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Diffuse-reflection-based single-ended laser absorption sensor for H2O temperature and concentration in kerosene-fuelled combustor
摘要： The design, optimization and demonstration of a compact, single-ended laser absorption sensor based on diffuse-wall-reflected signal is presented for temperature and H2O concentration measurements in a kerosene-fuelled aero-combustor. Challenges of laser measurements in such harsh, practical combustion environments involve strong beam-steering, low signal-to-noise ratio (SNR), and constrained optical access. We here present detailed characterization and optimization procedure of a single-ended optical configuration using a holed off-axis parabolic mirror as the pitch and catch optics, and the coked wall surface of the combustor as a diffuse reflector. A near-infrared distributed-feedback diode laser near 1.4 μm scanned at 1 kHz for direct absorption detection was used to access two H2O transitions for concentration and temperature measurement. Optical system design and adaptive Savitzky-Golay signal processing algorithm was used for noise suppression and SNR amelioration. The sensor was demonstrated under practical conditions in a kerosene-fuelled swirl combustor. High signal fidelity was achieved and allowed for single-scan H2O concentration detection limit of 122 ppm-m-Hz-1/2 despite a low reflected laser intensity level of ~50 μW. In situ, time-resolved measurements detected temperatures ranging from ~1100 K to 1300 K, and H2O concentration ranging from ~8% to 12% as global equivalence ratio varied between 0.2 and 0.45. The results revealed expected trend while demonstrating much faster response and less delay versus a comparing thermocouple. This successful field manifestation provides direct proof for the robustness and reliability of diffuse-reflection-based single-ended sensor system in engine combustion chamber environments.
关键词： single-ended,turbulent environment,combustion diagnostics,laser absorption sensing,kerosene-fuelled combustor
更新于2025-09-23 15:19:57
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Pulverized coal combustion application of laser-based temperature sensing system using computed tomography a?? Tunable diode laser absorption spectroscopy (CT-TDLAS)
摘要： The investigation of combustion phenomena in pulverized coal flames is significant for combustion optimization related to energy conservation and emission reduction. Real-time two dimensional (2D) temperature and concentration distributions play an important role for combustion analysis. The non-contact and fast response 2D temperature and concentration distribution measurement method was developed in this study. The method is based on a combination of computed tomography (CT) and tunable diode laser absorption spectroscopy (TDLAS). The accuracy evaluation of developed 32-path CT-TDLAS demonstrated its feasibility of 2D temperature measurement. 32-path CT-TDLAS was applied to CH4 and 5 kg/h coal combustion fields for 2D temperature measurement. The time-series 2D temperature distribution in coal combustion furnace was measured using 32-path CT-TDLAS measurement cell with kHz time resolution. The transient temperature field of combustion flame directly reflects the combustion mode and combustion stability. The measurement results demonstrate its applicability of CT-TDLAS to various types of combustor, especially the combustion fields with coal and ash particles. CT-TDLAS method with kHz response time enables the real-time 2D temperature measurement to be applicable for combustion analysis.
关键词： 2D temperature measurement,Computed tomography (CT),Tunable diode laser absorption spectroscopy (TDLAS),Time-series distribution,Coal combustion
更新于2025-09-23 15:19:57
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Influence of Precursor Concentration on Structural, Morphological and Optical Properties of Hematite (α-Fe <sub/>2</sub> O <sub/>3</sub> ) Nanoparticles
摘要： Background: We report for the first time that there is a considerable effect on the morphology and optical properties of hematite (α-Fe2O3) nanoparticles by varying the precursor concentrations from 1mmol to 3mmol. The nanoparticles were synthesized by combustion route using ferric nitrate, citric acid and ammonia as precursors at an annealing temperature range of 6000C. Phase purity, morphological studies and optical properties of the products were studied by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman spectroscopy and UV Visible spectroscopy. The as-synthesized hematite nanoparticles have a mesoporous granular and somewhat spherical structure with a bulk density ranging from 0.11 to 0.59gmcm-3. Conclusion: The band gap of the as-synthesized α-Fe2O3 nanoparticles decreases from 1.96eV-1.77eV with the decrease in the precursor concentration. Raman spectroscopy confirmed the formation of a hematite phase of iron oxide nanoparticles. Practical percentage yield of the products increased from 47% to 65% with decrease in precursor concentrations.
关键词： α-Fe2O3 nanoparticles,band gap,Optical properties,morphological studies,bulk density,Combustion synthesis
更新于2025-09-23 15:19:57
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Low-temperature synthesis and characterisation of its photocatalytic properties of BiNbO<SUB align="right">4 by combustion method using polyvinyl alcohol
摘要： BiNbO4 nanopowders were synthesised by polyvinyl alcohol sol-gel combustion method using freshly starting material Nb2O5. nH2O. The prepared samples were characterised by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and thermal gravimetric and differential thermal analysis. The orthorhombic single phase calcined at 750°C for 2 h in the air was thoroughly studied with the highest photocatalytic properties in 25 nm average size. Methyl orange was used to evaluate the photocatalytic properties of BiNbO4 under the visible light irradiation which was degraded by 98%. The regeneration ability of the catalyst was reduced by only 1.65% from 98.85% to 97.20% after using four-times without recovery.
