Partial Cracking Research Articles

The effects of NH3 pre-cracking and initial temperature on the intrinsic instability and NOx emissions of NH3/bio-syngas/air premixed flames

The study of the combustion characteristics of NH₃/bio-syngas/air under NH₃ partial cracking and elevated initial temperatures can enhance its feasibility as a practical fuel. The effects of NH₃ cracking rates (ζ) and initial temperature (T0) on the laminar burning velocity (SL), instability, and NO emissions of NH₃/bio-syngas/air premixed flames under different equivalence ratios are investigated. The results indicate that increasing ζ and T0 enhances the SL of the premixed flame, with ζ having a more pronounced effect on combustion enhancement. Virtual gas analysis reveals that pre-cracking primarily strengthens combustion through chemical effect. An increase in ζ significantly shifts the peak SL towards the fuel-rich region, while at any T0, the peak SL consistently occurs around Φ = 1.1. Increasing ζ and T0 reduces the critical radius (rc) and the critical Peclet number (Pec) of the premixed fuel, with rc decreasing more rapidly when ζ is below 30 %. The dimensionless growth rate (∑) increases with the rise in ζ and T0, consistently remaining positive, indicating an unstable state. Additionally, ∑ varies more significantly with T0 when T0 is below 450 K. When ζ is below 60 %, the NO mole fraction increases with the increase in ζ. However, at ζ = 80 %, the NO mole fraction is lower than at ζ = 40 %. Increasing T0 continually increases the NO mole fraction. Analysis of the NH3 reaction pathways indicates that NHi (i = 0, 1, 2) is closely related to the NO → N2 reduction reactions.

Extinction Behavior Characteristics of Ammonia Partial Cracking Simulated Fuels with Flame Interactions

Extinction Behavior Characteristics of Ammonia Partial Cracking Simulated Fuels with Flame Interactions

Impact of Overpressure on the Preservation of Liquid Petroleum: Evidence from Fluid Inclusions in the Deep Reservoirs of the Tazhong Area, Tarim Basin, Western China

The complexity of petroleum phases in deep formations plays an important role in the evaluation of hydrocarbon resources. Pressure is considered to have a positive impact on the preservation of liquid oils, yet direct evidence for this phenomenon is lacking in the case of deep reservoirs due to late destruction. Here, we present fluid-inclusion assemblages from a deep reservoir in the Tazhong area of the Tarim Basin, northwestern China, which formed as a direct consequence of fluid pressure evolution. Based on thermodynamic measurements and simulations of the coexisting aqueous and petroleum inclusions in these assemblages, the history of petroleum activities was reconstructed. Our results show that all analyzed fluid-inclusion assemblages demonstrated variable pressure conditions in different charging stages, ranging from hydrostatic to overpressure (a pressure coefficient of up to 1.49). Sequential petroleum charging and partial oil cracking may have been the main contributors to overpressure. By comparing the phases of petroleum and fluid pressures in the two wells, ZS1 and ZS5, it can be inferred that overpressure inhibits oil cracking. Thus, overpressure exerts an important influence on the preservation of liquid hydrocarbon under high temperatures. Furthermore, our results reveal that the exploration potential for liquid petroleum is considerable in the deep reservoirs of the Tarim Basin.

Quantitative comparison of the benefits of cracking and nanosecond repetitive pulsed discharges on the lean blow-off, emissions, and topology of ammonia premixed swirl flames

