Search

Hydrocracking catalysis is a controllable route to plastic waste upgrading. However, the mismatched acid site-driven C-C cleavage and C=C hydrogenation process on metal restrict the efficiency and selectivity in conventional metal/acid bi-functional catalyst. Herein, we introduce Al deficiency in Si-O(H)-Al structural units of Pt/zeolite socony mobil-5 (Pt/ZSM-5) through discharge driven reduction (DR) process to precisely control the ratio of metal to acid, achieving hydrocracking of low-density polyethylene (LDPE) waste at 270 °C with 87.7% conversion and liquid fuel (C5-C21) selectivity of 77.8%. Pair distribution function (PDF) and nuclear magnetic resonance (NMR) spectroscopy demonstrate the partial absent Al sites further resulting short-range local disorder Si-O(H)-Al. Upon pyridine infrared spectroscopy (Py-IR) and CO diffuse reflectance Fourier-transform infrared (CO DRIFT) analysis, the extraction of Al modulates Brønsted acid density of Pt/ZSM-5 with DR process (Pt/Z5DR), improves the interaction between Pt and ZSM-5 support, enhances the cationic of Pt. The metal-acid balance and electron-deficient Pt favor the matching speed of light olefins hydrogenation and the cracking of macromolecule intermediates. Moreover, density functional theory (DFT) calculations identify the thermodynamic stability of Pt/Z5DR and moderate adsorption capability towards light olefins. This work confirms the great potential of precisely controlled molar of metal to acid in metal/zeolite catalysts for LDPE upcycling, providing a viable path for dealing with PE plastic wastes. [ABSTRACT FROM AUTHOR]

A-site Sr or Ca substituted perovskite LaCr 0.7 Ni 0.3 O 3 (LSCN, LCCN) are prepared in this work as catalysts of simulated diesel fuel (N-hexadecane) steam reforming for the on-board hydrogen supplement of solid oxide fuel cells (SOFCs). The effect of different dopants on active metals dispersion and surface properties on catalyst performance is analyzed. The results of the investigation reveal that LCCN possesses the highest catalytic activity coupled with exceptional stability, achieving full fuel conversion at WHSV = 5 mL/g·h, S/C = 3.0, and 750 °C and keeping stable for 200 h, thereby emerging as a potential candidate for liquid fuel processing. SEM, H 2 -pulse chemisorption and XPS results confirm that the excellent performance is due to the high metal dispersion and steam activation capacity. The poor catalytic performance observed in LSCN is primarily attributed to the presence of Sr segregation and the formation of the SrCrO 4 second phase. Sr segregation decreases the steam activation ability of the catalyst as confirmed by XPS. DFT calculation also shows that Sr dopant and Sr segregation decrease the exsolution trend of metal Ni in the perovskite matrix, leading to poor metal dispersion. A simulated reforming gas is used in SOFC and the cell can keep stable for 120 h at a discharging current density of 0.4 A/cm2. This study analyzes the difference between Ca and Sr dopants, and reveals the detrimental effect of Sr segregation, which could enlighten the effect of surface tunning on the performance of perovskite catalysts. [ABSTRACT FROM AUTHOR]

It has been known that plastics with undegradability and long half‐times have caused serious environmental and ecological issues. Considering the devastating effects, the development of efficient plastic upcycling technologies with low energy consumption is absolutely imperative. Catalytic hydrogenolysis of single‐use polyethylene over Ru‐based catalysts to produce high‐quality liquid fuel has been one of the current top priority strategies, but it is restricted by some tough challenges, such as the tendency towards methanation resulting from terminal C−C cleavage. Herein, we introduced Ru nanoparticles supported on hollow ZSM‐5 zeolite (Ru/H‐ZSM‐5) for hydrocracking of high‐density polyethylene (HDPE) under mild reaction conditions. The implication of experimental results is that the 1Ru/H‐ZSM‐5 (~1 wt % Ru) acted as an effective and reusable bifunctional catalyst providing higher conversion rate (82.53 %) and liquid fuel (C5−C21) yield (62.87 %). Detailed characterization demonstrated that the optimal performance in hydrocracking of PE could be attributed to the moderate acidity and appropriate positively charged Ru species resulting from the metal‐zeolite interaction. This work proposes a promising catalyst for plastic upcycling and reveals its structure‐performance relationship, which has guiding significance for catalyst design to improve the yield of high‐value liquid fuels. [ABSTRACT FROM AUTHOR]

The utilization of liquid fuel will greatly expand the application scope of rotating detonation engines, and there are still great challenges to achieve high-performance liquid-fuel rotating detonation operation. In this paper, aviation kerosene was used as the liquid fuel to investigate the effects of fuel temperature on the propagation characteristics of rotating detonation waves in two combustor structures: annular and cavity. An electric heating tape was employed to heat the kerosene up to 390 K. The results demonstrate that increasing the temperature of kerosene enhances its atomization efficiency, leading to a marked enhancement in the peak pressure and propagation stability of detonation waves. Moreover, the duration required to establish a detonation wave is notably reduced, as low as 11.2 ms. Furthermore, the detonation wave velocity increases with fuel temperature, with significantly higher velocities observed in the cavity combustor structure compared to the annular combustor structure. In the cavity combustor, the detonation wave velocity can reach up to 74 % of the theoretical CJ value. The results verify the feasibility of improving the rotating-detonation performance via increasing liquid-fuel temperature, which can provide reference for the engineering application of rotating detonation. • Experiments and numerical simulations on liquid fuel RDW were well conducted. • Atomization characteristics of liquid fuel under two combustors were analyzed. • RDW propagation characteristics with changing liquid temperature were obtained. [ABSTRACT FROM AUTHOR]

Direct CO2 conversion to liquid hydrocarbons (HCs) in a single process was achieved using cobalt (Co) catalysts supported on lanthanum ion (La3+)‐doped cerium oxide (CeO2) under a gas stream of H2/CO2/N2=3/1/1. The yield of liquid HCs was the highest for 30 mol% of La3+‐doped CeO2, which was because extrinsic oxygen vacancy formed by doping La3+ could act as an effective reaction site for reverse water gas shift reaction. However, the excess La3+ addition afforded surface covering lanthanum carbonates, resulting in depression of the catalytic performance. On the other hand, bare CeO2 lead to an increase in the selectivity of undesirable methane, which arose from reduction of CO2 to CO proceeding by intrinsic oxygen vacancy generated by only Ce3+, and weaker CO2 capture ability of intrinsic oxygen vacancy than extrinsic one, resulting in the proceeding of Sabatier reaction on Co catalyst. The rational design of reaction sites presented in this study will contribute to sustainability. [ABSTRACT FROM AUTHOR]

