Boletín de Investigación N°14 - Departamento de Industrias USM

BOLETÍN DE INVESTIGACIÓN

ElBoletín de Investigación es una herramienta comunicacional cuyo campo de acción será exclusivamente interno, y su objetivo es poder contribuir a la visibilización de los proyectos de investigación a cargo de nuestros académicos, desde las distintas áreas de donde estos se agrupan. Es por ello que, en esta edición, nos enfocaremos a la presentación del Área de Gestión Tecnológica, incluyendo el resumen de los últimos trabajos a cargo de los investigadores del Departamento de Industrias de la Universidad Técnica Federico Santa María.

ÁREA DE GESTIÓN TECNOLÓGICA

PROFESOR RESPONSABLE Andrés Fuentes Castillo

REPRESENTANTE ACADÉCMICO DEL ÁREA DE DESARROLLO

Dr. Oscar Saavedra Rodríguez

OBJETIVO

El objetivo del área es la formación de recursos humanos de alta calidad y competencia de modo que contribuyen al desarrollo científicotecnológico de las Ciencias de la Ingeniería Industrial con un énfasis en la Gestión de la Energía, desde una perspectiva fundamental como aplicada, formando graduados con sólidos conocimientos teóricos/experimentales que pueden desempeñarse en diferentes industrias en las áreas de eficiencia energética y desarrollo sustentable, además con capacidad para la investigación independiente con estándar internacional.

ACADÉMICOS Y DOCENTES DEL ÁREA

RODRIGO DEMARCO rodrigo.demarco@usm.cl +56 32 2654650

Área de Especialización:

• Conversión de Energía Convencional.

• Optimización de ERNC.

• Simulación de Producción y Dispersión de Contaminantes.

ANDRÉS FUENTES CASTILLO andres.fuentes@usm.cl +56 32 2654650

Área de Especialización:

• Conversión de Energía Convencional.

• Modelación de la Combustión. •Modelación de Incendios Confinados y Abiertos.

MARÍA PILAR GÁRATE CHATEAU mariapilar.garate@usm.cl +56 2 32028290

Área de Especialización:

• Modelos de Gestión Ambiental.

• Políticas Públicas en el Área de ERNC y Eficiencia Energética.

• Modelos de Negocios para la implementación de proyectos que promuevan el desarrollo económico sustentable.

COLABORADORES USM

Rodrigo Araya. Miguel Becerra. Fabián Bustos. A. Cabrera.

Gonzalo Carvajal. Juan José Cruz.

Felipe Escudero. Nicolás Hernández.

Alejandro Jerez. José Morán. Julio Pino. Pablo Pinto. Gonzalo Severino. Juan Pablo Soussi. Miguel Valenzuela. Christopher Volkwein.

COLABORADORES

EXTERNOS

Francisco Cepeda – Ryerson University, Canadá. Fengshan Liu – National Research Council of Canadá, Canadá. Jorge Contreras – Pontificia Universidad Católica de Valparaíso, Chile.

Juan Carlos Elicer-Cortés – Universidad de Chile, Chile. Luis F. Figueira da Silva – Pontificia Universidade Católica do Rio de Janeiro, Brasil. Hugo Garcés – Universidad Católica de la Santísima Concepción, Chile.

Pedro Reszka – Universidad Adolfo Ibáñez, Chile.

A. Carlos Fernández-Pello – University of California, USA.

Jérôme Yon – Normandie Université, France.

Jean-Louis Consalvi – Aix-Marseille Université, France.

Juan Cuevas – The University of Queensland, Australia.

Luis E. Arias – Universidad de Concepción, Chile.

Alejandro J. Rojas – Universidad de Concepción, Chile.

María del Carmen Thomsen – University of California, USA.

Contenido

PUBLICACIONES EN REVISTAS CIENTÍFICAS

“Impact of water-vapor addition to oxidizer on the thermal radiation characteristics of non-premixed laminar coflow ethylene flames under oxygen-deficient conditions” – Cepeda, F., Demarco, R., Escudero, F., Liu, F. & Fuentes, A. Fire Safety Journal, Vol. 120, March 2021. DOI: 10.1016/j.firesaf.2020.103032

“Effects of Wildland Fuel Moisture Content on Radiant Heat Flux Emitted by a Laminar Non-Premixed Flame” – Pinto, P., Cabrera, A., Cruz, J. J., Contreras, J., Severino, G., Demarco, R., Elicer-Cortés, J. C. & Fuentes, A. Applied Thermal Enginnering, Vol. 181, November 2020. DOI: 10.1016/j. applthermaleng.2020.115968

“Influence of water-vapor in oxidizer stream in the sooting behavios for laminar coflow ethylene diffusion flames” – Cepeda, F., Jerez, A., Demarco, R., Liu, F. & Fuentes, A. Combustion and Flame, Vol. 210, December 2019, pp. 114-125. DOI: 10.1016/j.combustflame.2019.08.027

“Measurements and modeling of PAH soot precursors in coflow ethylene/ air laminar diffusion flames” – Jerez, A., Cruz, J. J., Figueira da Silva, L. F., Demarco, R. & Fuentes, A. Fuel, Vol. 236, January 2019, pp. 452-460. DOI: 10.1016/j.fuel.2018.09.047

“Life quality disparity: Anaysis of indoor comfort gaps for Chilean households” – Becerra, M., Jerez, A., Valenzuela, M., Garcés, H. O. & Demarco, R. Energy Policy, Vol. 121, October 2018, pp. 190-201. DOI: 10.1016/j. enpol.2018.06.010

