scholarly journals Numerical and Experimental Analysis of the Effect of a Swirler with a High Swirl Number in a Biogas Combustor

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2768
Author(s):  
Marco Osvaldo Vigueras-Zúñiga ◽  
Carlos Augusto Ramírez-Ruíz ◽  
Agustín L. Herrera-May ◽  
María Elena Tejeda-del-Cueto
Keyword(s):  
Numerical Model ◽  
Mole Fraction ◽  
Experimental Testing ◽  
Calorific Value ◽  
Clean Energy ◽  
Fuel Mixture ◽  
Pollutant Emissions ◽  
Low Velocity ◽  
Swirl Number ◽  
Flamelet Model

Climate change as a worldwide phenomenon is the cause of multinational agreements such as the Kyoto Protocol and the Paris Agreement with the goal of reducing greenhouse gas emissions. Biogas is one of the most promising biofuels for the integration of clean energy sources; however, biogas has the disadvantage of a low calorific value. To overcome this problem, mechanical devices such as swirlers are implemented in combustion chambers (CCs) to increase their combustion efficiencies. A swirler induces rotation in the airstream that keeps a constant re-ignition of the air–fuel mixture in the combustion. We present the numerical modeling using computational fluid dynamics (CFD) and experimental testing of combustion with biogas in a CC, including an optimized swirler in the airstream with a swirl number (Sn) of 2.48. A turbulence model of the renormalization group (RNG) was used to analyze the turbulence. Chemistry was parameterized using the laminar flamelet model. The numerical model allows visualizing the recirculation zone generated at the primary zone, and partially at the intermediate zone of the CC caused by the strong swirl. Temperature distribution profiles show the highest temperatures located at the intermediate and dilution zones, with the last one being a characteristic feature of biogas combustion. A strong swirl in the airstream generates low-velocity zones at the center of the CC. This effect centers flame, avoiding hot spots near the flame tube and flashback at the structural components. Regarding pollutant emissions, the goal of a biogas that generates less pollutants than nonrenewable gases is accomplished. It is observed that the mole fraction of NO in the CC is close to zero, while the mole fraction of CO2 after combustion is lowered compared to the original mole fraction contained in the biogas (0.25). The mole fraction of CO2 obtained in experimental tests was 0.0127. Results obtained in the numerical model for temperatures and mole fractions of CO2 and NO show a behavior similar to that of the experimental model. Experimental results for mole fraction of CO emissions are also presented and have a mean value of 0.0009. This value lies within allowed pollutant emissions for CO according to national environmental regulations.

scholarly journals Dynamic Loading of Lattice Structure Made by Selective Laser Melting-Numerical Model with Substitution of Geometrical Imperfections

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2129 ◽  
Author(s):  
Radek Vrána ◽  
Ondřej Červinek ◽  
Pavel Maňas ◽  
Daniel Koutný ◽  
David Paloušek
Keyword(s):  
Mechanical Properties ◽  
Numerical Model ◽  
Cross Section ◽  
Lattice Structure ◽  
Low Velocity Impact ◽  
Lattice Structures ◽  
Laser Melting ◽  
Low Velocity ◽  
Velocity Impact ◽  
Geometrical Imperfections

Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many thin struts, can lead to a great difference in prediction of their behavior. This article deals with the prediction of lattice structure mechanical properties under dynamic loading using finite element method (FEA) with inclusion of geometrical imperfections of the SLM process. Such properties are necessary to know especially for the application of SLM fabricated lattice structures in automotive or aerospace industries. Four types of specimens from AlSi10Mg alloy powder material were manufactured using SLM for quasi-static mechanical testing and determination of lattice structure mechanical properties for the FEA material model, for optical measurement of geometrical accuracy, and for low-velocity impact testing using the impact tester with a flat indenter. Geometries of struts with elliptical and circular cross-sections were identified and tested using FEA. The results showed that, in the case of elliptical cross-section, a significantly better match was found (2% error in the Fmax) with the low-velocity impact experiments during the whole deformation process compared to the circular cross-section. The FEA numerical model will be used for future testing of geometry changes and its effect on mechanical properties.

scholarly journals Measurement of Air-Fuel Ratio Fluctuations Caused by Combustor Driven Oscillations

1998 ◽  
Author(s):  
Rajiv Mongia ◽  
Robert Dibble ◽  
Jeff Lovett
Keyword(s):  
Power Spectrum ◽  
Mole Fraction ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Lean Premixed Combustion ◽  
Lean Premixed