Recent studies have increasingly focused on integrating detonation processes into engine technologies, advancing beyond the fundamental research phase of detonation research. The present study investigates the detonability and combustion characteristics of liquid fuels, specifically ethanol, with an emphasis on the effects of atomization properties facilitated by different atomizer designs to implement pulse detonation combustion engines. Oxygen was used as the oxidizer. We employed internal injectors (I45, I90, IB4) and atomizer venturis (VA, VB, VR) to examine how variations in liquid fuel atomization and atomizer configurations influence detonation. The occurrence of detonation was assessed using predicted Sauter mean diameters (SMDs) and exit velocities for different atomizer setups. Additionally, we evaluated the effects of nitrogen dilution at concentrations of 0%, 25%, and 50% on velocity variations and changes in detonation characteristics. The findings suggest that while higher exit velocities decrease SMD, facilitating detonation, excessively high velocities hinder detonation initiation. Conversely, lower exit velocities emphasize the role of SMD in initiating detonation. However, the introduction of nitrogen, which reduces the SMD, was found to decrease reactivity and impede detonation. [ABSTRACT FROM AUTHOR]

Maximizing the development of renewable energy plays a critical role in mitigating the climate crisis. Marginal land provides space for the development of biomass energy; however, it remains unclear how the amount and spatial distribution of marginal land that is suitable for energy crop development will change in the future. Here, we project energy marginal land changes in China following the shared socioeconomic pathway (SSP) and/or representative concentration path (RCP). We provide datasets of marginal land, agriculturally suitable land, and potentially suitable for energy crops under historical scenarios and six future scenarios (i.e. SSP1–1.9, SSP1–2.6, SSP4–3.4, SSP2–4.5, SSP4–6.0, and SSP3–7.0) for the period 2020–2100, with a spatial resolution of 5 km. Under the six scenarios, from 2020–2100, the area of suitable marginal land ranged from 1.90–16.28 (Jatropha curcas L.) to 37.37–73.97 (Panicum virgatum L.) (×104 km2), depending on the choice of energy crops and climate scenario. Based on the growing suitability of eight important bioenergy crops—Ricinus communis L., Saccharum officinarum L., Pistacia chinensis Bunge, Panicum virgatum L., Jatropha curcas L., Miscanthus giganteus J., Manihot esculenta Crantz, and Sorghum bicolor Moench—our dataset can be used to identify suitable locations for specific energy crops. This new synthetic dataset could support the development of multiscenario-based solutions related to carbon neutrality, ecosystem services, and energy transition.

For gas turbine combustors, injecting liquid fuel in crossflow can achieve superior mixing characteristics to improve performance and reduce emissions. Robust numerical design tools are needed to accelerate the development of low-emissions technologies. Atomization modeling is often facilitated by using the Lagrangian approach rather than the more complex and computationally expensive Volume-of-Fluid (VOF) approach. However, most Lagrangian breakup models rely on empirical constants that must be fully calibrated for jets in crossflow and representative conditions. A hybrid approach could deliver a better compromise between accuracy and computational cost. This study proposes and validates a novel numerical methodology for coupling the VOF and Lagrangian approaches using a stochastic breakup model with Adaptive Mesh Refinements for turbulent liquid fuel jets in crossflow under more representative gas turbine conditions. The predictions were validated in the near and far-field regions using datasets at high pressures (1-8 bar), Weber numbers (720-1172), and momentum flux ratios (6-33). The predictive capabilities and computational cost were also compared to the Lagrangian approach coupled with large eddy simulations (LES) and with the unsteady Reynolds-Averaged Navier-Stokes (RANS) methodology previously developed and validated by the authors. The effect of different VOF-Lagrangian transition criteria on the computational cost was also assessed and recommendations were provided for further improvements. The overall LES predictions were significantly improved by the proposed hybrid methodology. Although it tends to underpredict the spray trajectory and Sauter Mean Diameter compared to the URANS methodology, it better captures the diameter in the wake region and the droplet velocities. [ABSTRACT FROM AUTHOR]

This research presents an innovative approach to plastic waste management by converting it into alternative energy sources. The study focuses on transforming recyclable plastics like LDPE, HDPE, and PP into various types of oils through processes like pyrolysis, catalytic cracking, and hydrothermal liquefaction. Emphasizing the selection of high-quality, flammable plastics with low moisture content, the research highlights the importance of avoiding harmful substances to ensure health and environmental safety. The methodology includes the use of essential machinery for cleaning and processing plastics, such as reactor vessels and condensers. Results show that different plastics yield varying amounts of liquid fuel, with higher temperatures favouring the production of lighter oils. The conclusion underscores the potential of this technology to not only manage plastic waste sustainably but also to produce valuable fuels that can supplement or replace conventional diesel, thereby contributing to a circular economy. [ABSTRACT FROM AUTHOR]

Detonation engines are gaining prominence as next-generation propulsion systems that can significantly enhance the efficiency of existing engines. This study focuses on developing an injector utilizing liquid fuel and a gas oxidizer for application in detonation engines. In order to better understand the spray characteristics suitable for the pulse detonation engine (PDE) system, an injector was fabricated by varying the Venturi nozzle exit diameter ratio and the geometric features of the fuel injection hole. Analysis of high-speed camera images revealed that the Venturi nozzle exit diameter ratio plays a crucial role in determining the characteristics of air-assist or air-blast atomization. Under the conditions of an exit diameter ratio of Re/Ri = 1.0, the formation of a liquid film at the exit was observed, and it was identified that the film's length is influenced by the geometric characteristics of the fuel injection hole. The effect of the fuel injection hole and Venturi nozzle exit diameter ratio on SMD was analyzed by using droplet diameter measurement. The derived empirical correlation indicates that the atomization mechanism varies depending on the Venturi nozzle exit diameter ratio, and it also affects the distribution of SMD. The characteristics of the proposed injector, its influence on SMD, and its velocity, provide essential groundwork and data for the design of detonation engines employing liquid fuel. [ABSTRACT FROM AUTHOR]

Unlike the explosion limit of liquid fuel vapour, the explosion limit of aerosol is a function of the aerosol state. In this study, a prediction model of the lower explosion limit (LEL) of liquid fuel aerosol was established through theoretical analysis, and typical liquid fuels of n-heptane and n-hexane were used to observe the aerosol state and the lower explosion concentration limits in the experiments to verify the reliability of the established model for predicting the LEL of aerosol. The predicted LELs of the two n-heptane aerosols (D32 = 12.16 µm) and (D32 = 21.23 µm) are 3.59 and 3.62 times of that of n-heptane vapour, respectively. The relative errors for the predictive results are 5.4% and 8.8%, respectively, compared with the experimental results. The predicted LEL of n-hexane aerosol (D32 = 18.51 µm) is 3.5 times that of n-hexane vapour, and the relative error is 3.99% compared with the experimental results. [ABSTRACT FROM AUTHOR]

