Biodiesel substitution in a J69 aeronautic turbine engine: An experimental assessment of the effects on energy efficiency, technical performance and emissions

Biodiesel has been widely considered as an alternative fuel for aircraft and power generation turbine engines, but experimentation in literature is mostly limited to microturbines and technological challenges remain open regarding its sustainability. The present study publishes the experimental methodology and the obtained results of testing a full-scale turbojet engine J69-T-25A using blends of JetA1 and palm oil biodiesel with volume contents from 0% to 50%. An increased biodiesel FAME substitution and extended data analysis yields new findings. Biodiesel substitution up to 50% v/v drops the thrust force by 26,6% and raises the fuel consumption by 10,8%, causing a detriment in the efficiency near 76,3%. Albeit poor atomization is noticed, the rise in the excess air of combustion diminishes the CO and HC emissions. An optimum trade-off value of 15,8% of biodiesel volume content is found to avoid a significant reduction of efficiency and acceleration time, driving to a slight reduction in the GHG-emissions and a raise of 25% in the fuel costs. The employment of a biodiesel content above 30% harms the ignition at the start-up procedure of the engine and fosters cloudiness development at the exhaust gases during the shutdown.