In the last decade, ammonia has gained interest as an alternative fuel for the energy sector. The main advantages include its carbon neutrality and ease of storage at industrial scale. However, to consider ammonia as an alternative carbon-free fuel it is necessary to solve two main issues, namely flame stability and pollutant emission. In this work we compared two promising technologies used to enhance ammonia combustion, specifically partial cracking and plasma assisted combustion (PAC). The experiments were carried out for different blends of ammonia–hydrogen–nitrogen–air that reproduce the conditions of cracking as well as for pure ammonia assisted by nanosecond repetitive pulsed (NRP) discharges for the PAC. The cracking and PAC were compared for the same added power ratio at atmospheric conditions. Different added power ratios, from 0.1% to 4% of the flame’s total thermal power, were tested. The lean blow-off limits were measured for a range of bulk flow velocities between of 4 and 12 m/s. For the pollutant emissions, NOx, NH3, and N2O were considered. The effect of both strategies on the Laminar burning velocity (LBV) was explored by numerical simulations. For the same added power ratio, partial cracking extended the lean blow-off limits further than NRP discharges, even with a high pulse repetition frequency of 30 kHz. This result indicated that cracking was more effective in stabilizing the flame than PAC. Regarding NOx emissions, NRP discharges induced only a third of the increase observed with cracking. However, the reduction in N2O associated with cracking was twice as much as that for NRP discharges. Finally, cracking proved more efficient in reducing the flame height, which was supported by the simulations of LBV. These results suggest that PAC strategies optimized for hydrocarbon flames are less efficient on ammonia combustion, and that more work is needed to develop plasma actuators for NH3 combustion.Novelty and Significance statement This work marks the first one-to-one quantitative comparison between plasma actuation and thermal cracking on ammonia swirl flames. It serves as a pivotal exploration to assess and understand the economic aspects of these strategies, providing valuable insights into their efficiency and potential for practical implementation.

Delamination bridging response of Z‐pins under mixed mode loading: The influence of carbon and Kevlar Z‐pins

AbstractThis paper presents the effect of varying the type of Z‐pin on the delamination bridging performance of unidirectional composite laminates. Carbon and Kevlar Z‐pins were inserted in thick composite laminates using the pre‐hole insertion Z‐pinning process and their bridging performance characterized across the different mode‐mixity range. The bridging response indicated that Kevlar Z‐pin experienced load reduction driven by interfacial friction (Stage III), which was absent in the Carbon Z‐pin. When Mode II dominated the bridging crack, Kevlar Z‐pin showed partial pullout and fiber shear cracking, while the Carbon Z‐pin exhibited clean transverse fracture. Although the bridging load obtained by the Carbon Z‐pin was twice that of Kevlar Z‐pin, the Kevlar Z‐pin provided a higher interlaminar fracture energy. The superior bridging performance of Kevlar Z‐pin is correlated with the enhanced ductility. Moreover, the resin‐rich area was involved in deformation and provided the extra axial load of Z‐pin.Highlights The comparison of mixed‐mode bridging mechanism between Kevlar Z‐pin and Carbon Z‐pin. Reveal the variation of multi‐directional load and energy consumption with mixed‐mode angle in thick laminates. Detailed scanning electron microscope observation to understand failure characteristics of ductile Z‐pin. Evidence that the extra axial load of Z‐pin provided by resin‐rich area.

Direct numerical simulations of pure and partially cracked ammonia/air turbulent premixed jet flames

Ammonia has been identified as a promising fuel to diminish greenhouse gas emission. However, ammonia combustion presents certain challenges including low reactivity and high NO emission. In the present study, three-dimensional direct numerical simulations (DNS) of ammonia/air premixed slot jet flames with varying Karlovitz numbers (Ka) and cracking ratios were performed. Three cases were considered, including two pure ammonia/air flames with different turbulence intensities and one partially cracked ammonia/air flame with high turbulence intensity. The effects of turbulence intensity and partial ammonia cracking on turbulence–flame interactions and NO emission characteristics of the flames were investigated. It was shown that the turbulent flame speed is higher for the flames with high turbulence intensity. In general, the flame displacement speed is negatively correlated with curvature in negative curvature regions, while the correlation is weak in the positive curvature regions for highly turbulent flames. Most flame area is consumed in negatively curved regions and produced in positively curved regions. It was found that the NO mass fraction is higher in the flame with partial ammonia cracking compared to the pure ammonia/air flames. The NO pathway analysis shows that the NH → NO pathway is enhanced, while the NO consumption pathway is suppressed in the partially cracked ammonia/air flame. The NO mass fraction is higher in regions of negative curvature than positive curvature. Interestingly, the NO mass fraction is found to be negatively correlated with the local equivalence ratio, which is consistent in both the DNS and the corresponding laminar premixed flames.

