Evolutionary Process Research Articles

Dynamic mechanical properties and energy dissipation analysis of rubber-modified aggregate concrete based on SHPB tests

The fluctuation of the waveform curves in the Split Hopkinson Pressure Bar (SHPB) test can provide a more intuitive reflection of the material's dynamic deformation process, with different strain rates resulting in varying damage states and σ-ε curves. A Φ120×100 mm size SHPB experiment was conducted to study the dynamic mechanical properties of new rubber-modified aggregate concrete (RAC). Based on the different characteristics of waveform and σ-ε curves, combined with high-speed photography technology, the typical failure modes and dynamic compressive strength of rubber-modified aggregate concrete under different loading rates were analyzed. Furthermore, the energy dissipation capacity and mechanism of rubber-modified aggregate concrete at different stages was discussed. The reflected wave of RAC shows a "double-peak" trend of "first high and then low" instead of "first low and then high" of normal concrete due to its exceptional capacity of energy absorption and dissipation. As strain rate increases, a plateau period appears in the reflected wave before first peak. The evolution process is dominated by the energy storage mechanism until it hits the limit, then by the energy dissipation mechanism. These findings can help us design and use RAC materials under dynamic stress.

The variation in climate conditions and fire-related traits across Pinus (Pinaceae) species

Fire has long been recognized as a significant evolutionary factor for the genus Pinus (family Pinaceae). Many pine species have developed specific fire-adaptations, such as self-pruning, resprouting, and serotiny, to persist under various fire regimes. Fire-related traits, such as needle length, bark thickness, and plant height, also can affect the survival of pines in fire-prone environments. Investigating the climate conditions of pines and analyzing the variation in fire-adaptations and fire-related traits across pines can provide insights into the evolutionary process of the genus Pinus affected by fire. However, such studies are rare, particularly those focusing on the relationship among environmental conditions, fire-adaptations, and fire-related traits with a large number of pine species. In this study, we explored the variation in climate conditions and fire-related traits (including tree height, bark thickness, and leaf length) between fire-adapted and non-fire-adapted pines, as well as among three fire survival strategies (fire-tolerators, fire-embracers, fire avoiders). We also investigated the relationships between climatic conditions and fire-related traits/fire-adaptations (including resprouting, self-pruning, the grass stage, and serotiny) across the genus Pinus. Sixty-one out of 101 pine species were found to possess one or more fire adaptations and were classified as fire-adapted pines. We found that fire-adapted pines occupy warmer and more fire-prone habitats, and exhibit longer leaves, thicker bark, and taller habits than non-fire-adapted species. Our analysis did not indicate a significant difference between fire tolerators and embracers regarding traits and climate conditions, except that fire-tolerators have thicker bark and are more associated with wildfire-prone areas. Climate conditions appeared to significantly affect fire-related traits/fire-adaptations across the genus Pinus. These findings will facilitate our understanding the evolutionary process of fire adaptations/fire-related traits in the genus Pinus and will guide sustainable fire management in different pine forests.

Influence of initial correlations on evolution over time of an open quantum system

A novel approach to accounting for the influence of initial system–bath correlations on the dynamics of an open quantum system, based on the conventional projection operator technique, is suggested. To avoid the difficulties of treating the initial correlations, the conventional Nakajima–Zwanzig inhomogeneous generalized master equations (GMEs) for a system’s reduced statistical operator and correlation function are exactly converted into the homogeneous GMEs (HGMEs), which take into account the initial correlations in the kernel governing the evolution of these HGMEs. In the second order (Born) approximation in the system–bath interaction, the obtained HGMEs are local in time and valid at all timescales. They are further specialized for a realistic equilibrium Gibbs initial (at t=t0) system+bath state (for a system reduced statistical operator an external force at t>t0 is applied) and then for a bath of oscillators (Boson field). As an example, the evolution of a selected quantum oscillator (a localized mode) interacting with a Boson field (Fano-like model) is considered at different timescales. It is shown explicitly how the initial correlations influence the oscillator evolution process. In particular, it is shown that the equilibrium system’s correlation function acquires at the large timescale the additional constant phase factor conditioned by survived initial system–bath correlations.

