A computational study on square and helical magnetohydrodynamic generators including applications to a combined power cycle

IF 1.8 4区 工程技术 Q3 ENGINEERING, MECHANICAL
Cesar C. Pacheco, Gabriel L. Verissimo, Marcelo J. Colaço, Albino J. K. Leiroz, Manuel E. C. Cruz, Hugo F. L. Santos, Marcelo DeFilippo, Tomás S. Quirino
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Abstract

In this study, the performance of magnetohydrodynamic (MHD) generators working with seawater and with hot exhaust gas in a combined cycle was computationally investigated. The flow and electric potential coupled governing equations were solved using a commercial computational fluid dynamics code. For seawater applications, 2 geometries were studied: square-cross-section duct and helical channel. For both geometries, the influence of the magnetic field intensity, the flow rate and external electric circuit resistance on the device performance were analyzed. The energy structure of the MHD flow for the helical MHD generator was also analyzed. Finally, a combined power cycle equipped with the investigated MHD generators was studied to evaluate its effects on the thermal efficiency of the combined cycle. The results showed that the helical geometry resulted in 10, 30 and 44 times more electric power produced than the square-cross-section duct for Reynolds numbers of 104, 105 and 106, respectively. An analysis of the energy structure in the helical MHD flow indicated that variations in the magnetic field modified the conversion of mechanical energy into electrical power and lost due to viscous and turbulence effects. It is also shown that for Reynolds numbers of 105 and 106, viscous and turbulence effects dissipate 60% of the mechanical energy lost in the MHD generator, independently of the Hartman number. The results of the MHD-based combined power cycle analysis revealed that the use of the MHD generator improved the thermal efficiency of the combined cycle around 24%, reaching values of 67.5% and 67.3%.

Abstract Image

方形和螺旋形磁流体发电机计算研究,包括在联合动力循环中的应用
本研究通过计算研究了在联合循环中使用海水和热废气的磁流体动力(MHD)发电机的性能。使用商用计算流体动力学代码求解了流动和电动势耦合控制方程。针对海水应用,研究了两种几何形状:方形横截面管道和螺旋通道。针对这两种几何形状,分析了磁场强度、流速和外部电路电阻对设备性能的影响。此外,还分析了螺旋 MHD 发电机的 MHD 流能量结构。最后,研究了配备所研究的 MHD 发电机的联合动力循环,以评估其对联合循环热效率的影响。结果表明,在雷诺数为 104、105 和 106 时,螺旋几何形状产生的电能分别是方形横截面管道的 10、30 和 44 倍。对螺旋 MHD 流动中能量结构的分析表明,磁场的变化改变了机械能向电能的转化,并由于粘性和湍流效应而造成能量损失。研究还表明,在雷诺数为 105 和 106 时,粘滞和湍流效应耗散了 MHD 发电机中 60% 的机械能损失,与哈特曼数无关。基于 MHD 的联合动力循环分析结果表明,使用 MHD 发电机可将联合循环的热效率提高约 24%,达到 67.5% 和 67.3%。
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来源期刊
CiteScore
3.60
自引率
13.60%
发文量
536
审稿时长
4.8 months
期刊介绍: The Journal of the Brazilian Society of Mechanical Sciences and Engineering publishes manuscripts on research, development and design related to science and technology in Mechanical Engineering. It is an interdisciplinary journal with interfaces to other branches of Engineering, as well as with Physics and Applied Mathematics. The Journal accepts manuscripts in four different formats: Full Length Articles, Review Articles, Book Reviews and Letters to the Editor. Interfaces with other branches of engineering, along with physics, applied mathematics and more Presents manuscripts on research, development and design related to science and technology in mechanical engineering.
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