According to national statistical data, the total amount of straw in China is about 1 billion tons per year. However, traditional straw treatment methods have many limitations, such as the easy generation of greenhouse gases such as carbon dioxide and methane. Therefore, the utilization of straw resources has become a popular way to solve this problem. In this context, this paper conducts in-depth research on the resource utilization of straw and summarizes the new approaches and industrial applications that are currently applicable to China and can improve the added value of straw. Practice has proven that straw has broad application prospects in bio based materials, liquid fuels, wood fiber materials, and other fields. Therefore, it is necessary to vigorously develop straw comprehensive utilization technology and strive to promote the widespread application of high-value industries such as bio based materials, liquid fuels, and hydrogen, so as to fully tap their potential and inject new impetus into the efficient and sustainable development of China's energy sector, thereby improving China's economic benefits. [ABSTRACT FROM AUTHOR]

A series of fire tests were performed to study the effect of infiltration depth on the burning behavior and fuel residue of porous media bed soaked by liquid fuel. Ethanol was used as liquid fuel and quartz sand was used to naturally stack to form the porous media bed with different infiltration depths within the range of 60–180 mm. Burning rate, internal temperature of porous media bed, flame height, movement speed of fuel vapor zone, and fuel residue percentage was measured and analyzed. Results show that within current test scope, fuel mass loss rate in quasi stable period is negatively correlated with infiltration depth, and the relationship between mass loss rate and infiltration depth can be well characterized by power function. Quasi stable flame height also decreases gradually with the increase of infiltration depth. With the range of 78.5–79.2°C, the temperature growth retardation occurred inside sand bed, and sand bed was hence assessed as a distinct three-zone feature. The movement speed of vapor zone decreases linearly with the increase of infiltration depth, and the maximum measured value is about 0.041 mm/s. Axial temperature distribution of flame and plume can be well characterized based on McCaffery's plume relationship, but the length of continuous flame and intermittent flame zone is shortened to some extent. Within current test range, fuel residue percentage increases with the increase of infiltration depth and particle size, and maximum fuel residual percentage is at 5.29% in the case with 180 mm infiltration depth, which is obviously smaller than previous scholars' results. In addition to the depth of infiltration, the boiling point and viscosity of liquid fuel and the effective thermal conductivity of sand bed are also important influencing factors. [ABSTRACT FROM AUTHOR]

A CFD study is performed to check the integrated flow behaviour of the Liquid Fuel Ramjet Propulsion system by including air intakes, combustor and nozzle. Resolving both supersonic and subsonic flow scales in the same domain makes the simulations complex. Addition of combustion with stiff chemistry makes the simulations more difficult. Analyses are carried out using commercially available CFD software. Liquid fuel is injected as discrete phase and the flow turbulence is modelled using Realizable k-e turbulence model. Jet-A + air combustion has been simulated using combined finite rate/eddy dissipation model. Finite rate chemistry was modelled using three step chemistry which was obtained from the published literature. Flow structures such as oblique shocks, normal shocks and combustion are captured in the analyses. Normal shock with respect to the pressure obtained because of the pressure raise due to combustion is observed. Also, obtained CFD results are compared with that the experimental values that are conducted in connect pipe mode, for the same operating point, and a good agreement between the two are observed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ballistics / Dandao Xuebao is the property of Journal of Ballistics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The molecular species composition of major toxic species, such as soot, CO and unburnt hydrocarbons from a boundary layer diffusion flame over heptane or dodecane surface at microgravity is numerically investigated. A two-step global reaction model for gas-phase chemistry and a simplified soot model consisting of laminar smoke point type for soot inception are used. Thermal radiation is calculated using the discrete-ordinates method coupled with a non-grey model for the radiative properties of CO, CO2, H2O and soot. The numerical results provide further insights into the intimate coupling between burning rate, flame length, thermal radiation, and toxic products at reduced gravity level. The importance of oxidizer flow speed to the flame structure, soot formation and thermal radiation at microgravity is demonstrated. The amount of soot from the microgravity heptane/dodecane flames augments with an increase of oxidizer flow velocity from 0.1 to 0.3 m/s due to an enhancement of burning rate. This finding is contrasted to the case with porous gas burners relative to toxic species production from microgravity flames. For the burning of various liquid fuels, the radiative loss fraction in general increase in a range of 0.5 to 0.7 due to enhanced soot formation with augmentation of the oxidizer flow velocity.

BackgroundThe conversion of UF6, which is a primary nuclear product, to UF4 in fluoride molten salt phase is expected to be used in the preparation or reconstitution of nuclear fuel salt for molten salt reactors, thus simplifying the process of molten salt reactor fuel production. Determination of the concentration of the key intermediate UF3 plays an important role in obtaining the reaction parameters.PurposeThis study aims to establish a method for measuring UF3 concentration in solid fluoride molten salts.MethodsThe X-ray diffraction (XRD) was employed to test the homemade standards and obtain the internal standard curve of UF3. Firstly, the α-Al2O3 was taken as the internal standard to obtain the XRD peak height internal standard curve (R=0.986) and peak area internal standard curve of LiF-BeF2-UF3 molten salt. Then, these two internal standard curves were applied to measuring the known content of LiUF5 and UF3 solid mixed samples to compare their accuracies. Finally, measurements were conducted on rapidly cooled LiF-BeF2-UF3 solid molten salt samples and naturally cooled LiF-BeF2-UF3-LiUF5 solid molten salt samples to evaluate the stability and accuracy of the curve, and the relative error was obtained.ResultsIn the UF3 concentration range of 1.00~10.00 wt%, the correlation coefficient of the internal standard curve based on the peak area determined for of LiF-BeF2-UF3 molten salt is 0.995. Measuring results of solid mixed samples of LiUF5 and UF3 with known concentrations indicate that the peak area internal standard curve achieves better accuracy with a relative measurement error of no more than 8.7%. In addition, the results of the same content samples with different cooling methods confirm the good stability and accuracy of the proposed method with less than 5.4% relative standard deviation.ConclusionsThe established method can be used for the quantitative analysis of solid LiF-BeF2-UF3 and LiF-BeF2-UF3-LiUF5 molten salts with good measurement accuracy and repeatability.