Lean premixed combustion has emerged as a method of achieving low pollutant emissions from gas turbines. A common problem of lean premixed combustion is combustion instability. As conditions inside lean premixed combustors approach the lean flammability limit, large pressure variations are encountered. As a consequence, certain desirable gas turbine operating regimes are not approachable. In minimizing these regimes, combustor designers must rely upon trial and error because combustion instabilities are not well understood (and thus difficult to model). When they occur, pressure oscillations in the combustor can induce fluctuations in fuel mole fraction that can augment the pressure oscillations (undesirable) or dampen the pressure oscillations (desirable). In this paper, we demonstrate a method for measuring the fuel mole fraction oscillations which occur in the premixing section during combustion instabilities produced in the combustor that is downstream of the premixer. The fuel mole fraction in the premixer is measured with kHz resolution by the absorption of light from a 3.39 μm He-Ne laser. A sudden expansion combustor is constructed to demonstrate this fuel mole fraction measurement technique. Under several operating conditions, we measure significant fuel mole fraction fluctuations that are caused by pressure oscillations in the combustion chamber. Since the fuel mole fraction is sampled continuously, a power spectrum is easily generated. The fuel mole fraction power spectrum clearly indicates fuel mole fraction fluctuation frequencies are the same as the pressure fluctuation frequencies under some operating conditions.

Co-Combustion of Coal With Rice Husk and Bamboo in Power Generation

2007 ◽  
Author(s):  
Christopher Y. H. Chao ◽  
Philip C. W. Kwong ◽  
J. H. Wang
Keyword(s):  
Rice Husk ◽  
Power Plants ◽  
Fuel Mixture ◽  
Volatile Matter ◽  
Pollutant Emissions ◽  
Energy Output ◽  
Pollutant Emission ◽  
Firing Process ◽  
Excess Air ◽  
Unit Energy

In many Asian countries Coal is frequently used a major fuel in power plants. Burning coal creates quite a lot of environmental problems when compared to other cleaner fuels such as natural gas. Experimental study of co-combustion of coal and biomass was conducted in a laboratory scale combustion facility to evaluate the combustion and pollutant emission performance under different operation parameters. Rice husk and bamboo were used as the biomass fuels in this study. This paper reported the influence of the biomass blending ratio in the fuel mixture and the excess air ratio on the combustion behavior. It was noted that the combustion temperature and the energy output from the co-firing process were reduced compared to coal combustion alone owing to the fact that biomass has lower heating value compared to coal. However, the high volatile matter (VM) content of biomass improved the combustion time scale so that the carbon monoxide (CO) emissions were reduced substantially. In addition, the fuel nitrogen and sulfur content in biomass were lower than that of coal and hence suppressed the formation of nitrogen oxides (NOx) and sulfur dioxide (SO2) during the cocombustion process. The increase of excess air ratio also affected most of the pollutant emissions. The pollutant emission per unit energy output at different excess air ratios and biomass blending ratios were studied in detail in this paper. Attention should be paid to the high potential of slagging and fouling in the boiler when co-firing coal with biomass.

scholarly journals NUMERICAL PREDICTIONS AND MECHANICAL TESTING OF BRAIDED COMPOSITE STRUCTURES UTILISING DIGITAL IMAGE CORRELATION

2016 ◽  
Vol 7 ◽  
pp. 43
Author(s):  
Emil Pitz ◽  
Matei-Constantin Miron ◽  
Imre Kállai ◽  
Zoltán Major
Keyword(s):  
Numerical Model ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Composite Structures ◽  
Experimental Testing ◽  
Single Layer ◽  
Failure Criteria ◽  
Image Correlation ◽  
Braided Composites ◽  
Numerical Predictions

The current paper is describing the implementation of a multiscale numerical model for prediction of stiffness and strength in braided composites. The model is validated by experimental testing of single-layer braided tubes under torsional loading utilising digital image correlation (DIC). For the numerical model the entire braided structure is modelled at yarn detail level, taking into account the yarn behaviour as well as individual yarn-to-yarn interactions by using cohesive contact definitions. By means of Hashin’s failure criteria and cohesive contact damage, failure of the yarns and failure of the yarn-to-yarn interface is being accounted for. Thereby the material failure behaviour can be predicted. For validation of the model, torsion tests of biaxially braided single-layer composite tubes were performed. The strain distribution at the specimen surface was studied using the DIC system ARAMIS in 3D mode.

