COBEM99

S10 Fluidodinâmica de Escoamento Multifásico

Title:

TIME-FREQUENCY CHARACTERIZATION OF A VERTICAL GAS-LIQUID FLOW

Summary :

ONE OF THE BASIC ATTRIBUTES ASSOCIATED TO MULTIPHASE FLOWS IS THE EXISTENCE OF CHARACTERISTIC STRUCTURES, ACCORDING TO WHICH THE DIFFERENT PHASES OF THE FLUID FLOW. THE FORMATION OF ONE OF THOSE STRUCTURES, KNOWN AS CONFIGURATIONS OR FLOW REGIMES, IS DETERMINED BY THE FLOW RATES AND PHYSICAL PROPERTIES OF THE PHASES, BESIDES GEOMETRIC PARAMETERS, SUCH AS THE DIAMETER AND THE INCLINATION OF THE CONDUIT. FROM THE POINT OF VIEW OF PRACTICAL APPLICATIONS, THE MAIN IMPLICATION OF THE EXISTENCE OF THESE FLOW REGIMES ARE THEIR STRONG RELATIONSHIP WITH IMPORTANT OPERATIONAL VARIABLES, SUCH AS PRESSURE LOSSES, REACTION RATES, CHEMICAL BREAKUP, ETC. SO, IN A PROJECT STAGE, PHYSICAL MODELS CAPABLE OF PREDICTING UNDER WHICH CONFIGURATION A CERTAIN MULTIPHASE FLOW WILL FLOW ARE OF VITAL IMPORTANCE. IN SPITE OF THE EFFORT OF SEVERAL RESEARCHERS, RELIABLE MODELS EXIST ONLY FOR A RESTRICTED NUMBER OF SITUATIONS. THEREFORE, THE DEVELOPMENT OF METHODOLOGIES OF CHARACTERIZATION OF REGIMES IS IMPORTANT, NOT ONLY FOR THE PROJECT, BUT ALSO FOR THE EFFICIENT OPERATION OF MULTIPHASE EQUIPMENTS. IN THIS DIRECTION, TIME-FREQUENCY ANALYSIS APPEARS AS AN EXTREMELY PROMISING POSSIBILITY, MAINLY REGARDING ITS GENERALITY, I.E. THE APPLICATION OF A SAME METHODOLOGY FOR EVERY POSSIBLE FLOW CONFIGURATIONS. IN THIS WORK, GABOR TRANSFORM IS APPLIED IN THE ANALYSIS OF THE SIGNALS FROM A CONDUCTIVITY PROBE, INSTALLED IN AN EXPERIMENTAL CIRCUIT OF VERTICAL AIR-WATER FLOW. THE PROBE IS CONSTITUTED OF TWO PARIETAL RINGS MADE OF STAINLESS STEEL. THE SECTION OF TESTS, BUILT IN ACRYLIC TO ALLOW FLOW VISUALIZATION, IS 10 M HEIGH AND 50 MM INTERNAL DIAMETER. THE RESULTS DEMONSTRATE WITH CLARITY HOW THE FENOMENOLOGY TRANSLATES ITSELF IN THE TIME-FREQUENCY PLANE, AND SHOW THAT THE METHOD OF ANALYSIS CAN BE GENERALISED. WORDS KEY: MULTIPHASE FLOW, REGIMES, CHARACTERIZATION, TIME-FREQUENCY

Author :

Klein, Fabiana Lopes
Seleghim Jr., Paulo 0

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