Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-06-05
2001-05-22
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C073S861040
Reexamination Certificate
active
06236948
ABSTRACT:
The present invention relates to a process for determining a measured valued of a target measured variable of a multiphase flow, in particular, of a two-phase flow, with which a value of a pressure of the multiphase flow is measured as a primary measured variable by means of a measuring device.
Furthermore, the present invention relates to a device for determining a measured value of a target measured variable of a multiphase flow, in particular, of a two-phase flow, which comprises a measuring means for measuring a pressure of the multiphase flow as a primary measured variable.
A process of this type and a device of this type are known, for example, from the article “Verbesserte Speisewasserregelung durch kompaktes Me&bgr;system zur Massenstrom- und Dampfgehalts-bestimmung” (=Improved Feed-Water Regulation as a Result of a Compact Measuring System for the Determination of Mass Flow and Steam Content) by W. Kastner, C. Fischer and W. Krätzer, Erlangen, published in the journal BWK, Vol. 45 (1993), No. 12, pages 510 to 514. The cited publication discloses a measuring system for determining a measured value of the total mass flow and a measured value of the steam content of a water-steam flow in a steam generator which comprises a measuring means for measuring a differential pressure of the water-steam flow (a Venturi tube) and, in addition, a measuring means for measuring the mixture density of the water-steam flow (a gamma densitometer).
With this measuring system, the momentary proportion of steam mass is determined from the momentary value of the mixture density measured with the gamma densitometer and the momentary value of the total mass flow is determined from the momentary value of the differential pressure measured at the Venturi tube and the momentary value of the mixture density measured with the gamma densitometer.
In the case of the measuring device known from the cited publication and the measuring process carried out with it, it is a disadvantage that for determining a measured value of a desired target measured variable, namely the total mass flow, two primary measured variables, namely the differential pressure at the Venturi tube and the mixture density, have to be measured with two different, primary measuring means, namely a Venturi tube and a gamma densitometer. The necessity for two primary measuring means increases the space requirements of the measuring device, the required maintenance and the costs of the measuring device considerably.
Moreover, the gamma densitometer used in the known measuring system is a very expensive and complicated measuring means which, in addition, makes special safety precautions necessary on account of the use of radioactive material.
The object underlying the present invention is therefore to develop a process of the type specified at the outset, with which a desired target measured variable of a multiphase flow, for example, the total mass flow can be determined from one primary measured variable in a simple manner.
This object is accomplished in accordance with the invention, in a process of the type specified at the outset, in that
a development with respect to time (time development) of the primary measured variable is measured,
the measured time development of the primary measured variable is compared with reference time developments of the primary measured variable, each of which has a reference value of the target measured variable associated with it, and
the measured value of the target measured variable is determined from the reference values of the target measured variable as a function of the result of the comparison of the measured development of the primary measured variable with the reference developments of the primary measured variable.
The inventive concept is based on the knowledge that each state of the multiphase flow can be characterized by the fluctuation pattern of a primary measured variable, i.e. on the basis of its development with respect to time. On the basis of the fluctuation pattern of the primary measured variable, different flow states of the multiphase flow can therefore be differentiated distinctly from one another while such a differentiation would not be possible on its own on the basis of the respective average value of the primary measured variable since a plurality of flow states which have this average value exist for each average value of the primary measured variable and so a clear association of an average value of the primary measured variable with a specific state of the multiphase flow is not possible.
On account of the comparison of the measured development of the primary measured variable with the reference developments of the primary measured variable previously determined, that reference state of the multiphase flow can be determined which best fits the actual flow state. The reference value of the target measured variable associated with this reference state is closest to the actual value of the target measured variable.
The inventive process has a high flexibility since, irrespective of the type of primary measured variable, optional target measured variables of the multiphase flow can be determined since the measurement of the primary measured variable is not used directly for calculating the measured value of the target measured variable but merely serves to identify the actual state of the multiphase flow.
Furthermore, it is of advantage that only one measuring means for measuring a single primary measured variable is required in order to carry out the inventive process.
The inventive process can be used, in particular, for monitoring flows in horizontal or inclined steam generators or in the case of oil and gas conveyance in horizontal or inclined pipe sections.
An additional advantage results from the fact that a pressure of the multiphase flow is measured as primary measured variable since pressure measuring means can be realized less expensively and require less maintenance and they are also temperature-resistant and pressure-resistant to a large extent.
The pressure of the multiphase flow measured as primary measured variable can be a static pressure, a pitot pressure or a dynamic pressure of the multiphase flow. Additional pressures or pressure differences of the multiphase flow can also be considered, for example, the differential pressure of the flow determined by means of a Venturi tube.
The use of a dynamic pressure of the multiphase flow as primary measured variable is particularly preferred since the flow velocity of a phase of the multiphase flow can be concluded directly from the dynamic pressure in this phase. It is, therefore, possible to check the correct functioning of the inventive process by selecting the flow velocity of the relevant phase as target measured variable or as one of a plurality of target measured variables and comparing the measured value of this target measured variable determined by means of the inventive process with the measured value determined from the average value of the dynamic pressure in the relevant phase.
A time development of the pressure selected as primary measured variable which characterizes a specific flow state of the multiphase flow particularly well is obtained when the pressure of the multiphase flow is measured at a point which is essentially constantly in contact with the same phase of the multiphase flow.
If the multiphase flow is a flow which comprises a gaseous and at least one liquid phase, the pressure selected as primary measured variable is preferably measured in the liquid phase.
In order to be able to measure the pressure essentially constantly in a phase of the multiphase flow which has a high, specific weight, it may be provided for the pressure of the multiphase flow to be measured in the lower third, preferably near to the lowest point, of a cross section of a horizontal or inclined pipe having the multiphase flow flowing through it.
In order, on the other hand, to be able to measure the pressure of the multiphase flow essentially constantly in a phase of the multiphase flow which has a low,
Eck Markus
Geskes Peter
Kossok Norbert
Prasser Horst-Michael
Schuetz Peter
Deutsches Zentrum fuer Luft-und Raumfahrt e.V.
Hoff Marc S.
Lipsitz Barry R.
Raymond Edward
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