The development of a biofuels engine testing facility
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This report covers the development of a biofuels engine testing facility at Stellenbosch University. The motivation for the project was three fold: a) a desire to establish biofuels and engine testing know-how; b) to test the performance characteristics of biodiesel; and c) make a facility available for future research. The two main conclusions drawn from the initial test results are: 1) the test cell is fully operational and 2) biodiesel can be substituted for mineral diesel. To the author’s knowledge this is the first biofuel specific engine testing facility in South Africa. After a literature study the test cell was realised in three phases. • Firstly, the hardware layout was designed and the necessary equipment was sourced from respectable suppliers including the judicious use of good qaulity second hand components to minimize capital cost. • The test cell was then instrumented with new sensors. Key components among these are the K-type thermocouples, barometric pressure, humidity, oil pressure and an Allen-Bradley programmable controller to serve as a data acquisition card. Two software programs were chosen, ETA for the control of the test cell and RSLogix to program the programmable logic controller (PLC). • The complete system was then integrated, debugged and validated. The design methods and procedures have been documented throughout the project along with user manuals to facilitate further research. To determine the difference in combustion parameters between biodiesel and mineral diesel an autonomous power curve test was conducted. This revealed little difference in terms of performance between the two fuels, although biodiesel had on average a marginal 0.4% decrease in power over mineral diesel. The fuel consumption for pure biodiesel was found to be higher, which is as expected as it is has a lower calorific value than mineral diesel. As a final validation, an energy balance was conducted. Here the calculated calorific value of biodiesel was compared to the results from a calorie bomb test, and the two results were found to be within 2% of each of other.