Ingeniería Mecánica
https://ridda2.utp.ac.pa/handle/123456789/4770
2024-03-28T19:35:23ZAnálisis termomecánico de la influencia del desgaste geométrico de las herramientas en procesos de corte ortogonal de aceros inoxidables austeníticos
https://ridda2.utp.ac.pa/handle/123456789/5108
Análisis termomecánico de la influencia del desgaste geométrico de las herramientas en procesos de corte ortogonal de aceros inoxidables austeníticos
Marín, Nacarí
Esta Tesis se centra en el análisis termomecánico del efecto del desgaste geométrico de herramienta en el torneado en seco de aceros inoxidables austeníticos. Estos materiales son ampliamente utilizados en aplicaciones de elevada responsabilidad en diferentes sectores industriales. La información obtenida de este análisis puede ser aplicada en la mejora de distintos aspectos del mecanizado como la monitorización del estado de desgaste, el establecimiento de criterios de sustitución de herramienta o el control de daño debido al mecanizado con herramientas desgastadas. La metodología empleada se ha basado en técnicas experimentales y de modelización mediante elementos finitos.
Se han analizado varias geometrías de herramienta relacionadas con todos los tipos de desgaste, así como geometrías mixtas flanco-redondeo y flanco-chaflán.
Se han realizado ensayos de corte con herramientas con las geometrías indicadas, correspondientes a distintos tipos y niveles de desgaste, y en diferentes condiciones de corte.
En estos ensayos se determinaron las componentes de las fuerzas de mecanizado y las tensiones residuales producidas por el proceso de corte. Se ha desarrollado un modelo numérico del proceso objeto de estudio, que incorpora como aportaciones novedosas, el fenómeno de acomodación de filo, así como una ley de fricción híbrido-variable en el contacto herramienta-viruta. El modelo ha sido validado experimentalmente para todos los tipos de desgaste no combinados.
Adicionalmente se han realizado estudios relativos a la simulación numérica de pasadas sucesivas, y al efecto de las condiciones de deformación plana en los modelos bidimensionales. El análisis de estos estudios, considerando distintas geometrías de herramienta, constituye otra de las aportaciones de esta Tesis.
Esta Tesis se centra en el análisis termomecánico del efecto del desgaste geométrico de herramienta en el torneado en seco de aceros inoxidables austeníticos. Estos materiales son ampliamente utilizados en aplicaciones de elevada responsabilidad en diferentes sectores industriales. La información obtenida de este análisis puede ser aplicada en la mejora de distintos aspectos del mecanizado como la monitorización del estado de desgaste, el establecimiento de criterios de sustitución de herramienta o el control de daño debido al mecanizado con herramientas desgastadas. La metodología empleada se ha basado en técnicas experimentales y de modelización mediante elementos finitos.
Se han analizado varias geometrías de herramienta relacionadas con todos los tipos de desgaste, así como geometrías mixtas flanco-redondeo y flanco-chaflán.
Se han realizado ensayos de corte con herramientas con las geometrías indicadas, correspondientes a distintos tipos y niveles de desgaste, y en diferentes condiciones de corte.
En estos ensayos se determinaron las componentes de las fuerzas de mecanizado y las tensiones residuales producidas por el proceso de corte. Se ha desarrollado un modelo numérico del proceso objeto de estudio, que incorpora como aportaciones novedosas, el fenómeno de acomodación de filo, así como una ley de fricción híbrido-variable en el contacto herramienta-viruta. El modelo ha sido validado experimentalmente para todos los tipos de desgaste no combinados.
Adicionalmente se han realizado estudios relativos a la simulación numérica de pasadas sucesivas, y al efecto de las condiciones de deformación plana en los modelos bidimensionales. El análisis de estos estudios, considerando distintas geometrías de herramienta, constituye otra de las aportaciones de esta Tesis.
