Flame Interferences Research Articles

Multi-color space features and data regression neural network-based method for molten salt temperature detection in rare earth electrolytic processes

To address the online monitoring of molten salt temperature in the rare earth electrolysis process, this paper proposes a rare earth molten salt temperature detection model (MSTDM) based on multi-color space features and data regression neural networks. The model initially preprocesses the collected molten salt temperature images using techniques such as the Gaussian Mixture Model (GMM) and median filtering, followed by color space transformation. Subsequently, 19 hue features used for temperature quantification are extracted, including the channel responses of RGB, HSV, Lab, and Gray color spaces. Finally, a novel data regression neural network (CNN-BiLSTM-Attention) is employed to learn the long-term dependencies between molten salt hue features and temperature, predicting future molten salt temperatures. Experimental results indicate that using the GMM algorithm to filter out flame interference, introducing novel temperature prediction features, and constructing the CNN-BiLSTM-Attention network all enhance the performance of MSTDM in molten salt temperature prediction tasks. The model achieves a mean absolute error of 3.16 °C in predicting molten salt temperatures at rare earth smelting sites. This research not only provides an effective solution for online monitoring of molten salt temperatures in the rare earth electrolysis process but also offers a reliable reference for temperature monitoring in other fields.

The effect of flame interference between wood pellets on combustion characteristics

The effect of flame interference between wood pellets on combustion characteristics

Fiber-coupled LWIR hyperspectral sensor suite for non-contact component surface temperature measurements.

We report on the development of a robust fiber-coupled long-wavelength infrared (LWIR) hyperspectral sensor suite for accurate and reliable non-contact surface temperature measurements in propulsion systems with limited optical access. We first experimentally investigate various state-of-the-art LWIR optical fibers and identify the ideal fiber for efficient coupling and transmission of LWIR signals. The effects of the fiber material, structure, bending, and thermal heating on LWIR fiber transmission are characterized. Subsequently, we discuss the development of a fiber-coupled LWIR hyperspectral sensor using a multi-mode polycrystalline fiber. The temperature measurement accuracy and precision of the sensor are determined using a well-calibrated blackbody radiation source and heated thermal barrier coating. The sensor is integrated into a homemade water-cooled probe housing and environmental protection box and subsequently used for reliable combustor liner temperature measurements in a high-pressure, liquid-fueled combustor rig with no built-in optical access. We also discuss the measurement challenges associated with flame interference and potential solutions. The LWIR sensor shows significant promise in its application to surface temperature measurements, and our findings can aid propulsion system engineers and researchers in system design and operation optimization.

Pr3+ Luminescence to Improve the Range, Accuracy and Sensitivity of Temperature Measurement

For years, various contact techniques were used to measure temperature. Development of novel and evolving technologies raised the interest in elaboration of non-contact thermometry. Nowadays, this is radiation pyrometry which is the method of choice for such purposes. Yet, it has important limitations – sensitivity to stray light or reflected radiation as well as sensitivity to flame interferences. Also accuracy of temperature measurement, which is not better than ~2 K, is not always satisfactory. Today technologies do not fulfill the needs of temperature sensing in microelectronics, microoptics, photonics, microfluidics, nanomedicine and they require alternative solutions. Among promising approaches, overcoming the limitations of other techniques, luminescent methods are of great interest. While the idea is not new [1], a real breakthrough using this technique was not yet achieved. Combining a high sensitivity and accuracy as well as broad range of temperature usability within one temperature sensor appeared challenging [2,3]. In this presentation we shall prove that Pr3+ luminescence characteristics may offer a lot in this field. While in some compositions this ion generates only 4f®4f luminescence due to relaxation of the higher 3P0 and lower 1D2 levels, in some others also 5d®4f luminescence may take place. We explored the possibility to use all these three luminescent components to sense the temperature accurately and in a broad range. The main argument for that is that all the three emissions are characterized by different mechanisms of their thermal quenching. Furthermore, temperature strongly affects the non-radiative relaxation between the three levels. Our presentation will show first results of the approach presented above using data for Sr2GeO4:Pr and will prove a validity and potential of this new attitude. Figure 1 presents profound changes in emission spectra of Sr2GeO4:Pr in the range of 17-600 K. [1] P. Neubert, US2085508 A, 1937. [2] L. D. Carlos, F. Palacio, Thermometry at the Nanoscale: Techniques and Selected Applications, Royal Society of Chemistry, Oxfordshire 2016. [3] C. D. S. Brites, P. P. Lima, N. J. O. Silva, A. Millán, V. S. Amaral, F. Palacio, L. D. Carlos, Nanoscale 2012, 4, 4799. Figure 1