关键词： polyvinyl alcohol,BiNbO4 nanopowders,methylene orange degradation,combustion method
更新于2025-09-19 17:15:36
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A Novel Reddish Orange Luminescent Material Sr3B2O6:Sm3+
摘要： The Sm3+ doped Sr3B2O6 phosphors were synthesized using a solution combustion synthesis method followed by heating of the precursor combustion ash at 1000oC in air. The synthesized phosphors were characterized by powder XRD. The photoluminescence properties of Sm3+-doped Sr3B2O6 were investigated at room temperature. The photoluminescence spectra at room temperature show the f–f transitions typical of Sm3+. The emission spectrum of Sr3B2O6:Sm3+ exhibited four sharp emission peaks corresponding to 4G5/2 → 6H5/2 (563–572 nm), 4G5/2 → 6H7/2 (598–614 nm), 4G5/2 → 6H9/2 (647–666 nm), and 4G5/2 → 6H11/2 (705–714 nm) transitions of Sm3+. The relation between the charge transfer band of Sm3+ ion and the host composition was discussed.
关键词： Sr3B2O6,photoluminescence,combustion synthesis,Sm3+ ion
更新于2025-09-19 17:15:36
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Understanding strong knocking mechanism through high-strength optical rapid compression machines
摘要： Strong knocking combustion has become the greatest challenge for advanced internal combustion engines to pursue thermal efficiency limits at high power density conditions. Arising from enclosed space and extreme combustion situations, the fundamental mechanism for strong knocking combustion has still not been fully understood. In this study, synchronization measurement was performed through simultaneous pressure acquisition and high-speed direct photography, and knocking experiments were comparatively conducted under spark-ignition (SI) and compression-ignition (CI) conditions in a high-strength optical rapid compression machine (RCM) with flat piston design. Strong knocking phenomena were reproduced through varying initial thermodynamic conditions, and localized autoignition (AI) initiation and reaction wave evolutions were visualized, companied by synchronous pressure and temperature trajectories. The results show that compared with initial temperature, initial pressure and equivalence ratio exhibit greater influence on the variations of knocking severity. The weighting of different contributors can be further quantified by an effective energy density that shows positive but nonlinear correlations with knocking severity. However, the distinctions between CI and SI knocking characteristics at identical effective energy density also reflect the essential role of the interplay between primary flame propagation and end-gas AI progress. Visualized combustion images show that through improving end-gas thermodynamic state and reactivity sensitivity, the primary flame propagation can enhance localized AI initiation and secondary intensive AI evolutions, facilitating combustion mode transitions into developing detonation. The significant influence of primary flame propagation is diminished until ignition delay time becomes sufficiently short. Finally, with estimated thermal heterogeneities in flat-piston RCM configurations, the ignition modes of strong knocking cycles are quantified by a non-dimensional ignition regime diagram, and favorable scaling agreements with strong and mixed ignition regimes are observed.
关键词： Rapid compression machine,Effective energy density,Reaction wave propagation,Strong knocking combustion,Ignition regime
更新于2025-09-19 17:15:36
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HVO, RME and Diesel Fuel Combustion in an Optically Accessible Compression Ignition Engine
摘要： The current paper investigates the spray and combustion characteristics of Hydrotreated Vegetable Oil (HVO), petrol diesel (EN590), blends of HVO with petrol diesel (70% EN590 and 30% HVO) and Rapeseed oil Methyl Esters (RME) in an optically accessible compression ignition engine. Mie scattering and natural luminosity imaging are employed to measure the liquid spray and combustion behaviors. The spray and combustion processes are divided into four stages based on optical imaging. The morphology and quantitative analysis based on imaging provides a method for visualizing the in-cylinder spray and combustion behavior with four test fuels. The ignition delay and combustion characteristics detected from optical measurements are compared to those determined from cylinder pressure. The results show that the ignition delay of HVO and RME occurs earlier and the flame propagation at the premixed combustion stage proceeds faster compared to EN590 and HVO30. The spray and combustion characteristics of HVO30 are similar to EN590. However, ignition occurs earlier for HVO30 due to the higher CN. Comparison of the HVO and RME shows that there is a marginal difference in the ignition delay for these two fuels. However, the combustion duration of RME is shorter than that of HVO.