“Piloted Ignition Delay Times on Optically Thin PMMA Cylinders” –Hernández, N., Fuentes, A., Reszka, P. & Fernandez-Pello, C. Proceedings of the Combustion Institute, Vol. 37, Issue 3, 2019, pp. 3993-4000. DOI: 10.1016/j. proci.2018.06.053

“Impact of the Primary Particle Polydispersity on the Radiative Properties of Soot Aggregates” – Yon, J., Liu, F., Morán, J. & Fuentes, A. Proceedings of the Combustion Institute, Vol. 37, Issue 1, 2019, pp. 1151-1159. DOI: 10.1016/j.proci.2018.07.065

“Soot production modeling in a laminar coflow ethylene diffusion flame at different Oxygen Indices using a PAH-based sectional model” – Jerez, A. Consalvi, J. L., Fuentes, A. Liu, F. & Demarco, R. Fuel, Vol. 231, November 2018, pp. 404-416. DOI: 10.1016/j.fuel.2018.05.103

“Analysis of Soot Propensity in Combustion Processes Using Optical Sensors and Video Magnification” – Garcés, H. O., Fuentes, A., Reszka, P. & Carvajal, G. Sensors, Vol. 18, Issue 5, 2018, pp. 1514. DOI: 10.3390/s18051514

“Soot propensity by image magnification and artificial intelligence” – Pino, J., Garcés, H. O., Cuevas, J., Arias, L. E., Rojas, A. J. & Fuentes, A. Fuel, Vol. 225, August 2018, pp. 256-265. DOI: 10.1016/j.fuel.2018.03.141

“Spontaneous ignition of wildland fuel by idealized firebrands” – Hernández, N., Fuentes, A., Consalvi, J.L. & Elicer-Cortés, J.C. Experimental Thermal and Fluid Science, Vol. 95, July 2018, pp. 88-95. DOI: 10.1016/j.expthermflusci.2018.01.037

“Influence of primary particle polydispersity and overlapping on soot morphological parameters derived from numerical TEM images” – Morán, J., Cuevas, J., Liu, F., Yon, J. & Fuentes, A. Powder Technology, Vol. 330, May 2018, pp. 67-79. DOI: 10.1016/j.powtec.2018.02.008

“Numerical simulations of microgravity ethylene/air laminar boundary layer diffusion flames” – Contreras, J., Consalvi, J.L. & Fuentes, A. Combustion and Flame, Vol. 191, May 2018, pp. 99-108. DOI: 10.1016/j.combustflame.2017.12.013

“A calibrated soot production model for ethylene inverse diffusion flames at different Oxygen Indexes” – Demarco, R., Consalvi, J.L. & Fuentes, A. Fuel, Vol. 212, January 2018, pp. 1-11. DOI: 10.1016/j.fuel.2017.10.038

“Influence of soot aging on soot production for laminar propane diffusion flames” – Soussi, J.P., Demarco, R., Consalvi, J.L., Liu, F. & Fuentes, A. Fuel, Vol. 210, December 2017, pp. 472-481. DOI: 10.1016/j.fuel.2017.08.086

“Combustion Diagnostics by Calibrated Radiation Sensing and Spectral Estimation” –Garcés, H. O., Arias, L., Rojas, A., Cuevas, J. & Fuentes, A. IEEE Sensors Journal, Vol. 17, Nº 18, September 2017, pp. 5871-5879. DOI: 10.1109/JSEN.2017.2732440

“Life-cycle savings for a flat-plate solar water collector plant in Chile” – Araya, R., Bustos, F., Contreras, J. & Fuentes, A. Renewable Energy, Vol. 112, November 2017, pp. 365-377. DOI: 10.1016/j. renene.2017.05.036

“Soot measurements in candle flames” – Thomsen, M. C., Fuentes, A., Demarco, R., Volkwein, C., Consalvi, J. L. & Reszka, P. Experimental Thermal and Fluid Science, Vol. 82, April 2017, pp. 116-123. DOI: 10.1016/j.expthermflusci.2016.10.033

“Oxygen index effect on the structure of a laminar boundary layer diffusion flame in a reduced gravity environment” – Contreras, J., Consalvi, J. L. & Fuentes, A. Proceedings of the Combustion Institute, Vol. 36, Issue 2, 2017, pp. 3237-3245. DOI: 10.1016/j.proci.2016.06.065

PUBLICACIONES EN REVISTAS CIENTÍFICAS

“IMPACT OF WATER-VAPOR ADDITION TO OXIDIZER ON THE THERMAL RADIATION CHARACTERISTICS OF NON-PREMIXED LAMINAR COFLOW ETHYLENE FLAMES UNDER OXYGENDEFICIENT CONDITIONS”

Francisco Cepeda1, Rodrigo Demarco2, Felipe Escudero2, Fengshan Liu3 & Andrés Fuentes2.

1 Department of Mechanical and Industrial Engineering, Ryerson University, Canadá.

2 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

3 Measurement Science and Standards, National Research Council, Canadá.

Abstract

The effect of water-vapor addition to oxidizer on flame radiation is assessed experimentally and numerically through the study of laminar coflow ethylene-fueled non-premixed flames. Oxygen-deficient conditions were studied to closely represent real confined fire situations. Experimental soot volume fraction distributions, presented in a previous study, are complemented with temperature and radiation measurements. Experimental data are compared and complemented with numerical simulations. The relative importance of the thermal, chemical and dilution effects of water-vapor is also investigated through numerical modeling. Addition of water-vapor to oxidizer leads to a decrease in soot concentration, flame temperature, emitted radiation and radiant fraction, regardless of the Oxygen Index (OI). The measured temperatures in the sooting region by two-color pyrometry are in reasonably good overall agreement with the numerical predictions. Soot is the main radiation emitter in the ethylene flame under all the conditions studied, but its relative importance decreases with the water-vapor addition. CO2 is the second most important contributor. Depending on the OI, the relative importance of the water-vapor addition to flame radiation varies. At lower OI the dominant effect is thermal, while at higher OI (normal air condition) the effect of the watervapor is shared by the three effects: dilution, chemical, and thermal.

