Combustion and Flame
Papers 10313
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Abstract The ignition regime criteria proposed by Im et al. (2015) are extended to account for temperature and concentration fluctuations. The newly-developed criteria are applied to negative temperature coefficient (NTC) and non-NTC fuels. The statistical volume-averaged Sankaran number, S ¯ a , and the volumetric fraction of Sa S ¯ a regardless of the NTC and non-NTC characteristics of fuels over a wide range of initial mean temperatures and different fluctuation levels. Besides, the magnitude...
Abstract Ammonia (NH3) can be used as carbon-free alternative fuel for modern energy and transportation systems. Co-firing NH3 with syngas can overcome the high ignition energy and low burning velocities of pure NH3 flames on the one hand, while regarding the characteristics of syngas on the other hand, this strategy may have low-emission potential in real application, and a corresponding research can be helpful for validating or developing NH3 co-firing mechanisms with more complex fuels. The p...
Abstract The U.S. Department of Energy has a renewed interest in direct power extraction (DPE) technologies, such as a magnetohydrodynamic (MHD) generator, in conjunction with oxy-fuel combustion. As a topping cycle, this configuration can enable efficient CO2 capture, while offsetting oxygen separation penalties. In order to appropriately evaluate these cycles in the context of modern plant configurations, validated modeling tools are needed. In a prior publication (Bedick et al., 2016), an ele...
Abstract The high concentration of CO2 and low concentration of O2 at relatively low temperatures of 1123-1223 K are typical reactive atmospheres in the fuel reactor of a chemical looping with oxygen uncoupling (CLOU) unit. Char within this environment can be converted via lean-O2 oxidation and/or rich-CO2 gasification. Conventional models, which either considered the oxidation only or considered the oxidation and gasification contributions independently by simply adding the two individual conve...
Abstract Cu-based materials present as promising oxygen carrier candidates in chemical looping processes, in which CuO can either react directly with fuel gas via heterogeneous gas–solid reaction, or release gaseous O2 under suitable temperature and O2 partial pressure, and then react with fuel gas (even solid fuel) via combustion reactions. For comprehensive understandings of the complex reactions of the oxygen carrier in chemical looping processes, as well as for chemical looping reactor desig...
Abstract In this work we present a novel two-color differential absorption diagnostic near 5.6 μ m using an external-cavity quantum-cascade-laser (EC-QCL) for formaldehyde (CH2O) detection in high-temperature reacting gases. This diagnostic utilizes the narrow mid-infrared absorption features of CH2O in the R branch of the C=O stretching band. Specifically, the online and offline colors were chosen as 1787.05 cm-1 and 1787.85 cm-1, respectively. Compared to the previous Stanford work that target...
Abstract The accuracy of species thermochemical properties is important for predicting combustion characteristics by chemical kinetic models due to their impacts on chemical equilibria of elementary reactions and on backward rate coefficients. As they are frequently estimated based on the group additivity method, the underlying group values directly influence the model prediction accuracy. While a number of studies have recently aimed to improve the accuracy of group values, the dependence of ki...
Abstract This study explored the prediction of the effect of dilution on the ignition delay of syngas and hydrocarbon fuels from dimensionless parameters. In this regard, the dilution effect was categorized into two sub-effects. The first is a non-chemical effect, which mainly represents the effect of decreasing the fuel-air concentration and the effect of heat-release damping. The second is the chemical effect induced by participation of the diluent in the reaction pathway. Then, we derived the...
Abstract A detailed char gasification model is developed using a multiphase Eulerian–Lagrangian algorithm and thermally thick treatment. The model is first validated by both gasification and combustion experiments of a millimeter-sized char particle. Temperature and mass loss histories as well as the particle morphology evolution correspond well with the existing results. Then the steam gasification of a 5 mm char particle is simulated and detailed physical and chemical conversion processes insi...
Abstract Ammonium nitrate (AN, NH4NO3) constitutes the key ingredient of monofuels and civilian-grade explosives, attracting scientific interests aimed at improving their operational and safety performance. This study investigates the combustion properties of redox crystals comprising ammonium nitrate and simple saccharides, with the infrared spectroscopy, X-ray diffraction and molecular modelling. Furthermore, the thermogravimetric measurements afford the isoconversional analysis that yields th...
Top fields of study
Analytical chemistry
Premixed flame
Inorganic chemistry
Diffusion flame