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Innovation Research in Micro Scale Flows and Combustion

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J: Thermal Management".

Deadline for manuscript submissions: closed (15 March 2023) | Viewed by 9245

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Special Issue Editors

Dr. Maria Grazia De Giorgi

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Guest Editor

Department of Engineering for Innovation, University of Salento, Via Per Arnesano, I-73100 Lecce, Italy
Interests: energy systems; propulsive systems; fluid machinery; applied fluid dynamics; combustion
Special Issues, Collections and Topics in MDPI journals

Dr. Donato Fontanarosa

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Department of Engineering for Innovation, University of Salento, Lecce, Italy
Interests: aerospace engineering; micro-propulsion; multiphase flows; plasma flows; computational fluid dynamics; combustion; electric propulsion

Prof. Dr. Antonio Ficarella

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Special Issue Information

Dear Colleagues,

In recent years, microscale flows and combustion have aroused growing interest in both academic research and industrial communities, and have benefited from the rapid advancements in microfabrication technology. This considerable interest is due to the variety of applications. For instance, microscale phase change phenomena have shown a crucial role in high-performing micro heat transfer processes and thermal management systems for cooling and energy harvesting purposes. At the same time, the growing demand for micro-power generation technology for portable power devices has led to the development of novel micro-propulsion systems, such as microthrusters and unmanned micro-aerial vehicles, microreactors and microengines. Furthermore, microcombustors fueled with hydrogen, hydrocarbon, and syngas have also shown potential as next-generation energy systems thanks to their high energy density, simple structure and low pollutant emission.

The complex and unstable nature of microscale flows and combustion calls for further explorations aiming to discover new techniques and technological solutions to enhance the heat/mass transfer and combustion processes in such microfluidic devices. In this regard, the numerical and experimental methodologies for the characterization of these flows are constantly evolving.

We are inviting submissions for this Special Issue, focused on the abovementioned subject areas. Specific topics of interest for this Special Issue include, but are not limited to:

Heat and mass transfer in microscale flows;
Multiphase flows and phase change in microscale flows;
Fundamentals of microscale combustion;
Experimental methods for the characterization of microscale flows and microcombustion;
Numerical methods and simulations for microscale flows and microcombustion;
Microfabrication technologies and additive manufacturing;
Micromixers, microreactors, microturbines, and microcombustors;
Micro-propulsion systems and microengines;
Micro heat transfer systems: microchannel systems, micro-evaporators, micro heat sinks, micro heat exchangers, and microcoolers.

Dr. Maria Grazia De Giorgi
Dr. Donato Fontanarosa
Prof. Dr. Antonio Ficarella
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

microfluidics
microscale flows
microchannel flows
microcombustors
microreactors
microthrusters
micromixers
micronozzles
micro heat transfer systems

Published Papers (5 papers)

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Research

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20 pages, 6479 KiB

Open AccessArticle

Combustion Characteristics of Hydrogen/Air Mixtures in a Plasma-Assisted Micro Combustor

by Giacomo Cinieri, Donato Fontanarosa and Maria Grazia De Giorgi

Energies 2023, 16(5), 2272; https://doi.org/10.3390/en16052272 - 27 Feb 2023

Viewed by 1762

Abstract

This work performs an analysis of plasma-assisted non-premixed H₂-air flames in Y-shaped micro combustors in the presence of field emission dielectric barrier discharge (FE-DBD) plasma actuators. The combustion, flow, and heat transfer characteristics are numerically investigated, and the effect of sinusoidal plasma discharges on combustion performance is examined at various equivalence ratios (φ). A coupled plasma and chemical kinetic model is implemented, using a zero-dimensional model based on the solution of the Boltzmann equation and the ZDPlasKin toolbox to compute net charges and radical generation rates. The estimated body forces, radical production rates, and power densities in the plasma regions are then coupled with hydrogen combustion in the microchannel. Plasma-assisted combustion reveals improvements in flame length and maximum gas temperature. The results demonstrate that FE-DBDs can enhance mixing and complete the combustion of unreacted fuel, preventing flame extinction. It is shown that even in cases of radical and thermal quenching, these plasma actuators are essential for stabilizing the flame. Full article

(This article belongs to the Special Issue Innovation Research in Micro Scale Flows and Combustion)

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21 pages, 7204 KiB

Open AccessArticle

Enhancing Thermal Performance, Exergy and Thermodynamics Efficiency of Premixed Methane/Air Micro-Planar Combustor in Micro-Thermophotovoltaic Systems

by Jinshen Tong and Tao Cai

Energies 2023, 16(1), 118; https://doi.org/10.3390/en16010118 - 22 Dec 2022

Cited by 5 | Viewed by 1361

Abstract

The present work numerically investigates the effect of a cavity implemented in a premixed methane/air micro-combustor on enhancing its thermal performances and thermodynamic efficiencies for micro-thermophotovoltaic applications. The 3D time-domain numerical model is first validated by comparing its predictions with the experimental data available in the literature. Then it is applied to examine the effects of the cavity dimensionless axial location (x_c/L), cavity volume (V_c), the equivalence ratio ϕ and hydrogen blended ratio (α) on the temperature uniformity and enhancement of the combustor outer wall and exergy efficiency. It is found that implementing a cavity in the combustion chamber increases the outer wall mean temperature (OWMT) and the exergy efficiency up to approximately 65 K and 10%, respectively. The optimal cavity dimensionless axial location (x_c/L) is set to 1/9, and the height (H_{c_dims}) is 1/5, respectively. However, the cavity length L_c and angle θ_c are found to play negligible roles on improving thermal performance. Additionally, increasing the inlet velocity leads to a higher OWMT but a low exergy efficiency, regardless of the equivalence ratio. In general, this work confirms the feasibility of applying a cavity structure to enhance energy efficiency for micro-power generation systems. Full article