Fire Safety Journal, Vol. 120, March 2021. DOI: 10.1016/j.firesaf.2020.103032

“EFFECTS OF WILDLAND FUEL MOISTURE CONTENT ON RADIANT HEAT FLUX EMITTED BY A LAMINAR NON-PREMIXED FLAME”

Pablo Pinto1, A. Cabrera1, Juan José Cruz1, Jorge Contreras2, Gonzalo Severino1, Rodrigo Demarco1, Juan Carlos Elicer-Cortés3 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Escuela de Ingeniería de Transporte, Pontificia Universidad Católica de Valparaíso, Chile.

3 Departamento de Ingeniería Mecánica, Universidad de Chile, Chile.

Abstract

This work addresses the effect of wildland fuel moisture content on flame radiation. A wildland fuel layer composed of Pinus radiata needles was experimentally studied using a specially designed burner, which produced small bench-scale laminar, non-premixed flames. These flames were suitable for the study of their emitted radiation providing stable, repeatable and axisymmetric flames. Pine needles were dried and then rehydrated to obtain four different moisture contents. The radiant fraction was estimated as the ratio between the radiant emission from the flame and its heat release rate. The radiant emission was determined with measurements from a radiometer and image analysis of the flame shape in order to estimate the view factor between the flame and the radiometer. The mass loss rate was measured to determine the heat release rate from the flame. This study confirms the decrease in radiant emission by increasing fuel moisture content. Also, the results indicate a small variation in the radiant fraction, despite the clear variations observed in flame shape and mass loss. Additionally, correlations between results were determined with the purpose of characterizing the effect of moisture content on the radiant fraction.

Applied Thermal Enginnering, Vol. 181, November 2020.

DOI: 10.1016/j.applthermaleng.2020.115968

“INFLUENCE OF WÁTER-VAPOR IN OXIDIZER STREAM IN THE SOOTING BEHAVIOS FOR LAMINAR COFLOW ETHYLENE DIFFUSION FLAMES”

Francisco Cepeda1, Alejandro Jerez1, Rodrigo Demarco1, Fengshan Liu2 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Measurement Science and Standards, National Research Council, Canadá.

Abstract

The effects of adding water-vapor to the oxidizer stream on soot production in laminar coflow diffusion flames under different oxygen indices (OI) were investigated both experimentally and numerically. A modified coflow Güldertype burner was employed to produce the laminar ethylene flames for fifteen different conditions of the oxidizerstream from oxygen-deficient (OI 17%) to oxygen-enriched (OI 25%) conditions, and also without and with adding water-vapor into the oxidizer stream up to 10% on mole basis. The measured soot volume fractions were compared with numerical predictions obtained using the CoFlame code and a chemical kinetic mechanism that consists of reaction pathways up to 5-ring PAHs. The sectional soot model used to simulate the soot particles dynamics considers soot nucleation, surface growth, PAH condensation, oxidation, particle coagulation and fragmentation. Fairly good agreement between experimental and numerical results was found, as close as 1% and 5% of difference in the peak soot volume fraction for OI21% with 0% and 10% of water-vapor addition, respectively. Clear trends of increasing the soot volume fraction (peak and also overall) was observed with increasing OI, while a significant reduction was obtained with the addition of the water-vapor. For the cases analyzed, a reduction of the total soot content was up to 60%.

The chemical effects were numerically isolated using nonreacting water-vapor and analyzed, contributing especially to the soot oxidation rates. Finally, a study of the main reaction pathways was performed to better understand the chemical effects of water vapor. The results show that water vapor addition affects the concentrations of H and OH radicals and alters the formation and oxidation of soot precursors.

Combustion and Flame, Vol. 210, December 2019, pp. 114-125. DOI: 10.1016/j.combustflame.2019.08.027

“MEASUREMENTS AND MODELING OF PAH SOOT PRECURSORS IN COFLOW ETHYLENE/AIR LAMINAR DIFFUSION FLAMES”

Alejandro Jerez1, Juan José Cruz2, Luís Fernando Figueira da Silva2, Rodrigo Demarco1 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Mechanical Engineering Department, Pontificia Universidade Católica do Rio de Janeiro, Brazil.

Abstract

New experimental and numerical results of a laminar ethylene-air co-flow non-premixed flame are compared, in terms of soot volume fraction and temperature, and of polycyclic aromatic hydrocarbons (PAH) distributions. Measurements involved UVexcited laser induced incandescence (properly calibrated), planar laser induced fluorescence(PLIF), and deconvoluted two-color pyrometry. In order to evidence soot and PAH, the comparison of prompt and delayed detection is carried out at four spectral detection wavelengths (340, 400, 450 and 550 nm). Numerical results are obtained using a detailed gasphase chemical kinetics mechanism considering 94 species and 719 reactions, and a sectional soot model, together with a statistical narrow band correlated K (SNBCK) wide band model to account for radiation. Computed PAH, grouped by their number of rings, is found to exhibit a good correlation with experimental PLIF results at different spectral detection wavelengths. In particular, it is shown that 340 and 400 nm fluorescence signals indicate the presence of one up to four-ringed computed PAH, whereas the interpretation of measurements at larger wavelengths is found to be elusive, due to soot signal overlap. Furthermore, an interplaybetween temperature decrease, soot volume fraction increase and radiative heat transfer distribution with increasing fuel flow rate is also demonstrated.

