JP4480905B2 - Steam dryness or wetness measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring so-called dryness: X, which indicates the moisture content in steam, that is, the ratio of the mass of dry saturated steam to the total mass per unit volume of steam. When the dryness is X, the wetness is represented by (1-X). In various boilers, equipment using steam power, drying equipment, etc., it is necessary to measure the dryness of steam for heat management. This is because, for example, the dry state changes depending on the moisture content in the steam.
[0002]
[Prior art]
As a conventional steam dryness measuring device, there is a squeeze dryness meter that measures dryness by utilizing the isoenthalpy change of steam. This is done by injecting wet steam through the nozzle into the measuring vessel and adiabatic expansion (change in enthalpy) to form superheated steam. The dryness is measured using a figure, a saturated steam table or a superheated steam table.
[0003]
[Problems to be solved by the invention]
The above-mentioned conventional dryness meter has a problem that only a part of wet steam can be measured because the range of measurable vapor pressure and dryness is limited. That is, when the pressure or the dryness of the wet steam to be measured is low, the superheated steam state is not obtained after the adiabatic expansion, and therefore it cannot be measured.
[0004]
Moreover, in the above conventional dryness meter, the steam to be measured must be taken out from the steam pipe and supplied to the measuring container through the nozzle, and the measuring apparatus is enlarged and supplied to the measuring container outside the steam pipe. Since the steam was discharged out of the system, there was a problem that the steam loss increased.
[0005]
Accordingly, an object of the present invention is to provide an apparatus for measuring the dryness or wetness of steam, which has a wide range of dryness that can be measured, is simple, does not require supply for sampling outside the steam pipe, and has low steam loss. Is to provide.
[0006]
[Means for Solving the Problems]
The means of the present invention taken in order to solve the above problems is to measure the dryness or wetness of the flowing steam, and the dynamic pressure detecting means using a Pitot tube for detecting the dynamic pressure of the steam, and the dynamic pressure value detected by the dynamic pressure detection means, the flow rate of steam detected by the flow rate detecting means, the dynamic pressure value = pV 2/2 equation, however, V: flow velocity of the vapor, [rho: the specific weight, the ratio of steam Relational expression between specific weight or specific volume calculating means for calculating weight or specific volume, specific weight or specific volume of the steam and dryness or wetness, that is, ρ = X / v〃 + (1−X) / V ′ formula, where X is the degree of dryness of steam, v 〃 is the specific volume of saturated steam, and v ′ is the specific volume of saturated water, and the calculation control unit calculates the dryness or wetness of the steam. It exists in the dryness or wetness measuring apparatus of the vapor | steam characterized by comprising.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The dynamic pressure of the steam flowing down is detected by the dynamic pressure detecting means, and the specific weight or specific volume calculating means is used to calculate the specific weight or specific volume from the detected dynamic pressure value and the flow velocity of the steam according to the dynamic pressure value = ρV2 / 2. The specific volume can be calculated. Here, ρ is the specific weight of the steam, V is the flow velocity of the steam, and the specific volume: v can be obtained as the reciprocal of ρ.
[0011]
Between the specific weight or specific volume of steam and the dryness or wetness of steam, there is a relational expression expressed by a predetermined definition formula, and this relation with the value calculated by the specific weight or specific volume calculating means. From the equation, the dryness or wetness of the steam can be calculated.
[0012]
When the flow velocity of the steam to be measured is unclear, as shown in claim 2, the flow velocity detection means detects the flow velocity of the steam and supplies the detected flow velocity value to the specific weight or specific volume calculation means. can do.
[0013]
By a double tube with a static tube to pin toe tube, it can detect the dynamic pressure as the difference between total pressure and static pressure in the Pitot tube, both static.
[0014]
【Example】
In the present embodiment, an example in which the Pitot tube 1 is used as the dynamic pressure detection means is shown. In FIG. 1, the end opening 3 of the pitot tube 1 is disposed at substantially the center of the steam pipe 2 where the steam to be measured flows from the left side to the right side, and communicates with the upper pressure transducer 4. The pitot tube 1 of the present embodiment uses a single tube that can detect the total pressure of the fluid.
[0015]
Above the end opening 3, a pressure sensor 5 as a static pressure detecting means for detecting the static pressure of the steam to be measured is attached. By subtracting the static pressure detected by the pressure sensor 5 from the total pressure detected by the Pitot tube 1, the dynamic pressure of the steam to be measured can be obtained. In addition, when using the thing of the double pipe | tube system which equips the pitot tube 1 with a static pressure tube and can detect a static pressure, the pressure sensor 5 does not necessarily need to be attached. Further, even when the static pressure of the vapor to be measured is known, the pressure sensor 5 does not necessarily have to be attached.
