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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "I2: Energy and Combustion Science".

Deadline for manuscript submissions: closed (25 June 2023) | Viewed by 14394

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Special Issue Editors

Prof. Dr. Peiyong Wang

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Guest Editor

School of Aerospace Engineering, Xiamen University, Xiamen 361005, China
Interests: combustion and heat transfer modeling; thermocouple measurement correction

Prof. Dr. Fei Xing

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Guest Editor

School of Aerospace Engineering, Xiamen University, Xiamen 361005, China
Interests: combustion moedeling and experiment; fuel atomization

Special Issue Information

Dear Colleagues,

Energy and propulsion systems provide the foundation for modern industry and life. The more stringent emission and efficiency requirements have pushed the advances in energy and propulsion systems, which rely on the progress across multiple disciplines such as fluid and thermal sciences, design and optimization, manufacturing, automatic control, measurement and diagnostics, etc.

This Special Issue aims to present the most recent advances related to the theory, design and optimization, modelling, experimentation, and control of energy and propulsion systems.

Topics of interest for publication include, but are not limited to, the following:

Experimental and numerical investigation of combustion;
Experimental and numerical investigation of heat transfer;
Experimental and numerical investigation of atomization;
Combustion chemical kinetics;
Advanced modelling approaches;
High-temperature gas measurement with thermocouples and laser diagnostics;
System or component design and optimization for energy and propulsion systems;
System or component control for energy and propulsion systems.

Prof. Dr. Peiyong Wang
Prof. Dr. Fei Xing
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.

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Keywords

combustion and atomization
computational fluid dynamics
combustion measurement and diagnostics
experimental and numerical heat transfer
propulsion system optimization and control
energy system optimization and control

Published Papers (11 papers)

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Research

20 pages, 7370 KiB

Open AccessArticle

Acoustic Triggering of Combustion Instability in a Swirling Flame: An Experimental Study

by Yunpeng Liu, Yingwen Yan, Shoutang Shang and Hongyu Ma

Energies 2023, 16(14), 5568; https://doi.org/10.3390/en16145568 - 23 Jul 2023

Viewed by 1250

Abstract

Combustion instability is a common thermoacoustic coupling problem in combustion systems, and the pressure oscillations generated inevitably damage the combustion system. Studying the mechanism of combustion instability, especially the triggering problem of combustion instability, is particularly important for understanding combustion instability. This article adopts experimental research methods. The flame transfer function and flame describing function governing pressure pulsation were hereby measured to study the effect of heat release rate fluctuation on acoustic disturbance. By triggering combustion instability through ignition, the growth process of combustion instability was also studied. The results showed that flame pulsation amplitude shows a complex curvature when the frequency is lower than 200 Hz, while the growth rate of pulsation amplitude monotonically decreases as frequencies increase above 200 Hz. According to the considerable self−excited combustion instability tests, the oscillation amplitudes in the limit cycle state are generally greater than 0.4, while the pressure amplitudes in the limited state are less than 0.2, thus verifying the concept of a trigger threshold for low−frequency oscillation. In addition, analysis of the growth rate, the pressure and the attractor of the heat release pulsation observed after the triggering of combustion instability reveals that the triggering of combustion instability is a gradual coupling process between oscillation pressure and heat release rate pulsation. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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15 pages, 4539 KiB

Open AccessArticle

Further Development of Eddy Dissipation Model for Turbulent Non-Premixed Combustion Simulation

