8,334 research outputs found

    Quantitative Assessment of Flame Stability Through Image Processing and Spectral Analysis

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    This paper experimentally investigates two generalized methods, i.e., a simple universal index and oscillation frequency, for the quantitative assessment of flame stability at fossil-fuel-fired furnaces. The index is proposed to assess the stability of flame in terms of its color, geometry, and luminance. It is designed by combining up to seven characteristic parameters extracted from flame images. The oscillation frequency is derived from the spectral analysis of flame radiation signals. The measurements involved in these two methods do not require prior knowledge about fuel property, burner type, and other operation conditions. They can therefore be easily applied to flame stability assessment without costly and complex adaption. Experiments were carried out on a 9-MW heavy-oil-fired combustion test rig over a wide range of combustion conditions including variations in swirl vane position of the tertiary air, swirl vane position of the secondary air, and the ratio of the primary air to the total air. The impact of these burner parameters on the stability of heavy oil flames is investigated by using the index and oscillation frequency proposed. The experimental results obtained demonstrate the effectiveness of the methods and the importance of maintaining a stable flame for reduced NOx emissions. It is envisaged that such methods can be easily transferred to existing flame closed-circuit television systems and flame failure detectors in power stations for flame stability monitoring

    Microgravity combustion science: Progress, plans, and opportunities

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    An earlier overview is updated which introduced the promise of microgravity combustion research and provided a brief survey of results and then current research participants, the available set of reduced gravity facilities, and plans for experimental capabilities in the space station era. Since that time, several research studies have been completed in drop towers and aircraft, and the first space based combustion experiments since Skylab have been conducted on the Shuttle. The microgravity environment enables a new range of experiments to be performed since buoyancy induced flows are nearly eliminated, normally obscured forces and flows may be isolated, gravitational settling or sedimentation is nearly eliminated, and larger time or length scales in experiments are feasible. In addition to new examinations of classical problems, (e.g., droplet burning), current areas of interest include soot formation and weak turbulence, as influenced by gravity

    Towards recycling of challenging waste fractions: Identifying flame retardants in plastics with optical spectroscopic techniques

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    The use of plastics is rapidly rising around the world causing a major challenge for recycling. Lately, a lot of emphasis has been put on recycling of packaging plastics, but, in addition, there are high volume domains with low recycling rate such as automotive, building and construction, and electric and electronic equipment. Waste plastics from these domains often contain additives that restrict their recycling due to the hazardousness and challenges they bring to chemical and mechanical recycling. As such, the first step for enabling the reuse of these fractions is the identification of these additives in the waste plastics. This study compares the ability of different optical spectroscopy technologies to detect two different plastic additives, fire retardants ammonium polyphosphate and aluminium trihydrate, inside polypropylene plastic matrix. The detection techniques near-infrared (NIR), Fourier-transform infrared (FTIR) and Raman spectroscopy as well as hyperspectral imaging (HSI) in the short-wavelength infrared (SWIR) and mid-wavelength infrared (MWIR) range were evaluated. The results indicate that Raman, NIR and SWIR HSI have the potential to detect these additives inside the plastic matrix even at relatively low concentrations. As such, utilising these methods has the possibility to facilitate sorting and recycling of as of yet unused plastic waste streams, although more research is needed in applying them in actual waste sorting facilities

    Multispectral Mid-Infrared Camera System for Accurate Stand-Off Temperature and Column Density Measurements on Flames

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    Accurate measurement of temperature in flames is a challenging problem that has been successfully addressed by hyperspectral imaging. This technique is able to provide maps of not only temperature T (K) but also of column density Q (ppm-m) of the main chemical species. Industrial applications, however, require cheaper instrumentation and faster and simpler data analysis. In this work, the feasibility and performance of multispectral imaging for the retrieval of T and QCO2 in flames are studied. Both the hyperspectral and multispectral measurement methods are described and applied to a standard flame, with known T and QCO2, and to an ordinary Bunsen flame. Hyperspectral results, based on emission spectra with 0.5 cm resolution, were found in previous works to be highly accurate, and are thus considered as the ground truth to compare with multispectral measurements of a mid-IR camera (3 to 5 mum) with a six interference filter wheel. Maps of T and Q obtained by both methods show that, for regions with T -1300 K, the average of relative errors in multispectral measurements is for T (and can be reduced to 2.5% with a correction based on a linear regression) and for Q. Results obtained with four filters are very similar; results with two filters are also similar for T but worse for Q.The authors acknowledge the financial support from EURAMET through 17IND04 EM PRESS 2 project. This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union Horizon 2020 research and innovation programme. This work has been supported also by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M14), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation)

    Optical analysis of blast furnace gas combustion in a laboratory premixed burner

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    The use of blast furnace gas (BFG) as a fuel provides an alternative for waste stream valorization in the steel industry, enhancing the sustainability and decarbonization of its processes. Nevertheless, the implementation of this solution on an industrial scale requires a continuous control of the combustion due to the low calorific value of BFG. This work analyzes the combustion behavior and monitoring of BFG/CH4blends in a laboratory premixed fuel burner. We evaluate several stable combustion conditions by burning different BFG/CH4mixtures at a constant power rate over a wide range of air/fuel equivalence ratios. In addition, relevant image features and chemiluminescence emission spectra have been extracted from flames, using advanced optical devices. BFG combustion causes an increase in CO2and CO emissions, since those fuels are the main fuel components of the mixture. On the other hand, NOxemissions decreased because of the low temperature of combustion of the BFG and its mixtures. Chemiluminescence shows that, in the case of CH4combustion, peaks associated with hydrocarbons are present, while during the substitution of CH4by BFG those peaks are attenuated. Image flame features extracted from both ultraviolet and visible bandwidths show a correlation with the fuel blend and air/fuel equivalence ratio. In the end, methodologies developed in this work have been proven to be valuable alternatives with a high potential for the monitoring and control of BFG cofiring for the steel industry
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