Double-throttling three-differential-pressure wet-gas two-phase flow measurement system

Abstract

The invention belongs to the technical field of two-phase flow measurement and relates to a double-throttling three-differential-pressure wet-gas two-phase flow measurement system, which comprises a first throttling device and a second throttling device which are mutually connected. The first throttling device comprises a cone which is fixedly arranged in a measuring pipe. The second throttling device is a Venturi throttling device. Pressure sampling positions are respectively arranged at the upstream and the throat of the first throttling device. Pressure sampling positions are respectively arranged at the upstream, the throat and the downstream of the second throttling device. The pressure sampling positions at the upstream and the throat of the first throttling device are connected to a first differential pressure transmitter through external pressure guide pipes. The pressure sampling positions at the upstream and the throat of the second throttling device are connected to a second differential pressure transmitter through external pressure guide pipes. The pressure sampling positions at the throat and the downstream of the second throttling device are connected to a third differential pressure transmitter through external pressure guide pipes. The double-throttling three-differential-pressure wet-gas two-phase flow measurement system has the characteristics of simple structure, no movable part, convenience in implementation, wide measurement range, high accuracy, high safety and reliability and the like.

Description

technical field [0001] The invention belongs to the technical field of two-phase flow measurement and relates to a moisture two-phase flow measurement device. Background technique [0002] As a special form of gas-liquid two-phase flow, moisture exists widely in industrial processes. Both gas and liquid are fluids. When they flow alone, their flow laws are basically the same, and they all obey the basic mass conservation and energy conservation equations. The mathematical models are also basically similar. However, when they coexist and flow at the same time, due to the There are large differences in the characteristics of the medium, such as fluid density, viscosity, friction coefficient and other physical parameters. The two-phase fluids interact and influence each other. Liquid two-phase flow shows more complex characteristics than single-phase flow, and many criterion relations and analysis methods in single-phase flow cannot be directly applied to the study of wet gas-...

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Problems solved by technology

Practice has proved that the invention patent has the following disadvantages: (1) The throttling ratio range of the conical throttling device of the patented device is between 0.6 and 0.85, and the throttling ratio of the Venturi throttling device is between 0.3 and 0.5. Industrial field performance verification, the design has the disadvantage of narrow cross-measurement range, the range ratio is less than one-third, and its use is limited in the case of a large range of flow changes in the working condition; (2) the patented device is only in the specified throttle Two differential pressure signals are taken within the specific range, that is, the cone differential pressure and the front differential pressure signal of the Venturi. Since the two throttling devices are of a common structure, they are not fully optimized, resulting in shortcomings such as low measurement accuracy and wide measurement range. ; At the same time, the system does not consider the redundant design. When the device takes pressure randomly, such as blockage, etc., the whole system will immediately be in a paralyzed state, which will affect the normal operation of the system.

(3) The length of the throat of the conical core in this patented device is small, less than 1 mm. In the high-speed flow area of ​​the gas phase, because there is not enough acceleration space, the gas-liquid two-phase mixing is not sufficient, so the gas phase liquid The acceleration of the phase is insufficient, and the measured differential pressure signal is not sensitive enough to the liquid phase, resulting in a narrow range; (4) The device uses the tail flow field area of ​​the conical core to obtain pressure, and the amplitude of the cone differential pressure signal is not high , and the flow field is easy to form a vortex, and the quality of the differential pressure signal is poor, resulting in an unsatisfactory overall signal-to-noise ratio; (5) The downstream of the cone in the patented device is the static pressure recirculation zone generated by the vortex, when there are fine particles in the pipeline When there are impurities, the pressure channel is easy to block (6) The Venturi throat of the patented device is designed according to the standard Venturi, and the length of the throat and the diameter of the throat are designed at 1:1. In-depth research shows that the device is used to measure gas-liquid two-phase When the flow path is too small, the liquid phase is not accelerated by the gas phase when it passes through the throat, so that the gas-liquid two-phase mixing is not sufficient, which affects the quality of the throat pressure signal, so the signal-to-noise ratio needs to be improved; ( 7) The expansion angle design of the Venturi expansion section of the patented device is not ideal, making it easy to form backflow in the downstream expansion section, resulting in fluid accumulation, which ultimately affects the system's ability to identify higher liquid phase holdups; (8) The patented device takes The pressure method is a single-point pressure acquisition, and an external independent small gas-liquid isolation tank is used to realize gas-liquid isolation and pressure acquisition, the signal-to-noise ratio of the measurement signal is low, and the efficiency of gas-liquid isolation is low; (9) All sewage valves in the patented device Located at the lower end of the gas-liquid isolation tank, its existing design cannot realize the overall synchronous sewage discharge of the isolation tank and the main measuring pipeline; (10) All the gas-liquid isolation tanks in this patented device are located on one side of the metering tube, which affects the weight balance of the overall device Due to the existence of rotating torque after installation, it will affect the safety and service life of the device

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