[0016]
On the further upstream side of the pressure sensor 5, a flow velocity sensor 6 is attached as a flow velocity detection means for detecting the flow velocity of the steam to be measured passing through the steam pipe 2. The flow rate sensor 6 is configured by a sensor unit 6 and a flow rate converter 7 (not shown). Note that the flow rate sensor 6 is not necessarily attached when the flow rate of the passing steam is known.
[0017]
The pressure converter 4, the pressure sensor 5, and the flow rate converter 7 of the pitot tube 1 are electrically connected to an arithmetic control unit (not shown).
[0018]
In order to measure the dryness of steam: X or the wetness: (1-X), first, the total pressure of the steam to be measured is detected by the Pitot tube 1, and the dynamic pressure value as the difference between the total pressure and the static pressure. From the steam flow velocity V, the specific weight or specific volume calculating means calculates the specific pressure or specific volume of the steam according to the dynamic pressure value = ρV 2/2. The specific volume: v is obtained as the reciprocal of the specific weight: ρ.
[0019]
There is a predetermined relationship between the specific weight or specific volume of the steam and the dryness or wetness of the steam. That is, ρ = X / v〃 + (1−X) / v ′ is established. Here, ρ is the specific weight of steam, X is the dryness of steam, v 蒸 気 is the specific volume of saturated steam, and v ′ is the specific volume of saturated water. v〃 and v ′ can be uniquely determined from the steam table if the static pressure of the steam to be measured is known. Accordingly, the static pressure in the steam pipe 2 is measured by the pressure sensor 5, and v〃 and v ′ are calculated from the specific volume of saturated steam and the specific volume of saturated water for each pressure in the steam table stored in advance. Can be requested.
[0020]
In the above equation, ρ = X / v〃 + (1−X) / v ′, ρ, v〃, and v ′ can be obtained, whereby the dryness of the steam to be measured: X can be obtained. Degree: (1-X) can be obtained.
[0022]
As the flow rate sensor 6 in the present embodiment, a conventionally known sensor such as an electromagnetic type, an ultrasonic type, a vortex type, a thermal type, a turbine type, or a laser Doppler type can be used.
[0023]
In the present embodiment, the heat insulation of the steam pipe 2, the flow velocity sensor 6, the pitot pipe 1, etc. is not described, but the implementation is omitted as common sense.
[0024]
In the present embodiment, an example is shown in which the Pitot tube 1 is arranged directly on the downstream side of the flow velocity sensor 6, but by arranging a multilayer multi-row rectifier on the upstream side of the Pitot tube 1, the Pitot tube 1 is arranged. The pitot tube 1 can rectify the flow of the steam to be measured, and the dynamic pressure as the difference between the total pressure and the static pressure can be detected more accurately.
[0025]
Further, in this embodiment, an example having one end opening 3 as the Pitot tube 1 has been shown. However, particularly when the diameter of the steam pipe 2 is large, a plurality of holes receiving the total pressure and a plurality of receiving the static pressure. By using so-called averaged Pitot tubes provided with respective holes, the dynamic pressure of the steam to be measured can be detected more accurately.
[0026]
In the present embodiment, the flow velocity sensor 6, the pressure sensor 5, and the Pitot tube 1 are separately attached to the steam pipe 2. However, by integrating these as a sensing unit, an existing steam pipe is provided. This vapor dryness / wetness measuring device unit can be easily attached or detached by changing a part of the above.
[0027]
【The invention's effect】
As described above, according to the present invention, the specific weight or specific volume is calculated from the dynamic pressure and flow velocity of the steam to be measured, and the dryness is calculated from the relational expression between the specific weight or specific volume and the dryness or wetness of the steam. By calculating the degree or wetness, it is possible to measure the dryness or wetness without making the steam overheated. Alternatively, the wetness can be measured.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional configuration diagram of a vapor dryness or wetness measuring apparatus according to the present invention.
[Explanation of symbols]
1 Pitot pipe 2 Steam pipe 3 End opening 4 Pressure transducer 5 Pressure sensor 6 Flow rate sensor

Claims (1)

For measuring the dryness or wetness of the flowing steam, the dynamic pressure detecting means using a Pitot tube for detecting the dynamic pressure of the steam, the dynamic pressure value detected by the dynamic pressure detecting means, and the flow velocity detecting means from the flow rate of the detected steam dynamic pressure value = pV 2/2 equation, however, V: flow velocity of the vapor, [rho: the specific weight, a specific weight or specific volume calculation means for calculating a specific weight or specific volume of the steam, Relational expression between specific weight or specific volume of steam and dryness or wetness, that is, ρ = X / v〃 + (1-X) / v ′ formula, where X: dryness of steam, v〃 An apparatus for calculating the dryness or wetness of the steam based on the specific volume of saturated steam, v ′: the specific volume of saturated water, and a dryness or wetness measuring apparatus for steam .

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