Planar Laser-Induced Fluorescence Fuel Imaging During Gas-Turbine Relight

This experimental study investigates the influence of fuel distribution on ignition outcome during high-altitude relight of a gas turbine. Planar laser-induced fluorescence is used to image fuel inside a lean direct-injection combustor under realistic conditions. A novel apparatus is developed to permit planar laser-induced fluorescence imaging, in which large quantities of poorly atomized fuel impinges on the internal surfaces of the combustor. Results reveal high variability in atomization quality. In the absence of flame, small droplets are confined to areas of recirculating flow, whereas large droplets impact on the walls. All fuel is introduced through a pilot air-blast atomizer close to the injector centerline. However, comparatively little fuel is apparent near the igniter tip because the outside swirlers of the fuel injector create a fast-moving stream of fuel-free air that flows directly below the upper combustor wall. The droplet size and fuel concentration in the main recirculation zone do not differ radically at test conditions with markedly different fuel-to-air ratios, suggesting that turbulent straining is a more important factor than equivalence ratio in the failure of ignition when the airflow rate is high. In the presence of flame, medium-sized burning droplets are observed close to the injector centerline. Flame interference resulting from fluorescence of polycyclic aromatic hydrocarbons is apparent, but small, suggesting that kerosene planar laser-induced fluorescence is a useful tool for the analysis of all stages of altitude relight.

Improved multiple-pass Raman spectrometer

An improved Raman gain spectrometer for flame measurements of gas temperature and species concentrations is described. This instrument uses a multiple-pass optical cell to enhance the incident light intensity in the measurement volume. The Raman signal is 83 times larger than from a single pass, and the Raman signal-to-noise ratio (SNR) in room-temperature air of 153 is an improvement over that from a single-pass cell by a factor of 9.3 when the cell is operated with 100 passes and the signal is integrated over 20 laser shots. The SNR improvement with the multipass cell is even higher for flame measurements at atmospheric pressure, because detector readout noise is more significant for single-pass measurements when the gas density is lower. Raman scattering is collected and dispersed in a spectrograph with a transmission grating and recorded with a fast gated CCD array detector to help eliminate flame interferences. The instrument is used to record spontaneous Raman spectra from N(2), CO(2), O(2), and CO in a methane-air flame. Curve fits of the recorded Raman spectra to detailed simulations of nitrogen spectra are used to determine the flame temperature from the shapes of the spectral signatures and from the ratio of the total intensities of the Stokes and anti-Stokes signals. The temperatures measured are in good agreement with radiation-corrected thermocouple measurements for a range of equivalence ratios.

183 多点点火を用いた炭化水素-空気混合気の火炎干渉に関する考察(熱工学II)

183 多点点火を用いた炭化水素-空気混合気の火炎干渉に関する考察(熱工学II)

Systematic investigation of aluminium interferences with the alkaline earths in flame atomic absorption spectrometry

