Biogas Combustion in Premixed Flames or Electrochemical Oxidation in SOFC: Exergy and Emission Comparison

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Francesco Quesito ◽  
Massimo Santarelli ◽  
Pierluigi Leone ◽  
Suresh K. Aggarwal
Keyword(s):  
Fuel Cells ◽  
Electrochemical Oxidation ◽  
Premixed Flames ◽  
Chemical Species ◽  
Chemical Oxidation ◽  
Point Of View ◽  
Operating Conditions ◽  
Partially Premixed Flames ◽  
Exhaust Stream ◽  
Partially Premixed

In the future energy pathway, characterized by flexibility of technologies and fuels, biogas could represent an alternative to conventional natural gas in feeding multiple types of technologies, both traditional thermal machines (chemical reactions), and innovative electrochemical generators such as fuel cells (electrochemical reactions). To compare the two pathways of energy production, two criteria are considered: (a) environmental analysis (emissions) and (b) exergy analysis. The results of the environmental and exergy comparison are presented and discussed in case of two selected transformation processes: partially premixed flames (PPFs, for chemical processes) and solid oxide fuel cells (SOFCs, for electrochemical processes), for a range of operating conditions. From an environmental point of view, the PPF exhaust stream has significant traces of NOx and C2H2, which are precursors of atmosphere pollution, while the SOFC exhaust stream does not contain such chemical species due to the absence of combustion. From a exergy point of view, the utilisation of the biogas in form of electrochemical oxidation in a SOFC indicates significantly higher exergetic efficiency compared to the chemical oxidation in partially premixed flames.

Structure and Extinction of Heptane/Air Partially Premixed Flames

AIAA Journal ◽  
2002 ◽  
Vol 40 (11) ◽  
pp. 2289-2297 ◽  
Author(s):  
Hongshe Xue ◽  
Suresh K. Aggarwal
Keyword(s):  
Premixed Flames ◽  
Partially Premixed Flames ◽  
Partially Premixed

Numerical Analysis of Equivalence Ratio Fluctuations in a Partially Premixed Gas Turbine Combustor Using Large Eddy Simulations

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Ping Wang ◽  
Qian Yu ◽  
Prashant Shrotriya ◽  
Mingmin Chen
Keyword(s):  
Reaction Mechanism ◽  
Equivalence Ratio ◽  
Flame Temperature ◽  
Premixed Flames ◽  
Large Eddy Simulations ◽  
Combustion Model ◽  
Inlet Channel ◽  
Large Eddy ◽  
Partially Premixed Flames ◽  
Partially Premixed

In the present work, the fluctuations of equivalence ratio in the PRECCINSTA combustor are investigated via large eddy simulations (LES). Four isothermal flow cases with different combinations of global equivalence ratios (0.7 or 0.83) and grids (1.2 or 1.8 million cells) are simulated to study the mixing process of air with methane, which is injected into the inlet channel through small holes. It is shown that the fluctuations of equivalence ratio are very large, and their ranges are [0.4, 1.3] and [0.3, 1.2] for cases 0.83 and 0.7, respectively. For simulating turbulent partially premixed flames in this burner with the well-known dynamically thickened flame (DTF) combustion model, a suitable multistep reaction mechanism should be chosen aforehand. To do that, laminar premixed flames of 15 different equivalence ratios are calculated using three different methane/air reaction mechanisms: 2S_CH4_BFER, 2sCM2 reduced mechanisms and GRI-Mech 3.0 detailed reaction mechanism. The variations of flame temperature, flame speed and thickness of the laminar flames with the equivalence ratios are compared in detail. It is demonstrated that the applicative equivalence ratio range for the 2S_CH4_BFER mechanism is [0.5, 1.3], which is larger than that of the 2sCM2 mechanism [0.5, 1.2]. Therefore, it is recommended to use the 2S_CH4_BFER scheme to simulate the partially premixed flames in the PRECCINSTA combustion chamber.

Time and Space Series Analysis of Spectral Radiation Intensities for a Partially Premixed Turbulent Flame

2003 ◽  
Author(s):  
Yuan Zheng ◽  
Jay P. Gore
Keyword(s):  
Single Point ◽  
Turbulent Flame ◽  
Premixed Flames ◽  
Model Parameters ◽  
Time And Space ◽  
Spectral Radiation ◽  
Series Analysis ◽  
Partially Premixed Flames ◽  
Partially Premixed ◽  
Premixed Turbulent Flame

A recently developed technique called time and space series analysis was used to calculate the mean and fluctuating spectral radiation intensities leaving diametric and chord-like paths in turbulent partially premixed flames. A standard flame (Flame D) from Sandia Workshop on Turbulent Non-premixed Flames was selected to allow an evaluation of the radiation calculations at least at the single point statistics level. Measurements of spectral radiation intensities using a fast infrared array spectrometer provide an evaluation of the computations and also allow estimation of the length and time scales of scalar fluctuations, which appear as model parameters in the time and space series analysis modeling.

scholarly journals A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

2018 ◽  
Vol 22 (5) ◽  
pp. 862-882 ◽  
Author(s):  
Zhi X. Chen ◽  
N. Anh Khoa Doan ◽  
Shaohong Ruan ◽  
Ivan Langella ◽  
N. Swaminathan
Keyword(s):  
Mixture Fraction ◽  
A Priori ◽  
Premixed Flames ◽  
Progress Variable ◽  
Partially Premixed Flames ◽  
Partially Premixed

Gravity, radiation, and coflow effects on partially premixed flames

2004 ◽  
Vol 16 (8) ◽  
pp. 2963-2974 ◽  
Author(s):  
Xiao Qin ◽  
Ishwar K. Puri ◽  
Suresh K. Aggarwal ◽  
Viswanath R. Katta
Keyword(s):  
Premixed Flames ◽  
Partially Premixed Flames ◽  
Partially Premixed

Numerical Prediction of Partially Premixed Flames Based on Extended BML Model Coupled With Mixing Transport and ILDM Chemical Model

2003 ◽  
Author(s):  
Alexander Maltsev ◽  
Amsini Sadiki ◽  
Johannes Janicka
Keyword(s):  
Transport Model ◽  
Algebraic Closure ◽  
Turbulent Transport ◽  
Premixed Flames ◽  
Turbulence Models ◽  
Variable Density ◽  
Transport Equations ◽  
Numerical Prediction ◽  
Partially Premixed Flames ◽  
Partially Premixed

To improve the numerical prediction of partially premixed flames occurring in gas turbine combustors the extension of the well-known Bray-Moss-Libby model for premixed combustion is presented. The model modification based on the algebraic closure for a mean chemical source term is coupled to the mixing transport model providing variable equivalence ratio distinguishing partially premixed flames. Finite rate chemistry is incorporated by means of ILDM model solving transport equations for two reaction progress variables conditioned on the flame front. Multivariate presumed PDF model is used for the turbulence chemistry interaction treatment. Turbulence models of two levels of complexity are applied in order to investigate the influence of non-gradient turbulent transport phenomenon. Redistribution terms in second moment transport equations are extended to take into account strongly variable density effects. Model combinations considered are assessed simulating piloted partially premixed flame. The obtained results agree well with experimental data.

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