Bibliografias temáticas / Tdlas/wms

Literatura científica selecionada sobre o tema "Tdlas/wms"

Autor: Grafiati

Publicado: 20 de julho de 2024

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Artigos de revistas sobre o assunto "Tdlas/wms"

Xiao, Xiao, Jianquan Zhang, Guopeng Zhou, Fengqi Yu, George N. Lawrence e Zhibin Wang. "Study on the Technique for Wavelength Modulation Spectroscopy with Narrow Band Interference Filter Based External Cavity Diode Laser". Journal of Physics: Conference Series 2597, n.º 1 (1 de setembro de 2023): 012012. http://dx.doi.org/10.1088/1742-6596/2597/1/012012.

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Abstract In this study, an improved tunable external cavity diode laser (ECDL) is proposed. It is on the basis of narrow band interference filter, and its theoretical research is carried out as the light source of tunable diode laser absorption spectrum-wavelength modulation spectrum (TDLAS-WMS) system. The proposed model can use piezoelectric ceramic actuator to change and modulate its output central wavelength so that the laser central wavelength could periodically scan the absorption spectral band of the desired gas. Compared with the tunable monolithic diode laser, the narrow band interference filter based tunable ECDL might be able to accurately sense the type and concentration of a large variety of gases. Therefore, it can be used in the TDLAS-WMS system for high precision gas sensing and is expected to replace the tunable monolithic diode laser.

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Jiang, Chunlei, Yunfei Liu, Bo Yu, Shuxin Yin e Peng Chen. "TDLAS-WMS second harmonic detection based on spectral analysis". Review of Scientific Instruments 89, n.º 8 (agosto de 2018): 083106. http://dx.doi.org/10.1063/1.5031683.

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Liang, Tiantian, Shunda Qiao, Xiaonan Liu e Yufei Ma. "Highly Sensitive Hydrogen Sensing Based on Tunable Diode Laser Absorption Spectroscopy with a 2.1 μm Diode Laser". Chemosensors 10, n.º 8 (11 de agosto de 2022): 321. http://dx.doi.org/10.3390/chemosensors10080321.

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As a new form of energy, hydrogen (H2) has clean and green features, and the detection of H2 has been a hot topic in recent years. However, the lack of suitable laser sources and the weak optical absorption of H2 limit the research concerning its detection. In this study, a continuous-wave distributed feedback (CW-DFB) diode laser was employed for sensing H2. Tunable diode laser absorption spectroscopy (TDLAS) was adopted as the detection technique. The strongest H2 absorption line, located at 4712.90 cm−1 (2121.83 nm, line strength: 3.19 × 10−26 cm−1/cm−2 × molec), was selected. We propose a H2-TDLAS sensor based on the wavelength modulation spectroscopy (WMS) technique and a Herriott multipass gas cell (HMPC) with an optical length of 10.13 m to achieve a sensitive detection. The WMS technique and second harmonic (2f) demodulation technique were utilized to suppress system noise and simplify the data processing. The 2f signal of the H2-TDLAS sensor, with respect to different H2 concentrations, was measured when the laser wavelength modulation depth was at the optimal value of 0.016 cm−1. The system’s signal-to-noise ratio (SNR) and minimum detection limit (MDL) were improved from 248.02 and 0.40% to 509.55 and 0.20%, respectively, by applying Daubechies (DB) wavelet denoising, resulting in 10 vanishing moments. The Allan variance was calculated, and the optimum MDL of 522.02 ppm was obtained when the integration time of the system was 36 s.

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Mu, Ye, Tianli Hu, He Gong, Ruiwen Ni e Shijun Li. "A Trace C2H2 Sensor Based on an Absorption Spectrum Technique Using a Mid-Infrared Interband Cascade Laser". Micromachines 9, n.º 10 (19 de outubro de 2018): 530. http://dx.doi.org/10.3390/mi9100530.

