ANALYTICAL EVALUATION OF HEAT FLOW PATTERN IN BIODIESEL OPERATED ENGINE CYLINDER

摘要

There has been a global search for alternative fuels that are environmentally friendly to replace and or compliment the conventional fossil fuels used in running engines. This is in line with the global action to reduce CO_2 emissions hence ameliorating the effect of climate change. Biodiesel fuels have been adjudged to be clean energy with minimal environmental pollution during combustion. Hence, biodiesel fuels for running compression ignition engines have been developed from various feedstocks such as vegetable oils, animal fat, and waste or used cooking oils. The properties of these biodiesels have been reported to be dependent on the feedstock type and therefore vary according to the source feedstock. In carrying out this present study on the effects of utilising biodiesel fuel on the compression ignition engine, a numerical study of temperature distribution in the cylinder liner of biodiesel-powered compression ignition engine is presented. Biodiesel produced from palm kernel oil is used. Eight nodes in the cylinder liner spanning the top section of the liner, midpoint and the interface between the liner and the block were used as data source as it is established that sharp-edged points are most likely regions for thermal stress. Of the eight nodes selected, four were edge nodes and the other four were nodes at the interface with varying conditions. Model equations used for the study were developed and subsequently transformed using the finite difference method. Numerical solutions were obtained from computer codes written in MATLAB programming language. The obtained results from this code were compared to results obtained from commercial software (ANSYS FLUENT) for same geometry and boundary conditions. Results on the cylinder liner showed steady state temperatures were reached in about five minutes using both the MATLAB code and ANSYS FLUENT and both results showed a similar trend of temperature distribution in the radial direction. However, the MATLAB code showed higher temperatures at the upper section of the liner material as compared to the midpoint of the liner whereas ANSYS FLUENT showed the midpoint section to possess maximum temperatures as compared to the cylinder head section. Both results agree with the lower section having least temperature distribution. Further analyses were carried out on the midpoint of the cylinder and the cylinder head section and factors responsible for the discrepancies discussed. The outcome of this study presents palm kernel based biodiesel as an alternative fuel in cylinder engines while highlighting sections of the engine that require design attention in terms of heat flux and engine stability.