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![Frequency spectrum of the heat of reaction of the hydrogen flame and the heat fluxes of the heating bands. a Time-frequency analysis of the heat of reaction of the flame and b the heat fluxes of the heating bands, as the hydrogen mass flow rate is set to ṁH2=1.0×10-5kgs-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot m_{{\mathrm{H}}_2} = 1.0 \times 10^{ - 5}\,{\mathrm{{kg}}}\,{\mathrm{s}}^{ - 1}$$\end{document}, and the surface temperature of the heating bands is suddenly increased from 300 to 1300 K at t = 2.0. Mathematically, TH = 300 at t ≤ 2.0 and TH = 1300 K at 2 < t ≤ 4.0 s](publication/332879596/figure/fig6/AS:959992970637332@1605891568385/Frequency-spectrum-of-the-heat-of-reaction-of-the-hydrogen-flame-and-the-heat-fluxes-of.png)
Frequency spectrum of the heat of reaction of the hydrogen flame and the heat fluxes of the heating bands. a Time-frequency analysis of the heat of reaction of the flame and b the heat fluxes of the heating bands, as the hydrogen mass flow rate is set to ṁH2=1.0×10-5kgs-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot m_{{\mathrm{H}}_2} = 1.0 \times 10^{ - 5}\,{\mathrm{{kg}}}\,{\mathrm{s}}^{ - 1}$$\end{document}, and the surface temperature of the heating bands is suddenly increased from 300 to 1300 K at t = 2.0. Mathematically, TH = 300 at t ≤ 2.0 and TH = 1300 K at 2 < t ≤ 4.0 s
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Unlike hydrocarbon fuel, hydrogen is 'green' and attracting more and more attentions in energy and propulsion sectors due to the zero emission of CO and CO 2. By applying numerical simulations, we explore the physics of how a hydrogen-burnt flame can sustain pulsating combustion and its impact on the thermodynamic properties of a standing-wave comb...
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Citations
... Mu et al. 15 investigated the near-field and far-field noise pressure levels and directivity of the two nozzles using the Lighthill equation excited by a quadrupole under fluid input. Zhao et al. 16 studied the dynamic flame-acoustics-heater interaction by numerical simulation. ...
The impedance matching is essential in producing high-intensity acoustic waves. This paper studies the impedance calculation methods of modulators and double-chamber Helmholtz resonators based on fluid mechanics, aeroacoustics, and electro-acoustic analogy principles. The results: ① The impedance expression of the resonators is derived. ② The impedance variation law of the chamber volume, the stator size, the air supply pressure, the air supply flow, and the working frequency is calculated. ③ The impedance-matching design scheme of the two-chamber Helmholtz low frequency and high acoustic intensity generator is given. Based on the experimental results of the high acoustic intensity generating device that the author has manufactured in the closed space, the correctness of the impedance calculation and matching design scheme in this paper is verified. This method has guiding significance for the design of high-intensity acoustic generating devices in confined space.
... Electrochemical storage of renewable energy has many advantages, such as rapid, cost-effective, and easy accessibility. "Hydrogen energy" privileges have been developed for portable power devices and stationary fuel cells, including the highest energy density, light weight, and environmental cleanliness [9][10][11][12][13]. Despite this, inadequate infrastructure can limit the concept of "hydrogen economics". ...
... Recently, as the Micro-Electro-Mechanical System (MEMS) is widely used in parts manufacturing, information, automotive industry, biomedical engineering, aerospace, military and other fields [1][2][3], high technology requirements such as lightweight, miniaturization and sustainability are proposed for the power supply mode of MEMS [4][5][6][7]. The hydrocarbon-combustion-based micro power system has the advantages of small size, light weight, high energy density, convenient inflation and low-carbon clean combustion [8][9][10], which is an important breakthrough to solve the above energy supply technology of MEMS. ...
... In summary, a general understanding of the phenomenon of shock diffraction in quiescent flow has been built, but the research mainly focuses on the phenomenon with single-side shock diffraction without crossflow. However, it is more observable in aerospace applications that shocks interact with supersonic crossflow, for example, pulse jets in shock wave/boundary layer interaction, 2,4 combustion, [15][16][17][18] or unstarted shock expelled out of the inlet. [19][20][21] Nevertheless, the research on the shock diffraction-dominated flow could be more extensive. ...
