Navegando por Assunto "Blade element theory"

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Acesso aberto (Open Access)
Uma abordagem matemática aplicada ao projeto de turbinas hidrocinéticas e eólicas com difusor utilizando a teoria do elemento de pá
(Universidade Federal do Pará, 2019-04-30) VAZ, Déborah Aline Tavares Dias do Rio; VAZ, Jerson Rogério Pinheiro; http://lattes.cnpq.br/1623983294183975
It is known surrounding a turbine with diffuser may significantly increase its power. This effect has attained considerable attention as it shows theoretically the possibility of achieving a power coefficient about 2 times greater than an ordinary turbine. However, the effect of the diffuser efficiency has not been implemented into blade element momentum yet, as well as the use of minimum pressure coefficient criterion to avoid cavitation during the optimization of the hydrokinetic chord along the blade. Hence, this work presents a novel approach to design diffuser-augmented hydro turbines considering the diffuser efficiency. Based on the blade element momentum, new expressions for the axial induction factor and thrust are obtained. In addition, both efficiency and load generated on a diffuser are considered to the extension of existing formulation to determine power coefficient in cases where diffuser losses are taken into account through efficiency (ηd) and area ratio (β). To assess the proposed model, a comparative evaluation of two different diffusers (flanged conical diffuser and flanged lens diffuser) is performed. Numerical and theoretical results are compared for a shrouded turbine equipped with 83% efficiency diffuser. The relative difference observed for the maximum power coefficient between the proposed model and an actuator disk model with diffuser is about 5.3%. For the hydro turbine with flanged conical diffuser, the mass flow rate is about 20% higher than for a bare turbine, while for the turbine with flanged lens diffuser the increase is only 2.4%. Also, for the flanged conical diffuser the power is increased by 53%. Furthermore, it is observed that the proposed blade element momentum with diffuser achieved good agreement with the numerical model, providing improved results compared to other models available in the literature. The optimization model of hydrokinetic chord shows relevant results in relation to the prevention of cavitation.
Acesso aberto (Open Access)
Estudo do comportamento hidrodinâmico de medidores de vazão de gás liquefeito de petróleo utilizado a teoria do elemento de pá com efeito de grade
(Universidade Federal do Pará, 2021-04-28) PEREIRA, Tiago Miranda; VAZ, Jerson Rogério Pinheiro; http://lattes.cnpq.br/1623983294183975; https://orcid.org/0000-0001-6440-4811
Turbine flowmeters are widely applied in industry to quantify transferred amounts of liquid products, even for commercial purposes, due to its high accuracy and large operational range. The development of engineering computational tools to analyze and improve performance of such meters offers to the engineer the possibility of contribution to society, increasing quality of measurements and minimizing distortions in supply chain potentially harmful to final consumers. Most turbine flowmeters have several blades, becoming the determination of lift and drag coefficients still challenge. This makes cascade effect indeed relevant, without which the performance of the turbine can be overestimated by the Blade Element Theory (BET) analysis. Hence, the present work proposes the application of BET to the analysis of hydrodynamic behavior of turbine flowmeters applied to Liquefied Petroleum Gas (LPG) measurement. The proposed model calculates the cascade effect correction due to the local solidity throughout turbine blades length, in order to accurately predict lift and drag coefficients at each blade section. Operational parameters of the studied equipment are obtained from the proposed computational model and compared to the field performance of an existent measurement system for several conditions within the operational range, revealing satisfactory coherence. For this analysis, computational fluid dynamics (CFD) techniques are employed, through the finite volume method. For validation of the CFD model, computational results are compared to in-situ data acquired during regular operation of the measurement system. Cavitation susceptibility is also evaluated through the CFD model, in order to provide indication of boundary limits inside which operational conditions are maintained within specifications. As a result, the study indicates that turbine flowmeter performance can be predicted by the proposed computational modeling strategy based on the BET analysis and field results of angular velocity and linearity can be accurately reproduced.