X-ray compressed ultrafast photography under the constraint of time-integrated-image for X-pinch

This paper presents a time-integrated-image-constrained X-ray compressed ultrafast photography system for comprehensive measurement of the aluminum X-pinch evolution process. The system incorporates a pinhole and a scintillator to convert the X-ray video to fluorescence video. The fluorescence video is recorded by a compressed ultrafast photography channel and a time-integrated imaging channel respectively. By recording the fluorescence video instead of the self-emission visible light video, the long tailing effect can be significantly inhibited, which is more conducive to the image reconstruction of the compressed ultrafast photography channel. In addition, by combining the time-integrated imaging channel, the reconstruction quality is significantly improved. Based on the “Qin-I” pulsed power facility, we recorded the continuous two-dimensional X-ray evolution process of aluminum X-pinch for the first time. Our results contribute to deep insights into the temporal-spatial distribution of the X-pinch imploding plasma. It can also offer direction for the assessing of X-ray backlight photography applications at the X-pinch facility.

Evolution of pore structure and diagenetic stages of late Permian shales in the Lower Yangtze Region, South China

This study examines the evolution characteristics of shale pores in the Late Permian Longtan Formation located in the Lower Yangtze region of South China. The complete process of thermal evolution of the samples was achieved through thermal simulation experiments while identifying qualitatively the pore types and their development characteristics using field emission-scanning electron microscope (FE-SEM). Quantitative analysis of pore size distribution was conducted through mercury intrusion capillary pressure (MICP), nitrogen (N2) and carbon dioxide (CO2) adsorption experiments. The paper comprehensively analyzed the pore evolution characteristics and controlling factors of shale in the study area, with an analysis of diagenetic differences. Findings reveal that during the pore evolution process, both morphology and pore size are influenced by thermal maturity. The pore volume is dominated by mesopores and macropores, while the specific surface area is mainly dominated by mesopores and micropores. Thermal evolution promotes the formation of micropores and mesopores but hinders the development of macropores. Moreover, clay minerals transformation and mineral dissolution make certain contributions to the development of micropores. The diagenesis in the study area is controlled primarily by the pyrolysis of organic matter. Pyrite and clay minerals are the first to dissolve, followed by calcite and quartz. Five stages of evolution characterization have been identified from low-mature stage (Ro = 0.88 %) to overmature stage (Ro = 3.35 %) in combination with diagenesis. The development of pore structure and its influencing factors vary across different stages. The influencing factors mainly include hydrocarbon generation from organic matter, compaction, mineral transformation, and dissolution. The process of hydrocarbon generation in organic matter occurs throughout the entire pore evolution process, resulting in the development of numerous micropores and mesopores. Compaction primarily impacts pore development during the early diagenetic stage, causing a substantial transition of primary mineral pores from macropores to mesopores. Mineral transformation and dissolution take place during and after the middle diagenetic stage. The former governs the development of mesopore-sized clay interlayer pores, while the latter primarily generates micropores.

An LADM-based profile for marine geo-regulation: A case study of China

With the rapid development of the marine economy, the transfer, lease and other transactions of marine use right in China's coastal areas have emerged continuously. At the same time, to promote the effective protection of marine environment and resources, the establishment and reform of marine property rights system has become a very important part. To play the basic role of the market and environmental protection in the utilization of marine resources, it is very important to establish the corresponding property right registration system. In response, the central government has proposed the establishment of a unified registration system for real estate and natural resources nationwide, including in marine areas. Therefore, this study takes China's marine administration as the research object and constructs a conceptual model based on LADM, which serves as an important basis for the subsequent registration system development. Specifically, this study first summarizes the evolution process of China's marine administration system since the founding of China. Secondly, it puts forward the existing marine rights system. Then, based on the LADM standard and the instance-level diagram for marine administration activities, the corresponding LADM-based profile is developed. The core improvement of this model lies in the improved structuring of marine-related rights, restrictions and responsibilities (as well as related source documents), which is an important preparation for the expansion of land information infrastructure to the sea.

Evolution and Competitive Struggles of Lactiplantibacillus plantarum under Different Oxygen Contents.

Lactiplantibacillus (Lb.) plantarum is known as a benign bacterium found in various habitats, including the intestines of animals and fermented foods. Since animal intestines lack oxygen, while fermented foods provide a limited or more oxygen environment, this study aimed to investigate whether there were genetic differences in the growth of Lb. plantarum under aerobic vs. anaerobic conditions. Genomic analysis of Lb. plantarum obtained from five sources-animals, dairy products, fermented meat, fermented vegetables, and humans-was conducted. The analysis included not only an examination of oxygen-utilizing genes but also a comparative pan-genomic analysis to investigate evolutionary relationships between genomes. The ancestral gene analysis of the evolutionary pathway classified Lb. plantarum into groups A and B, with group A further subdivided into A1 and A2. It was confirmed that group A1 does not possess the narGHIJ operon, which is necessary for energy production under limited oxygen conditions. Additionally, it was found that group A1 has experienced more gene acquisition and loss compared to groups A2 and B. Despite an initial assumption that there would be genetic distinctions based on the origin (aerobic or anaerobic conditions), it was observed that such differentiation could not be attributed to the origin. However, the evolutionary process indicated that the loss of genes related to nitrate metabolism was essential in anaerobic or limited oxygen conditions, contrary to the initial hypothesis.