Recent studies have increasingly focused on integrating detonation processes into engine technologies, advancing beyond the fundamental research phase of detonation research. The present study investigates the detonability and combustion characteristics of liquid fuels, specifically ethanol, with an emphasis on the effects of atomization properties facilitated by different atomizer designs to implement pulse detonation combustion engines. Oxygen was used as the oxidizer. We employed internal injectors (I45, I90, IB4) and atomizer venturis (VA, VB, VR) to examine how variations in liquid fuel atomization and atomizer configurations influence detonation. The occurrence of detonation was assessed using predicted Sauter mean diameters (SMDs) and exit velocities for different atomizer setups. Additionally, we evaluated the effects of nitrogen dilution at concentrations of 0%, 25%, and 50% on velocity variations and changes in detonation characteristics. The findings suggest that while higher exit velocities decrease SMD, facilitating detonation, excessively high velocities hinder detonation initiation. Conversely, lower exit velocities emphasize the role of SMD in initiating detonation. However, the introduction of nitrogen, which reduces the SMD, was found to decrease reactivity and impede detonation.

This study experimentally explored the effects of equivalence ratio settings on ethanol fuel combustion oscillations with a laboratory-scale combustor. A contrary flame equivalence ratio adjusting trend was selected to investigate the dynamic characteristics of an ethanol atomization burner. Research findings denote that optimizing the equivalence ratio settings can prevent the occurrence of combustion instability in ethanol burners. In the combustion chamber, the sound pressure amplitude increased from 138 Pa to 171 Pa and eventually dropped to 38 Pa, as the equivalence ratio increased from 0.45 to 0.90. However, the sound pressure amplitude increased from 35 Pa to 199 Pa and eventually dropped to 162 Pa, as the equivalence ratio decreased from 0.90 to 0.45. The oscillation frequency of the ethanol atomization burner presents a migration characteristic; this is mainly due to thermal effects associated with changes in the equivalence ratio that increase/decrease the speed of sound in burnt gases, leading to increased/decreased oscillation frequencies. The trend of the change in flame heat release rate is basically like that of sound pressure, but the time-series signal of the flame heat release rate is different from that of sound pressure. It can be concluded that the reversible change in equivalence ratio will bring significant changes to the amplitude of combustion oscillations. At the same time, the macroscopic morphology of the flame will also undergo significant changes. The flame front length decreased from 25 cm to 18 cm, and the flame frontal angle increased from 23 to 42 degrees when the equivalence ratio increased. A strange phenomenon has been observed, which is that there is also sound pressure fluctuation inside the atomized air pipeline, and it presents a special square waveform. This study explored the equivalence ratio adjusting trends on ethanol combustion instability, which will provide the theoretical basis for the design of ethanol atomization burners. [ABSTRACT FROM AUTHOR]

The porous medium combustion (PMC) is an emerging area in liquid fuel combustion, which has the ability to reduce emission and increase the fuel economy. Various operational parameters will affect the performance of liquid fuel-fired Porous Medium Burner (PMB). So, this present work focuses on finding the effect of operational parameters on the performance of PMB and to optimize it. This study was conducted in a double-layered porous burner with selfaspirated pressurized stove. Three input factors were selected, namely, fuel pressure (bar), throttle angle (°), and type of burner (Conventional burner (CB), PMB). The three output responses selected are thermal efficiency (ηth), CO (ppm), and NOX (ppm) emissions. The inscribed central composite design (ICCD) was used to design the experimental run. The response surface methodology (RSM) with desirability approach was used to optimize the multi-objective responses. The statistical analysis with ANOVA confirmed the significance of all the three input variables on the output responses. The regression model was developed with quadratic fit and it well predicts the burner performance and emission with R² value close to 1. The multi-objective optimum input settings are found by desirability approach, i.e. fuel pressure = 1.60 bar, throttle angle = 161.3°, and burner type = PMB. The corresponding optimized responses are found as ηth = 58.39%, CO = 201. 49 ppm, and NOX = 6.43 ppm. The above optimum settings and responses are confirmed with experimental confirmation test, which is in the satisfactory level. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamic quenching of fuel fluorescence by ketone dopants in liquid phase is investigated to suggest an optical method for two-phase flow visualization in a liquid-fueled combustor. The fuel fluorescence is triggered by high peak-power 266 nm laser pulses. It is found that ketones can serve as quenchers absorbing the fluorescence of a widely used liquid fuel, exo-THDCPD (exo-tetrahydrodicyclopentadiene). The impact of the dynamic quenching on the fuel fluorescence is validated under various ambient temperature conditions to simulate two-phase fuel flows in preheated ambient air. The signal intensity ratio with and without the dopants (quenching ratio) is below 0.4 % near 290 nm when the ketone concentration in the mixture is 5 %, while the quenching effect is insignificant in the spectral range above 325 nm. As a result, the proposed technique is successfully demonstrated in a model supersonic combustor, delineating vapor-dominant regions in the two-phase supersonic flows. [ABSTRACT FROM AUTHOR]

Optimization can streamline experimental trials by evaluating the parameters and parameter interactions used as the basis for a more optimal downstream process. This study aims to optimize the microwave-assisted pyrolysis process in producing bio-oil from microalgae using response surface methodology (RSM) complemented by an investigation of the reaction mechanisms. A number of key parameters (microwave power, absorbent-to-microalgae ratio, and pyrolysis time) were fine-tuned using a face-centered central composite design. The result showed that microwave technology in slow pyrolysis could produce the bio-oil from microalgae 12 times shorter than conventional heating and quadratic model with a high precision (R2 = 0.9832, R2adj = 0.9616) from RSM optimization in predicting experimental values yielded a peak bio-oil yield of 19.11% under specific conditions: 20 min of pyrolysis time, a 0.19 (w/w) microwave absorber to microalgae ratio, and 583 W power. As the complex biomass, the reaction mechanism in chlorella sp. towards this technology including decarboxylation, decarbonylation, dehydration, cracking, deoxygenation, and esterification was proved in GCMS analysis, revealing the presence of key functional groups such as aliphatic, aromatics, alcohols, nitrogenous compounds, fatty acid methyl esters (FAME) and Polycyclic Aromatics Hydrocarbons (PAHs).