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In this study, tunable diode laser absorption spectroscopy (TDLAS) combined with wavelength modulation spectroscopy (WMS) was used to develop a trace C2H2 sensor based on the principle of gas absorption spectroscopy. The core of this sensor is an interband cascade laser that releases wavelength locks to the best absorption line of C2H2 at 3305 cm−1 (3026 nm) using a driving current and a working temperature control. As the detected result was influenced by 1/f noise caused by the laser or external environmental factors, the TDLAS-WMS technology was used to suppress the 1/f noise effectively, to obtain a better minimum detection limit (MDL) performance. The experimental results using C2H2 gas with five different concentrations show a good linear relationship between the peak value of the second harmonic signal and the gas concentration, with a linearity of 0.9987 and detection accuracy of 0.4%. In total, 1 ppmv of C2H2 gas sample was used for a 2 h observation experiment. The data show that the MDL is low as 1 ppbv at an integration time of 63 s. In addition, the sensor can be realized by changing the wavelength of the laser to detect a variety of gases, which shows the flexibility and practicability of the proposed sensor.

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Lu, Rong Jun, De Ming Shen, Qian Qian Du, Bao Zhen Huang e Jian Shu Shi. "Tuning Characteristics of DFB Diode Laser and its Application to TDLAS Gas Sensor Design". Applied Mechanics and Materials 511-512 (fevereiro de 2014): 173–77. http://dx.doi.org/10.4028/www.scientific.net/amm.511-512.173.

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Static and dynamic tuning characteristics of Distribute Feedback (DFB) diode lasers are investigated with practical laser devices. These characteristics are the basic guidelines for practical TDLAS sensors design. Static tuning characteristics help to select suitable diode lasers from limited available laser devices with specific wavelength and to set an appropriate working current and temperature. Dynamic tuning characteristics decide the sweep speed of current slope in both direct absorb Spectroscopy (DAS) and wavelength modulation Spectroscopy (WMS). Because of nonlinearity in the relation between wavelength and tuning current, the measured spectral line position should be corrected by the dynamic characteristics. For WMS, current tuning efficient and IM/AM (Intense modulation/Amplitude modulation) differential phase could be utilized to optimize laser modulation and harmonic components demodulation.

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Zhu, Xiaorui, Shunchun Yao, Wei Ren, Zhimin Lu e Zhenghui Li. "TDLAS Monitoring of Carbon Dioxide with Temperature Compensation in Power Plant Exhausts". Applied Sciences 9, n.º 3 (28 de janeiro de 2019): 442. http://dx.doi.org/10.3390/app9030442.

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Temperature variations of flue gas have an effect on carbon dioxide (CO2) emissions monitoring. This paper demonstrates accurate CO2 concentration measurement using tunable diode laser absorption spectroscopy (TDLAS) with temperature compensation methods. A distributed feedback diode laser at 1579 nm was chosen as the laser source for CO2 measurements. A modeled flue gas was made referring to CO2 concentrations of 10–20% and temperatures of 298–338 K in the exhaust of a power plant. Two temperature compensation methods based on direct absorption (DA) and wavelength modulation (WMS) are presented to improve the accuracy of the concentration measurement. The relative standard deviations of DA and WMS measurements of concentration were reduced from 0.84% and 0.35% to 0.42% and 0.31%, respectively. Our experimental results have validated the rationality of temperature compensations and can be further applied for high-precision measurement of gas concentrations in industrial emission monitoring.

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Xu Jun, 徐俊, 李云飞 Li Yunfei, 程跃 Cheng Yue, 檀剑飞 Tan Jianfei, 刘东 Liu Dong e 周振 Zhou Zhen. "基于TDLAS-WMS的甲烷泄漏遥测系统研制". Laser & Optoelectronics Progress 60, n.º 6 (2023): 0628006. http://dx.doi.org/10.3788/lop213323.

