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    Modelling and simulation of combustion of Bio-derived fuels in a PT6A-27 turboprop engine.
    (The University of Zambia, 2023) Chisenga, Rodgers Bwalya
    The motivation for venturing in alternative jet fuels has partly been due to the elevated level and volatility of the price of Jet A (a kerosene-based aviation gas turbine fuel) and environmental impacts on global climate change and air quality. The model of the annular combustor for the PT6A-27 engine was created using SOLIDWORKS and exported to ANSYS DESIGN MODELER for further conversion from a solid geometry into a fluid-based model. Creation of the computational mesh for the geometry using ANSYS MESHING was done in preparation for the setting up of the CFD simulation in ANSYS FLUENT. The simulation also included, setting material properties and boundary conditions for a non premixed combustion problem, initiating the calculation with residual plotting, calculating the solution using the pressure-based solver and visually examining the flow and temperature fields using the post-processing in ANSYS FLUENT. In the non-premixed combustion, the Standard k-ε 2 equation turbulence model was used. The fuel blend from the range of 30% bioethanol and 70% biodiesel (BE30-BD70) to 70% bioethanol and 30% biodiesel (BE70-BD30) indicated a combustion characteristic consistency with that obtained from the combustion of Jet-A1. Further, from the comparisons of the blends in terms of performance and single biofuel combustion simulation the best blend combination was 40% bioethanol with 60% biodiesel (BE40-BD60) whose adiabatic flame temperature was about 2260 Kelvins. The single biofuel combustion simulation best pick was 100% biodiesel whose adiabatic flame temperature was about 2310 Kelvins. The blend of 40% bioethanol to 60% biodiesel was observed to have a reduced Fuel NOx footprint. However, the rise in the calorific energy content of the fuel blend due to the presence of biodiesel in the mixture contributed to the increase in Thermal NOx production, albeit still less than that obtained from a pure hydrocarbon fuel of JetA-1. A pure JetA-1 hydrocarbon fuel had a production rate of Thermal NOx ranging from 0.002699526 Kgmol/m3 s to 0.002705489 Kgmol/m3 s. The Prompt NOx rate for Jet fuel was observed to be 1.789729 × 10−6Kgmol/m3 s . On the selected fuel blend of biofuels at the proportions of 40% bioethanol and 60% biodiesel, the observed production rate values of Thermal NOx and Prompt NOx were a range of 4.798448 × 10−6Kgmol/m3 s to 5.01322 × 10−6Kgmol/m3 s and 2.054488 × 10−7Kgmol/ m3 s respectively. This was indicative of a reduction in both Thermal and Prompt NOx when the two groups of fuels (Jet-A against 40BE & 60BD blend) were compared. These results showed that reduction of NOx emissions is achievable for a blend of 40% bioethanol and 60% biodiesel in a combustion reaction as a substitute for the hydrocarbon JetA in the PT6A 27 turboprop engine