An insight into the characteristics of some oxidized low-grade coals of Indian origin

ABSTRACT The conversion of coal to a hydrophilic state presents a significant challenge for process engineers, especially when treating oxidized coals in flotation-based beneficiation plants. Flotation of oxidized coal often requires a substantial consumption of oily collectors, resulting in unacceptably low yields. To address this, several pre-processing methods have emerged for coal deoxidation, including mild grinding, surface activation, and ultrasonic or microwave treatment. However, their effective application depends on a thorough understanding of the degree of oxidation in the coals. Therefore, it is crucial to gain insights into the nature of oxidized coal before initiating the deoxidation process. This present study provides various characterization techniques such as XRD, SEM-EDS, FTIR Spectroscopy, Raman Spectroscopy, TGA, and Zeta Potential Analysis employed on oxidized low-grade coals. The study revealed that the proximate analysis of low-grade coals KC, DC, RC, and PC contains varying ash percentages of 32.65%, 44.47%, 25.44%, and 37.53%, respectively, with SiO2 and Al2O3 comprising over 80% of the total ash. XRD characterizations identified quartz and kaolinite as major mineral phases in all samples, while SEM-EDS confirmed rough coal surfaces with peeling, off-white aggregations, and surface pores. HGI value ranging from 80 to 91 was attributed to partial decomposition and surface cracking due to oxidation. FTIR spectra revealed pronounced oxidation behavior, with strong −OH peaks in the 3600–3700 cm−1 range. Zeta potential analysis affirmed the oxidized nature of the coals with a pH below 3.1 and an extremely negative zeta potential beyond 3.1. The findings mentioned above showcase the distinct characteristics of oxidized low-grade coals, which serve as crucial indicators for exploring coal beneficiation, especially through the flotation process.

Damage evolution in spark plasma sintered boron carbide under scratch and indentation loading conditions

Spark plasma sintered boron carbide (B4C) has been tested for damage evolution characteristics. Three distinct failure regions were identified during the scratch process of B4C, based on the observed transitions in the induced tangential force pattern and fracturing. B4C exhibited significant elastic recovery effect (50%) under both scratch (1–50 N) and indentations (5–100 mN) loading conditions. The sequence of transition from the nucleation of cracking and its propagation resulting to amorphization were identified. Scratch grooves were characterized with partial bow type Hertzian cracking, radial cracking and an onset of chipping (up to 75 N) and extensive spallation and fragmentation (76–100 N). The spallation regions were characterized with numerous randomly oriented slip lines suggesting failure dominated by the shear deformation. Raman spectra from spallation regions reveal peaks corresponding to amorphous B4C, inferring the occurrence of amorphization concentrated at the localized shear bands. At higher loads (>75 N), grain boundary fractures were observed in addition to simple cleavage fracture, which contributes for deteriorating material performance, by extensive cracking. The hardness and elastic modulus of B4C measured by nanoindentation were 44 GPa ± 6.6 GPa and 560 GPa ± 47 GPa, respectively.

Anionic Ni-Based Metal-Organic Framework with Li(I) Cations in the Pores for Efficient C2H2/CO2 Separation.

Acetylene (C2H2) is widely used as a raw material for producing various downstream commodities in the petrochemical and electronic industry. Therefore, the acquisition of high-purity C2H2 from a C2H2/CO2 mixture produced by partial methane combustion or thermal hydrocarbon cracking is of great significance yet highly challenging due to their similar physical and chemical properties. Herein, we report an anionic metal-organic framework (MOF) named LIFM-210, which has Li+ cations in the pores and shows a higher adsorption affinity for C2H2 than CO2. LIFM-210 is constructed by a unique tetranuclear Ni(II) cluster acting as a 10-connected node and an organic ligand acting as a 5-connected node. Single-component adsorption and transient breakthrough experiments demonstrate the good C2H2 selective separation performance of LIFM-210. Theoretical calculations revealed that Li+ ions strongly prefer C2H2 to CO2 and are primary adsorption sites, playing vital roles in the selective separation of C2H2/CO2.

Utilization of Waste Hydrocarbon Gases

A variety of natural and anthropogenic sources of hydrocarbon gases make a significant contribution to the global emission of greenhouse gases. Reducing the anthropogenic emission of industrial hydrocarbon gases is impossible without new technologies that would allow their cost-effective utilization. The paper describes a number of new promising technologies based on autothermal gas-phase processes of partial oxidation and oxidative cracking of various hydrocarbons, such as associated petroleum gases, coalbed methane, refinery gases, and biogas, which open up prospects for a significant reduction in their flaring or emission into the atmosphere. Among the technologies under consideration are those involving their processing for subsequent use in the energy sector and low-tonnage production of various demanded chemicals.

