organic chemicals: methanol, ethylene glycol, xylene Wait
4． Special fluid oil + HC gas + water filled with sand: H2O + N2 + air; H2O + CO2 etc. Performance characteristics
1. Installation of straight pipe requires low upstream straight pipe: 0-3D; downstream straight pipe: 0-1D.
In actual installation, the flow state of the fluid in the pipeline is rarely ideal. If the flow meter is installed on a pipeline where the fluid flow cannot be fully developed, such as elbows, valves, shrink tubes or expanded tubes, tee joints, etc., it will interfere with the development of the flow. If there are not enough upstream and downstream straight pipe sections to flow in the pipe, When shaping, the velocity distribution in the pipeline will be distorted or vortices will be generated. The velocity distribution will deviate from the typical parabolic surface and exponential surface. Measurement with other flowmeter technologies may produce substantial errors.
Due to the characteristics of the shape and central installation position of the V-cone flow sensor, it directly interacts with the high-velocity region of the flow. The V-cone forces the high-velocity region to mix with the low velocity near the wall of the tube. It must be "flat" toward a fully developed flow shape, which can be re-formed upstream of the cone, so that using a V-cone sensor requires a shorter straight pipe section than other flow measuring instruments to form a fully developed flow in the tube . When the fluid flows near the V-cone, it can produce a flat flow distribution, so compared to other differential pressure instruments, it can play a more shaping role on the upstream interference factors. V cone upstream straight tube: 0-3D; downstream straight tube: 0-1D. This is beneficial to users of large diameter, expensive pipelines, or users of shorter running pipelines. Some special conditions, such as single or double elbows are not on the same plane or close to the upstream of the instrument, in this case the V-cone can still produce a flat flow regime. This means that when different flow patterns approach the cone, a predictable flow pattern will always be produced, ensuring that the meter accurately measures.
2.Wide range ratio
Flow (small flow) can be measured in the lower Reynolds number range (Re≥8000). The typical range ratio is 10: 1. Selecting appropriate parameters can achieve 50: 1. Because the V-cone is suspended in the center of the pipe, it directly interacts with the high-velocity area, forcing the high-velocity area to mix with the low-velocity near the pipe wall; when the flow decreases, the V-cone continues to interact with the maximum flow velocity in the pipe. Function, when other differential pressure instruments may not detect the differential pressure signal, the V cone sensor can still generate a differential pressure signal (when the Reynolds number is as low as 8000, the sensor can also generate a differential pressure signal). This is the biggest advantage of the V-cone flowmeter when detecting small flow.
The accuracy of the primary element of the V-cone sensor is ± 0.5%. The accuracy of the flow measurement system depends on the accuracy level of the V-cone sensor, the accuracy level of the differential pressure transmitter, and the secondary instrument.
4, good repeatability
V cone sensor repeatability is better than 0.1%
5. The V-cone sensor is resistant to wear and tear, and the long-term stability of the sensor is good. As the shape of the V-cone is a shrinking fluid, a vacuum effect is generated on the surface of the cone, which will not impact the abrupt surface. Leave the beta side. This means that the β side will not be worn by the dirty fluid, so the β coefficient remains unchanged, and the V-cone sensor has the characteristics of good long-term stability. However, the sharp edges of throttling components such as orifice plates are often subject to wear, and the β coefficient changes to affect the stability of the detection.
6. Good signal stability Differential pressure detection generally has "signal fluctuations". Even when the flow is stable, the signal generated by the primary component will fluctuate due to interference. For example, the orifice plate flowmeter will form a long eddy current behind the orifice plate. This long eddy current will produce high amplitude, low frequency orifice signals and interfere with the flowmeter reading. For the V-cone sensor, the fluid passes through the V-cone and forms a short eddy current behind the V-cone, which generates a low-amplitude, high-frequency signal and converts it into a stable V-cone signal. Its signal fluctuation is 1/10 of that of the orifice plate. See the figure below: V-cone and orifice signals.
7. Small permanent pressure loss Because the fluid has no impact on the smooth surface of the abrupt V cone, the permanent pressure loss of the V cone sensor is lower than that of the orifice plate. Similarly, due to the stability of the V-cone signal, the full-scale V-cone differential pressure signal at the same flow rate is lower than other differential pressure instruments. This reduces permanent fluid pressure loss. The same β value, the pressure loss is 1/3 to 1/5 of the orifice plate.
8, V cone β coefficient calculation range is wide: Because of the unique geometry of the V cone of the V cone sensor, its β coefficient range is wide. The standard β coefficient range is 0.45, 0.55, 0.65, 0.75, 0.85.
V锥体的传感器不堵塞，不粘附，无任何滞留死区，特别适用于脏污介质的流量测量：由于V锥传感器是基于流体流过V锥"一扫而过"的设计理念，不可能在管内有流体中的颗粒、残渣、凝结物沉积的滞留区域。 9. V-cone flowmeter The V-cone sensor is non-blocking, non-adherent, and has no dead zone. It is especially suitable for the measurement of the flow of dirty media. "Design philosophy, it is impossible to have a retention area where particles, residues, and condensates in the fluid are deposited in the tube. It has a self-cleaning function and is suitable for the flow measurement of dirty fluids, such as: coke oven medium gas, blast furnace medium gas, raw oil, residue oil, etc.
10. Can measure high temperature and high pressure medium: the working temperature is up to 850 ℃, the maximum pressure is 40MPa.
11, complete specifications, flexible installation methods: flange type, wafer type, direct welding type can be selected. The pipe diameter is from 15mm to 2000mm.