scholarly journals Can hydrogen enriched biogas be used as domestic fuel? - Part II: Pollutants Emission from Combustion of Biogas/H2/air Fuel Mixture

2021 ◽  
Vol 28 (2) ◽  
pp. 68-74
Author(s):  
Udaya Kahangamage ◽  
Yi Chen ◽  
Quan Zhou ◽  
Chun Wah Leung
Keyword(s):  
Thermal Performance ◽  
Biogas Production ◽  
Fuel Mixture ◽  
Pollutant Emissions ◽  
Emission Characteristics ◽  
Environmentally Conscious ◽  
Performance And Emission ◽  
Wide Range ◽  
Pollutants Emission ◽  
Domestic Fuel

Biogas is considered a sustainable source of energy which is largely untapped owing to its inherent weaknesses such as low thermal performance and potentially harmful emissions. Its thermal performance and emission characteristics can be enhanced through the technique of enriching with higher grade fuel. In this research study, biogas enriched with hydrogen was tested for its emission characteristics. A synthetic biogas identified as BG60 (60% CH4 and 40% CO2) enriched with 20% hydrogen (80%BG60-20%H2) was used for the test. Experiments were carried out for combustion of the enriched gas for a wide range of Reynolds numbers and equivalence ratios. The results indicate that the enriched fuel emits less CO and NOx than commonly used domestic fuel LPG. It also has a better thermal and emission performance than BG60. The low pollutant emissions compared with LPG, use of renewable feedstock for biogas production, and competitive cost may make the blended 80%BG60-20%H2 an attractive sustainable alternative domestic fuel choice for environmentally conscious urban dwellers of modern cities.

scholarly journals Finite Element Analysis of the Multilayered Honeycomb Composite Material Subjected to Impact Loading

2017 ◽  
Vol 54 (1) ◽  
pp. 180-179 ◽  
Author(s):  
Raul Cormos ◽  
Horia Petrescu ◽  
Anton Hadar ◽  
Gorge Mihail Adir ◽  
Horia Gheorghiu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Composite Material ◽  
Experimental Testing ◽  
Finite Element Models ◽  
The Finite Element Method ◽  
Low Velocity ◽  
Element Analysis ◽  
Element Simulation ◽  
Different Levels

The main purpose of this paper is the study the behavior of four multilayered composite material configurations subjected to different levels of low velocity impacts, in the linear elastc domain of the materials, using experimental testing and finite element simulation. The experimental results obtained after testing, are used to validate the finite element models of the four composite multilayered honeycomb structures, which makes possible the study, using only the finite element method, of these composite materials for a give application.

scholarly journals Swirler geometry effects (dh/do ratio) on synthetic gas flames: Part 1: Combustion and emission characteristics

Energetika ◽  
2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Harun Yilmaz ◽  
Omer Cam ◽  
Ilker Yilmaz
Keyword(s):  
Room Temperature ◽  
Swirling Flow ◽  
Pollutant Emissions ◽  
Emission Characteristics ◽  
Atmospheric Conditions ◽  
Data Logger ◽  
Swirl Number ◽  
Synthetic Gas ◽  
Performance Results ◽  
The City

Swirling flows increase combustion performance via favouring flame stability, pollutant emissions, and combustion intensity. The strength of a swirling flow is characterized by a parameter known as swirl number, which is highly related to the dh/do ratio. In this study, effects of the swirler dh/do ratio on combustion and emission characteristics of the synthetic gas flames of premixed 20%CNG/30%H2/30%CO/20%CO2 mixture were experimentally investigated in a laboratory-scale swirl stabilized combustor. For this purpose, twelve different swirl generators were designed and manufactured. dh/do ratios of these swirlers were set as 0.30 and 0.50, and the geometric swirl number was varied between the values of 0.4 and 1.4 (at 0.2 intervals). All experiments were conducted at a fuel-lean equivalence ratio (ϕ = 0.6), room temperature, and local atmospheric conditions of the city of Kayseri, Turkey. A data logger was utilized to plot axial and radial temperatures and NOx, CO, and CO2 profiles, which were exploited to assess combustion and emission performance. Results showed that the dh/do ratio had a non-monotonic effect on the behaviour of combustion and emission of the tested synthetic gas mixture. Depending on the swirl number, increments and decrements were observed in temperature and emission values.

scholarly journals Wavelet analysis of flame blowout of a liquid-fueled swirl burner with quarls