Exogenous N-hexanoyl-l-homoserine lactone mitigates acid rain stress effects through modulation of structural and functional changes in Triticum aestivum leaf

Acid rain (AR) is a global environmental problem that causes a number of morphological, physiological and molecular changes in plants. N-acyl homoserine lactones, as bacterial quorum sensing signal molecules, mediate a number of physiological processes in plants. In this study, we have demonstrated for the first time the stress-protective role of AHL foliar treatment under conditions of abiotic stress - acid rain. The effects of simulated acid rain (SAR), treatment of plants with N-hexanoyl-l-homoserine lactone (C6-HSL) solution, and a combination of these two factors on the microstructure of the leaf surface, photosynthetic pigments, secondary metabolites, and lipoxygenase activity in winter wheat plants were analyzed. It was established that on the fourth day following treatment of 14-day-old plants with C6-HSL, the thickness of the outer cell wall of the leaf epidermis, together with the cuticle layer, increased by 15 %. SAR treatment resulted in a significant thinning of the cell wall (33 %), while pretreatment with C6-HSL followed by SAR reduced cell wall thickness by only 9 %. Under SAR, the cuticular wax layer was destroyed and there were unequal wax lamellae on the epidermal surface, while in C6-HSL treated plants only partial cracking of the cuticular wax layer, slight destruction of the wax lamellae, and formation of wax crusts took place. C6-HSL induced a significant increase in total chlorophyll content under non-SAR conditions, and significantly mitigated the decrease of total chlorophyll content caused by SAR. Lipoxygenase activity, the content of total phenols, flavonoids, and proline increased after treatment of plants with C6-HSL solution alone and in combination with SAR. This is the first report on the possibility of using C6-HSL as an ecological biostimulator under conditions of AR.

Kinetic Study for Plasma Assisted Cracking of NH3: Approaches and Challenges.

Ammonia is considered as one of the promising hydrogen carriers toward a sustainable world. Plasma assisted decomposition of NH3 could provide cost- and energy-effective, low-temperature, on-demand (partial) cracking of NH3 into H2. Here, we presented a temperature-dependent plasma-chemical kinetic study to investigate the role of both electron-induced reactions and thermally induced reactions on the decomposition of NH3. We employed a plasma-chemical kinetic model (KAUSTKin), developed a plasma-chemical reaction mechanism for the numerical analysis, and introduced a temperature-controlled dielectric barrier discharge reactor for the experimental investigation using 1 mol % NH3 diluted in N2. As a result, we observed the plasma significantly lowered the cracking temperature and found that the plasma-chemical mechanism should be further improved to better predict the experiment. The commonly used rates for the key NH3 pyrolysis reaction (NH3 + M ↔ NH2 + H + M) significantly overpredicted the recombination rate at temperatures below 600 K. Furthermore, the other identified shortcomings in the available data are (i) thermal hydrazine chemistry, (ii) electron-scattering cross-section data of NxHy, (iii) electron-impact dissociation of N2, and (iv) dissociative quenching of excited states of N2. We believe that the present study will spark fundamental interest to address these shortcomings and contribute to technical advancements in plasma assisted NH3 cracking technology.

Reversible cycling performance of a flat-tube solid oxide cell for seawater electrolysis

Hydrogen production by electrolysis of seawater using a reversible solid oxide cell (rSOC) can potentially realize offshore wind power energy storage.In this work, a flat-tube solid oxide cell was used to simulate the “peak shaving and valley filling” aspects usually encountered with wind power, and the reversible cycle of charge and discharge of seawater electrolysis was studied.The results show that the reversible cell runs successfully for more than 1000 h with 31 cycles under the charging voltage of less than 1.22 V and the discharge voltage of higher than 0.71 V. During the reversible operation, the charging degradation rate was 0.73 mV/h and the discharge degradation rate was 0.82 mV/h. The overall calculated efficiency during one reversible cycle was up to 104.9%.Under reversible cycle, the performance degradation of the cell is similar to that under constant current electrolysis, and is mainly due to the coarsening and loss of fuel electrode nickel and the partial cracking of electrolyte/air electrode interface.

