Determination of autoignition delay and lean blowout characteristics of alternative jet fuels in a small-scale gas turbine
Creators: name: YILDIRIM, Ulas
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401907
subject: Petroleum and reservoir engineering

description: The objective of this dissertation is to demonstrate that a small-scale gas turbine can be used to measure the lean blowout and autoignition delay characteristics of jet fuels produced from conventional and alternative feedstock. Validation methods are an essential component in determining the effects of alternatively produced jet fuels on gas turbine performance. Multiple approaches have previously been used to measure the lean blowout and autoignition delay characteristics of jet fuels including large test rigs, shock tubes, reciprocating compression machines and constant volume combustion chambers. However, the study of lean blowout and autoignition delay characteristics of conventional and alternative jet fuels using a small-scale gas turbine has before now, as evidenced by the literature, not been comprehensively undertaken. Based on their small size, ease of modification and low cost of operation, small-scale gas turbines present an opportunity as an alternative cost-effective method to detect the incidence of lean blowout and autoignition delay characteristics of conventional and alternative jet fuels. <br><br>
An AMT Olympus HP microturbine was modified by installing thermocouples along the length of its combustor to observe temperature variations during experiments. Additionally, the engine control unit was reprogrammed to allow the ability to conduct lean blowout and autoignition delay experiments of test fuels. Following these modifications, the lean blowout and autoignition delay characteristics of eight different liquid fuels produced from diverse feedstock were experimentally compared in the modified small-scale gas turbine within the low temperature region where temperatures range between 500-650 K. <br><br>
For the autoignition delay experiments the results for the conventionally produced F-34 and 50 per cent (v/v) blends of F-34/ATJ and F-34/SIP were compared to available literature to demonstrate the unique and complementary nature of the current experimental work. The results from present work showed good agreement with reported trends within the literature. The results also demonstrated that the device was capable of detecting the two phases that fuels undergo following fuel injection. The first phase involves fuel droplets heating up and evaporating at a rate dependent upon the fuel physical properties such as volatility, viscosity, and surface tension. While the second phase encompasses a rise in temperature which is attributed to fuel chemical composition. For the entire process, the results from the small-scale gas turbine clearly demonstrated its abilities to measure the differences in the physical delay  and chemical delay times reflecting the physico-chemical differences of the different fuels. <br><br>
For the lean blowout experiments experimental work was conducted close to the typical engine inlet (T3/P3) temperatures and pressures within the flight operating range which was based on the mean line characteristics of several gas turbines. The results from present work showed good agreement with reported trends within the literature. A correlation matrix was developed which highlighted that there is strong dependence between equivalence ratio, initial boiling point (TIBP), combustor inlet temperature (T3A) and derived cetane number (DCN) which have been shown to have an impact on lean blowout boundaries.