Leszek Petryka

Time Delay Estimation in Two-Phase Flow Investigation Using the γ-Ray Attenuation Technique

Time delay estimation is an important research question having many applications in a range of technologies. Measurement of a two-phase flow in a pipeline or an open channel using radioisotopes is an example of such application. For instance, the determination of velocity of dispersed phase in that case is based on estimation of the time delay between two stochastic signals provided by scintillation probes. The proper analysis of such signals, usually in presence of noise, requires the use of advanced statistical signal processing. In this paper, the simulation studies of time delay estimation were carried out with the use of the following differential methods: average magnitude difference function, and average square difference function and proposed combined methods comprising the above-mentioned differential and cross-correlation functions are presented. Attached simulations have been carried out for models of stochastic signals corresponding to the signals obtained in gamma-ray absorption measurements of gas-liquid flow in a horizontal pipeline. The standard uncertainties of time delay estimations have been determined for each of the methods. Improved metrological properties have been stated in the combined methods in comparison with the classical cross-correlation procedure.

Modelling of dynamic experiments in MCNP5 environment

The design of radiation measurement systems includes a modelling phase which ascertains the best 3D geometry for a projected gauge. To simulate measured counts by a detector, the widely-used rigorous phenomenological model is used. However, this model does not consider possible source or/and detector movement during a measurement interval. Therefore, the phenomenological model has been successfully modified in order to consider such a displacement during the time sampling interval in dynamic experiments. To validate the proposed model, a simple radiation system was accurately implemented in the MCNP5 code. The experiments confirmed the accuracy of the proposed model.

Radioisotpe measurement of two-phase flow in pipeline using conditional averaging of signal

The paper illustrates use of the gamma-absorption method fortify with analysis based on conditional averaging of signals applied in an investigation of two-phase flows. An example of its application to the gaseous phase transported by a liquid in a horizontal pipeline was evaluated. In the measurements on laboratory installation two 241Am radioactive sources and probes with NaI(Tl) scintillation crystals have been used. Exemplary results of the mean velocity determination of the minority phase in the examined flow are demonstrated, and the evaluation of its uncertainty has been presented. Results obtained by use of the both described method and cross-correlation one have been compared.

Velocity measurement of two-phase liquid-gas flow in a horizontal pipeline using gamma densitometry

This paper presents application of gamma-ray absorption method to liquid-gas flow investigation in a pipeline. In the described measurement two sealed 241Am radioactive sources and probes with NaI(Tl) scintillation crystals have been used. For the analysis of digital signals provided by detectors, a traditional cross-correlation function (CCF), and modified correlation methods based on the quotient of CCF and average magnitude difference function (AMDF), as well as the quotient of CCF, and average square difference function (ASDF) have been proposed. Exemplary results of the mean velocity determination of the gaseous phase transported by a liquid in the water-air mixture flow were demonstrated and the evaluation of its uncertainty have been presented.

Evaluation of the structures size in the liquid-gas flow by gamma-ray absorption

The rapid development of tomography methods particularly electrical, X and gamma rays allows for a wide range of the information about flow structure. However, all of such methods are quite complicated. At the same time much simpler systems as the measuring system of gamma rays absorption, allows to obtain a all key flow information which describe the two-phase flow. In the article the results of analyzes of radiometric signal that not only allow to recognize the type of flow, but also the assessment of forming structures are presented. Calculation and interpretation of the data were based on the crosscorrelation and cross-spectral density function. In order to verify the calculations the photographic documentation made during the measurements was used.

Determination of void fraction in two phase liquid-gas flow using gamma absorption

Full description of a two-phase liquid-gas flow requires the designation of lot parameters. First one, which describes which part of the pipeline is fulfilled by the gas, is the void fraction. Moreover the share of gas in a flowing mixture determines the structure of the flow and also affects the velocity of the individual phases. In that case void fraction can be determined by use the gamma absorption method, as well as other flow parameters may be evaluated by the same equipment. In addition the article presents the calibration of radiometric set, which consists of gamma radiation source Am-241 and scintillation probe NaI(Tl), for determination of the void fraction, illustrated by exemplary results of the described method application to various structures of air-water flow in the horizontal pipeline.