MODELLING AND SIMULATION OF BIODIESEL BLENDS PERFORMANCE IN COMPRESSION IGNITION ENGINES

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Department of Engineering

ABSTRACT
This research was conducted to investigate the suitability of using a renewable, sustainable and environmentally friendly biodiesel as part or full substitute of the petroleum diesel. Biodiesel from Cotton, Jatropha and Neem seeds, were produced and their compositions were analysed using Gas Chromatography-Mass Spectroscopy. The biodiesels were then blended with petro-diesel, thereby forming binary blends and multi-blends in different percentages and the physico-chemical properties for all the blends were determined and analysed. The physico-chemical properties of different biodiesel feedstocks from past literature were reviewed and their mean values computed. The performance of the biodiesel and the blends in a stationary multi cylinder Compression Ignition engine at full load with variable speeds of 1000 rpm, 1500 rpm, 2000 rpm and 2500 rpm were investigated and the composition of their exhaust gas emissions were recorded and analysed. A model was developed for the compression ignition engine with the test rig’s specifications using the GT-Power modelling software. The primary data obtained were used to validate the modelled engine during simulation, while the performance of biodiesels from the secondary data sources were further simulated under similar conditions. The results revealed that, the Cotton, Jatropha and Neem seed oils are reliable sources of biodiesel which are renewable and have the potential to replenish the partial energy demands in an eco-friendly way. The physico-chemical properties of most the fuels and blends conform to the ASTM standards, which suggests that they are suitable for use in CI engines operations. The quality of atomisation, combustion, fuel droplets and air-fuel mixing can be improved in CI engines by using these blends. The best performances in terms of brake power were recorded by using B10J, B20C B20J, and B30C blends. In terms of brake specific fuel consumption, the least value was generated by B10C, the Jatropha blend B25J is the overall best blend at most speeds. B30J has very low brake mean effective pressure at all speeds, while at maximum speed the highest value of brake mean effective pressure was generated by B30C. The highest values of brake thermal efficiency were recorded with B20J and B15N blends. Pure biodiesel samples and the B15C, B15J, B20C and B20J gave the lowest NOx and CO2 emissions. The values of SO2 emissions were null for most of the fuels except B20C at all speeds and B15C at 2500rpm in both cases which have a negligible SO2 value of not more than 0.12 % in all cases. The engine performance simulation in GT-power confirms that the software is valid to be used in compression ignition engine simulation with biodiesel from any feedstock and at all speeds because both experimented and simulated results are very close with identical curves. The simulation of the secondary fuel data revealed that, highest brake specific fuel consumption was depicted by castor followed by coconut and then tallow, the highest brake mean effective pressure was observed during the simulation of the compression ignition engine performance with sun flower, tallow, waste cooking oil and soy biodiesels correspondingly. The highest brake thermal efficiency values were depicted by soy, sunflower, palm and safflower in descending order during the Cussons stationary 4 cylinder CI engine simulations with GT Power software.