Innovation of the global international ship registry system: Evolution process and future reforms

The innovation and governance of the global international ship registry system have become key to achieving sustainable development for maritime nations worldwide. For a long time, many maritime nations have chosen to fly flags of convenience for commercial or political reasons, causing major maritime nations to lose effective control over their fleets. To counteract the negative impacts of flags of convenience, major maritime nations have established international ship registry systems. This paper analyzes the development process and basic characteristics of the global international ship registry system, points out the main problems in its implementation, and proposes major directions for innovation and governance of the international ship registry system worldwide. By reviewing the development history of the global international ship registry system, evaluating key issues in its implementation, and constructing future reform and governance directions, this paper aims to provide policy innovation suggestions for the ship registry policy reforms of global maritime nations.

The Activity Patterns and Grouping Characteristics of the Remaining Goitered Gazelle (Gazella subgutturosa) in an Isolated Habitat of Western China.

Wildlife activity patterns, which reveal the daily allocation of time and energy, are crucial for understanding survival pressures, adaptive strategies, and behavioral characteristics in different environments. Among ungulates, grouping behavior is a prevalent adaptive trait that reflects the population structure, mating systems, and life history strategies formed over long-term evolutionary processes. This study aimed to elucidate the daily activity patterns and grouping characteristics of the rare goitered gazelle (Gazella subgutturosa) in the Helan Mountains of western China from 2022 to 2023 using camera trap monitoring. With a total of 3869 camera days of effective trapping, we recorded 442 independent detections of goitered gazelles. The results revealed the following: (1) Goitered gazelle is primarily active during the day, showing an activity pattern similar to crepuscular animals, with two activity peaks occurring after dawn and before dusk. (2) Daily activity patterns showed both seasonal and sex differences. In the warm season, morning activity peaks occurred earlier, and afternoon peaks occurred later compared to the cold season. The overlap in daily activity patterns between females and males in the warm season was lower than that in the cold season, and this trend persisted throughout the year. (3) The number of times different types of groups were observed varied significantly, with single males and single females accounting for a larger proportion of all observed groups. There was no significant difference in group size across seasons, with groups typically consisting of 1-2 individuals. Our study provides detailed insights into the temporal ecology and population structure of goitered gazelles in arid and semi-arid ecosystems. This information will guide the identification of future conservation priorities and the development of management plans for the reserve.

Experimental and numerical study on the mechanical behavior of layered rock anchored by CRLD anchor cable

The study of the mechanical behavior of layered anchored rock is essential for addressing the stability control challenges of surrounding rock of the roadway in layered rock masses. This paper focuses on a novel constant resistance large deformation (CRLD) anchor cable and conducts a comparative study on the uniaxial compressive mechanical behavior of unanchored rock, conventional high-strength (HS) anchor cable, and CRLD anchor cable anchored rock under different bedding dip angles α (30°, 45°, 60°, 75°, and 90°). The strength characteristics, failure characteristics, and acoustic emission characteristics of various specimen types were analyzed with emphasis. The results indicate that with the increase of bedding dip angle, the elastic modulus, peak strength, and residual strength of all specimen types exhibit a trend of decreasing first and then increasing. Compared to unanchored and HS anchored rock, the values of various mechanical parameters for CRLD anchored rock show varying degrees of improvement. The failure modes of various specimen types under different bedding dip angles can be classified into five categories based on the characteristics of the crack distribution. Through comparison, it was found that the CRLD anchor cable can effectively restrict the occurrence of bedding shear failure within the anchored zone in layered rocks with smaller dip angles (30°, 45°). It also transforms the failure mode of layered rocks with larger dip angles (60°, 75°) from a single mode of bedding shear failure to a mixed mode of bedding-bedrock failure. However, under a bedding dip angle of 90°, the two types of anchored rocks exhibit similar failure forms. Comparing the acoustic emission characteristics of the two types of anchored rocks, it is observed that under different bedding dip angles, CRLD anchored rocks exhibit a more uniform distribution of acoustic emission counts, a smoother energy release process, and significantly lower peak count and cumulative energy values. Finally, a numerical model for layered CRLD anchored rocks was constructed based on the discrete element method. The reliability of the experimental results from the physical model in this study was verified by statistically analyzing the quantity evolution process and orientation distribution of microcracks in the numerical model.