2010-12-01T00:00:00ZSimultaneous Biochar and Syngas Production in a Top-Lit Updraft Biomass Gasifier
https://ridda2.utp.ac.pa/handle/123456789/5100
Simultaneous Biochar and Syngas Production in a Top-Lit Updraft Biomass Gasifier
James Rivas, Arthur
Biomass materials can be converted to a wide variety of products, e.g., biochar and syngas through thermochemical conversions. In this study, the thermochemical conversion of biomass residues was carried out in a top-lit updraft gasifier. This gasifier type has been extensively used in developing countries to reduce air pollutants in biomass burning while cooking. However, little literature is found related to the quality and quantification of the products. The goal of this study was to investigate top-lit updraft gasification as a potential alternative to the production of biochar and syngas from biomass residues.
The first objective was to understand the effect of the airflow rate and insulation on the overall top-lit updraft gasification process through the quantification of the products and co-products. The results showed that increasing the airflow rate from 8 to 20 lpm proportionally increased the reaction temperature up to 868oC. This increase in temperature negatively impacted the produced biochar which decreased (e.g., from 39.3% to 31.3%, rice hulls – with insulation) with the increase in airflow rate. Little effect in the syngas composition was noticed when varying the airflow, but significant reduction of the tar content (e.g., from 58.7 to 11.8 g/m3, wood chips – without insulation) was observed with the addition of insulation and increase of airflow, enhancing the quality of the produced biochar.
The second objective was to investigate the effect of airflow rate and insulation on the properties of the produced biochar. The properties of the biochar were significantly affected by the airflow and the insulation, but their variations were also governed by the properties of the biomass. Due to the large amount of ash in rice hulls (23%), biochar presented decreasing carbon content as the air flow increased, which was opposite to wood chips biochar because of the low ash content in the untreated wood chips (0.57%). In addition, the BET surface area of the biochar increased up to 332 m2 /g when increasing the airflow, but it further increased to 405 m2 /g with the addition of insulation.
Biomass materials can be converted to a wide variety of products, e.g., biochar and syngas through thermochemical conversions. In this study, the thermochemical conversion of biomass residues was carried out in a top-lit updraft gasifier. This gasifier type has been extensively used in developing countries to reduce air pollutants in biomass burning while cooking. However, little literature is found related to the quality and quantification of the products. The goal of this study was to investigate top-lit updraft gasification as a potential alternative to the production of biochar and syngas from biomass residues.
The first objective was to understand the effect of the airflow rate and insulation on the overall top-lit updraft gasification process through the quantification of the products and co-products. The results showed that increasing the airflow rate from 8 to 20 lpm proportionally increased the reaction temperature up to 868oC. This increase in temperature negatively impacted the produced biochar which decreased (e.g., from 39.3% to 31.3%, rice hulls – with insulation) with the increase in airflow rate. Little effect in the syngas composition was noticed when varying the airflow, but significant reduction of the tar content (e.g., from 58.7 to 11.8 g/m3, wood chips – without insulation) was observed with the addition of insulation and increase of airflow, enhancing the quality of the produced biochar.
The second objective was to investigate the effect of airflow rate and insulation on the properties of the produced biochar. The properties of the biochar were significantly affected by the airflow and the insulation, but their variations were also governed by the properties of the biomass. Due to the large amount of ash in rice hulls (23%), biochar presented decreasing carbon content as the air flow increased, which was opposite to wood chips biochar because of the low ash content in the untreated wood chips (0.57%). In addition, the BET surface area of the biochar increased up to 332 m2 /g when increasing the airflow, but it further increased to 405 m2 /g with the addition of insulation.
