JP3381122B2 - Steam dryness measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the dryness of steam flowing through a steam pipe. In various boilers and equipment using steam power, it is necessary to know the dryness X indicating the content of moisture in the steam, that is, the ratio of the mass of the dry saturated steam to the total mass per unit volume of the steam flow. This is because the enthalpy of the steam varies depending on the water content. 2. Description of the Related Art As a conventional steam dryness measuring device, there is an aperture dryness meter. This is achieved by adiabatically expanding (equally changing the enthalpy) the wet steam to be measured in the measurement chamber through the nozzle to form superheated steam, and detecting the pressure P1 upstream of the nozzle, the pressure P2 in the measurement chamber, and the temperature T in the measurement chamber. Using the saturated steam table and the superheated steam table, the dryness X1 of the upstream steam is calculated as X1 = ( E6- E1) / ( E3- E1). In the above equation, E1 is the enthalpy of the saturated water at the pressure P1, E3 is the enthalpy of the saturated steam at the pressure P1, and E6 is the enthalpy of the superheated steam at the pressure P2 and the temperature T. [0003] In the above-mentioned conventional diaphragm dryness meter, superheated steam must be produced. Therefore, there is a problem that it cannot be measured when the steam pressure is low or when the steam dryness is small. there were. Therefore, the technical problem of the present invention is:
An object of the present invention is to provide a steam dryness measuring device that can measure the dryness easily with a wide range of measurable dryness. [0004] The technical means of the present invention taken to solve the above-mentioned technical problems includes a throttle mechanism provided in the middle of a steam pipe and a steam upstream of the throttle mechanism. A first flow meter for measuring the flow rate, a second flow meter for measuring the steam flow rate on the downstream side of the throttle mechanism, a first pressure sensor for detecting a pressure on the upstream side of the throttle mechanism, and a downstream side of the throttle mechanism. A second pressure sensor for detecting pressure, and a dryness of the upstream steam is calculated based on a flow value measured by the first and second flow meters and a pressure value detected by the first and second pressure sensors. In a steam dryness measuring apparatus provided with a calculation unit for performing the above. The operation of the above technical means is as follows.
The wet steam on the upstream side is adiabatically expanded on the downstream side through the throttle mechanism, and at least a part of the saturated water is re-evaporated. The steam flow rate value measured by the first flow meter and the second flow meter differs depending on the re-evaporated steam amount. [0006] The steam flow value W1 measured by the first flow meter
Is the dryness of the wet steam on the upstream side of the throttle mechanism as X1, the total amount of heat on the upstream side of the throttle mechanism as Q, and from the pressure value P1 detected by the first pressure sensor and the saturated steam table, W1 = Q / (E2
+ E1 / X1). In the above equation, E
1 is the enthalpy of the saturated water at the pressure P1, and E2 is the latent heat of the saturated steam at the pressure P1. The steam flow value W measured by the second flow meter
2 is the total fluid flow upstream or downstream of the throttle mechanism as W, the total heat quantity downstream of the throttle mechanism as Q (equal enthalpy change and equal to the total heat quantity upstream of the throttle mechanism),
From the pressure value P2 detected by the pressure sensor and the saturated steam table, it can be expressed as W2 = (Q−W · E4) / E5. In the above equation, E4 is the enthalpy of the saturated water at the pressure P2, and E5 is the latent steam saturation vapor at the pressure P2.
Heat . Here, the total fluid flow rate W can be represented by W = W1 / X1. From the above three equations, the dryness X1 of the steam on the upstream side of the throttle mechanism is X1 = (W1 · E1-W1 · E4) / (W
2 · E5−W1 · E2).
In this relational expression, W1 and W2 are measured by the first flow meter and the second flow meter. E1 and E2 can be read from the saturated steam table based on the pressure value detected by the first pressure sensor. Similarly, E4 and E5 can be read from the saturated steam table based on the pressure value detected by the second pressure sensor. Since it can be read, it can be determined by storing it in the arithmetic unit or inputting it. Therefore, the degree of dryness of the steam on the upstream side of the throttle mechanism can be calculated by solving this relational expression by the calculation unit. In the above description, the dryness of the steam on the upstream side of the throttle mechanism is calculated. The dryness of the steam on the downstream side of the throttle mechanism can be calculated as follows. The same symbols as those described above have the same meaning. The steam flow value W2 measured by the second flow meter is W2 = Q / (E5 + E4 / X2) where X2 is the dryness of the steam on the downstream side of the throttle mechanism.