Fuel, Vol. 236, January 2019, pp. 452-460. DOI: 10.1016/j.fuel.2018.09.047

“LIFE QUALITY DISPARITY: ANAYSIS OF INDOOR COMFORT GAPS FOR CHILEAN HOUSEHOLDS”

Miguel Becerra1, Alejandro Jerez1, Miguel Valenzuela1, Hugo O. Garcés2 & Rodrigo Demarco1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Computer Science Department, Universidad Católica de la Santísima Concepción, Chile.

Abstract

According to the last report of the Organization for Economic Co-operation and Development (OECD), Chile leads the iniquity ranking among the member countries. This inequality goes far beyond the income of a family or the movement between social statements. This work attempts to appreciate this gap in the life quality of the people, precisely in the context of the indoor environmental quality. The methodology involves the Predicted Mean Vote (PMV) for measuring thermal comfort, using the Predicted Percentage of Dissatisfied (PPD) as dimensionless index; and the CO2 concentration as indicated by the ASHRAE-55 standard. The sample involves 20 households in the city of Santiago de Chile, distributed in 5 socioeconomically disparate communes. The National Monitoring Network (RENAM) was used as database, from which information of indoor environmental variables was obtained for 3 winter months. Based on the results, economic inequality is easily confirmed for thermal comfort aspects. A significant difference is shown for the cluster with lowest income, which presented the worst conditions. This difference is even more remarkable when the levels of CO2 are compared. Finally, government policies should consider economic aspects in reducing the iniquity gap, jointly with air quality, energy efficiency and thermal comfort of houses.

Energy Policy, Vol. 121, October 2018, pp. 190-201.

DOI: 10.1016/j.enpol.2018.06.010

“PILOTED IGNITION DELAY TIMES ON OPTICALLY THIN PMMA CYLINDERS”

Nicolás Hernández1, Andrés Fuentes1, Pedro Reszka2 & A. Carlos Fernández-Pello3.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Chile.

3 Department of Mechanical Engineering, University of California Berkeley, USA.

Abstract

The theory to predict ignition of solid fuels exposed to incident radiant heat fluxes has permitted to obtain simple correlations of the ignition delay time with the incident heat flux which are useful in practical engineering applications. However, the theory was developed under the assumption that radiation does not penetrate into the solid phase. In the case of semi-transparent solids, where the penetration of radiation plays an important role in the heating and subsequent ignition of the fuel, the predictions of the classical ignition theory are not applicable. A new theory for the piloted ignition of optically thin cylindrical fuels has been developed. The theory uses an integral method and an approximation of the radiative transfer equation within the solid to predict the heating of an inert solid. An exact and an approximate analytical solution are obtained. The predictions are compared with piloted ignition experiments of clear PMMA cylinders. The results indicate that for opticallythin media, the heating and ignition are not sensible to the thermal conductivity of the solid, they are highly dependent on the in-depth absorption coefficient. Using the approximate solution, the correlation was established. This correlation is adequate for engineering applications, and allows the estimation of effective properties of the solid fuel. The form of the correlation that was obtained is due to the integral method used in the solution of the heat equation, and does not imply that the semi-transparent solid behaves like a thermally thin material. The approximate solution presented in this article constitutes a useful tool for pencil-and-paper calculations and is an advancement in the understanding of solid-phase ignition processes.

Proceedings of the Combustion Institute, Volume 37, Issue 3, 2019 , pp. 3993-4000.

DOI: 10.1016/j.proci.2018.06.053

“IMPACT OF THE PRIMARY PARTICLE POLYDISPERSITY ON THE RADIATIVE PROPERTIES OF SOOT AGGREGATES”

Jérôme Yon1, Fengshan Liu2, José Morán3 & Andrés Fuentes3.

1 Normandie Université, France.

2 Measurement Science and Standards, National Research Council of Canada, Canada.

3 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

Abstract

Combustion generated soot appears as fractal aggregates formed by polydisperse nearly spherical primary particles. Knowledge of their radiative properties is a prerequisite for laser based diagnostics of soot. In this parametric study, the effect of primary particle polydispersity on soot aggregate absorption and scattering properties is investigated numerically. Two series of fractal aggregates formed by normal and lognormal distributed primary particles of different levels of standard deviation were numerically generated for typical flame soot with a fractal dimension and prefactor fixed to and kf ≈ 1.5, respectively. Three aggregate sizes consisting of 50 and 150 monomers per aggregate were investigated. Due to the uncertainty in soot refractive index, radiative properties were calculated by considering two different refractive indices at λ ≈ 532 nm recommended in the literature using the Discrete Dipoles Approximation and the Generalized Multiparticle Mie method. The results are interpreted in terms of correction factors to the Rayleigh–Debye–Gans theory for fractal aggregates (RDG-FA) for the forward scattering cross section A and for the absorption cross section h. It is shown that differential cross section for vertically polarized incident light, total scattering and absorption cross sections are well predicted by the RDG-FA theory for all considered aggregates formed by normally ( 30%) and lognormally (σgeo ≤ 1.6) distributed primary particles. The refractive index is found to be of greater impact than primary particle polydispersity on the importance of multiple scattering. The radiative force per unit laser power experienced by the soot aggregates was found primarily determined by the aggregate volume, regardless of the level of primary particle polydispersity.