Plastics are one of the most widely used materials, and, in most cases, they are designed to have long life spans. Since plastic and packaging waste pollute the environment for many years, their disposal is of great importance for the environment and human health. In this paper, a system was developed to store liquid fuel from plastic and organic waste mixes without solidification, which then can be used as fuel in motor vehicles and construction machinery. For this purpose, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and organic wastes and clay, zeolite, and MCS23-code materials (50% magnetite- %25 calcium oxide- %25 sodium chloride) were heated in a closed medium at temperatures ranging from 300 to400 oC and subsequently re-condensed. The study conducted twenty tests, involving various types and rates of plastic and organic materials, as well as different rates of catalysts. Among these tests, the highest liquid fuel yield (67.47%) was achieved in Test 9, where 50% PVC-50% PET waste, 75 g of clinoptilolite, and 500 g of MCS23 waste were collectively used. Notably, Test 12 exhibited the highest density value (79.8 kg/m3), while the best viscosity value (2.794 mm2/s) was observed in Test 2. Across all samples, flash point values were found to be below 40oC. The most favorable yield point value was recorded in Test 2 (-6oC). The samples displayed ash content within the range of 0 to0.01% (m/m)] and combustion heat values of 35.000> J/g which fall within the standard range. The incorporation of MCS23 with clinoptilolite additives is believed to have a significant impact on obtaining high-yield products with improved fuel properties.

The objective of this work is to assess the accuracy and limitations of two different semi-empirical soot models: the Laminar Smoke Point (LSP) and soot-yield approach. A global soot formation model based on the LSP concept is embedded within FDS6.7. Quantitative comparisons were made from turbulent buoyant pool fires between several computational results and well-instrumented experimental databases on the soot volume fraction, mass loss rate, heat release rate and gas temperature. The LSP model in combination with soot oxidation and surface growth is validated for most of the methane, ethylene and heptane turbulent buoyant pool fires, covering a wide range of fuel likely to form soot. This paper aims to broaden the scope of the validation of the available semi-empirical soot modelling. For the porous methane and ethylene burner, the LSP model was found to provide a better description of the soot volume fraction. The overall visual soot distribution is also numerically reproduced with the soot-yield approach, but as expected, there are some differences between the prediction and the measurement regarding the magnitude of soot volume fraction. The computed radiant heat flux was compared with experimental data for heptane flame, showing that predictions using both the LSP and soot-yield models were found to be twice the value of experimental data, although the measured HRR (Heat Release Rate) is reliably reproduced in the numerical simulation. For the heptane buoyant pool fires, a sufficient accuracy of the numerical model is confirmed only in some of the locations as compared to the experimental results. It is demonstrated that neither the temperature nor the soot volume fraction can be reliably calculated in the necking flame flapping region when the pyrolysis rate of condensed fuel (heptane) is coupled with radiation/convection heat feedback. This implies that an accuracy of prediction on the turbulent buoyant pool fires depends on the studied fire scenario regardless of the semi-empirical soot models.

The synthesis of alternative fuels from biomass has emerged to be a vital strategy to maintain sustainable development. Long-chain levulinate esters (LEs) are a class of good biofuel candidates because they have similar structures to biodiesels and superior heating values. The synthesis of long-chain LEs with effective heterogeneous catalysts has always been challenging. In this work, a few heterogeneous phosphotungstate catalysts were facilely prepared, among which the V3+ exchanged phosphotungstic acid catalyst (VPW) was the most active for the alcoholysis of furfuryl alcohol (FA) and 1-hexanol into 1-hexyl levulinate (HL). A maximum HL yield of 63% was achieved at 180 °C. The VPW catalyst could be reused without obvious decrement of activity. The system was also applicable to the alcoholysis of FA with other hexanols and 1-octanol into various long-chain LEs.

Not only its abundant resources, but also low rank coal (LRC) can be transformed into different valuable chemical products via syngas. This review focuses on technology of microwave-assisted pyrolysis (MAP) applied on LRC as a promising technique of thermochemical conversion that can transform LRC into high quality syngas. A confined number of reviews has been selected and evaluated to observe current status and challenges of the technology, including essential production factors, pretreatment of LRC, and heating characteristics of MAP. Experimental research on catalytic and non-catalytic of the technology focusing on the product distribution resulting from conventional pyrolysis (CP) are also discussed. The best yields of char, tar, and syngas from CP at 900 °C were 2%, 41%, and 58%, respectively. Meanwhile, the best yields of char, oil and syngas from MAP at 620 °C were 32%, 15% and 53%, respectively. Finally, this review evaluates the advantages and challenges of the technology and the milestones to be achieved in near future.

Developing low-cost and high-activity catalysts is one of the keys to promoting the catalytic pyrolysis of waste plastics to fuels for plastic recycling. This work studied the effect of clay as the catalyst on mixed plastic pyrolysis for fuel and energy recovery. Four kinds of clay, including nanoclay, montmorillonite, kaolin, and hydrotalcite, were used as catalysts for the pyrolysis of mixed plastic consisted of polyethylene terephthalate, polystyrene, polypropylene, low-density polyethylene, and high-density polyethylene. The product yield and distribution varied with different clay in pyrolysis. The highest yield of oil was 71.0 % when using montmorillonite as the catalyst. While the highest contents of gasoline range hydrocarbons and diesel range hydrocarbons in the oil were achieved when using kaolin and nanoclay, respectively as catalysts. For the gas products, the CO, C2H4, C2H6, C3H6, and C4H10 increased with decreased CO2 in the gaseous products when using clay as catalysts. In general, the mild acidity of clay catalyst was essential to improve the oil yields and the proportion of the gasoline or diesel range fuels in the catalytic pyrolysis of mixed plastic waste.

As a traditional fossil fuel, petroleum fuel is prone to spill fires during storage, transportation, and use, which poses a significant threat to the secure utilization of energy. This research aims to investigate the effect of porous media on the combustion characteristics of spill fire. Quartz sand (diameter is 1.5 mm) is selected as a porous material, and continuous oil spill fire experiments under different oil discharge rates (25–100 mL·min−1) are carried out on both smooth substrate and porous bed. The spread process, burning rate, flame height and spread speed are measured and analyzed. The results show that no burning layer shrinkage occurs during the spread process. There is a significant increase in the stable burning length and in the time required to reach the quasi-steady burning phase. The burning rate of spill fire on a porous bed is negatively correlated with the thickness of the sand layer and positively correlated with the oil discharge rate, but it is still lower than the burning rate of pool fire under the same equivalent diameter. Transformer oil spill fire propagation speed is divided into three stages: acceleration-uniform-deceleration. When the oil discharge rate is 50 mL·min−1, the uniform propagation speed of flame is 0.55, 0.11 and 0.03 cm·s−1 respectively. Flame height is positively correlated with oil discharge rate and negatively correlated with sand thickness. Furthermore, a dimensionless coefficient, d*, is introduced to modify the flame height and burning rate models, and the correctness of the modified model is verified by experimental data. This study is informative for the safe use of liquid fuels. [ABSTRACT FROM AUTHOR]

