Semester

Spring

Date of Graduation

2020

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

V’yacheslav Akkerman

Committee Co-Chair

Mohsen Ayoobi

Committee Member

Hailin Li

Abstract

Increasing demands in the next-generation portable power-generation devices such as unmanned aerial vehicles (UAV), microsatellite thrusters, micro-chemical reactors and sensors calls for fuels with high specific energy and low emissions to meet the current demand of green energy. Fuel-lean synthesis gas (syngas) meets both these requirements exhibiting a promising route to a clean and green environment. Thus, it is of critical importance to characterize syngas combustion and understand its properties in the micro-combustion industry. In addition to complicated flame dynamics in microscale systems, varying the syngas-fuel mixture composition as well as the boundary conditions and geometry of a combustor significantly affect the burning process in the system. This work investigates the characteristics of a premixed syngas flame in a horizontal two-dimensional micro-channel of length 20 mm and half-width 1 mm by means of computational simulations using the ANSYS Fluent commercial software. A fixed temperature gradient is employed at the upper wall such that the temperature grows linearly, from 300 K at the inlet to 1500 K at the outlet to account for the conjugate heat transfer. The chemical kinetics of the combustion process is imitated by the San Diego mechanism with 46 species and 235 reactions, which is implemented using the Chemkin mechanism in ANSYS Fluent. Stoichiometric premixed burning of syngas comprised of carbon monoxide (CO), methane (CH4) and hydrogen (H2), with various compositions and inlet fuel-air flow velocities, is considered. Various properties of the combustion process such as ignition, stabilization and extinction are characterized. It is further shown how instabilities can be eliminated by increasing the inlet flow velocity to form a stable, stationary flame. As a result, it is demonstrated how various combustion characteristics depend on the inlet velocity and composition of a syngas mixture.

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