Proceedings of the Combustion Institute, Vol. 37, Issue 1, 2019, pp. 1151-1159.

DOI: 10.1016/j.proci.2018.07.065

“SOOT PRODUCTION MODELING IN A LAMINAR COFLOW ETHYLENE DIFFUSION FLAME AT DIFFERENT OXYGEN INDICES USING A PAH-BASED SECTIONAL MODEL”

2 Aix-Marseille Université, France.

3 Measurement Science and Standards, National Research Council of Canada, Canada.

Abstract

A numerical study is carried out to, first of all, investigate the capability of a Polycyclic Aromatic Hydrocarbon (PAH)-based sectional particle dynamics soot model in the prediction of soot production in laminar coflow ethylene diffusion flames. The effects of different oxygen mole fractions in the oxidizer stream, called Oxygen Index (OI), ranging from to oxygenenriched conditions up to are investigated. Secondly, the relative importance of species responsible for the increase in both soot formation and oxidation rates with increasing the OI is analyzed. The soot production model considers a detailed description of nucleation via collisions among heavy PAHs, particle aggregation, PAH condensation, surface growth and oxidation through the hydrogen abstraction acetyleneaddition (HACA) mechanism, and fragmentation of soot aggregates. Model predictions are compared with previously-published experimental data and numerical predictions obtained with a semi-empirical acetylene-based soot production model [Comb. Flame 160: 786–795 (2013)]. Results indicate that the flame structure, soot volume fraction and flame cross-section integrated soot volume fraction predicted by the PAH-based sectional soot model are in good agreement with the experimental data over the entire range of OI considered. The temperature and the concentrations of soot precursors increase with the OI, leading to higher soot nucleation, condensation, surface

growth, and oxidation rates. Results show that the PAH-based sectional soot model represents a significant improvement over the semiempirical acetylene based two-equation soot model studied earlier, especially in conditions far from the normal air conditions (21% of O2). With increasing the OI, the non-dimensional zone of influence does not change for the flame cross-section integrated soot formation rates but increases for the integrated soot oxidation rate. Nucleation occurs just above the burner rim and displays the largest increase in its rate with increasing the OI. Nucleation and condensation are mainly dependent on the concentrations of BGHIF and BAPYR. Condensation is also affected by the increase in the number of aggregates available for collision. Soot formation is mainly dominated by surface growth, through HACA, with a significant influence of soot condensation closer to the burner surface, regardless of the level of OI. The surface growth through HACA is mainly controlled not only by the acetylene concentration and the associated kinetic rate, but also by the specific soot surface area. Oxidation by O2 is found to dominate at the top of the flame, while oxidation by OH is dominant at the middle height of the flame. The oxidation rate by O2increases more rapidly with increasing the OI than that by OH.

Fuel, Vol. 231, November 2018, pp. 404-416. DOI: 10.1016/j.fuel.2018.05.103

Alejandro Jerez1, Jean-Louis Consalvi2, Andrés Fuentes1, Fengshan Liu3 & Rodrigo Demarco2.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

“ANALYSIS OF SOOT PROPENSITY IN COMBUSTION PROCESSES USING OPTICAL SENSORS AND VIDEO MAGNIFICATION”

Hugo O. Garcés1, Andrés Fuentes2, Pedro Reszka3 & Gonzalo Carvajal4.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Computer Science Department, Universidad Católica de la Santísima Concepción, Chile.

3 Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Chile.

4 Departamento de Electrónica, Universidad Técnica Federico Santa María, Chile.

Abstract

Industrial combustion processes are an important source of particulate matter, causing significant pollution problems that affect human health, and are a major contributor to global warming. The most common method for analyzing the soot emission propensity in flames is the Smoke Point Height (SPH) analysis, which relates the fuel flow rate to a critical flame height at which soot particles begin to leave the reactive zone through the tip of the flame. The SPH and is marked by morphological changes on the flame tip. SPH analysis is normally done through flame observations with the naked eye, leading to high bias. Other techniques are more accurate, but are not practical to implement in industrial settings, such as the Line Of Sight Attenuation (LOSA), which obtains soot volume fractions within the flame from the attenuation of a laser beam. We propose the use of Video Magnification techniques to detect the flame morphological changes and thus determine the SPH minimizing observation bias. We have applied for the first time Eulerian Video Magnification (EVM) and Phase-based Video Magnification (PVM) on an ethylene laminar diffusion flame. The results were compared with LOSA measurements, and indicate that EVM is the most accurate method for SPH determination.

Sensors, Vol. 18, Issue 5, 2018, pp. 1514. DOI: 10.3390/s18051514

“SOOT PROPENSITY BY IMAGE MAGNIFICATION AND ARTIFICIAL INTELLIGENCE”

Julio Pino1, Hugo O. Garcés2, Juan Cuevas3, Luis E. Arias4, Alejandro J. Rojas4 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Computer Science Department, Universidad Católica de la Santísima Concepción, Chile.

3 School of Civil Engineering, The University of Queensland, Australia.

4 Departamento de Ingeniería Eléctrica, Universidad de Concepción, Chile.

Abstract

This paper presents the results of two novel approaches to measure the soot propensity of a flame and their comparison with the Line of Sight Attenuation (LOSA) method. Both approaches are based on the detection of the Smoke Point Height (SPH), concept used to determine when a flame is in a sooting state. The first approach is based on the detection of morphological changes in the flame, identified through their amplification via the Eulerian Video Magnification algorithm. Results show an effective amplification of the flame geometry, allowing the visualization of variations on the flame tip unable to be detected by the naked human eye and therefore the detection of SPH. The second approach is based on the application of Artificial Intelligence models to classify flame images regarding their sooting propensity, taking advantage of the knowledge acquired from a referential data set. Both approaches provide an accurate classification when compared to the conventional method of LOSA. Furthermore, both approaches show a greater implementation potential in practical combustion devices than the conventional method of LOSA, due to their reduced hardware and technical requirements.