2015-01-01T00:00:00ZMeasurement and control of greenhouse gas emissions from beef cattle feedlots
https://ridda2.utp.ac.pa/handle/123456789/5098
Measurement and control of greenhouse gas emissions from beef cattle feedlots
Aguilar, Orlando
Emission of greenhouse gases (GHGs), including nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from open beef cattle feedlots is becoming an environmental concern; however, scientific information on emissions and abatement measures for feedlots is limited. This research was conducted to quantify GHG emissions from feedlots and evaluate abatement measures for mitigating emissions. Specific objectives were to: (1) measure N2O emissions from the pens in a commercial cattle feedlot; (2) evaluate the effectiveness of surface amendments in mitigating GHG emissions from feedlot manure; (3) evaluate the effects of water application on GHG emissions from feedlot manure; and (4) compare the photo-acoustic infrared multi-gas analyzer (PIMA) and gas chromatograph (GC) in measuring concentrations of N2O and CO2 emitted from feedlot manure.
Field measurements on a commercial beef cattle feedlot using static flux chambers combined with GC indicated that N2O emission fluxes varied significantly with pen surface condition. The moist/muddy surface had the largest median emission flux; the dry and compacted, dry and loose, and flooded surfaces had significantly lower median emission fluxes.
Pen surface amendments (i.e., organic residues, biochar, and activated carbon) were applied on feedlot manure samples in glass containers and evaluated for their effectiveness in mitigating GHG emissions. Emission fluxes were measured with the PIMA. For dry manure, all amendments showed significant reduction in N2O and CO2 emission fluxes compared with the control (i.e., no amendment). For moist manure, biochar significantly reduced GHG emissions at days 10 and 15 after application; the other amendments had limited effects on GHG emissions.
The effect of water application on GHG emissions from feedlot manure was evaluated. Manure samples (with and without water application) were placed in glass containers and analyzed for GHG emission using a PIMA. For the dry manure, GHG emissions were negligible. Application of water on the manure samples resulted in short-term peaks of GHG emissions a few minutes after water application.
Comparison of the GC and PIMA showed that they were significantly correlated but differed in measured concentrations of N2O and CO2. The PIMA showed generally lower N2O concentrations and higher CO2 concentrations than the GC.
Emission of greenhouse gases (GHGs), including nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from open beef cattle feedlots is becoming an environmental concern; however, scientific information on emissions and abatement measures for feedlots is limited. This research was conducted to quantify GHG emissions from feedlots and evaluate abatement measures for mitigating emissions. Specific objectives were to: (1) measure N2O emissions from the pens in a commercial cattle feedlot; (2) evaluate the effectiveness of surface amendments in mitigating GHG emissions from feedlot manure; (3) evaluate the effects of water application on GHG emissions from feedlot manure; and (4) compare the photo-acoustic infrared multi-gas analyzer (PIMA) and gas chromatograph (GC) in measuring concentrations of N2O and CO2 emitted from feedlot manure.
Field measurements on a commercial beef cattle feedlot using static flux chambers combined with GC indicated that N2O emission fluxes varied significantly with pen surface condition. The moist/muddy surface had the largest median emission flux; the dry and compacted, dry and loose, and flooded surfaces had significantly lower median emission fluxes.
Pen surface amendments (i.e., organic residues, biochar, and activated carbon) were applied on feedlot manure samples in glass containers and evaluated for their effectiveness in mitigating GHG emissions. Emission fluxes were measured with the PIMA. For dry manure, all amendments showed significant reduction in N2O and CO2 emission fluxes compared with the control (i.e., no amendment). For moist manure, biochar significantly reduced GHG emissions at days 10 and 15 after application; the other amendments had limited effects on GHG emissions.
The effect of water application on GHG emissions from feedlot manure was evaluated. Manure samples (with and without water application) were placed in glass containers and analyzed for GHG emission using a PIMA. For the dry manure, GHG emissions were negligible. Application of water on the manure samples resulted in short-term peaks of GHG emissions a few minutes after water application.
Comparison of the GC and PIMA showed that they were significantly correlated but differed in measured concentrations of N2O and CO2. The PIMA showed generally lower N2O concentrations and higher CO2 concentrations than the GC.
2013-05-01T00:00:00Z