And the steam flow value W1 measured by the first flow meter is W
1 = (Q−W · E1) / E2, and the total fluid flow rate W is
Since W = W2 / X2, the dryness X2 of the steam on the downstream side of the throttle mechanism is X2 = (W2 · E4−W2 · E1) / (W
1 · E2−W2 · E5). An embodiment showing a specific example of the above technical means will be described (see FIG. 1). A throttle mechanism 2 is provided in the middle of a steam pipe 1 for supplying wet steam. On the upstream side of the throttle mechanism 2, a first flow meter 3 for measuring a steam flow rate is installed, and a first pressure sensor 4 for detecting pressure and a first temperature sensor 5 for detecting temperature are attached. A second flow meter 6 for measuring a steam flow rate is installed downstream of the throttle mechanism 2, and a second pressure sensor 7 for detecting pressure and a second temperature sensor 8 for detecting temperature are attached. The first and second flow meters 3 and 6, the first and second pressure sensors 4 and 7, and the first and second temperature sensors -5 and 8 are connected to the calculation unit 9. As the throttle mechanism 2, a nozzle, a venturi, an orifice, or the like can be used. As the first and second flowmeters 3 and 6, for example, positive displacement flowmeters or the like can be used. In this embodiment, an example using a vortex flowmeter is shown. The first and second vortex type flow meters 3 and 6 measure the mass flow rate by multiplying the volume flow rate of the steam by the specific weight of the steam. The steam flow values W1 and W2 measured by the first and second flow meters 3 and 6 are sent to the calculation unit 9. Further, the pressure value P detected by the first and second pressure sensors-4, 7
1, P2 and the temperature values T1, T2 detected by the first and second temperature sensors -5, 8 are sent to the arithmetic unit 9. The calculation section 9 stores the saturated steam table and the superheated steam table as tables, and also stores the dryness calculation formula. The processing process in the arithmetic unit 9 is as follows.
First, the pressure value P1 and the temperature value T1 on the upstream side of the throttle mechanism 2 are set.
Then, it is determined whether or not the upstream steam is superheated steam. If the upstream steam is superheated steam, the degree of superheat of the upstream steam is calculated from the superheated steam table. If the upstream steam is not superheated steam, it is determined from the pressures P2 and T2 on the downstream side of the throttle mechanism 2 whether or not the downstream steam is superheated steam. If the downstream-side steam is superheated steam, the dryness of the upstream-side steam is calculated by a conventional relational expression X1.
= ( E6- E1) / ( E3- E1). If it is not superheated steam, the dryness of the upstream steam is calculated by the relational expression of the present invention, X1 = (W1 · E1−W1 · E).
4) Calculated based on / (W2 · E5−W1 · E2),
The dryness of the downstream steam is calculated as X2 = (W
2 ・ E4-W2 ・ E1) / (W1 ・ E2-W2 ・ E5)
Calculated based on In the above three equations, E1 is the pressure P1
, The enthalpy of saturated water at E2, the latent heat of saturated steam at pressure P1 , and E3 at latent pressure P1.
E4 is the enthalpy of the saturated water at the pressure P2, E5 is the latent heat of the saturated steam at the pressure P2, and E6 is the enthalpy of the superheated steam at the pressure P2 and the temperature T.
It is enthalpy . The present invention has the following specific effects. As described above, according to the present invention, the degree of dryness can be measured without overheating the steam, so that the range of measurable dryness is widened and the dryness can be easily measured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a steam dryness measuring apparatus according to an embodiment of the present invention. [Description of Signs] 1 Steam pipe 2 Throttle mechanism 3 First flow meter 4 First pressure sensor 5 First temperature sensor 6 Second flow meter 7 Second pressure sensor 8 Second temperature sensor 9 Operation unit

Claims (1)

(57) [Claims 1] A throttle mechanism provided in the middle of a steam pipe, a first flow meter for measuring a steam flow rate upstream of the throttle mechanism, and a steam flow rate downstream of the throttle mechanism A second flow meter for measuring the pressure, a first pressure sensor for detecting the pressure on the upstream side of the throttle mechanism,
A second pressure sensor that detects the pressure downstream of the throttle mechanism
And a calculation unit for calculating the dryness of the steam based on the flow value measured by the first and second flow meters and the pressure value detected by the first and second pressure sensors. Steam dryness measuring device.