Fuel, Vol. 225, August 2018, pp. 256-265.

DOI: 10.1016/j.fuel.2018.03.141

Nicolás Hernández1, Andrés Fuentes1, Jean-Louis Consalvi2 & Juan Carlos Elicer-Cortés3.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Aix-Marseille Université, France.

3 Departamento de Ingeniería Mecánica, Universidad de Chile, Chile.

Abstract

The spontaneous ignition of a forest fuel layer by idealized firebrands was carried out experimentally in a bench scale apparatus designed to understand the relationship between the time to ignition and incident radiative heat flux on a ring-shaped forest fuel litter. Time to ignition, mass loss, radial temperatures and incident radiative heat flux were measured. The fuel samples were Radiata Pine needles, representative of Chilean forests and the influence of the physical characteristics of the fuel load were analyzed. The firebrand was idealized using a cylindrical electric heater capable of releasing heat flux up to 26.7 kW/m2. For the fuel beds considered the inverse of ignition time was found to be linearly dependent on the incident radiative heat flux, typically observed for thermally thin solid fuels. Several tests were carried out in order to estimate the critical (minimum) heat flux for spontaneous ignition for two forest fuel loads. Additionally, a quasi-linear relationship between mass loss rate and incident radiative heat flux was experimentally determined.

Experimental Thermal and Fluid Science, Vol. 95, July 2018, pp. 88-95. DOI: 10.1016/j.expthermflusci.2018.01.037

José Morán1, Juan Cuevas2, Fengshan Liu3, Jérôme Yon4 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 School of Civil Engineering, The University of Queensland, Australia.

3 Measurement Sciencie and Standards, National Research Council of Canada, Canada.

4 Normandie Université, France.

Abstract

Experimental studies of soot morphology based on analysis of transmission electron microscopy (TEM) images usually neglect the potential effects of primary particle polydispersity and overlapping. In this study, fractal aggregates of different sizes consisting of polydisperse and overlapping primary particles were numerically generated using typical fractal dimension and prefactor relevant to soot. A total of 3600 simulated two-dimensional projections for each primary particle size distribution and level of overlapping considered was produced and analyzed using two TEM image analysis methods commonly used in the literature to evaluate the effects of primary particle polydispersity and overlapping on the recovered morphological parameters of soot. Fairly large deviations in the recovered number of primary particles in aggregates were obtained by both methods considered using the procedure commonly used in the literature. A recommendation was proposed to improve the accuracy of the retrieved number of polydisperse primary particles in an aggregate. We show that the results obtained by using both the Tian et al. (2006) and Brasil et al. (1999) methods can be significantly improved by using the recommended modification for primary particle polydispersity levels commonly encountered in flame soot. Finally, we recommend to use the modified Tian et al. 2006 method for recovering the number of primary particles of aggregates consisting of both polydisperse and overlapped primary particles.

Powder Technology, Vol. 330, May 2018, pp. 67-79.

DOI: 10.1016/j.powtec.2018.02.008

“SPONTANEOUS IGNITION OF WILDLAND FUEL BY IDEALIZED FIREBRANDS”

“INFLUENCE OF PRIMARY PARTICLE POLYDISPERSITY AND OVERLAPPING ON SOOT MORPHOLOGICAL PARAMETERS DERIVED FROM NUMERICAL TEM IMAGES”

Jorge Contreras1, Jean-Louis Consalvi2 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Aix-Marseille Université, France.

Abstract

Microgravity ethylene/air laminar boundary layer diffusion flames were studied numerically. Two oxidizer velocities of 250 and 300 mm/s and three fuel injection velocities of 3, 4, and 5 mm/s were considered. A detailed gas-phase reaction mechanism, which includes aromatic chemistry up to four rings, was used. Soot kinetics was modeled by using a pyrenebased model including the mechanisms of nucleation, heterogeneous surface growth and oxidation following the hydrogen-abstraction acetylene-addition (HACA) mechanism, polycyclic aromatic hydrocarbon (PAH) surface condensation and soot particle coagulation. Radiative heat transfer from CO, CO2, H2O and soot was calculated using the discrete ordinate method (DOM) coupled to a wide-band correlated-k model. Model predictions are in quantitative agreement with the available experimental data. Model results show that H and OH radicals, responsible for the dehydrogenation of sites in the HACA process, and pyrene, responsible for soot nucleation and PAH condensation, are located in a thin region that follows the stand-off distance. Soot is produced in this region and, then, is transported inside the boundary layer by convection and thermophoresis. The combustion efficiency is significantly lower than 1 and is reduced as the flow residence time increasing, confirming that these sooting micro-gravity diffusion flames are characterized by radiative quenching at the flame trailing edge. In particular, this quenching phenomenon explains the increase in flame length with the oxidizer velocity observed in previous experimental studies. The effects of using approximate radiative-property models, namely the optically-thin approximation and gray approximations for soot and combustion gases, were assessed. It was found that the re-absorption and the spectral dependence of combustion gases and soot must be taken into account to predict accurately temperature, soot volume fraction, flame geometry and flame quenching.

Combustion and Flame, Vol. 191, May 2018, pp. 99-108. DOI: 10.1016/j.combustflame.2017.12.013

“A CALIBRATED SOOT PRODUCTION MODEL FOR ETHYLENE INVERSE DIFFUSION FLAMES AT DIFFERENT OXYGEN INDEXES”

Rodrigo Demarco1, Jean-Louis Consalvi2 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Aix-Marseille Université, France.

