Mohamed, Mostafa Amin (2018) Simulation of biogas in open-flow MILD combustor. Coursework Masters thesis, University of Southern Queensland. (Unpublished)
Abstract
The world’s demand of energy is expected to increase by 28% in the next 25 years. The industry consumes about 50% of that forecasted demand. While finding sources of energy in the earth’s life was a challenge, it becomes even more competitive and essential to replace the unavoidable depletion of the fossil fuels. Fossil fuels of solid, liquid or gas forms are transformed to thermal energy by suitable combustion methods. Therefore, the anticipated higher rates of combustion will produce more greenhouse emissions.
While a long-term solution to fulfill the projected consumption of the fossil fuels and to reduce the resulted pollution of their combustion becomes inevitable, a curative solution of transforming the useful wastes into biofuels, specifically biogas, grows to an extent of best practice to the communities to get rid of their wastes, to produce replacement for fossil fuels, and to reduce the greenhouse effect of CO2. Nevertheless, biogas can partially secure a supply of energy consumption in local communities, its low calorific values and high corrosivity nature limit its applications.
Also, some essential improvements of the combustion process turn-out to be important to minimize the involved produced pollutants and to enhance its efficiency. The Moderate or Intense Low-Oxygen Dilution (MILD) combustion regime has been introduced as a promising key method to raise the combustion productivity and lower the developed emissions.
Though, the MILD technique has accomplished different degrees of success in many applications, it is still under development and requires more investigations in the combustion of biogas in open-flow furnaces. In the current study, Computational Fluid Dynamic (CFD) model is developed to simulate the combustion of biogas in an open-flow furnace. The MILD combustion mode is then initiated by adjusting the air to fuel ratios and the air pre-heat temperatures. While the current design allows exhaust gases recirculation which dilutes the inlet mixture, the MILD combustion is achieved at high air to fuel momentum ratios. After that, a percent of the exhaust gases is recirculated to enter the furnace at certain height to dilute the fresh air before mixing with fuel and raising the reactants temperature.
The CFD numerical model is conducted using ANSYS Fluent 18.2 academic version. The model encompassed 3D model of the open-flow furnace that is governed by the Reynolds Averaged Navier-Stokes (RANS) equations which are solved utilizing the realizable k- turbulent model. The combustion species defined by the none-premixed combustions are studied under chemical equilibrium and non-adiabatic energy treatment from the thermo chemical database by ANSYS.
The resulted simulations revealed the possibility to produce MILD combustion using low calorific value fuel such as biogas. Enhancing the fuel and air mixture by increasing the inlet air momentums will lead to better homogeneity of the furnace temperature and will develop lean mixture to start up the MILD regime. Increased air velocities lead to exhaust gases recirculation due to the limited outlet cross-section, that dilutes the entrainment air which is main factor of creating the MILD conditions. Even furnace temperature profiles occurred at higher air inlet velocities and higher preheat temperatures. In addition, flames are diminished until it disappeared totally in the 15% O2 fraction mole cases. Wall temperatures has no significant effect on the predicted results when compared at same air inlet velocities, same preheat temperatures, same mixture conditions, and for different O2 fraction moles.
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| Item Type: | Thesis (Non-Research) (Coursework Masters) |
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| Item Status: | Live Archive |
| Additional Information: | Current UniSQ staff and students can request access to this thesis. Please email research.repository@unisq.edu.au with a subject line of SEAR thesis request and provide: Name of the thesis requested and Your name and UniSQ email address. |
| Faculty/School / Institute/Centre: | Current - Faculty of Health, Engineering and Sciences - No Department (1 Jul 2013 -) |
| Supervisors: | Wandel, Andrew |
| Qualification: | Master of Engineering Sciences (Mechanical Engineering) |
| Date Deposited: | 15 Jul 2026 04:37 |
| Last Modified: | 15 Jul 2026 04:37 |
| URI: | https://sear.unisq.edu.au/id/eprint/53234 |
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