To effectively address the challenges posed by global warming, a prompt and coordinated effort is necessary to conduct an extensive study aimed at reducing CO 2 emissions and overcoming the obstacles presented by expensive and scarce fossil fuel resources. This study primarily focuses on comparing two different methodologies for preparing Na-promoted Fe 3 O 4 -based catalysts for the CO 2 hydrogenation into hydrocarbon mixtures. Three catalysts were synthesized and tested: two samples were impregnated with a different amount of Na (1 wt% and 5 wt%), while a third one was obtained via coprecipitation with NaOH. As the latter catalyst exhibited the best performance, it was combined with zeolites in two ways: physical mixtures and core-shell structures. MFI-type zeolites were used in both configurations and a conventional structure was compared to a hierarchical one. As a result, mesopores increased successfully both the CO 2 conversion from 37% to 40% and the liquid hydrocarbon (C 6+) selectivity from 29% to 57%, doubling the C 6+ yield. On the other hand, NH 3 -TPD and XPS measurements demonstrated that the intimate contact between the two materials in the core-shell structures led to the migration of Na from the oxide to the zeolite reducing the concentration of strong acid sites and, consequently, the liquid hydrocarbon yield. [Display omitted] • Hydrocarbons production via modified Fischer-Tropsch has been investigated. • Hierarchical MFI-zeolite doubled the C 6+ liquid hydrocarbons yield. • The evolution of iron carbides formation was studied by in situ XRD. • XPS analysis coupled with the results of NH 3 -TPD confirm the hypothesis of Na migration. • Na migration was identified as a deactivating phenomenon in core-shell structures. [ABSTRACT FROM AUTHOR]

To explore the combustion characteristics of liquid fuel moderate and intense low-oxygen dilution (MILD) combustion, the MILD combustion process was investigated by numerical simulation, and the effects of air and fuel inlet conditions on flue gas reflux ratio, flow field and pollutant emission were analyzed in detail. The results show that the flow field structure in MILD combustion chamber plays a decisive role in fuel air mixing.With the increasing of equivalence ratio, the combustion chamber temperature is increased accordingly with increased CO emission, and the NOx emission is also increased. When the equivalence ratio is 0.9, the emission of NOx reaches a peak value. With the increasing of air inlet velocity, the temperature distribution on the central surface of the combustion chamber is uniform without obvious local high-temperature peak point, and the NOx emission is decreased, while the CO emission is decreased with latter increasing. The emission of CO is the lowest when the air inlet velocity is 110 m/s. With the increasing of fuel inlet velocity, the peak temperature in the combustion chamber is increased with increased NOx emission, and the CO emission is decreased with latter increasing. [ABSTRACT FROM AUTHOR]

The objective of this work is to assess the accuracy and limitations of two different semi-empirical soot models: the Laminar Smoke Point (LSP) and soot-yield approach. A global soot formation model based on the LSP concept is embedded within FDS6.7. Quantitative comparisons were made from turbulent buoyant pool fires between several computational results and well-instrumented experimental databases on the soot volume fraction, mass loss rate, heat release rate and gas temperature. The LSP model in combination with soot oxidation and surface growth is validated for most of the methane, ethylene and heptane turbulent buoyant pool fires, covering a wide range of fuel likely to form soot. This paper aims to broaden the scope of the validation of the available semi-empirical soot modelling. For the porous methane and ethylene burner, the LSP model was found to provide a better description of the soot volume fraction. The overall visual soot distribution is also numerically reproduced with the soot-yield approach, but as expected, there are some differences between the prediction and the measurement regarding the magnitude of soot volume fraction. The computed radiant heat flux was compared with experimental data for heptane flame, showing that predictions using both the LSP and soot-yield models were found to be twice the value of experimental data, although the measured HRR (Heat Release Rate) is reliably reproduced in the numerical simulation. For the heptane buoyant pool fires, a sufficient accuracy of the numerical model is confirmed only in some of the locations as compared to the experimental results. It is demonstrated that neither the temperature nor the soot volume fraction can be reliably calculated in the necking flame flapping region when the pyrolysis rate of condensed fuel (heptane) is coupled with radiation/convection heat feedback. This implies that an accuracy of prediction on the turbulent buoyant pool fires depends on the studied fire scenario regardless of the semi-empirical soot models. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Detonation engines are gaining prominence as next-generation propulsion systems that can significantly enhance the efficiency of existing engines. This study focuses on developing an injector utilizing liquid fuel and a gas oxidizer for application in detonation engines. In order to better understand the spray characteristics suitable for the pulse detonation engine (PDE) system, an injector was fabricated by varying the Venturi nozzle exit diameter ratio and the geometric features of the fuel injection hole. Analysis of high-speed camera images revealed that the Venturi nozzle exit diameter ratio plays a crucial role in determining the characteristics of air-assist or air-blast atomization. Under the conditions of an exit diameter ratio of Re/Ri = 1.0, the formation of a liquid film at the exit was observed, and it was identified that the film’s length is influenced by the geometric characteristics of the fuel injection hole. The effect of the fuel injection hole and Venturi nozzle exit diameter ratio on SMD was analyzed by using droplet diameter measurement. The derived empirical correlation indicates that the atomization mechanism varies depending on the Venturi nozzle exit diameter ratio, and it also affects the distribution of SMD. The characteristics of the proposed injector, its influence on SMD, and its velocity, provide essential groundwork and data for the design of detonation engines employing liquid fuel.