Abstract

A numerical investigation was carried out in order to gain insights into the soot production mechanisms by studying the effect of the oxygen concentration of the oxidant stream, known as Oxygen Index (OI), on soot production and flame radiation in laminar Inverse Diffusion Flames (IDF). Several laminar axisymmetric IDF were simulated, varying the OI from 17% to 35%. All flames were fueled with pure ethylene. Comparisons to experimental data were intended to assess and improve the capabilities of a two-equation acetylene/benzene-based semi-empirical soot production model and a Full-Spectrum correlated-k (FSCK) radiative property model. Higher OI were found to generate shorter flames, presenting higher temperatures and an increase in the soot production and energy irradiated. Results show that simulations predict correctly the experimental behavior observed by changing the OI, but reliable predictions are limited to values under 25%. In order to improve the generality of the results, the soot production model was modified, incorporating the soot surface aging effect in an approximated way on the surface growth mechanism, and then it was calibrated. A square root dependence was considered in the specific soot surface area rather than a linear dependence. A sensitivity analysis shows that the surface growth process is the most sensitive in terms of predicting the soot content produced. Simulations after calibration were in satisfactory agreement with the experimental measurements, presenting accurate predictions from both local and overall points of view. Results demonstrate that IDF is a relevant configuration to obtain insights concerning soot modeling, providing a decoupled oxidation process, similar residence times at different OI, and thermal age controlled by temperature alone. Results also demonstrate that considering an aging effect on the soot surface reactivity is necessary in order to properly model the variations induced by changing the OI.

Fuel, Vol. 212, January 2018, pp. 1-11. DOI: 10.1016/j.fuel.2017.10.038

“NUMERICAL SIMULATIONS OF MICROGRAVITY ETHYLENE/AIR LAMINAR BOUNDARY LAYER DIFFUSION FLAMES”

Juan Pablo Soussi1, Rodrigo Demarco1, Jean-Louis Consalvi2, Fengshan Liu3 & Andrés Fuentes1

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Aix-Marseille Université, France.

3 Measurement Sciencie and Standards, National Research Council of Canada, Canada.

Abstract

A numerical analysis was conducted to investigate the effect of varying the Oxygen Index (OI) of the oxidizer stream between 21 and 35% on soot production and thermal radiation emitted by laminar axisymmetric propane diffusion flames at atmospheric pressure. The extended enthalpy defect flamelet model, an acetylene/benzene-based twoequation semi-empirical soot production model, and the Full-Spectrum correlated-k radiative property model were used in the numerical simulations. The focus of this study is to demonstrate that it is important to account for the soot aging effect to correctly predict how increasing OI affects the predicted soot production. Three soot surface growth rate models were considered. The first model neglects the soot aging effect and assumes the soot surface growth rate is linearly dependent on soot surface area. The second and third models account for the soot aging effect by assuming the soot surface growth rate is proportional to the squareroot of soot surface area and assuming a particle sizedependent sublinear soot surface area, respectively. The predicted flame height, soot volume fraction, radially integrated soot volume fraction and radiant fraction were compared to available experimental data. The first soot model predicted a much higher soot loading increase with increasing OI than observed experimentally. The second and third soot models improve considerably the predicted general behavior of soot loading increase with OI. Soot and combustion gases make comparable contribution to flame radiation under the conditions studied. When the soot aging effect is properly taken into account, the relatively efficient numerical code assessed in this study becomes a suitable tool for predicting soot production and thermal radiation in laminar propane diffusion flames at different OI conditions. Moreover, increasing OI of the oxidizer stream is a remarkable way to enhance the flame radiation where the correct estimation of soot production is essential to predict the radiant fraction of the flame.

Fuel, Vol. 210, December 2017, pp. 472-481. DOI: 10.1016/j.fuel.2017.08.086

“COMBUSTION DIAGNOSTICS BY CALIBRATED RADIATION SENSING AND SPECTRAL ESTIMATION”

Hugo O. Garcés1, Luis E. Arias2, Alejandro J. Rojas2, Juan Cuevas3 & Andrés Fuentes4.

1 Computer Science Department, Universidad Católica de la Santísima Concepción, Chile.

2 Electrical Engineering Department, Universidad de Concepción, Chile.

3 School of Civil Engineering, The University of Queensland, Australia.

4 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

Abstract

Optimization of combustion processes holds the promise of maximizing energy efficiency, at the same time lowering fuel consumption and residual gases emissions. In this context, the current common operation setting in combustion processes could be improved by the introduction of passive optical sensors, which can be located close the flame, thus eliminating the inherent transport delay in current setups that only infer the combustion quality by measuring residual gases emissions. However, there is a tradeoff for flame detection between spatialspectral resolutions, depending on the optical sensor scheme. In this paper, we present the fundamentals to avoid this constraint, obtaining a combined high spectral and spatial resolution measurement suitable for combustion diagnostics and control. The core of this proposal is to use the flame images from a lowspectral resolution charge-coupled device camera, combined with a spectral recovery method. This method is based on the off-line samples measured on the continuous component of flame spectra, providing a set of vector basis to estimate a calibrated flame spectra at each pixel. The results of the spectral recovery process verify the suitability of the method in terms of goodness-of-fit coefficient and root mean square error metrics, enabling hyper-spectral measurements based on the combination of different optical sensors. Then, continuous estimated spectra along the flame are used to calculate the energy transfer released by radiation, useful for combustion diagnostics.