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ZHAO Chenglong, 赵成龙, 黄丹飞 HUANG Danfei, 刘智颖 LIU Zhiying, 王昱琪 WANG Yuqi, 钟艾琦 ZHONG Aiqi, 张耹铭 ZHANG Qinming e 孟凡宏 MENG Fanhong. "开放型TDLAS-WMS技术CO2痕量气体检测". ACTA PHOTONICA SINICA 51, n.º 2 (2022): 0230001. http://dx.doi.org/10.3788/gzxb20225102.0230001.

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Ban, Deyue, Nan Li, Yongqiu Zheng e Chenyang Xue. "CO2 Measurement under Different Pressure and Vibration Conditions Using Tunable Diode Laser Absorption Spectroscopy". Photonics 11, n.º 2 (4 de fevereiro de 2024): 146. http://dx.doi.org/10.3390/photonics11020146.

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The greenhouse effect resulting from fuel combustion has drawn growing attention, and CO2 emissions from fossil fuel power stations are one of the main sources of greenhouse gases. It is crucial to monitor the concentration of CO2 in the flue gas ducts of these stations. However, pressure and vibration caused by the combustion of boilers make the measurement of CO2 in flue gas ducts extremely challenging. In this study, tunable diode laser absorption spectroscopy (TDLAS) combined with Wave Modulation Spectroscopy (WMS) was employed to measure the concentration of CO2 under different pressure and vibration conditions in the laboratory. The absorption line of CO2 at the wavenumber 6357.38 cm−1 was recorded under varying pressure conditions ranging from 0 to 1.4 atm, acceleration conditions ranging from 0 to 7.7 m/s2, and a combination of both. Firstly, a negative linear correlation was found between the pressure and the amplitude of the second harmonic, with a maximum relative error of 4.645% observed at a pressure of 1.4 atm. Secondly, the maximum acceleration that the system can withstand was determined to be 7.3 m/s2, as it was not possible to provide a sufficiently low fitting error at higher accelerations. For the combined effects of the pressure and vibration, a dramatic increase in the relative error of amplitude can be observed within the acceleration range of 5.0~6.0 m/s2 while under the pressure conditions of 0.6 atm, 1.0 atm, and 1.4 atm. Moreover, the maximum endurable acceleration decreases with the increase in pressure, which infers that effective measurements can be achieved when the acceleration is below 5 m/s2 within the pressure range of 0~1.4 atm. This suggests that TDLAS combined with WMS possesses a potential for online measuring of CO2 concentrations in flue gas ducts within a certain acceleration range. This work can provide some insights for stable gas detection using TDLAS under varied pressure and vibration conditions.

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Luo, Qiwu, Chunhua Yang, Cao Song, Jian Zhou e Weihua Gui. "TDLAS/WMS Embedded System for Oxygen Concentration Detection of Glass Vials with Variational Mode Decomposition". IFAC-PapersOnLine 53, n.º 2 (2020): 11626–31. http://dx.doi.org/10.1016/j.ifacol.2020.12.644.

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Mais fontes

Teses / dissertações sobre o assunto "Tdlas/wms"

Lambe, Derek. "WATER VAPOR AND CARBON DIOXIDE SPECIES MEASUREMENT IN NARROW CHANNELS". Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4022.

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A novel method has been implemented for measuring the concentration of gas species, water vapor and carbon dioxide, within a narrow channel flow field non-invasively using tunable diode laser absorption spectroscopy (TDLAS) in conjunction with a laser modulated at a high frequency [Wavelength Modulation Spectroscopy (WMS)] tuned to the ro-vibrational transition of the species. This technique measures the absorption profile which is a strong function of the species concentration across short path lengths and small time spans, as in PEM fuel cells during high load cycles. This method has been verified in a transparent circular flow 12 cm path length and a 12 mm rectangular flow channel. Distinct absorption peaks for water vapor and carbon dioxide have been identified, and concentrations of water vapor and carbon dioxide within the test cells have been measured in situ with high temporal resolutions. A comparison of the full width at half maximum (FWHM) of the absorption lineshapes to the partial pressure of water vapor and carbon dioxide showed a predominantly linear relationship, except in the lower partial pressure regions. Test section temperature was observed to have very minimal impact on these curves at low partial pressure values. A porous media like a membrane electrode assembly (MEA) similar to those used in PEM fuel cells sandwiched between two rectangular flow channels was also tested. Some of the scattered radiation off the MEA was observed using a photodiode at high gain, allowing for more localized species detection. The technique was used to monitor the humidity on either side of the MEA during both temperature controlled and super-saturated conditions. The measurements were observed to be repeatable to within 10 %.
M.S.A.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Aerospace Engineering MSAE

