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Catalytic Combustion as a Pollution Prevention Technology to Achieve Ultra-Low Emissions in Power Generating Ground-Based Gas Turbine Engines
Published in Nada Assaf-Anid, Hazardous and Industrial Wastes Proceedings of the Thirty-Third Mid-Atlantic Industrial and Hazardous Waste Conference, 2001
Mitchell O. Stokes, Marco J. Castaldi, Lance L. Smith, Hasan Karim, Shahrokh Etemad, William C. Pfefferle
Figure 2 below shows the effects of mixing on the production of NOx for methane and air at a range of adiabatic flame temperatures. These results were generated by incorporating the Chemkin II chemical kinetics package[1] along with the Gas Research Institute (GRI) chemical reaction mechanism for methane combustion[2]. The reaction was then modeled in two steps. The first step models a recirculation zone using a perfectly stirred reactor (PSR) model[3] while in the second step the flow structure is modeled as a plug flow reactor (PFR)[4]. For the plot shown, the PSR residence time was 0.5 ms and the PFR residence time 15ms for a nominal reaction time of “16” ms. The level of mixing was simulated by appropriately weighting the NOx over a discretized domain assuming a Gaussian distribution.
The Simulation of Powder Processing with Eulerian Finite Element Methods
Published in Y. Kishino, Powders and Grains 2001, 2020
The chemical kinetics are modeled with an Arrhenius rate equation. There are many methods for constructing the species evolution equations for chemical reactions. The method chosen here closely follows the approach taken by (Kee et al. 1996) in CHEMKIN, a software package for treating chemical kinetics, developed at Sandia National Laboratory.
Effects of Karlovitz Number on Flame Surface Wrinkling in Turbulent Lean Premixed Methane-Air Flames
Published in Combustion Science and Technology, 2018
The results presented in this work are obtained using the in-house code HOLOMAC (High-Order LOw-MAch number Combustion; Motheau and Abraham, 2016). It solves the 3D Navier–Stokes conservation equations under the low Mach-number assumption (Giovangigli, 1999) for multi-component mixtures. An interface with CHEMKIN is implemented for computing the chemical reactions and transport properties. Spatial discretization is performed using a sixth-order implicit compact scheme (Lele, 1992). The time integration is based on a Strang operator-split strategy. Convection terms are advanced in time using a second-order Adams–Bashforth (AB2) scheme, while the diffusion terms are integrated using a stabilized explicit Runge–Kutta–Chebyshev (RKC) method. The momentum equation is solved using a projection-correction method. The divergence condition is enforced up to machine precision by solving a variable-coefficient Poisson equation for pressure using a spectral solver based on fast Fourier transform. A sixth-order accurate spatial filter is applied to remove any spurious high-wavenumber oscillations. Mixture-averaged transport properties are used for viscosity and thermal conductivity, and effective binary diffusivity is used to model diffusion of species. The reader is advised to refer to the work by Motheau and Abraham (2016) for further details on the numerics of the code.
Computational simulation of incineration of chemically and biologically contaminated wastes
Published in Journal of the Air & Waste Management Association, 2021
Paul Lemieux, Timothy Boe, Anna Tschursin, Martin K. Denison, Kevin Davis, Dave Swensen
Modeling has been used to simulate high-temperature combustion systems in the past, particularly for predicting formation and control of nitrogen oxides (NOx) (Glarborg, Miller, and Kee 1986). CHEMKIN (ANSYS 2020) is a proprietary software originally developed by Sandia National Laboratories to solve the complex system of differential equations that is required to predict the behavior of complex sets of reactions. CHEMKIN has a limitation of only being applicable for ideal reactors and does not include complex fluid dynamics found in full-scale incinerators (Daly and Nag 2001).
Effects of Fuel Unsaturation on Transient Ignition and Flame Development in Sprays
Published in Combustion Science and Technology, 2018
Saurabh Sharma, Suresh K. Aggarwal
In order to provide an overall perspective, we first present results for the ignition of homogeneous n-heptane/air and 1-heptene/air mixtures in a constant-pressure reactor at diesel engine conditions. The objective is to highlight the effect of fuel unsaturation on ignition under spatially homogeneous conditions. Another objective is to examine the effect of fuel sensitivity (S = RON-MON) on the ignition behavior, since by definition, S = 0 for n-heptane and 13 for 1-heptene, as reported by Tanaka et al. (2003). RON and MON here refer to research and motor octane numbers, respectively. Simulations were performed using the CHEMKIN software. Figure 2 presents the predicted ignition delay times versus initial temperature for the two fuels at different equivalence ratios (Ø). There are several observations from these results. First, for temperatures below 1000 K, the ignition behavior is strongly affected by the presence of a double bond. In particular, at lower temperatures, n-heptane ignition chemistry is characterized by the NTC region and two-stage ignition (Curran et al., 1998). In contrast, the ignition delay (tign) for 1-heptene increases almost monotonically with the decrease in temperature, although the rate of increase decreases at lower temperatures. Second, at a given Ø, 1-heptene has a longer ignition delay time than n-heptane up until a particular temperature (defined here as “transition temperature”). At this transition temperature, tign trend reverses and 1-heptene has lower tign than n-heptane as temperature further increases. Moreover, as indicated in Figure 2, this transition temperature shifts to higher values as Ø is increased. This ignition delay behavior and the associated transition temperature are related to the effect of octane or fuel sensitivity (S) on ignition as discussed in several studies (Singh et al., 2017; Westbrook et al., 2017). As noted earlier, S = 0 and 13 for n-heptane and 1-heptene, respectively. It is also important to mention that previous studies dealing with the effect of the position and number of double bonds have observed two-stage ignition and NTC behavior for the ignition of unsaturated hydrocarbons at lower temperatures (Bounaceur et al., 2009; Mehl et al., 2008). Thus, one may observe a similar behavior for the ignition of 1-heptene at lower temperatures (600–800 K), and should be explored.