Genome-Wide Identification and Molecular Evolutionary History of the Whirly Family Genes in Brassica napus.

Whirly transcription factors are unique to plants, playing pivotal roles in managing leaf senescence and DNA repair. While present in various species, their identification in Brassica napus L. (B. napus) and their differences during hybridization and polyploidy has been elusive. Addressing this, our study delves into the functional and evolutionary aspects of the Whirly gene family during the emergence of B. napus, applying bioinformatics and comparative genomics. We identified six Whirly genes in B. napus. In Brassica rapa L. (B. rapa), three Whirly genes were identified, while four were found in Brassica oleracea L. (B. oleracea). The results show that the identified Whirly genes not only have homology but also share the same chromosomal positions. Phylogenetic analysis indicates that Whirly genes in monocots and dicots exhibit high conservation. In the evolutionary process, the Whirly gene family in B. napus experienced events of intron/exon loss. Collinearity insights point to intense purifying selection post-duplication. Promoter regions housed diverse cis-acting elements linked to photoresponse, anaerobic initiation, and methyl jasmonate responsiveness. Notably, elements tied to abscisic acid signaling and meristem expression were prominent in diploid ancestors but subdued in tetraploid B. napus. Tissue-specific expression unveiled analogous patterns within subfamily genes. Subsequent qRT-PCR analysis spotlighted BnAWHY1b's potential significance in abiotic stress response, particularly drought. These findings can be used as theoretical foundations to understand the functions and effects of the Whirly gene family in B. napus, providing references for the molecular mechanism of gene evolution between this species and its diploid ancestors.

A damage-related adaptive self-consistent clustering analysis method with localized refinement capability for the damage problem of 3D woven composites

In this work, a Damage-related Adaptive Self-Consistent Clustering Analysis (DASCA) method is developed to achieve higher solving accuracy for 3D damage problems than Self-Consistent Clustering Analysis (SCA) method, which is applied to investigate the mesoscale damage behavior of 3D woven composites (3DWC). The developed clustering adaptivity framework is based on the characteristics of the damage problem, which consists of five fundamental stages: evaluation of the adaptivity conditions, selection criterion of potential damage clusters, online adaptive clustering analysis, update of the cluster database and adaptive rewind of the analysis process. In the second stage, the clusters with the highest potential to enter the damage state are identified and marked as adaptivity target clusters. In the solving process, the distribution of clusters can achieve problem-dependent dynamic adjustments, ensuring that clusters are concentrated on the regions of interest. Though the numerical examples of 3DWC, the DASCA solutions, using fewer clusters and less computational cost, exhibit higher prediction accuracy for macroscopic mechanical performance, first damage initiation moments and damage evolution process than the SCA solutions.

Quantitative calculation of rock strain concentration and corresponding damage evolution analysis

Understanding the critical strain and damage evolution process of sandstone can help engineers more accurately predict the failure modes and critical states of sandstone in actual engineering structures. Therefore, this article quantitatively analyzes the strain field data obtained through digital image correlation (DIC), and for the first time establishes a strain concentration calculation model (SCCM) to analyze the critical strain, compaction, and damage evolution process of sandstone under uniaxial compression conditions. The experimental results show that both elastic and plastic strain zones exist on the specimen surface. The proportion curve of strain concentration calculated by SCCM indicates that the strain field ε1 generally undergoes two stages: the elastic strain fluctuation stage and the plastic strain development stage. In contrast, the strain field ε2 exhibits roughly three stages: a rapid change phase, a slow change phase, and a stability phase. Microscopic strain analysis reveals an overlap between the compaction and damage processes of the specimen, and the critical strain value εmd for micro-damage in the specimen is significantly smaller than values obtained by traditional discrimination methods. Specifically, when the defect width of the specimen is 15 mm and 40 mm, the mean εmd vaules are approximately 0.006016 and 0.00539, respectively. In contrast, the mean critical strain values determined by traditional discrimination methods are 0.0180 and 0.0178, respectively. The above research results provide a new method for analyzing the strain field data of geotechnical materials, serving the optimization of engineering structure design.

