Publication: Development of moderate or intense low oxygen dilution (MILD) combustion chamber fueled by syngas
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Date
2024-07
Authors
Mohamad Nazirul Aiman bin Mazlan
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Abstract
The combustion process is still heavily depended upon for energy generation in today’s society. MILD combustion serves as a promising sustainable alternative to conventional combustion to take us one step closer to a net zero emissions society. However, due to the lack of research into this technology, our knowledge of how it functions and how it can be implemented into current technology is limited. The specific usage of MILD for combustion of low-grade biomass producer gas is more obscure with only a few research done in far between. Thus, this study aims to create and optimize a compact and simple combustion chamber capable of achieving MILD combustion while using low-grade bio-derived producer gas as its fuel. The work done includes the usage of ANSYS Fluent to execute the computational fluid dynamics (CFD) simulations to obtain the maximum temperature increase (ΔT), Damköhler number (Da), carbon monoxide (CO) and nitrogen oxides (NOx) emissions of the modeled chamber. Two stages of Design of Experiments (DOE) were done with the first stage to optimize the chamber’s geometry and the second stage to optimize the swirler’s geometry. A total of 18 CFD simulation cases and results were analyzed using Minitab’s Analysis of Variance (ANOVA) and Response Optimizer to determine which variables will significantly affect the MILD combustion as well as determining the most optimal design. Through DOE 1, it is concluded that the optimal chamber’s geometry is the chamber with a width (Dc) and length (Lc) of 200mm and 1000mm respectively due to the increasing volume of the chamber producing higher residence time which promotes better mixing of reactants. Through DOE 2, it is concluded that the optimal swirler’s geometry is the design with swirler’s angle (ϴswirler) and number of blades (Nblades) of 30⁰ and 8 respectively due to it producing a stronger vortex field inside of the chamber which enhances the fuel-air mixing level. In the end, the most optimal design is the one with Dc = 200mm, Lc = 1000mm, ϴswirler = 30⁰ and Nblades = 8 which produces CO of 1969.77 ppm mole; NOx of 15.46 ppm mole; Da of 0.2991 and a ΔT of 333.45 ⁰C.