Development of a novel method for measuring the interfacial creep strength of laser cladding coatings

In this study, the effect of IN713 coating applied by the laser cladding method on the creep behavior of GTD-111 superalloy by a small punch creep test was investigated. For this purpose, the creep behavior of the specimens in different parts in three conditions of casting, solution heat treatment, and aging was compared. The results showed that the specimen selected from the coating-substrate interface shows the highest creep resistance among other parts. This is attributed to the obstacle to the movement of dislocations by the coating-substrate interface from the substrate to coating. Also, in the aged specimens, due to the increase in γ′ phase volume fraction, the highest creep resistance was obtained. The heat-affected zone (HAZ) of the casting specimen had the lowest creep position due to the formation of partial liquation and cracking by γ-γ′ eutectic, M5B3 boride, Ni-Zr interface, and MC carbide. This problem was solved by performing solution heat treatment before coating and aging after coating.

Seismic dynamic analysis and structural integrity assessment of the PWR spent fuel pool under beyond design basis earthquake

A series of numerical analyses were carried out to assess the safety of spent fuel pool (SFP) of a pressurized water reactor (PWR) power plant in Taiwan. These analyses performed seismic force evaluation and 3D nonlinear finite element analysis (FEA) for the SFP under beyond design basis earthquake (BDBE). In addition, this study considered various in-structural response spectra (ISRS) with various damping ratios and the reduced factors to account for the partial cracking effects from BDBE. In the seismic force evaluation, the results show that the pool base takes the greatest uniform equivalent loading resulted from the cooling water, racks, and spent fuel components. For the walls, the south wall suffers the greatest equivalent force. The results of 3D FEA indicated that the largest values of stress and strain appear at the bottom corner near south wall of the channel between the main pool and cask loading pit for the overall SFP structure. It is also found that the influences of cracking effects on the seismic force calculation and structural analysis are significant. But comparing the results of numerical analysis by 5% damping ratio with 0.7 reduced factor and 10% damping ratio with 0.5 reduced factor, the impacts on the liner of the SFP are insignificant. Because the cooling water leakage depends on the liner failure, the influence on the leakage is small.

Preliminary investigations on the catalytic hydrogenation of polycyclic aromatic hydrocarbons via WGSR

The water-gas shift reaction (WGSR) is a crucial reaction in the direct liquefaction of lignite in a syngas (CO + H2) system. In this study, anthracene was utilized as a polycyclic model compound of lignite, to which hydrogen is donated by the H2/D2 produced from CO and H2O/D2O via the WGSR. The results show that the model compound of the polycyclic aromatic hydrocarbon in coal (anthracene) undergoes partial cracking and polycondensation under non-hydrogen-donor conditions at 400 °C. In addition, WGSR catalyzed by NiO can generate hydrogen for the hydrogenation of anthracene. Comparing the mass spectra of deuterated products with those of conventional hydrogenation products by isotope labeling, the alkyl side chain positions of toluene, 1,4-xylene, methylnaphthalene, 1,1-diphenylethylene, methylanthracene and other compounds are prone to deuteration, enabling speculation of the main hydrogenation route of anthracene, which provides theoretical support for the catalytic hydrogenation in direct liquefaction of lignite in a syngas (CO + H2) system.

Colored cotton wastes valuation through thermal and catalytic reforming of pyrolysis vapors (Py-GC/MS)

This study aims to analyze the products of the catalytic pyrolysis of naturally colored cotton residues, type BRS (seeds from Brazil), called BRS-Verde, BRS-Rubi, BRS-Topázio and BRS-Jade. The energy characterization of biomass was evaluated through ultimate and proximate analysis, higher heating value, cellulose, hemicellulose and lignin content, thermogravimetric analysis and apparent density. Analytical pyrolysis was performed at 500 °C in an analytical pyrolyzer from CDS Analytical connected to a gas chromatograph coupled to the mass spectrometer (GC/MS). The pyrolysis vapors were reformed at 300 and 500 °C through thermal and catalytic cracking with zeolites (ZSM-5 and HZSM-5). It has been noticed that pyrolysis vapor reforming at 500 °C promoted partial deoxygenation and cracking reactions, while the catalytic reforming showed better results for the product deoxygenation. The catalyst reforming of pyrolysis products, especially using HZSM-5 at 500 °C, promoted the formation of monoaromatics such as benzene, toluene, xylene and styrene, which are important precursors of polymers, solvents and biofuels. The main influence on the yields of these aromatic products is due to the catalytic activity of ZSM-5 favored by increased temperature that promotes cracking reactions due expanded zeolites channels.