Evolution of self-assembled amphiphilic colloidal particles in strong-flavor Chinese baijiu

This study proposed the evolution of self-assembled amphiphilic colloidal particles in Strong-Flavor (SF) Baijiu based on Ostwald ripening for the first time. The evolution process occurs in two stages: disordered amphiphilic molecules self-assemble into small colloidal particles and subsequently undergo Oswald ripening to form larger hydrophobic particles. Microscopic observations revealed the average size of oil-like spherical colloidal particles in Baijiu increased from 1.86 μm to 2.96 μm while the number of particles decreased by 39.50% during the 16-year cellaring process of SF Baijiu, consistent with the particle size trend observed via laser scattering. During fusion process, the charge-to-mass ratio of positively charged colloidal particles decreased, leading ζ-potential decreased from 23.7 mV to 4.66 mV within 16 years of storage. The electrochemical impedance spectroscopy approach tracked the unidirectional variation in the dielectric constant during evolution of SF Baijiu, reflecting the gradual expansion of colloidal particles, which aligns with the evolution trend observed in molecular dynamics simulations. By integrating direct microscopic observations of amphiphilic colloidal particles with electrochemical techniques, the evolution of Baijiu samples is capable to be evaluated in-situ, laying the foundation for intelligent Baijiu aging monitoring technology.

Study on the meso-damage characteristics of RC beam under shear failure based on acoustic emission and numerical analysis

Material meso-scopic damage is the fundamental cause of the degradation of the macroscopic mechanical properties of structures, so it is vital to appraise the meso-damage process of various material components. Acoustic emission (AE) technology as a nondestructive testing method can cover the shortage of traditional test to detect the meso-damage. Therefore, in this study, four-point shear tests were conducted on reinforced concrete (RC) beams and AE signals were collected during tests. Results indicated that the shear failure process of RC beam could be divided into three stages based on the correlation between the cumulative AE energy and load-time. Meanwhile, the finite element model (FEM) was established to intuitively obtain the meso-damage evolution process of RC beam in different failure stages. It was observed that the mortar damage, the ITZ damage, the aggregate damage and the reinforcement plasticity damage occurred inside the RC beam and the meso-damage all showed stage characteristics. Besides, the correlation between AE signals and different meso-damage were established by combining the wavelet packet and the cluster analysis. Based on these analysis, the method of assessing the damage severity of RC beam under shear failure was proposed eventually.

Crystal facet/interface anchored Janus activity of BiOBr in driving photocatalytic water splitting

Constructing Janus junctions is expected to provide a novel perspective for analyzing the intrinsic photocatalytic activity of bismuth oxyhalide. Herein, Janus-typed BiOBr(010)/BiOBr(001) homojunction with efficiently photocatalytic H2 evolution has been achieved by a hydrothermal synthesis. The experimental results show that the designed Janus-typed junction can effectively elevate the carrier lifetime, significantly enhance the photocurrent, and prominently reduce the overpotential. The potential difference (0.34 eV) between (010) facet and (001) facet can drive the carrier transport at the interface for Janus junctions. Theoretical calculations indicate that the designed Janus junction has a stable mechanical structure, providing certain support for the long lifetime of the photocatalyst in the photocatalytic process. The carrier distributions in the Janus junction exhibit the typical characteristic distribution. Interestingly, the photo-generated electrons are only localized in BiOBr(001) component, which embodies significantly a role of n-type semiconductor. This essentially activates HER activity (32 µmol/h g−1) of Janus junction. The holes preferentially localize in the BiOBr(010) component of Janus junction. This component undertaking p-type role reduces the free energy of the rate determining step (from OH* to O*) in the oxygen evolution process (0.88 eV). The Janus junction intensively suppresses the carrier recombination probability at the high symmetry point (reciprocal space) in BiOBr. Ab initio molecular dynamics calculations show that the adsorbed water is easy to decompose on the surface of Janus junction. The obtained results of the photocatalytic water splitting further confirm that the designed BiOBr(010)/BiOBr(001) has Janus characteristics, which are consistent with theoretical calculations and tracer tracing results. The diffusion characteristics of hydrogen also evidence that the interaction of the internal electric field in the Janus junction can drive the HER performance. Additionally, these results offer us a unique angle of view to regulate the charge carrier dynamics by the highly oriented facet coupling for the layered semiconductor.

