초록 ▼

A capacitive sensor for measuring flow parameters of a two-phase flow, a device for measuring phase concentration of a two-phase flow, and a system and method for measuring flow parameters of a two-phase flow is disclosed. In the capacitive sensor, at least one pair of electrodes is twisted by 180°

A capacitive sensor for measuring flow parameters of a two-phase flow, a device for measuring phase concentration of a two-phase flow, and a system and method for measuring flow parameters of a two-phase flow is disclosed. In the capacitive sensor, at least one pair of electrodes is twisted by 180° in a common direction into a spiral shape. Edge guard electrodes are twisted in the common direction and are formed between adjacent electrode edges. Problems of non-homogeneous sensitivity distribution of a measuring field and soft field effect can be effectively addressed, thereby allowing reliable and accurate measurement of phase concentration of a two-phase flow. The system for measuring flow parameters of the two-phase flow can output signals with a current of 4˜20 mA to a PLC system or communicate with an industrial process control computer or with a remote control computer system in a operating room.

대표청구항 ▼

1. A capacitive sensor comprising: a dielectric material pipe; andat least one pair of electrodes wrapped outside an external surface of the dielectric material pipe and twisted into a spiral shape in a common direction along a longitudinal direction of the dielectric material pipe,wherein the at le

1. A capacitive sensor comprising: a dielectric material pipe; andat least one pair of electrodes wrapped outside an external surface of the dielectric material pipe and twisted into a spiral shape in a common direction along a longitudinal direction of the dielectric material pipe,wherein the at least one pair of electrodes are twisted by 180°. 2. A capacitive sensor according to claim 1, wherein the capacitive sensor is used in a pipeline structure section of a phase concentration measuring device. 3. A capacitive sensor according to claim 2, wherein a connecting structure provided on at least one end of the pipeline structure section hermetically connects the phase concentration measuring device with the capacitive sensor to a pipeline for the two-phase flow to be detected. 4. A capacitive sensor according to claim 3, further comprising: at least one edge guard electrode having a strip shape and located between adjacent electrode edges of the at least one pair of electrodes, wherein the edge guard electrode is wrapped outside the external surface of the dielectric material pipe and twisted into a spiral shape in a common direction of the at least one pair of electrodes. 5. A capacitive sensor according to claim 2, wherein the pipeline structure section comprises a screen shield to enclose the dielectric material pipe and the capacitive sensor, wherein the screen shield is made of a material capable of resisting electromagnetic interference, a filler located between the screen shield and the dielectric material pipe, and a protecting tube to surround the screen shield. 6. A system for measuring flow parameters of a two-phase flow, comprising: a phase concentration sensor, comprising: a dielectric material pipe comprising a dielectric material through which a two-phase flow passes; andat least one pair of electrodes wrapped outside an external surface of the dielectric material pipe and twisted into a spiral shape in a common direction by 180° along a longitudinal direction of the dielectric material pipe; anda velocity sensor, comprising: an upstream capacitive sensor; anda downstream capacitive sensor,wherein the upstream capacitive sensor and the downstream capacitive sensor are identical and the velocity sensor is provided along the longitudinal direction of the pipe for the two-phase flow either upstream or downstream with respect to the phase concentration sensor. 7. A system according to claim 6, wherein the phase concentration sensor further comprises: at least one edge guard electrode comprising a strip shape and located between adjacent electrode edges of the at least one pair of electrodes, wherein the edge guard electrode is wrapped outside the external surface of the dielectric material pipe and twisted into a spiral shape in the common direction of the at least one pair of electrodes. 8. A system according to claim 6, wherein the upstream capacitive sensor and the downstream capacitive sensor of the velocity sensor are an array of capacitive sensors aligned in a same manner. 9. A system according to claim 8, further comprising: a data acquisition and processing unit configured to receive signals from the phase concentration sensor and the velocity sensor, to calculate concentration of a working medium phase in the two-phase flow, velocity of the two-phase flow, and a mass flow rate of the two-phase flow, and to output signals; andan auto-calibration unit configured to receive the output signals from the data acquisition and processing unit and to calibrate the mass flow rate of the working medium phase. 10. A system according to claim 9, wherein the output signals comprise a current between 4-20 mA. 11. A system according to claim 9, wherein the output signals are transmitted via at least one of a CAN bus or a 485 bus. 12. A system according to claim 9, further comprising: a programmable logic controller (“PLC”) to receive signals from the data acquisition and processing unit, wherein the PLC is located in an electrical room. 13. A method for measuring flow parameters of a two-phase flow, comprising: measuring volume concentration of a working medium phase in a two-phase flow through a pipeline comprising: measuring a capacitance induced on at least one pair of electrodes twisted and located on an external surface of a dielectric material pipe that is connected to the pipeline when the two-phase flow flows through the dielectric material pipe; andcalculating the volume concentration of the working medium phase according to an expression C=K·[∈g+(∈s−∈g)·β], wherein C is the capacitance value measured by the at least one pair of electrodes, K is a characteristic parameter determined by a structure dimension, ∈s and ∈g are dielectric permittivities of the working medium phase and a carrier phase in the two-phase flow respectively, and β is the volume concentration of the working medium phase; andmeasuring a velocity of the two-phase flow comprising: providing identical upstream and downstream capacitive sensors in a common direction at either upstream or downstream sides of the at least one pair of electrodes;measuring random time sequence signals induced at the upstream capacitive sensor and the downstream capacitive sensor respectively when the two-phase flow flows through the dielectric material pipe;correlating the random time sequence signals and calculating a transition time for the two-phase flow to pass through the upstream and downstream sensors; andcalculating the velocity of the two-phase flow according to an expression ν=L/τ, wherein ν is the velocity of the two-phase flow, L is a distance between the upstream and downstream sensors, and τ is the transition time. 14. A method according to claim 13, further comprising: after obtaining the random time sequence signals at the upstream and downstream sensors, converting the random time sequence signals into pulse sequence signals with randomly varied widths by passing the random time sequence signals through a zero crossing detecting circuit and calculating the transition time in accordance with the expression: τ=(τ1+τ2)/2, wherein τ1=tm−ti, τ2=tn−tj, tj, ti are two adjacent timings of low-to-high jumping in an upstream zero crossing pulse sequence respectively; tn, tm are two adjacent timings of low-to-high jumping in a downstream zero crossing pulse sequence respectively; and (tj−ti)−(tn−τm)<±Δ, ±ΔI is two times the maximum absolute error of the system measurement. 15. A method according to claim 14, further comprising: calculating the mass flow rate of the two-phase flow according to an expression Q=A·ρ·ν˜β, wherein Q is the mass flow rate of the two-phase flow, A is a cross-sectional area of the pipeline for the two-phase flow, and ρ is a real density of the working medium phase. 16. A method according to claim 13, further comprising: calculating the mass flow rate of the two-phase flow according to an expression Q=A·ρ·ν·β, wherein Q is the mass flow rate of the two-phase flow, A is a cross-sectional area of the pipeline for the two-phase flow, and ρ is a real density of the working medium phase. 17. A method according to claim 13, wherein the at least one pair of electrodes is twisted into a spiral shape in a common direction along a longitudinal direction of the dielectric material pipe. 18. A method according to claim 13, wherein the dielectric material pipe and the pipeline have a same inner diameter.