The process of combustion of a liquid fuel layer (diesel, kerosene, gasoline, separated petroleum, and oil) in the presence of CO2 hydrate has been studied. These fuels are widely used in engineering, which explains the great interest in effective methods of extinguishing. Extinguishing liquid fuels is quite a complicated scientific and technical task. It is often necessary to deal with fire extinction during oil spills and at fuel burning in large containers outdoors and in warehouses. Recently, attention to new extinguishing methods has increased. Advances in technology of the production, storage, and transportation of inert gas hydrates enhance the opportunities of using CO2 hydrate for extinguishing liquid fuels. Previous studies have shown a fairly high efficiency of CO2 hydrate (compared to water spray) in the extinction of volumetric fires. To date, there are neither experimental data nor methods for determining the dissociation rate of CO2 hydrate powder at the time of the gas hydrate fall on the burning layer of liquid fuel. The value of the dissociation rate is important to know in order to determine the temperatures of stable combustion and, accordingly, the mass of CO2 hydrate required to extinguish the flame. For the first time, a method jointly accounting for both the combustion of liquid fuel and the dissociation rate of the falling powder of gas hydrate at a negative temperature is proposed. The combustion stability depends on many factors. This paper defines three characteristic modes of evaporation of a liquid fuel layer, depending on the prevalence of vapor diffusion or free gas convection. The influence of the diameter and height of the layer on the nature of fuel evaporation is investigated. [ABSTRACT FROM AUTHOR]

The French National Center for Scientific Research (CNRS) is carrying out design studies on a nuclear electric propulsion (NEP) engine based on a molten salt reactor (MSR). A NEP engine based on liquid nuclear fuel could allow developing a core design with relatively high power densities and temperatures while using simple reactivity control systems and keeping low pressure and temperature gradients in the fuel. Nevertheless, the design work of such an engine poses significant technical challenges and requires the use of advanced numerical simulation tools. Different MSRs for space are currently being studied. In this work, a MSR concept using a fast neutron spectrum is investigated using a multiphysics tool based on a numerical coupling between the OpenFOAM (computational fluid dynamics) and SERPENT 2 (Monte Carlo neutronics) codes. The analysis of this paper is focused on the reactor core coupled neutronic and thermal-hydraulic phenomena. Steady state full-power conditions are calculated for two different fast MSR designs using low-enriched uranium (LEU) and highly enriched uranium. The results show that the proposed core layout and materials allow obtaining a satisfactory temperature distribution in the core (maximal values and gradients) without significant penalization of the reactor operating conditions. A reactivity control strategy excluding the use of control rods is studied for the LEU concept. Transient and safety studies are also performed and show acceptable performance. [ABSTRACT FROM AUTHOR]

A self-sustained porous burner without a sprayed atomizer was built for diesel oil. It consisted of metal fiber felt as an evaporator upstream and ceramic foam as an emitter downstream. The liquid fuel underwent film boiling in the porous evaporator and was rapidly evaporated by the heat recirculated from the porous emitter to the porous evaporator through intense irradiative heat flux. The effect of the porous structure and its installation location on the performance of the porous burner was investigated. The results indicated that the evaporation and combustion of liquid fuel could be prompted by the radiation of porous media. The position of the flame moved downstream, and the flame temperature decreased when the distance between the metal fiber felt and the ceramic foam was increased. The lowest NOx concentration was obtained when the distance between the foam and the metal fiber felt was 90 mm. When the diameter of the central hole of the ceramic foam was increased, the position of the flame moved towards the burner outlet, and the flame temperature and NOx emission declined. The flame temperature of the divergent configuration as emitter was higher than that of the convergent configuration, and the flame temperature of the C–D configuration was higher than that of the D–C configuration. Different ceramic foam structures had a significant effect on the temperature and emission in the combustion chamber, which showed that the evaporation and radiation performance of inert porous media burners with different structures is quite different. [ABSTRACT FROM AUTHOR]

Hydrogen transfer using a hydrogen donor solvent is promising for converting cellulose to liquid fuel. Alcohol and cyclic compounds are used as a hydrogen donor solvent, but the solvent affects the properties of liquid fuel. Therefore, the cellulose-derived liquid fuel and the solvent need to be separated. We focus on a straight-chain aliphatic hydrocarbon as a hydrogen source and solvent. Hydrogen transfer is expected by using palladium on activated catalyst (Pd/C) in combination with a solvent because palladium can dehydrogenate alkanes and is used as a hydrogenation metal. After the reaction, straight-chain aliphatic hydrocarbons remain in the cellulose-derived liquid fuel because they are similar to transportation fuel. Our previous study has reported that cellulose is converted into hydrocarbons by liquefaction using hexadecane containing Pd/C. However, the factors for deriving the optimum reaction conditions are unclear, such as the conversion route of cellulose to hydrocarbon and the formation mechanism of a solid component. In this study, we investigate the mechanism of the conversion of cellulose. The results indicate that the cellulose-derived oxygenates absorb on cellulose surface and form a solid component. In contrast, when Pd/C was added to tetradecane solvent, the oxygenates are hydrogenated to solvent-soluble compounds, resulting in suppressing the formation of solid components. The solvent-soluble compounds are deoxygenated to ketones, and then, the compounds changed to cyclopentanones and cyclohexanones which are the number of carbons > 6 at 330 °C because aldol condensation with the ketones occurs. Subsequently, the ketones are deoxygenated to hydrocarbons containing C10–C20 at 350 °C. [ABSTRACT FROM AUTHOR]

Plastics are one of the most widely used materials, and, in most cases, they are designed to have long life spans. Since plastic and packaging waste pollute the environment for many years, their disposal is of great importance for the environment and human health. In this paper, a system was developed to store liquid fuel from plastic and organic waste mixes without solidification, which then can be used as fuel in motor vehicles and construction machinery. For this purpose, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and organic wastes and clay, zeolite, and MCS23-code materials (50% magnetite-%25 calcium oxide-%25 sodium chloride) were heated in a closed medium at temperatures ranging from 300 to 400°C and subsequently re-condensed. The study conducted twenty tests, involving various types and rates of plastic and organic materials, as well as different rates of catalysts. Among these tests, the highest liquid fuel yield (67.47%) was achieved in Test 9, where 50% PVC-50% PET waste, 75 g of clinoptilolite, and 500 g of MCS23 waste were collectively used. Notably, Test 12 exhibited the highest density value (79.8 kg/m³), while the best viscosity value (2.794 mm2/s) was observed in Test 2. Across all samples, flash point values were found to be below 40°C. The most favorable yield point value was recorded in Test 2 (-6°C). The samples displayed ash content within the range of 0 to 0.01% (m/m)] and combustion heat values of 35.000> J/g which fall within the standard range. The incorporation of MCS23 with clinoptilolite additives is believed to have a significant impact on obtaining high-yield products with improved fuel properties. [ABSTRACT FROM AUTHOR]