Shock diffraction is a widespread phenomenon in aerospace applications, such as shock tunnel nozzle and jet exciter exit, impacting their performance significantly. This paper focuses on the transient evolution of double-sided shock diffraction in both quiescent and supersonic crossflows by unsteady numerical simulations. The characteristics of the shock wave and the vortex are revealed. In the quiescent flow, the double-sided shock diffraction exhibits remarkable symmetry. The diffracted shock retains a self-similar nature, but its intensity distribution displays non-uniform characteristics, which gradually weakens from the center to both sides. The vortices on both sides also exhibit symmetrical behavior, with their trajectory behaving in linear tendency. When the supersonic crossflow interacts with the diffracted shock, an upward-moving separation shock and an asymmetric diffracted shock are generated. The vortices remain confined beneath the boundary layer and exhibit different shapes. Moreover, due to the rapid motion of the separation shock, the relative Mach number is introduced into the free-interaction theory (FIT) to predict the shock angle of the separation shock. The F(x¯) values corresponding to the separation point and pressure plateau are determined to be 3.04 and 4.68, respectively. The results evaluated by modified FIT show a good agreement with the values of simulation and experiment.
... The production of ammonia (NH 3 ), as well as hydrogen storage, is the main industrial use for hydrogen. [2, 9,32] As an energy storage material, hydrogen is a substance of the hydrogen economy, which substitutes fossil fuel in several combustion engines. [33] It was mentioned that hydrogen offers a way to store electricity through chemical hydrogen bonds. ...
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... In Fig. 9, it can be seen that both NH3 and CH4 are getting consumed inside the combustor, and no traces of unburnt fuel is observed at the exit of the combustor in all the cases. The location of the flame is strongly correlated with the OH radicals concentration [63]. A large amount of OH radicals is observed at the exit of the dumb combustor since the flame is stabilized in the downstream zone of the combustor. ...
Ammonia is now being explored as a potential gas turbine fuel because of its renewable and carbon-free nature.
Ammonia combustion possesses various limitations, such as high NO emissions, low burning velocity, and high
auto-ignition temperature. Moreover, dual-fuel combustion approaches can be used to mitigate these drawbacks.
However, the limitations of available information about the resulting emissions are insufficient to encourage
widespread adoption. In this work, an NH
3
/CH
4
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combustion chamber to preheat the incoming air, while two perforated discs are mounted between the combustor and annular zone for uniform distribution of air. Eight Zirconia foams (4 of 10 PPI and 4 of 20 PPI) are
stacked at the upstream side of the combustor. Experimentally, air preheat temperature, combustor exit temperature, NO, and CO emissions are analyzed and measured for various ammonia addition (0–41 % by weight) percentages, equivalence ratio of 1.0, and heat inputs of 17 & 21 kW for 10 PPI and a combination of 10 and 20 PPI
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porous cases. The chemical kinetic analysis shows that the HNO and HCO radicals act as the main intermediate
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... 12 Extensive research [16][17][18] has been conducted to optimize the design and the acoustic noise damping performance of such resonators at a low frequency range, typically below 800 Hz. 3,12,18 It is possible that a Helmholtz resonator [35][36][37] is mechanically coupled with a flexible membrane additionally, which can be used as a coupling sidewall/element to improve the transmission loss 38,39 and stabilize combustion systems. 40,41 Previous experimental and numerical studies [42][43][44][45] have shown that Helmholtz resonators could be applicable for sound absorption [46][47][48][49] over large bandwidths provided multiple resonators that tuned in different frequencies; [50][51][52][53][54][55] Helmholtz resonator allows narrow frequency bandwidth with high transmission loss. [56][57][58][59][60][61][62] Besides, estimated transmission loss [63][64][65][66] can be improved by inserting acoustic porous materials. ...