by Xingyou Li, Yongliang Chen and Peiyong Wang

Energies 2023, 16(13), 5043; https://doi.org/10.3390/en16135043 - 29 Jun 2023

Cited by 1 | Viewed by 1052

Abstract

In view of the application limits of the modified eddy dissipation model (MEDM) in simulations of weakly turbulent flow, compressible flow, and internal flow, an improved eddy dissipation model (IEDM) is proposed. The IEDM model uses the dissociation reactions to obtain the correct combustion temperature instead of the specific heat compensation used in the MEDM model. This extends the application in compressible flow simulation. The simulation accuracy of the IEDM model for weakly turbulent flow is improved by using the accurate transport property and model. The maximum ε/k is limited to give a reasonable reaction rate near walls, and the expression for the model parameter A is also updated. Nine turbulent flames including seven jet flames and two opposed jet flames are simulated with the improved model. Compared with the experimental data of the jet flames, the peak temperature differences with the MEDM model and the IEDM model are 189 and 161 K, respectively, indicating the minor accuracy improvement of the IEDM model. Compared with the experimental data of the opposed flames, the peak temperature differences with the MEDM model and the IEDM model are 131 and 7 K, respectively, indicating the significant accuracy improvement of the IEDM model. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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17 pages, 5631 KiB

Open AccessArticle

First-Order Linear Active Disturbance Rejection Control for Turbofan Engines

by Hui-Yu Jin and Yang Chen

Energies 2023, 16(6), 2743; https://doi.org/10.3390/en16062743 - 15 Mar 2023

Viewed by 1257

Abstract

Proportional-integral (PI) control is widely used in turbofan-engine control, while first-order linear active disturbance rejection control (FOLADRC) is a possible approach to update it. This paper investigates FOLADRC. In methodology, it proposes a new block diagram of FOLADRC, which shows that FOLADRC can be viewed as a PI controller, a low-pass feedback filter, and a pre-filter. The low-pass filter helps to reject high-frequency measurement noise, while the pre-filter can attenuate overshoot in step response. In simulation, 14 published linearized model matrices of NASA’s CMAPSS-1 90k engine model are used to verify the above theory. Simulations show one FOLADRC controller can be simultaneously used for the 14 linear models and guarantee that all the 14 low-pressure turbine speed control loops have enough phase margin and no overshoot. Thus, replacing several PI controllers with one FOLADRC controller is possible, and FOLADRC can be used to simplify the control system design of turbofan engines. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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12 pages, 3748 KiB

Open AccessArticle

Experimental Study on Denitration Transformation of CFB Boiler Burning Fujian Anthracite

by Wenting Zhou, Hongzhou He and Huanghuang Zhuang

Energies 2023, 16(6), 2535; https://doi.org/10.3390/en16062535 - 8 Mar 2023

Cited by 2 | Viewed by 1091

Abstract

Two 75 t/h medium-temperature separated circulating fluidized bed boilers burning Fujian anthracite were upgraded with low NOx combustion (LNC). By reducing the effective cross-sectional area of the air distributor (from 13.43 m² to 11.38 m²), improving the secondary air rate (from 40% to 45%), adjusting the secondary air supply method (adding a layer of upper secondary air, raising the height of the lower secondary air nozzle (0.4 m), and increasing the secondary air speed (from 48 m/s to 54 m/s), the reform of low nitrogen combustion was carried out. The transformation achieved remarkable results, i.e., the original NOx emission concentration can be controlled between 140–160 mg/m³ after the transformation, and the lowest value is below 120 mg/m³. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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22 pages, 10399 KiB

Open AccessArticle

Imprecise P-Box Sensitivity Analysis of an Aero-Engine Combustor Performance Simulation Model Considering Correlated Variables

by Hongjie Tang, Shicheng Zhang, Jinhui Li, Lingwei Kong, Baoqiang Zhang, Fei Xing and Huageng Luo

