Análise modal e caracterização hidroeletromecânica de uma bancada experimental com bombas funcionando como turbinas

Abstract

This work presents the improvement and experimental validation of a modular test bench for the study of Pumps as Turbines (PATs) coupled to a three-phase synchronous alternator, aimed at the laboratory simulation of small-scale hydrogenerator systems. The research included the physical reorganization of the components, the definition of the mechanical coupling system, the assembly of the hydraulic circuit, the instrumentation of the test bench, and the dynamic validation of the structure through experimental modal analysis and operational vibration assessment. Three PATs were tested, corresponding to the INI 40-250, INI 40-200, and INI 32-200 models, hydraulically driven by a pump operating as a pump in a closed circuit. The tests were carried out under no-load conditions, without an electrical load connected to the alternator, allowing the measurement of flow rate, inletpressure, average flow velocity, rotational speed of the PAT-alternator set, and no-load terminal voltage. From these data, the total hydraulic head, available hydraulic power, estimated electrical frequency, and complementary performance indicators were calculated. The results showed that the INI 40-200 presented the best compatibility with the nominal condition of the alternator, reaching 1844 rpm, 226 V under no-load operation, and an estimated electrical frequency of 61.47 Hz. The INI 32-200 reached 1606 rpm and the highest calculated hydraulic head, while the INI 40-250 reached 1440 rpm, remaining farther from the nominal rotational speed. The maximum available hydraulic powers were approximately 1.73 kW, 1.69 kW, and 1.55 kW for the INI 40-200, INI 32-200, and INI 40-250 PATs, respectively. Based on these powers and hypothetical global efficiencies, a preliminary possible electrical power range between approximately 0.45 kW and 1.00 kW was estimated, with a reference value of 0.87 kW for the INI 40-200. Since no direct torque measurement or operation with electrical load was performed, the efficiency, effective mechanical power, and useful electrical power were not experimentally determined. There fore, the estimates of mechanical power, torque, and electrical power were treated only through sensitivity analysis using assumed efficiencies. It is concluded that the test bench was validated as an experimental platform for the comparative characterization of PATs under no-load operation, allowing the identification of hydraulic and electromechanical limitations of the set and indicating the INI 40-200 as the most promising alternative for future tests with electrical load.