Effect of the thermal stress on the defect evolution at GaAs/Si wafer bonding with a-Ge intermediate layer

In this paper, the bonding of GaAs wafer and Si wafer is achieved by introducing an amorphous Ge as the intermediate layer. Dislocations are observed on the GaAs surface when the GaAs/Si bonded wafers are annealed at 150 °C. The dislocation density is found to increase with the increase of the annealing temperature (from 150 °C to 350 °C). This feature can be explained by the increase of the thermal stress in the GaAs wafer due to the thermal mismatch between GaAs and Si wafers. With higher annealing temperature, such as 300 °C and 350 °C, some pits which originate from the partial cracking of GaAs surface are observed at the boundary of the bonded and unbonded regions. According to the stress simulation, the thermal stress at the bonding interface increases rapidly and reaches its maximum near the boundary of the bonded and unbonded regions, leading to the cracking of GaAs surface (formation of pits). In addition, large numbers of dislocations are generated near the pits. This may be attributed to the reduction of the nucleation energy of dislocations.

Integrating Electromagnetic Acoustic Transducers in a Modular Robotic Gripper for Inspecting Tubular Components

Tubular structures are critical components in infrastructure such as power plants. Throughout their life, they are subjected to extreme conditions or suffer from defects such as corrosion and cracks. Although regular inspection of these components is necessary, such inspection is limited by safety-related risks and limited access for human inspection. Robots can provide a solution for automatic inspection. The main challenge, however, lies in integrating sensors for nondestructive evaluation with robotic platforms. As part of developing a versatile lizard-inspired tube inspector robot, in this study the authors propose to integrate electromagnetic acoustic transducers into a modular robotic gripper for use in automated ultrasonic inspection. In particular, spiral coils with cylindrical magnets are integrated into a novel friction-based gripper to excite Lamb waves in thin cylindrical structures. To evaluate the performance of the integrated sensors, the gripper was attached to a robotic arm manipulator and tested on pipes of different outer diameters. Two sets of tests were carried out on both defect-free pipes and pipes with simulated defects, including surface partial cracking and corrosion. The inspection results indicated that transmitted and received signals could be acquired with an acceptable signal-to-noise ratio in the time domain. Moreover, the simulated defects could be successfully detected using the integrated robotic sensing system.

Femtosecond Laser Trimming with Simultaneous Nanostructuring to Fine Piercing Punch to Electrical Amorphous Steel Sheets.

A CVD (Chemical Vapor Deposition) diamond coated tungsten carbide (WC) and cobalt (Co) sintered alloy punch was trimmed by the femtosecond laser machining to sharpen its edge with about 2 μm and to simultaneously make nanostructuring to its side surface. In addition to the sharpened edge, its edge profile was formed to be homogeneous enough to reduce the damage layer width by piercing the electrical amorphous steel sheet stack. Each brittle sheet in the stacked work was damaged to have three kinds of defects by piercing; e.g., the droop-like cracking in the thickness and at the vicinity of hole, the wrinkling in peak-to-valley with partial cracking on the peaks, and the circumferential cracking. When using the WC (Co) punch with the inhomogeneous edge profile in the sharpened edge width, these three damages were induced into each sheet and the maximum damage width exceeded 80 μm. When using the punch with the sharpened edge and homogeneous edge profile, the wrinkling mode was saved and the total affected layer width was significantly reduced to less than 20 μm. Through the precise embossing experiments, this effect of punch edge profile condition to the induced damages was discussed with a statement on the nanostructuring effect on the reduction of damaged width in electrical amorphous steel sheets. The developed tool with the sharpened edge and homogenous edge condition contributes to the realization of a low iron loss motor with a reduced affected layer width.