Helmholtz resonators are widely applied in industries to reduce the transmission of unwanted noise and passively attenuate tonal noise in pipes/ducts. For example, internal combustion engines take advantage of Helmholtz resonators by combining air box, subwoofers and perforated pipes/plates to reduce engine noise emission nowadays. However, the main drawback of the conventional Helmholtz resonators includes a very narrow bandwidth. To broaden the effective noise damping frequency range of Helmholtz resonators, a number of different improved designs are reported and tested recently in the literature such as applying an array of separated resonators or implementing mechanical-coupled Helmholtz resonators. In this work, we conduct a brief review on the aeroacoustics damping performance of coupled Helmholtz resonators over low frequency range. The noise damping performances could be characterized and quantified in terms of transmission loss and sound absorption coefficient. Both definitions are discussed. Comparison is then made between the separately working resonators and the mechanical-coupled ones. This is achieved by replacing the sharable flexible sidewall with a rigid sidewall. The effect of the mean grazing flow is also discussed and examined on the noise damping performances. An experimental case study of the present authors is included. Additionally, to improve the noise damping performance further, an overview of the resonators neck with different noise damping materials inserted is conducted. Finally, 3D numerical approaches in simulating the aeroacoustics damping performances of coupled Helmholtz resonators are reviewed. This case study and brief overview provides a guidance on improving the design of coupled Helmholtz resonators and an array of Helmholtz resonators.
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... In order to reduce the NO x emission, many scholars have carried out many researches [213]. Atmanli [214] experimentally evaluated the performance and emission characteristics of engine fueled with n-pentanol/diesel/hazelnut oil blended fuel (PDH) and n-butanol/diesel/ hazelnut oil blends (BDH). ...
The application of oxygenated alternative fuels in diesel engines is an effective way to solve the energy crisis and environmental pollution. Higher alcohols (butanol and pentanol), as oxygenated and renewable fuels, are considered as new promising alternative fuels for diesel engine due to their good physicochemical properties and excellent combustion and emission characteristics in engines. The combustion is a complex process and has a significant impact on performance and emission characteristics of compression ignition (CI) engines. There are complicated relationships among CI engine, environment and fuel physicochemical properties, which interacts with each other. Therefore, it is important to investigate the synergistic effects of alternative fuels and their additives on CI engines. In recent years, the research on the advanced alcohols and its additives had made great progress. However, few people have reviewed the synergistic effect of higher alcohols and its additives on diesel engines. Therefore, this paper takes the combustion, performance and emission aspects of higher alcohols and its additives on the diesel engine as a starting point. Firstly, the physicochemical properties and preparations of higher alcohols are described, and their advantages are highlighted. Then, the effects of higher alcohols and its additives on the combustion, performance and emission characteristics of CI engines are summarized in terms of neat fuel, dual-fuel injection and multi-fuel blends, exhaust gas recirculation (EGR), injection strategy and advanced combustion mode. Finally, some important conclusions and discussions on the future development and experimental research direction are put forward, which will be helpful for the research on the use of higher alcohol in CI engines.
... Research on new energy to maintain the sustainable development of the environment has become a necessary research direction in all countries (Włodarczyk et al. 2021). Many new energy sources are worthy of research and promotion (Zhao et al. 2019a), such as solar, ocean, wind, and biomass, which are clean and less harmful to the environment (Vujanović et al. 2021). The rapid development of new energy significantly impacts the automobile industry. ...
As countries around the world pay more attention to environmental protection, the corresponding emission regulations have become more stringent. Exhaust pollutants cause great harm to the environment and people, and diesel engines are one of the most important sources of pollution. Diesel particulate filter (DPF) technology has proven to be the most effective way to control and treat soot. In this paper, we review the latest research progress on DPF regeneration and ash. Passive regeneration, active regeneration, non-thermal plasma-assisted DPF regeneration and regeneration mechanism, DPF regeneration control assisted by engine management, and uncontrolled DPF regeneration and its control strategy are mainly introduced. In addition, the source, composition, and deposition of ash are described in detail, as well as the effect of ash on the DPF pressure drop and catalytic performance. Finally, the issues that need to be further addressed in DPF regeneration research are presented, along with challenges and future work in ash research. Over all, composite regeneration is still the mainstream regeneration method. The formation of ash is complex and there are still many unanswered questions that require further in-depth research.