This work establishes a generic multiphysics tool for liquid-fueled molten salt reactors (LFMSRs) to select key installation locations and specify the expected operating temperature range for the development of advanced instrumentation and control systems, particularly distributed temperature sensors using fiber optics. A commercial computation fluid dynamics package (STAR-CCM+) is used to formulate a neutronics and thermal-hydraulic coupled solver, showing good agreement with a recent benchmark problem developed for evaluating the coupling methodology of neutronics and thermal hydraulics. The multiphysics model is then applied to the reference molten chloride salt fast reactor (MCFR) design under development by TerraPower based on publicly available information. The available two-dimensional axisymmetric model for the reactor core is used for coupling calculations, and system component details are leveraged using the lumped method to complete the energy balance. The dynamic responses of the MCFR model are investigated during operational transients, such as unprotected loss-of-flow and uniform perturbation scenarios. Maximum temperature and local temperature distributions are characterized during unprotected loss of flow and unprotected loss of heat sink events. The thermal responses of the fuel salt and core components are analyzed from induced perturbation of the system parameters, such as the flow rate and the heat sink capacity. The results motivate the use of continuous monitoring of the temperature variation in real time along the reflector region with the use of fiber optics to validate the multiphysics code to support a reactor's licensing basis, as well as to support the structural longevity and improve safety in LFMSRs. [ABSTRACT FROM AUTHOR]

Assessing acidic influence in conversion of hospital plastic waste into liquid fuel with kaolin base supported catalysts was carried out using samples collected from a tertiary University teaching Hospital Sokoto, which encompassed Drip bags (Linear low density polyethylene LLDPE), Hand gloves (Polyethylene terephthalate PET) and Urine bags (Polyureathane PU). Uncatalyzed pyrolysis was first carried out using thermal cracking only at 300, 350, and 4000C. Catalyzed pyrolysis was also carried out using three different active catalyst mounted on same support and equal catalytic ratio of active catalyst to support. CuO/Kaolin-SO4, FeO/Kaolin-SO4 and CaO/Kaolin-SO4. The liquid fuel obtained from uncanalyzed and catalyzed pyrolysis of the sample were all subjected to GCMS and FTIR analysis. Uncatalyzed pyrolysis was first carried out using thermal cracking only at 300, 350, and 4000C. Catalyzed pyrolysis was also conducted using three different active catalyst mounted on same support and equal catalytic ratio of active catalyst to support. Fe2O3/Kaolin-SO4 (CAT.D), CuO/Kaolin-SO4 (CAT.E), and CaO/Kaolin-SO4 (CAT.F). The catalytic activities of all the three synthesized catalysts were successfully tested in the conversion of hospital plastic waste in to liquid fuel. However the conversion using (CAT.D) was found to be more promising and selective to liquid fraction then followed by CAT. E and F. Therefore, the results shows that CAT.D has lower cocking tendency that result to high liquid than the other catalysts. The FTIR and GC/MS analysis revealed that the chemical composition and carbon number distribution of the liquid fraction which indicate the presence of paraffinic, naphthenic and olefins hydrocarbons as the dominant component in the liquid fraction obtained, and high amount of lower hydrocarbon range was also obtained using CAT.D. Thus, sulphated kaolin catalyst (CAT.D) was found to be better in modifying the product than CAT.E and F. [ABSTRACT FROM AUTHOR]

The method of determining the biobased carbon content in liquid fuel samples is standardized, but different laboratories use different protocols during sample preparation and perform the measurements using different machines. The accelerator mass spectrometry (AMS) laboratories use different combustion, preparation, and graphitization methods for the graphite production for the spectrometric measurements. As a result, the intercomparison between the laboratories is inevitable to prove precision and accuracy and to demonstrate that the results are comparable. In this study, we present the results of an intercomparison campaign involving three 14C accelerator mass spectrometry laboratories. Five samples were used in the measurement campaign, including two biocomponents (fatty acid methyl ester, hydrotreated vegetable oil), one fossil component (fossil diesel), and two blends (mixtures of fossil and biocomponent with 90–10% mixing ratio) in the laboratories of CEDAD (Italy), ETH (Switzerland), and INTERACT (Hungary). The results presented by the laboratories are comparable, and all three laboratories could determine the biobased carbon content of the samples within 1% relative uncertainty, which is acceptable in the scientific, economic, and industrial fields for biocomponent determination. [ABSTRACT FROM AUTHOR]

Rotating detonation combustors (RDCs) are among the combustors that use supersonic combustion waves known as detonation waves, and are expected to simplify engine systems and improve thermal efficiency due to their supersonic combustion and compression performance using shock waves. Research is also being actively conducted worldwide on a cylindrical RDC; a RDC without an inner cylinder, which is expected to simplify and downsize the combustor. However, most of the research was performed using gas propellants, and liquid propellants were rarely used. Since liquid propellants are used in many combustors, it is important to evaluate the performance of RDCs with liquid propellants. In this study, a cylindrical RDC with a liquid ethanol-gas oxygen mixture was constructed and tested at a flow rate of 31.5 « 5.0 g/s, an equivalence ratio of 0.46-1.39, and a back pressure of 14.5 « 2.5 kPa. The thrust was shown to depend strongly on the combustor bottom pressure history. In addition, the start-up process of the cylindrical RDC with liquid fuel was clarified by self-luminous and CH+ radical visualizations. It was found that the detonation wavefront propagated at a distance of 2-3mm from the combustor bottom, and the main combustion region was 10-15mm in height. [ABSTRACT FROM AUTHOR]

This study experimentally explored the effects of equivalence ratio settings on ethanol fuel combustion oscillations with a laboratory-scale combustor. A contrary flame equivalence ratio adjusting trend was selected to investigate the dynamic characteristics of an ethanol atomization burner. Research findings denote that optimizing the equivalence ratio settings can prevent the occurrence of combustion instability in ethanol burners. In the combustion chamber, the sound pressure amplitude increased from 138 Pa to 171 Pa and eventually dropped to 38 Pa, as the equivalence ratio increased from 0.45 to 0.90. However, the sound pressure amplitude increased from 35 Pa to 199 Pa and eventually dropped to 162 Pa, as the equivalence ratio decreased from 0.90 to 0.45. The oscillation frequency of the ethanol atomization burner presents a migration characteristic; this is mainly due to thermal effects associated with changes in the equivalence ratio that increase/decrease the speed of sound in burnt gases, leading to increased/decreased oscillation frequencies. The trend of the change in flame heat release rate is basically like that of sound pressure, but the time-series signal of the flame heat release rate is different from that of sound pressure. It can be concluded that the reversible change in equivalence ratio will bring significant changes to the amplitude of combustion oscillations. At the same time, the macroscopic morphology of the flame will also undergo significant changes. The flame front length decreased from 25 cm to 18 cm, and the flame frontal angle increased from 23 to 42 degrees when the equivalence ratio increased. A strange phenomenon has been observed, which is that there is also sound pressure fluctuation inside the atomized air pipeline, and it presents a special square waveform. This study explored the equivalence ratio adjusting trends on ethanol combustion instability, which will provide the theoretical basis for the design of ethanol atomization burners.