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Norén, Edvin. "Simultaneous detection of potassium, water vapor and temperature with tunable diode laser absorption spectroscopy". Thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105950.

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Existing tunable diode laser absorption spectroscopy (TDLAS) sensors for potassium (K) and for water vapor (H2O) and temperature were combined to enable simultaneous measurements in combustion and gasification processes. In-situ real-time detection of the above mentioned combustion parameters will improve the understanding of ash-formation during thermochemical conversion of biomass. Simultaneous measurements facilitate the experimental procedure and decrease the methodological uncertainty introduced by the heterogeneous nature of the pellets. The K sensor is based on direct absorption spectroscopy (DAS), whereas the H2O system employs wavelength modulation spectroscopy (WMS) together with two-line thermometry for temperature assessment. Two methods for combining the laser beams were evaluated, the first involving dichroic elements, the second using available fiber optic combiners. The latter method was considered advantageous. An existing LabVIEW program was modified to allow for simultaneous signal generation and data acquisition for both sensors. The sensors were then tested separately in a low pressure K cell and in ambient air. The combined sensor was applied to simultaneous measurements above various pelletized biofuels during combustion in a single pellet reactor (SPR). Significant difference in absolute concentration and time histories were observed between fuels, in particular for K and temperature. Significant K concentrations were only observed during the devolatilization phase. The combined sensor will be useful in fundamental combustion research.

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Lan, Lijuan [Verfasser], Jia [Akademischer Betreuer] Chen, Jia [Gutachter] Chen e Mark [Gutachter] Wenig. "Development of a CO2 sensor using TDLAS-WMS and its application for emission analysis in Munich / Lijuan Lan ; Gutachter: Jia Chen, Mark Wenig ; Betreuer: Jia Chen". München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1212178173/34.

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Cocola, Lorenzo. "Tunable diode laser absorption spectroscopy for oxygen detection". Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422063.