Energies 2023, 16(5), 2362; https://doi.org/10.3390/en16052362 - 1 Mar 2023

Cited by 1 | Viewed by 1311

Abstract

Uncertainties are widely present in the design and simulation of aero-engine combustion systems. Common non-probabilistic convex models are only capable of processing independent or correlated uncertainty variables, while conventional precise probabilistic sensitivity analysis based on ideal conditions also fails due to the presence of uncertainties. Given the above-described problem, an imprecise p-box sensitivity analysis method is proposed in this study in accordance with a multi-dimensional parallelepiped model, comprising independent and correlated variables in a unified framework to effectively address complex hybrid uncertainty problems where the two variables co-exist. The concepts of the correlation angle and correlation coefficient of any two parameters are defined. A multi-dimensional parallelepiped model is built as the uncertainty domain based on the marginal intervals and correlation characteristics of all parameters. The correlated variables in the initial parameter space are converted into independent variables in the affine space by introducing an affine coordinate system. Significant and minor variables are filtered out through imprecise sensitivity analysis using pinching methods based on p-box characterization. The feasibility and accuracy of the method are verified based on the analysis of the numerical example and the outlet temperature distribution factor. As indicated by the results, the coupling between the variables can be significantly characterized using a multi-dimensional parallelepiped model, and a notable difference exists in the sensitivity ranking compared with considering only the independence of the variables, in which input parameters (e.g., inlet and outlet pressure, density, and reference flow rate) are highly sensitive to changes in the outlet temperature distribution factor. Furthermore, the structural parameters of the flame cylinder exert a secondary effect. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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16 pages, 5645 KiB

Open AccessArticle

Optimal Control of TBCC Engines in Mode Transition

by Zengming He, Junlong Zhang and Hongfei Sun

Energies 2023, 16(4), 1791; https://doi.org/10.3390/en16041791 - 11 Feb 2023

Cited by 1 | Viewed by 1772

Abstract

This paper mainly studies the optimal control problem of turbine-based combined cycle (TBCC) engines in the mode-transition stage. Based on the TBCC scheme proposed by Xiamen University, an aerothermodynamic model is established as a verification model for the validity of control laws. To reduce the complexity of control design, a control-oriented linear parameter-varying (LPV) model with Mach number as a scheduling variable is established under a given flight path. The design of mode-transition points and distribution of air-flow-rate among paths during the mode-transition process are transformed into linear quadratic (LQ) optimal control problems for an LPV system under the initial and terminal as well as process constraints. By optimizing the opening of the splitters of the inlet and the fuel flow in each channel, the optimal mode-transition points are found to achieve coordinated control and complete the high-precision thrust tracking during the mode-transition process. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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14 pages, 5363 KiB

Open AccessArticle

Flow and Combustion Characteristics of Wave Rotor–Trapped Vortex Combustor System

by Yiqin Kang, Chenlu Wang, Gangyi Fang, Fei Xing and Shining Chan

Energies 2023, 16(1), 326; https://doi.org/10.3390/en16010326 - 28 Dec 2022

Viewed by 1265

Abstract

Breaking through the limit of conventional compression and combustion, wave rotor and trapped vortex combustors are able to improve the thermal efficiency of gas turbines. Detailed two-dimensional numerical simulations based on Ansys Fluent were performed to study the flow and combustion characteristics of the wave rotor–trapped vortex combustor system. The calculated pressure characteristics agree with the experimental results giving a relative error for average pressure of 0.189% at Port 2 and of 0.672% at Port 4. The flow stratification characteristics and the periodic fluctuations were found to benefit the zonal organized combustion in the trapped vortex combustor. For the six cases of different rotor speeds, as the rotor speed increased, the oxygen mass fraction at the combustor inlet rose and then fell. The proportion of exhaust gas recirculation fell at first and then rose, and the combustion mode became unstable with the dominant frequencies of the fluctuations increasing. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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20 pages, 8152 KiB

Open AccessArticle

Effect of Stagger Angle of Rotor Channels on the Wave Rotor

by Shining Chan, Yeyu Chen, Fei Xing and Huoxing Liu

Energies 2022, 15(24), 9455; https://doi.org/10.3390/en15249455 - 13 Dec 2022

Viewed by 1369

Abstract

A wave rotor optimizes the use of energy resources by enhancing thermodynamic cycles, and further optimization of wave rotor geometry is emerging as an attractive research area. Among the geometric features, the stagger angle of channels lacks sufficient study in spite of its important effects. To address this question, this work developed and applied the velocity triangle models to modify the basic geometry of wave rotors for different stagger angles, and investigated the flow fields with two-dimensional numerical methods. Results showed that: (1) different stagger angles worked out similar unsteady pressure wave systems and kept nearly constant compression and expansion ratios of the wave rotor; (2) increased stagger angle made the inlet and outlet flows turn toward the axial direction, which was beneficial to compact and light-weighted integration of the wave rotor to a gas turbine; (3) increased stagger angle made the wave rotor consume more shaft power, but even the maximum shaft power was small. This work revealed a critical mechanism how the velocity variation across an unsteady pressure wave produced rim work in a staggered channel, and made a recommendation to comprehensive optimization of wave rotor geometry for better integration in a gas turbine and acceptable shaft power consumption. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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13 pages, 3832 KiB