(This article belongs to the Special Issue Innovation Research in Micro Scale Flows and Combustion)

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13 pages, 3592 KiB

Open AccessArticle

Turbulence Structure and Dynamics Investigation of Turbulent Swirl Flow in Pipe Using High-Speed Stereo PIV Data

by Djordje S. Čantrak and Novica Z. Janković

Energies 2022, 15(15), 5417; https://doi.org/10.3390/en15155417 - 27 Jul 2022

Cited by 4 | Viewed by 1867

Abstract

Turbulent swirl flow, which exists in numerous turbomachinery systems, is the focus of this paper. It consumes a significant amount of energy, so it is a subject of investigation for many researchers. It is even more present in ventilation systems, as numerous axial fans are still installed without guide vanes. The experimental investigation of the turbulent swirl flow behind an axial fan in a pipe, installed in a test rig with a free inlet and ducted outlet, as defined in the international standard ISO 5801, is presented in this paper. Moreover, in this paper, the axially restricted case is studied. A designed axial fan generates a Rankine vortex with a complex structure, and research on the vortex turbulence structure and dynamics is presented. On the basis of the HSS PIV (high-speed stereo particle image velocimetry), measurement results are calculated using invariant maps. All states of turbulence anisotropy are thoroughly analyzed by applying the invariant theory on HSS PIV results. Vortex dynamics is observed on the basis of the total velocity minima positions and their repetitions. Both methods are correlated, and important conclusions regarding vortex behavior are deduced. Full article

(This article belongs to the Special Issue Innovation Research in Micro Scale Flows and Combustion)

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15 pages, 3820 KiB

Open AccessArticle

Combustion Performance of Methane/Air in a Micro Combustor Embedded Hollow Hemispherical Slotted Bluff Body

by Yunzhe Liao, Chenghua Zhang, Yanrong Chen and Yunfei Yan

Energies 2022, 15(11), 4033; https://doi.org/10.3390/en15114033 - 31 May 2022

Cited by 2 | Viewed by 1170

Abstract

With the rapid development of micro-energy power systems, the performance of micro-combustors as key components is in urgent need of further improvement. Aimed at enhancing combustion performance, a hollow hemispherical bluff body was used to analyze the methane combustion process. In this paper, we exploited the detailed reaction mechanism of methane/air with a laminar finite-rate model; the numerical analysis of methane combustion in the micro-combustor was carried out by Ansys Fluent software. The combustion, flow and thermal characteristics of the micro-combustor embedded with a hollow hemisphere bluff body (MCEHB) and the micro combustor embedded with a slotted hollow hemisphere bluff body (MCESHB) are compared, and the effect of slot width ratio on the combustion characteristics and thermal performance is discussed in detail. The results showed that the bluff body slotting treatment is not only beneficial to improving the velocity and temperature distribution behind the bluff body but also can improve the conversion rate of methane, especially at high inlet velocities. However, the conversion rate of methane is also affected by the slot width. When the slot width ratio below 0.5, the slot width corresponding to the peak methane conversion increased with the inlet velocity. Moreover, the bluff body slotting treatment can improve the wall temperature distribution, meanwhile expanding the high temperature area at the inner wall, thereby reducing the wall temperature fluctuation in the rear part of the micro-combustor. In addition, the optimal slot width ratio B increases with the inlet velocity. Since the inlet velocity is lower than 0.5 m/s, the optimal slot width ratio B is in the range of 0.3–0.375. However, as the inlet velocity exceeds 0.5 m/s, the optimal slot width ratio B moves to the range of 0.375–0.553. Furthermore, both large and small slot widths bring obvious temperature fluctuations to the micro combustor; the uneven wall temperature distribution phenomenon is detrimental to working performance. Therefore, the slot width ratio B of 0.375 only brings slight temperature fluctuations, indicating this is an optimal slot width ratio that should be chosen. This work has reference value for optimizing the design of the bluff body structure and improving the combustion performance of methane in the micro combustor. Full article

(This article belongs to the Special Issue Innovation Research in Micro Scale Flows and Combustion)

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Review

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19 pages, 2083 KiB

Open AccessReview

Micro-Explosion Phenomenon: Conditions and Benefits

by Dmitrii V. Antonov, Roman M. Fedorenko and Pavel A. Strizhak

Energies 2022, 15(20), 7670; https://doi.org/10.3390/en15207670 - 18 Oct 2022

Cited by 7 | Viewed by 2454

Abstract

Adding water to fuel droplets is known to lead to puffing and micro-explosion. Puffing and micro-explosion lead to a rapid increase in the liquid fuel surface area. This, in turn, leads to an increase in the fuel evaporation rate and the formation of a homogeneous fuel vapor/air mixture. The latter is important for improving the efficiency of combustion technologies, including those used in internal combustion engines. The effects produced by puffing and micro-explosion lead to a reduction in fuel consumption, improved fuel/air mixing, and a reduction in harmful emissions. The contributions of puffing and micro-explosion to fire extinguishing have also been discussed in many papers. In this paper, we review the state of the art in the investigation of composite droplet micro-explosion and discuss the sufficient conditions for the start of puffing/micro-explosion as well as child droplet characteristics. Full article

(This article belongs to the Special Issue Innovation Research in Micro Scale Flows and Combustion)

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