IEEE Sensors Journal, Vol. 17, Nº 18, September 2017, pp. 5871-5879.

DOI: 10.1109/JSEN.2017.2732440

“INFLUENCE OF SOOT AGING ON SOOT PRODUCTION FOR LAMINAR PROPANE DIFFUSION FLAMES”

“LIFE-CYCLE SAVINGS FOR A FLAT-PLATE SOLAR WATER COLLECTOR PLANT IN CHILE”

Rodrigo Araya1, Fabián Bustos1, Jorge Contreras1 & Andrés Fuentes1

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

Abstract

In Chile, flate-plate solar water collector (FPSWC) plants have not yet been sufficiently developed despite the excellent solar conditions of the country’s territory. Two of the main parameters affecting the behavior of these plants are the collection area and the water storage volume. In this paper, an energy performance model of an FPSWC plant is used along with genetic algorithms (GAs) to optimize the combination of these two parameters in order to produce the maximum lifecycle savings (LCS). This model is applied to 182 locations in Chile and 6 consumption profiles with the purpose of creating a solar map for this kind of plant throughout the country. The financial results show that the installation of an optimized FPSWC plant is convenient in all the analyzed locations. Furthermore, results are noteworthy in the northern zone of Chile with respect to the others due to excellent meteorological conditions. A sensitivity analysis was carried out at the locations with higher and lower LCS, showing that consumption temperature mainly affects zones with higher radiation. This study allows us to provide evidence that the utilization of FPSWC plants should be promoted in order to induce rapid growth and development of this important technology in Chile.

Renewable Energy, Vol. 112, November 2017, pp. 365-377. DOI: 10.1016/j.renene.2017.05.036

“SOOT MEASUREMENTS IN CANDLE FLAMES”

María del Carmen Thomsen1, Andrés Fuentes2, Rodrigo Demarco1, Christopher Volkwein1, JeanLouis Consalvi3 & Pedro Reszka4

1 Department of Mechanical Engineering, University of California, USA.

2 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

3 Aix-Marseille Université, France.

4 Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Chile.

Abstract

Soot volume fractions and soot temperatures have been measured for the first time on candle flames.

Measurements on laminar steady flames were carried out using candles with wick diameters of 2, 3 and 4mm. Wick length was varied between 4 and 10mm. The shape of the candle flame was obtained from CH∗ spontaneous emissions. Measured flame heights show an increase with wick dimensions, approaching an asymptotic value for increasing wick lengths. Soot volume fractions were obtained from laser extinction measurements with the Modulated Absorption/Emission (MAE) technique.

A deconvolution technique and a regularization procedure were applied to the data. Radial profiles of soot volume fractions increase when varying the wick dimensions; this effect is produced by the greater amount of fuel released by the wick. Radially integrated soot volume fractions were also calculated, presenting a similar behavior to the soot volume fraction radial profiles. The peak integrated soot volume fraction was found at approximately half the flame height, independent of the wick dimensions and burning rates. Soot temperature was obtained from emission measurements at two different wavelengths considering the attenuation of the soot particles in the optical path length. A deconvolution and regularization procedure was carried out in order to obtain temperature profiles for different heights in the flame. The observed increase in soot production and soot temperature profiles was directly related to the higher burning rate experienced by the candle. The results show that peak integrated soot volume fractions are proportional to both the mass loss rates and the flame heights.

Experimental Thermal and Fluid Science, Vol. 82, April 2017, pp. 116-123.

DOI: 10.1016/j.expthermflusci.2016.10.033

Jorge Contreras1, Jean-Louis Consalvi2 & Andrés Fuentes1.

1 Departamento de Industrias, Universidad Técnica Federico Santa María, Chile.

2 Aix-Marseille Université, France.

Abstract

Forty-five experimental flames established over a flat plate were analyzed. A diffusion flame generated from a porous ethylene burner discharging into a parallel oxidizer flow provided a laminar boundary layer. All experiments were conducted in parabolic flights that provide twenty-two seconds of microgravity conditions. Soot production was tracked using the laserinduced incandescence technique, while the spontaneous emission of OH* was used in order to identify the reaction zone. The study was focused on the influence of the oxygen index, the oxidizer flow velocity, and the fuel injection velocity on the flame geometry, characterized by the standoff distance, flame length and the soot production. A dimensionless procedure of transport equations and a scaling analysis were carried out in order to interpret the experimental results and to understand the flame extinction process at the trailing edge. The stand-off distance is found to exhibit three regimes as the distance from the burner leading edge increases: a convection-controlled regime close to the burner leading edge, followed by a

diffusion-controlled regime and then a third regime at the burner trailing edge due to the appearance of tridimensional effects. Experimental results shows that the flame length decrease with the oxygen index and increases with the fuel injection velocity and the oxidizer velocity. This latter evolution is opposite to that observed in ‘closed-tip’ diffusion flame, showing that the flame length is controlled by radiant quenching at the flame trailing edge. Concerning soot production, it is observed that the characteristic length scale of soot volume fraction evolves in an opposite manner with the flame length, showing that this latter is not relevant to define the soot residence time. A residence time based on the integrated soot volume fraction and on the oxidizer flow was found appropriate to study soot formation processes.

Proceedings of the Combustion Institute, Vol. 36, Issue 2, 2017, pp. 3237-3245. DOI: 10.1016/j.proci.2016.06.065

“OXYGEN INDEX EFFECT ON THE STRUCTURE OF A LAMINAR BOUNDARY LAYER DIFFUSION FLAME IN A REDUCED GRAVITY ENVIRONMENT”