A novel approach to precessing jet stabilization: Design and heat transfer analysis

IF 5.8 2区 工程技术 Q1 ENGINEERING, MECHANICAL
Cristina D’Angelo, Gerardo Paolillo, Carlo Salvatore Greco, Gennaro Cardone, Tommaso Astarita
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Abstract

Originally developed to improve mixing efficiency in industrial burners, precessing jets have gained significant interest due to their wide range of applications, despite the challenges introduced by their inherent instability. To enhance control over the jet precessing motion, the present study introduces a novel precessing jet nozzle inspired by the feedback-channel mechanism characteristic of sweeping jets. The heat transfer performance of this device is examined using infrared thermography and the heated thin-foil heat flux sensor; the results are compared with those of a conventional precessing jet (CPJ). To characterize the heat transfer behaviour of the investigated precessing jets impinging on a foil, the Nusselt number distribution over the impingement surface is analysed at ten nozzle-to-foil distances, corresponding to normalized spacings z/d ranging between 1/6 and 3, being z the axial distance between the nozzle exit section and the foil and d the nozzle exit diameter. The Reynolds number is set to 1.55×104 for all the tests performed. Time-averaged analyses are performed for both jets, while phase-averaged analyses can be performed only for the stabilized precessing jet (SPJ). Indeed, its regular periodic motion allows phase identification, whereas the strong instability of the CPJ limits the investigation to time-averaged analysis. The findings reveal that the SPJ effectively stabilizes the precessing motion, generating a broader and more uniform Nusselt number distribution over the foil. In contrast, the CPJ generates higher Nusselt number values at all z/d, with higher heat transfer rates centred around the stagnation point, resulting in a less uniform Nusselt number distribution.
处理射流稳定的新方法:设计和传热分析
最初是为了提高工业燃烧器的混合效率而开发的,加工射流由于其广泛的应用而获得了极大的兴趣,尽管其固有的不稳定性带来了挑战。为了加强对射流加工运动的控制,本研究利用扫射射流的反馈通道特性,设计了一种新型的射流加工喷嘴。采用红外热像仪和加热薄箔热流传感器对该装置的传热性能进行了测试;并将结果与传统的加工射流(CPJ)进行了比较。为了描述所研究的射流撞击箔片的传热行为,在10个喷嘴到箔片的距离上分析了撞击表面上的努塞尔数分布,对应于归一化间距z/d在1/6到3之间,其中z为喷嘴出口部分与箔片之间的轴向距离,d为喷嘴出口直径。所有已执行的测试都将雷诺数设置为1.55×104。对两种射流都进行了时间平均分析,而相位平均分析只能对稳定处理射流(SPJ)进行。事实上,它的规则周期运动允许相位识别,而CPJ的强不稳定性限制了对时间平均分析的调查。结果表明,SPJ有效地稳定了加工运动,在箔上产生了更宽、更均匀的努塞尔数分布。相比之下,CPJ在所有z/d都产生更高的努塞尔数值,以驻点为中心的传热率更高,导致努塞尔数分布不太均匀。
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来源期刊
CiteScore
10.30
自引率
13.50%
发文量
1319
审稿时长
41 days
期刊介绍: International Journal of Heat and Mass Transfer is the vehicle for the exchange of basic ideas in heat and mass transfer between research workers and engineers throughout the world. It focuses on both analytical and experimental research, with an emphasis on contributions which increase the basic understanding of transfer processes and their application to engineering problems. Topics include: -New methods of measuring and/or correlating transport-property data -Energy engineering -Environmental applications of heat and/or mass transfer
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