关键词： natural luminosity,optical compression ignition engine,combustion process,renewable diesels
更新于2025-09-19 17:15:36
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Effect of Bi <sup>3+</sup> ion on upconversion-based induced optical heating and temperature sensing characteristics in the Er <sup>3+</sup> /Yb <sup>3+</sup> co-doped La <sub/>2</sub> O <sub/>3</sub> nano-phosphor
摘要： The upconversion-based optical heating and temperature sensing characteristics are investigated in the Er3+/Yb3+/Bi3+ tri-doped La2O3 nano-phosphor synthesized through a solution combustion method. The structural measurements reveal an increase in lattice parameters and particles size of the phosphor on increasing the concentrations of Bi3+ ions. The energy dispersive spectroscopic (EDS) measurements confirm the presence of La, Er, Yb, Bi and O elements in the tri-doped phosphor. The absorption spectra show the large number of bands due to Er3+, Yb3+ and Bi3+ ions. The Er3+/Yb3+ co-doped phosphor gives strong green emission bands at 523 and 548 nm upon 976 nm excitation due to 2H11/2 / 4I15/2 and 4S3/2 / 4I15/2 transitions of Er3+ ion, respectively. The emission intensity of these bands is enhanced upto 15 times in the presence of Bi3+ ions. The emission intensities of the 523 and 548 nm bands vary non-linearly with the pump power. The fluorescence intensity ratio (FIR) of the thermally coupled 523 and 548 nm emission bands shows efficient optical heating in the tri-doped phosphor. The FIR of the 523 and 548 nm emission bands further varies with the increase in temperature of the phosphor. The relative temperature sensing sensitivity has been calculated to be 71 × 10?4 K?1 at 450 K for the tri-doped phosphor. Thus, the Er3+/Yb3+/Bi3+ tri-doped La2O3 nano-phosphor may provide a platform to use it in the photonic devices, as an optical heater and temperature sensor.
关键词： La2O3 nano-phosphor,temperature sensing,optical heating,solution combustion method,Er3+/Yb3+/Bi3+ tri-doped,upconversion
更新于2025-09-19 17:15:36
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Spectroscopic investigation of red Eu3+ doped ceria nanophosphors and promising color rendition for warm white LEDs
摘要： Europium-ion doped CeO2 phosphors with different Eu3+ concentrations were synthesized via sol-gel combustion synthesis. X-ray diffraction patterns revealed the formation of pure cubic structure of CeO2 even after the incorporation of 35 mol% Eu3+. The excitation spectra of CeO2:Eu3+ displayed a broad band (330- 370 nm) and several sharp peaks (393- 532 nm) owing to the charge transfer (CT) from O2- to Ce4+ ions and f-f transitions of Eu3+ ions respectively. The evaluation of CT band was explained on the basis of environmental factors. The phosphors were illuminated with blue light and showed the characteristic red luminescence corresponding to the 5D0→ 7FJ transitions of Eu3+ as confirmed from XPS. The emission was observed to increase with the increase in the Eu3+ concentration upto 35 mol% without any quenching. Judd-Ofelt parameters were evaluated using the emission spectroscopy to explain the variation in ligand environment and enhancement of red color purity to 80%. The thermal stability of present phosphors was measured by estimating activation energy and TG-DSC analysis. Robust blue-excitation and sharp red-emission with high color-purity and promising thermal stability in fabricated WLEDs indicated the suitability of CeO2:Eu3+ phosphors for white light emitting diodes with quantum yield efficiency up to 84.6%.
关键词： color purity,sol-gel assisted combustion,photoluminescence,WLED,charge transfer
更新于2025-09-19 17:13:59
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Laser induced ultrafast combustion synthesis of solution-based AlO <sub/>x</sub> for thin film transistors
摘要： Solution processing of amorphous metal oxides using excimer laser annealing (ELA) has been lately used as a viable option to implement large-area electronics, offering high quality materials at a reduced associated cost and process time. However, the research has been focused on semiconductor and transparent conductive oxide layers rather than on the insulator layer. In this work we present amorphous aluminum oxide (AlOx) thin films produced at low temperature (≤150 °C) via combustion synthesis triggered by ELA, for oxide thin film transistors (TFTs) suitable for manufacturing flexible electronics. The study showed that combining ELA and combustion synthesis leads to an improvement in the dielectric thin film’s densification in a shorter time (≤15 min). Optimized dielectric layers were obtained combining a short drying cycle at 150 °C followed by ELA treatment. High breakdown voltage (4 MV cm?1) and optimal dielectric constant (9) was attained. In general, TFT devices comprising the AlOx fabricated with a drying cycle of 15 min followed by ELA presented great TFT properties, a high saturation mobility (20.4 ± 0.9 cm2 V?1 s?1), a small subthreshold slope (0.10 ± 0.01 V dec?1) and a turn-on voltage ≈0 V. ELA is shown to provide excellent quality solution-based high-k AlOx dielectric, that surpass other methods, like hot plate annealing and deep ultraviolet (DUV) curing. The results achieved are promising and expected to be of high value to the printed electronic industry due to the ultra-fast film densification and the surface/area selective nature of ELA.
关键词： thin film transistors,excimer laser annealing,solution processing,amorphous metal oxides,combustion synthesis,flexible electronics
更新于2025-09-19 17:13:59