Addressing epistasis in the design of protein function

Mutations in protein active sites can dramatically improve function. The active site, however, is densely packed and extremely sensitive to mutations. Therefore, some mutations may only be tolerated in combination with others in a phenomenon known as epistasis. Epistasis reduces the likelihood of obtaining improved functional variants and dramatically slows natural and lab evolutionary processes. Research has shed light on the molecular origins of epistasis and its role in shaping evolutionary trajectories and outcomes. In addition, sequence- and AI-based strategies that infer epistatic relationships from mutational patterns in natural or experimental evolution data have been used to design functional protein variants. In recent years, combinations of such approaches and atomistic design calculations have successfully predicted highly functional combinatorial mutations in active sites. These were used to design thousands of functional active-site variants, demonstrating that, while our understanding of epistasis remains incomplete, some of the determinants that are critical for accurate design are now sufficiently understood. We conclude that the space of active-site variants that has been explored by evolution may be expanded dramatically to enhance natural activities or discover new ones. Furthermore, design opens the way to systematically exploring sequence and structure space and mutational impacts on function, deepening our understanding and control over protein activity.

Aspartic acid/ thiourea − derived N and S − doped porous carbon as a metal-free electrocatalyst for oxygen and hydrogen evolution reactions

The preparation of high-efficiency electrocatalysts for the oxygen and hydrogen evolution process (OER and HER) using an easy, green, and facile preparation method is crucial for the effective and economical use of clean energy sources. Heteroatom-doped carbon nanomaterials are effective metal-free electrocatalysts for HER and OER reactions. Herein, N and S co-doped porous carbon nanocomposite (NS-PC) was constructed as a low-cost metal-free catalyst via pyrolysis of the Thiourea and L-aspartic acid. Doping heteroatoms (N and S) into the carbon structure can induce charge redistribution, expose many active sites, accelerate charge transfer, and thus effectively improve the catalytic activity. The NS-PC electrocatalyst demonstrates proper bifunctional electrocatalytic performance for HER and OER with long-term stability in KOH electrolytes. As a result, the NS-PC requires an overpotential of 139 mV and 315 mV in the current density of 10 mA cm– 2 and the Tafel slope of 59.6 and 69.8 mV dec−1 for HER and OER, respectively. As-papered NS-PC electrocatalyst offers the development of multi-functional electrocatalysts in the water splitting process using biological substances such as amino acids.

Active flow control on unsteady cloud cavitation: Insights into jet dynamics

Unsteady cloud cavitation significantly impairs the performance of marine systems. Active flow control method has shown promise in effectively reducing cavitation, yet its specific mechanisms of action require elucidation. This study investigates continuous water injection on a NACA66 (MOD) hydrofoil as an active control against unsteady cloud cavitation. Results show notable reductions in cavitation volume: 52.57 % at a cavitation number of 0.83 and 86.24 % at 1.29. Employing the Lagrangian approach, the study tracks ideal particles to explore the jet's behavior and its interaction with cavitation. The interaction between the jet and cavitation is reciprocal: cavitation draws the jet, which in turn alters the cavitation's structure. The jet's movement is synchronized with the evolution process of cavitating flow, effectively limiting the spread of attached cavitation, disrupting cloud integrity, and encircling scattered clouds to prevent their growth. The analysis identifies the jet's streamwise direction as critical in suppressing cavitation, with the normal direction providing supplementary support, and the spanwise direction having minimal impact. Furthermore, the jet promotes a condensation-dominant state in local flow regions, hindering cavitation growth by altering the water-vapor mass transport process.

Flame evolution characteristics during ignition of a combined flameholder fueled by RP-3 liquid kerosene

This paper proposes a combined flameholder comprising a pilot flameholder and a bluff body flameholder, interconnected by a radial V-gutter. The configuration of this combined flameholder is widely utilized in current afterburners and ram combustors, and its outstanding performance in future advanced combined cycle engines has been proved. To avoid the issue of uniform airflow at the inlet observed in most previous studies, this research installed a diffuser to simulate relatively realistic inlet airflow conditions of combustor. Particle Image Velocimetry (PIV) and high-speed camera are employed to measure the flow field structure of the combined flameholder, as well as the ignition flame evolution process under inlet Mach number of 0.3 – 0.5, temperature of 500 – 700 K, and pressure of 0.05 – 0.1 MPa. This paper reveals the combustion organization method of the combined flameholder through combining flow field characteristics and the ignition flame evolution process. Furthermore, the research findings indicate that flame evolution processes, flame projection area, and ignition delay time are significantly influenced by the inlet conditions. The variations in these flame evolution characteristics with different inlet conditions are summarized and the contributing factors are analyzed. The results of the paper are expected to serve as a reference for the optimization and design of flame stabilization systems in current and future afterburners and ram combustors.