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The evolution of diode laser sources for optical communications during the last years led to commercial availability of devices which are suitable for gas absorption spectroscopy in the near and mid infrared. In this work it is shown how the traditional limits of Tunable Diode Laser Absorption Spectroscopy are addressed with digital signal processing techniques and careful optical design towards the realization of gas sensing instruments with the stability, robustness and reliability that are required in an industrial environment. Being one of the most challenging gases to be sensed with this technique, oxygen was considered under many measurement aspects such as: • Non invasive monitoring; • Gas in scattering media sensing; • Sensing with back-scattering targets; • Pressure measurement techniques for weak absorption signals; • Time resolved, dynamic sensing; • Temperature measurement through absorption spectroscopy. Many of these aspects were considered together, leading to the developement of instruments tailored for real life industrial applications such as: • Oxygen sensing in partially transparent containers such as wine or soft drink bottles; • Monitoring of double glazing insulating glass gas filling machines; • Oxygen sensing in containers with backscattering targets such as food packagings. Other applications for the technique and experiments involving Gas in Scattering Media Absorption Spectroscopy were explored during a 6 months period at the Lunds Universitet - Lunds Tekniska Högskola - Atomfysik (Sweden) under the supervision of Prof. S. Svanberg: • Gas probing into porous fruit samples; • Gas sensing inside the human body as a medical diagnosis technique; • Oxygen measurement in fully scattering food containers; • Multi-line absorption spectroscopy as a temperature measurement.
L’evoluzione delle sorgenti laser a diodo per le comunicazioni ottiche negli ultimi anni ha portato ad una disponibilità commerciale di dispositivi che si prestano alla spettroscopia di assorbimento di gas nel vicino e medio infrarosso. In questo lavoro si mostra come i limiti tradizionali della spettroscopia di assorbimento a diodi laser sintonizzabili vengano affrontati con tecniche di elaborazione numerica di segnali ed una attenta progettazione ottica rivolta alla realizzazione di strumenti per il rilevamento di gas caratterizzati dalla stabilità, robustezza ed affidabilità necessari per un ambiente industriale. Trattandosi di uno dei gas più critici per il rilevamento con questa tecnica, l’ossigeno è stato affrontato sotto molteplici aspetti di misura come: • Monitoraggio non invasivo; • Rilevazione di gas in mezzi diffondenti; • Rilevazione tramite bersagli retrodiffondenti; • Tecniche di misura di pressione per deboli segnali di assorbimento; • Rilevazione dinamica con risoluzione temporale; • Misure di temperatura attraverso spettroscopia di assorbimento. Molti di questi aspetti sono stati considerati simultaneamente portando allo sviluppo di strumenti appropriati ad un uso nel mondo reale in applicazioni industriali quali: • Rilevazione di ossigeno in contenitori parzialmente trasparenti come bottiglie di vino e bibite; • Controllo di macchine per il riempimento di pannelli isolanti in vetrocamera; • Rilevazione di ossigeno in contenitori con bersagli retrodiffondenti, quali confezioni alimentari. Altre applicazioni della tecnica ed esperimenti sulla spettroscopia di assorbimento di gas in mezzi porosi sono stati esplorati durante un periodo di 6 mesi presso Lunds Universitet - Lunds Tekniska Högskola - Atomfysik (Svezia) sotto la supervisione del Prof. S. Svanberg: • Analisi di gas in campioni porosi di frutta; • Rilevazione di gas all’interno del corpo umano come tecnica per la diagnostica medica; • Misura di ossigeno in contenitori completamente diffondenti per alimenti; • Spettroscopia di assorbimento multi-riga come misura di temperatura.

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Caville, Sylvain. "Spectroscopie embarquée pour la distribution verticale d'ammoniac (NH3) et de dioxyde de carbone (CO2)". Electronic Thesis or Diss., Reims, 2024. http://www.theses.fr/2024REIMS008.