2019 ◽  
Vol 67 (5) ◽  
pp. 394-403
Author(s):  
Viktor Józsa ◽  
Gergely Novotni
Keyword(s):  
Wavelet Transformation ◽  
Acoustic Noise ◽  
Operating Regime ◽  
Pollutant Emissions ◽  
Swirl Number ◽  
Axial Thrust ◽  
Lean Blowout ◽  
Swirl Combustion ◽  
Thrust Control ◽  
Flame Shape

Lean swirl combustion is the leading burner concept today, used in several steadyoperating applications to ensure awide operating range and low pollutant emissions. Approaching lean blowout is highly desired by design to achieve the lowest possible NOX emission. It was shown earlier that quarls could significantly extend the operating regime of liquid-fueled swirl burners. In the present study, the accompanying acoustic noise is evaluated by continuous wavelet transformation to show the effect of various quarl geometries on lean flame blowout. However, the desired flame shape of swirl burners is V, first, and a straight flame, and then a transitory regime can be observed before the developed V-shaped flame through increasing the swirl number. If the axial thrust is excessive, blowout might occur in earlier stages. Presently, the characteristic bands before blowout were analyzed and evaluated at various quarl geometries, swirl numbers, and atomizing pressures. The latter parameter also acts as an axial thrust control to adjust the swirl number. firstly, a straight flame, then a transitory regime can be observed before the developed V-shaped flame through increasing the swirl number. If the axial thrust is excessive, blowout might occur in earlier stages. Presently, the characteristic bands before blowout were analyzed and evaluated at various quarl geometries, swirl numbers, and atomizing pressures. The latter parameter also acts as an axial thrust control to adjust the swirl number.

Considerations Regarding the Use of Fuel Cells in Combined Heat and Power for Stationary Applications

2021 ◽  
pp. 239-275
Author(s):  
Andrei Mircea Bolboaca
Keyword(s):  
Energy Demand ◽  
Alternative Energy ◽  
Clean Energy ◽  
Combined Heat And Power ◽  
Pollutant Emissions ◽  
Energy Technologies ◽  
Energy Demands ◽  
New Energy ◽  
Energy Conversion Systems ◽  
Polluting Emissions

Covering the energy demands under environmental protection and satisfying economic and social restrictions, together with decreasing polluting emissions, are impetuous necessities, considering that over half of the pollutant emissions released in the environment are the effect of the processes of electricity and heat production from the classic thermoelectric powerplant. Increasing energy efficiency and intensifying the use of alternative resources are key objectives of global policy. In this context, a range of new energy technologies has been developed, based on alternative energy conversion systems, which have recently been used more and more often for the simultaneous production of electricity and heat. An intensification of the use of combined energy production correlated with the tendency towards the use of clean energy resources can be helpful in achieving the global objectives of increasing fuel diversity and ensuring energy demand. The chapter aims at describing the fuel cell technology, in particular those of the SOFC type, used in the CHP for stationary applications.

scholarly journals Test campaign of a ducted wind turbine in real operating conditions

2019 ◽  
Vol 113 ◽  
pp. 03005
Author(s):  
Enrico Valditerra ◽  
Massimo Rivarolo ◽  
Aristide F. Massardo ◽  
Marco Gualco
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Energy Production ◽  
Electrical Energy ◽  
Clean Energy ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Ambient Conditions ◽  
Wind Speeds ◽  
Electrical Energy Production

Wind turbine installation worldwide has increased at unrested pace, as it represents a 100% clean energy with zero CO2 and pollutant emissions. However, visual and acoustic impact of wind turbines is still a drawback, in particular in urban areas. This paper focuses on the performance evaluation of an innovative horizontal axis ducted wind turbine, installed in the harbour of Genova (Italy) in 2018: the turbine was designed in order to minimize visual and acoustic impacts and maximize electrical energy production, also during low wind speed periods. The preliminary study and experimental analyses, performed by the authors in a previous study, showed promising results in terms of energy production, compared to a traditional generator ( factor >2.5 on power output). In the present paper, the test campaign on a scaled-up prototype, installed in the urban area of Genova, is performed, with a twofold objective: (i) comparison of the ducted innovative turbine with a standard one, in order to verify the increase in energy production; (ii) analysis of the innovative turbine for different wind speeds and directions, evaluating the influence of ambient conditions on performance. Finally, based on the obtained results, an improved setup is proposed for the ducted wind turbine, in order to further increase energy production mitigating its visual impact.

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