Open AccessArticle

Thermocouple Effective Length under Sinusoidal Gas Temperature Condition

by Qinghuang Huang, Zhiwei Liu, Xingyou Li and Peiyong Wang

Energies 2022, 15(22), 8701; https://doi.org/10.3390/en15228701 - 19 Nov 2022

Viewed by 962

Abstract

When a thermocouple is used to measure gas temperature, the measured temperature is the thermocouple bead temperature, which is not equal to the gas temperature. The bead temperature results from its energy balance. Through the wire convection and conduction, the temperature of the bead is related to the gas temperature within a certain geometric range around it, and this range is quantified by the effective length. Under the sinusoidal incoming gas temperature condition, the analytical expression for the effective length is deduced, and its accuracy is validated by the one-dimensional numerical solution. The differences between the analytical and numerical effective lengths are less than 10.5% for the test cases. Similar to that under the uniform incoming gas temperature condition, the effective length under the sinusoidal gas temperature condition increases with the thermal conductivity and the diameter of the wire and decreases with the heat transfer coefficient of the wire. The influence of the amplitude, wavelength and phase of the gas temperature on the effective length are very weak, meaning that the theoretical expression under the uniform gas temperature can calculate the effective length under the non-uniform gas temperature with good accuracy. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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22 pages, 393 KiB

Open AccessArticle

Stability of the Steady States in Multidimensional Reaction Diffusion Systems Arising in Combustion Theory

by Qingxia Li and Xinyao Yang

Energies 2022, 15(21), 8010; https://doi.org/10.3390/en15218010 - 28 Oct 2022

Cited by 1 | Viewed by 922

Abstract

We prove that the steady states of a class of multidimensional reaction–diffusion systems are asymptotically stable at the intersection of unweighted space and exponentially weighted Sobolev spaces, paying particular attention to a special case, namely, systems of equations that arise in combustion theory. The steady-state solutions considered here are the end states of the planar fronts associated with these systems. The present work can be seen as a complement to the previous results on the stability of multidimensional planar fronts. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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15 pages, 7058 KiB

Open AccessArticle

Numerical Demonstration of Unsupervised-Learning-Based Noise Reduction in Two-Dimensional Rayleigh Imaging

by Minnan Cai, Hua Jin, Beichen Lin, Wenjiang Xu and Yancheng You

Energies 2022, 15(15), 5747; https://doi.org/10.3390/en15155747 - 8 Aug 2022

Viewed by 1403

Abstract

The conventional denoising method in Rayleigh imaging in a general sense requires an additional hardware investment and the use of the underlying physics. This work demonstrates an alternative image denoising reconstruction model based on unsupervised learning that aims to remove Mie scattering and shot noise interference from two-dimensional (2D) Rayleigh images. The model has two generators and two discriminators whose parameters can be trained with either feature-paired or feature-unpaired data independently. The proposed network was extensively evaluated with a qualitative examination and quantitative metrics, such as PSNR, ER, and SSIM. The results demonstrate that the feature-paired training network exhibits a better performance compared with several other networks reported in the literature. Moreover, when the flame features are not paired, the feature-unpaired training network still yields a good agreement with ground truth data. Specific indicators of the quantitative evaluation show a promising denoising ability with a peak signal-to-noise ratio of ~37 dB, an overall reconstruction error of ~1%, and a structure similarity index of ~0.985. Additionally, the pre-trained unsupervised model based on unpaired training can be generalized to denoise Rayleigh images with extra noise or a different Reynolds number without updating the model parameters. Full article

(This article belongs to the Special Issue Recent Advances in Thermofluids, Combustion and Energy Systems)

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