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L’ammoniac (NH3) est un polluant atmosphérique émis à 80 % par l’agriculture, qui contribue à l’eutrophisation et l’acidification des milieux naturels. C’est aussi un précurseur de particules fines (PM2.5) nocives pour la santé. Malgré ce rôle scientifique et sociétal majeur, nos connaissances sur l’ammoniac atmosphérique restent très limitées. La mesure du profil vertical de NH3 constitue l’une des clés permettant d’approfondir ces connaissances. C’est pourquoi, l’objectif principal de cette thèse est de développer un instrument de mesure de l’ammoniac embarquable dans un ballon captif afin de mesurer ces profils verticaux. Un état de l’art de la mesure de NH3 a d’abord été réalisé à travers l’analyse des données de la campagne AMICA (Analyse Multi-Instrumentale des Concentrations d’Ammoniac) à l'automne 2021. Il a montré la nécessité de concevoir un instrument sans système de prélèvement pour éviter les biais liés à l’adsorption de NH3. Afin de tester et valider les techniques de spectroscopie infrarouge (DAS et WMS) envisagées pour la mesure de NH3, un premier instrument pour la mesure du CO2 (premier gaz à effet de serre d'origine anthropique) a été développé et a permis de réaliser des mesures de profils verticaux. NH3 étant bien plus difficile à détecter que le CO2, une cellule optique à grande longueur de parcours a été conçue afin d’améliorer la sensibilité de l’instrument. Plus généralement, les outils conçus et mis en place au cours de cette thèse peuvent s’appliquer à la mesure de toutes les espèces atmosphériques d’intérêt et en particulier à celles présentes à l’état de traces
Ammonia (NH3) is an atmospheric pollutant, emitted at 80 % by agriculture, which contributes to the eutrophication and acidification of natural environments. It is also a precursor of fine particles (PM2.5) that are harmful to human health. Despite this major scientific and societal role, our knowledge about atmospheric ammonia is still very limited. Measuring the vertical profile of NH3 is one of the keys to improving this knowledge. For this reason, the main objective of this thesis is to develop an ammonia measurement instrument that can be embedded in a tethered balloon to measure these vertical profiles. To begin, a state of the art of NH3 measurement was carried out through the data analysis of the AMICA campaign (Multi-Instrumental Analysis of Ammonia Concentrations) in autumn 2021. It highlighted the need to design an instrument without a sampling system to avoid bias due to NH3 adsorption. To assess the infrared spectroscopy techniques (DAS and WMS) intended for NH3 detection, a first instrument aimed at atmospheric CO2 measurements (main anthropogenic greenhouse gas) was developed and used to carry out vertical profiles. As NH3 is much more difficult to detect than CO2 , a long-path optical cell was designed to improve the instrument’s sensitivity. On a more general level, the tools developed and implemented during this thesis can be applied to the measurement of all the atmospheric species of interest, and in particular those that exist in trace quantities

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Vujanic, Dragan. "Tunable diode laser trace gas detection with a vertical cavity surface emitting laser". Master's thesis, 2009. http://hdl.handle.net/10048/648.

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Thesis (M. Sc.)--University of Alberta, 2009.
Title from PDF file main screen (viewed on Oct. 19, 2009). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Electrical and Computer Engineering, University of Alberta. Includes bibliographical references.

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Trabalhos de conferências sobre o assunto "Tdlas/wms"

Geng, Jingxuan, Lijuan Lan, Qiwu Luo e Chunhua Yang. "Development of an atmospheric CO2 sensor based on TDLAS-WMS". In Global Intelligent Industry Conference 2020, editado por Liang Wang. SPIE, 2021. http://dx.doi.org/10.1117/12.2590791.

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An, Xinchen, Xiaomeng Fang, Xiang Liu e Wenjian Kuang. "A Multiband Infrared Detection System Using Time-Sharing Multiplexing and TDLAS-WMS". In 2023 6th International Conference on Electronics Technology (ICET). IEEE, 2023. http://dx.doi.org/10.1109/icet58434.2023.10212022.

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Luo, Qiwu, bingxing zhou e Chunhua Yang. "Dynamic sparse residual oxygen prediction method for encapsulated pharmaceutical vials under TDLAS/WMS framework". In 9th Symposium on Novel Photoelectronic Detection Technology and Applications (NDTA2022), editado por Wenqing Liu, Hongxing Xu e Junhao Chu. SPIE, 2023. http://dx.doi.org/10.1117/12.2666217.

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Guha, Avishek, e Ingmar Schoegl. "Limited View Tomography of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy: Simulation of an Algebraic Reconstruction Technique". In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89507.

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Temperature and concentration distributions of a simulated flame were reconstructed with the help of computer tomography and tunable diode laser absorption spectroscopy (TDLAS). Reconstructions were based on the simulated numerical values of temperature and concentration of a stationary flame. Integrated absorption measurements along the line-of-sight (LOS) across the flames due to absorption by water vapor (H2O) in the near infra-red (NIR) region, specifically the 6930–6940 cm−1 range, were simulated to obtain the projection values for tomography. Spectroscopic parameters for the absorptions transitions, such as line-strengths, transition wavenumbers, collisional broadening coefficients and coefficients for their temperature dependency were selected from the HITRAN 2004 database. Simulated LOS data are inverted using a multiplicative algebraic reconstruction technique (MART), which are known to outperform traditional filtered back projection methods for cases with limited numbers of views. Based on spatially resolved reconstructions of spectroscopic data, temperature and concentration distributions are calculated using the wavelength modulation spectroscopy with second harmonic detection (WMS-2f) technique. A parametric study based on the number of views, orientation of views and number of rays per view required by the ART is performed in order to assess requirements for an acceptable reconstruction.

