Biodiesel is a promising alternative to petroleum-based diesel fuel because it is renewable and its extensive use in unmodified engines has proved to be very successful. However, its future use may be limited by the higher oxides of nitrogen (NOx) emissions that are typically generated relative to petroleum diesel. This paper deals with the numerical investigations on the use of Waste Animal Fat (WAF) as alternative fuel in diesel engine. The advanced CFD code CONVERGE is used to perform this work. Computational methods were developed to estimate the physical and thermodynamic properties of biodiesel for combustion modeling. The data of physical WAF properties were input in the fuel library into CONVERGE program for modeling of the spray, ignition, combustion, and NOx emissions of biodiesel in diesel engine. The result validation is based on experimental data obtained from the a single cylinder direct injection diesel engine operated at its rated speed of 1800 rpm with a large range of applied loads. Comparison with the neat diesel fuel in achieved. The engine combustion parameters such as pressure, temperature, heat release rate are determined, and exhaust emissions (soot and NOx) are also evaluated at all operating conditions. Results show that when the engine is operated with WAF fuel, the combustion characteristics are slightly changed when compared to the neat diesel fuel. Also, the use of WAF fuel leads simultaneously to reduce soot and nitrogen oxides (NOx) species. This work is an achieved step with in-cylinder simulation of WAF fuel combustion and has illustrated that advancing the injection timing to 30 CA BTDC, improves pressure and consequently the brake thermal efficiency when using WAF fuel. In addition, the results reported in this paper illustrate that the numerical simulation can be one of the most powerful and beneficial tools for the internal combustion engine design, optimization and performance analysis.
Key words: Diesel engine, waste animal fats, combustion, simulation, polluants.
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