| Summary: | Federal Aviation Administration (FAA) is actively conducting research and development for unleaded aviation gasoline (AVGAS) transition for almost 20 years. Recent research with 200 unleaded blends and full-scale engine tests on 45 high-octane unleaded blends has not found a "drop-in" replacement for AVGAS. In this study, analysis of compatibility via optimisation of Lycoming O-320 engine fuelled with blends of RON 97, RON 98, RON 100 and AVGAS was carried out. This is to determine the compatibility, usability and safety of motor gasoline fuel to be used as aviation fuels using the response surface methodology (RSM). Vapor lock (VL) and carburettor icing (CI) analyses were conducted using principal component analysis (PCA). ASTM D7826 was used as a guideline in the evaluation process. The engine was run under varied engine speed of 2000-2700 RPM. Brake horsepower (BHP), brake thermal efficiency (BTHE), brake specific fuel consumption (BSFC), exhaust gas temperature (EGT), relative knock index (RKI), carbon dioxide (CO2), carbon monoxide (CO), unburned hydrocarbon (UHC) and nitrogen oxide (NOx) were recorded during the experiments. Response surface equations were developed to predict the values of output parameters. Analysis of variance was carried out to observe the most significant parameters affecting the responses. Optimisation was performed using the RSM optimisation of desirability. The next objective of the study was to measure the VL and CI tendencies of selected fuels by the application of factor analysis known as PCA. Study considered sixteen variables for VL and CI assessments each, using the selected and calculated fuel properties. Twenty-three aviation fuels' data from literatures were collected. Model equations explaining the VL and CI tendencies of the aviation fuels were derived, and their respective factor scores were calculated. The model was applied to the 14 fuels in this study and their respective factor scores were calculated. All the fuels were ranked using the factor score from the best to worst. RSM results indicated that when the engine was run with a speed of 2300 rpm, RON 98 fuel gave optimum solution. The corresponding values of BHP, BTHE, BSFC, EGT, RKI, CO2, CO, UHC and NOx were 146.37 Hp, 28.1%, 0.2792 kg/kW-hr, 375.58 ℃, 58.26%, 7.34%, 7.12%, 233.66 ppm and 51.83 ppm respectively. The desirability of 0.717 for RSM optimisation was obtained. Factor analysis results showed that PCA indicated cumulative variance of 86.77% and 86.78% for VL and CI respectively. Best VL and CI tendencies was shown by RON 98 with factor score of -0.64278 and -0.1982 respectively. The findings showed that motor gasolines (MOGAS) RON 97, RON 98 and RON 100 were able to outperform the commercial AVGAS in terms of VL and CI. The study concluded that MOGAS has a great ability to outperform AVGAS in terms of performance, detonation, emission, vapor lock and carburettor icing.
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