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Sur, Ritobrata, Thomas J. Boucher, Michael W. Renfro e Baki M. Cetegen. "In-Situ Optical Measurements of Water Vapor Concentration and Temperature in a Proton Exchange Membrane Fuel Cell at Steady State and Under Dynamic Cycling". In ASME 2009 7th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2009. http://dx.doi.org/10.1115/fuelcell2009-85093.

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A robust, accurate and fast in-situ sensor was developed for detection of water vapor partial pressure and temperature simultaneously at the anode and cathode channels of a PEM fuel cell. Tunable diode laser absorption spectroscopy (TDLAS) utilizing wavelength modulation (WMS) was employed for these measurements. This method determines the ratio of the second and first harmonics (2f/1f) of the spectroscopic absorption profile of water vapor by the aid of a software lock-in amplifier. Measurements were taken using a diode laser emitting around a wavelength of 1471 nm where the water vapor absorption exhibits significant sensitivity to partial pressure and temperature. Measurements of water vapor concentration and temperature in were taken at steady and dynamic operating conditions in the anode and cathode gas channels near the inlet and outlet ports of a serpentine channel PEM fuel cell with Nafion membrane of active area 50 cm2. Different load and inlet humidity conditions were tested to characterize the operation at different conditions. The partial pressure of water vapor increases towards the exit of both the gas channels, but the increase is found to be more significant on the cathode side. The dynamic operation of the fuel cell was also examined in this study as well as the simultaneous measurements at the anode and cathode gas channels.

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Eder, Alexander J., Bayu Dharmaputra, Marcel Désor, Camilo F. Silva, Alex M. Garcia, Bruno Schuermans, Nicolas Noiray e Wolfgang Polifke. "Generation of Entropy Waves by Fully Premixed Flames in a Non-Adiabatic Combustor With Hydrogen Enrichment". In ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/gt2023-102833.

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Abstract Thermoacoustic combustion instability is a major concern in gas turbine combustors with hydrogen-enriched fuels. Unsteady combustion not only generates acoustic waves, but it may also result in fluctuations of burnt gas temperature, referred to as entropy waves. They are convected by the mean flow through the combustor and can cause indirect combustion noise when they are accelerated at the exit. In this work, we demonstrate that entropy waves occur in a fully premixed burner due to unsteady heat transfer at the combustion chamber wall. This mechanism of entropy generation is often neglected in the literature. This work shows an additional mechanism in CH4-H2-air flames, through which entropy may be created even in the fully premixed case. This is due to differential diffusion which generates local fluctuations in equivalence and carbon-to-hydrogen ratios. An adiabatic flame temperature is defined based on these two quantities to examine the influence of differential diffusion on the generation of entropy fluctuations. The generation of entropy waves is investigated by applying system identification (SI) to time series data obtained from a broadband forced large eddy simulation (LES) coupled with a heat conduction solver. The entropy transfer function (ETF) and flame transfer function (FTF) identified are then compared to experimental data obtained with tunable diode laser absorption spectroscopy with wavelength modulation spectroscopy (TDLAS-WMS) for measuring temperature fluctuations, and the multi-microphone method (MMM), respectively. After validating the computational setup, the entropy frequency response is identified at various positions within the combustion chamber, and the effects of generation and convective dispersion of entropy waves are qualitatively investigated. We show that a fully premixed turbulent system may exhibit significant entropy waves caused by wall heat losses and differential diffusion of hydrogen.

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