Aluminium interferes with the absorption of Mg and Ca in the air-acetylene flame to such an extent that the corresponding absorbances may fall even to zero. This well-known chemical interference can be overcome with the nitrous oxide-acetylene flame, completely in the case of Mg, however only to a restricted extent in the case of Ca. Mg and Ca with concentrations of the AAS-working range in aqueous solutions and Cl− or NO 3 − as anions (in an aqueous HCl or HNO3 matrix, respectively), were determined in the air-acetylene flame with continuously rising Al portions and with (or without) 0.25% Cs as radiation buffer, in order to quantify the degree of these interferences. The same was done to evaluate the extent of the suppression of those interference when using a releaser or protector reagent in both the air-acetylene and the nitrous oxide-acetylene flame. After the decrease of absorption in the air-acetylene flame by forming thermally stable Mg or Ca aluminates, a rapid increase (positive interference) occurs unexpectedly in the presence of Cl−±Cs and with further rising Al contents. This effect still appears for Ca also in the hotter nitrous oxideacetylene flame, however, only in a restricted extent. In the air-acetylene flame the undisturbed absorptions for Mg and Ca (i.e. the starting data without Al) are nearly reached again within the range of the positive interference. This supports the assumption that in consequence of a continuous equilibrium change in the flame because of the rising Al content and in the presence of Cl− and ±Cs the formation of only pure Al oxides now generates the release of Mg and Ca (instead of the thermally stable aluminates in the beginning). In the air-acetylene flame interferences of 1000 mg/l Al are completely removed by an addition of 1% releaser-La, when measuring up to 0.2 mg/l Mg and up to 4 mg/l Ca. The extent of releasing Mg and Ca is effective only up to that Al concentration range which leads to the absorption maximum of Mg and Ca. In the nitrous oxideacetylene flame 5000 mg/l Al are compensated when determining up to 1 mg/l Mg. In the case of Ca, which is detected up to 4 mg/l, interferences of 1000 mg/l Al are only avoided by using the nitrous oxide acetylene flame together with 1% releaser-La. The excellent sensitivity of Ca in this flame (in contrast to the air-acetylene flame) permits a strong dilution, lowering thereby the interfering Al concentration, too. For Mg the same option is valid because of its high sensitivity in the air-acetylene flame.

Determination of trace metals in biological materials by iodides extraction and atomic absorption spectrometry

Extraction of arsenic, mercury, gold, silver, antimony, indium, bismuth, tellurium, cadmium, zinc and copper iodides with methylisobutylketone was examined in the sulfuric acid of concentrations from 0 to 15 normalities. Although, arsenic and zinc iodides were extracted from 6 to 12 normalities, extraction of other metal-iodides were carried out in more wide range of sulfuric acid concentrations almost from 2 to 12 normalities. Iron, sodium, potassium, magnesium and calcium iodides, these, being chief biological elements of inorganic substances, were not extracted in the least into methylisobutylketone layer from sulfuric acid solution. Copper and zinc were normal elements of biological materials and were extracted into methylisobutylketone layer by this procedures. The flame interferences of copper and zinc were not recognized in determinations of gold, silver, antimony, indium, bismuth, tellurium and cadmium. To investigate the influences of biological elements, mock solutions of human blood and urine were prepared. The addition of mock blood does not excessively interfere with determinations of arsenic, mercury, indium, bismuth, tellurium, cadmium, silver and antimony with the exception of gold. However, with addition of mock urine negative interferences were strongly seen in antimony determination, while in mercury, indium and silver determinations only slight interferences were observed. To examine the influences of sample preparation techniques, gold, silver, indium, cadmium and copper were treated both by wet ashing (nitric acid and sulfuric acid) and dry ashing.(ABSTRACT TRUNCATED AT 250 WORDS)

A Method for the Determination of Cadmium in Plant Material by Atomic Absorption Spectroscopy

A method for determining cadmium in plant material by direct aspiration of a solution of the ashed sample in an alcohol-water solvent mixture was investigated. The method was applied to samples containing 0.35 to 3.10 µg of Cd per g. Operating conditions for using an acetylene-air flame were established and flame interference effects minimized; no significant interference was noted from other elements present in plants. Wet and dry ashing procedures provided comparable results. The recovery of added cadmium ranged from 87 to 104%, most values being near 100%. Comparing the AOAC and atomic absorption methods indicated that the atomic absorption method is as reliable and accurate as the official AOAC colorimetric method. Furthermore, it is simpler and faster. A preliminary investigation of the feasibility of using an electrically heated tantalum boat for this type of analysis indicated significant interference by other substances in the sample. Further study of the heated vaporization technique is needed.

Determination of Trace Metals in Sodium Dithionite‐Citrate Extracts of Soils and Sediments by Atomic Absorption

AbstractA general method has been developed for the analysis of Co, Cu, Ni, Mo, and Zn in dithionite‐citrate extracts of soils and sediments. Because of the high Zn content of dithionite, it is necessary to preclean the dithionite‐citrate solution before it is used to extract soils or sediments. This precleaning lowers the detection level significantly for other trace elements as well. Since Fe causes flame interferences in the determination of several first transition series elements by atomic absorption, the size of the individual sample aliquot taken to chelation‐solvent concentration is varied to provide a constant quantity of Fe (5,000 µg). The standards and blanks are adjusted to the same Fe content. This approach is necessitated by the wide differences in the Fe concentrations of the dithionitecitrate extracts. Following pH adjustments and addition of ammonium‐1‐pyrrolidine dithiocarbamate, the trace metals (and Fe) are concentrated via two successive 10‐ml methyl isobutyl ketone extractions. Quantities of Fe much greater than 5,000 µg interfere in the solvent concentration step. Natural organics released by the dissolution of free‐Fe and ‐Mn oxides, to the extent that they are represented by fulvic acids, do not cause any significant interference in the ammonium‐1‐pyrrolidine dithiocarbamate methyl isobutyl ketone extraction of the trace metals due to the releasing effect of the Fe present.

Study on the elimination of interferences in the determination of calcium by atomic absorption spectrophotometry

Optimum conditions and the influence of 53 ions on the determination of calcium by atomic absorption spectrophotometry have been investigated. In the nitrous oxide-acetylene flame interferences are caused by elements with low ionisation potentials. In the air-acetylene flame a number of cations and anions interfere by the formation of refractory compounds. The simple standard additions procedure was unable to overcome these interferences in the concentration ranges investigated, but did give accurate results when used in combination with a releasing agent (strontium).

The determination of microgram amounts of sulphate by emission spectroscopy of barium with a nitrous oxide-acetylene flame

The sulphate content of aqueous solutions has been determined indirectly, in the ranges 0·5 to 5·0 and 1·0 to 10·0 p.p.m., from barium emission measurements. By using a slight excess of barium, the sulphate is precipitated in a 50 per cent. solution of propan-2-ol and its concentration is calculated from the decrease in the barium content of the solution. The amount of barium in solution is determined from its emission at 553·55 nm in a nitrous oxide-acetylene flame. The only major flame interference detected is that from the band emission of calcium; 410 p.p.m. of calcium gave an emission intensity equal to that of 1 p.p.m. of barium. Sulphate has been determined in both pure solutions and in synthetic sample solutions containing other electrolytes. Major interferences were noted for potassium and ammonium oxalate, sodium orthovanadate, nickel chloride and to a lesser extent for sodium fluoride and perchloric acid. The sulphur content of biological material, digested by oxygen-flask combustion, has been determined satisfactorily by using this method.

Overexcitation Interferences in Atomic Absorption Spectrophotometry with an Air–Acetylene Flame

IN recent years, atomic absorption Spectrophotometry has established itself as a valuable analytical technique for trace metal analysis and a large number of procedures are now available for the determination of metals in a wide variety of matrices1,2. In most cases, only qualitative interference effects have been considered, and very little research appears to have been directed towards the flame chemistry of the technique. This would help to elucidate the mechanism of metal vapour production and the causes or mechanisms by which flame interferences are produced. The only interference phenomena which are now well established are those relating to ionization and to the formation of thermally stable compounds such as single or mixed oxides.