P000 International Symposium on Sustainable Aviation (ISSA-2017), Kiev, Ukraine, 10 – 13 September, 2017 Table 1. The technical and calculated data of the engine Sustainable aviation metrics for an aircraft gas turbine engine from thermodynamic perspective Ozgur Balli 1’st Air Supply and Maintenance Center, Turkish Air Forces, Eskisehir, Turkey. balli07balli@yahoo.com Introduction Global warming, one facet of global climate change, refers to an increase in the average temperature of the atmosphere and oceans, which seemingly has occurred in recent decades and is projected to continue(Boyaghchi and Molaie, 2015). Aviation activities contribute to climate change, noise and local air quality impacts, and consequently affect the health and quality of life of public (EASA, 2016).Therefore, it is essential to find ways to reduce the emissions to protect air and environment. The ways reducing the emissions in aviation sector can be the removal of older aircrafts, the installing new technology turbofan/turboprop engines on aircrafts, the using of clean energy resources as biodiesel and hydrogen, the increasing the thermodynamic efficiency of aircraft engines and the improvements in aircraft operational management (Saravanamutto et al., 2009). To determine and increase the efficiency of the gas turbine based aircraft engines, the exergy analysis must be examined in addition to energy analysis because the exergy analysis is a very useful tool to detect the location, the magnitude and the causes of thermodynamic inefficiencies within the system. It can play an important issue in developing environmental strategies. Additionally, exergy methods can also play a key role in improving sustainability of thermal processes and systems (Aydın, 2013). Measuring aviation sustainability and considering progress towards or away from related policy objectives are a complex operation. The evaluation of aviation sustainability can be achieved by selecting a true set of sustainability metrics. Balli (2017) developed some exergetic sustainability indicators for a high by-pass turbofan engine used on commercial aircrafts. These indicators conducted comprehensive parametric study on how system and operation related aspects affect efficiency, environmental impact and sustainable development. The aims of this study present several sustainable aviation metrics from thermodynamic perspective to evaluate the sustainability level of aircraft engines. The JT15D-4 model medium by-pass turbofan engine used on the business jets is selected for application and investigation. Methods / Analysis The sustainable aviation metrics suggested in this study are consists of the energy efficiency, the specific fuel consumption, specific thrust, the exergy efficiency, the fuel exergy waste ratio, the productivity lack ratio, the waste exergy cost rate, the exergetic sustainability index, the sustainable efficiency factor, the environmental effect factor and the ecological effect factor. Results The specific fuel consumption and specific thrust of the JT15D turbofan engine are calculated to be 0.0158 kg/kN-s and 0.3159 kN/kg/s while the engine produces 11.24 kN-total thrust. When the engine thrust converts to engine power, the engine generates total 1614.47 kW-thrust powers. The energy efficiency of the engine is obtained to be 0.2115 because the engine consumes 7634.67 kW-fuel energy rates. According to the results of exergy analysis, the exergy efficiency of the engine is found to be 0.1992 hence the engine uses up 8104.97 kW-fuel exergy rates. Total waste exergy rate is calculated to be 6490.5 kW. Based on the exergy analysis; the exergy efficiency, fuel exergy waste ratio, productivity lack ratio and waste exergy cost rate are obtained to be 0.8008, 4.0202 and 0.0118x10-6 kW/$, respectively. Based on the sustainability analysis, the sustainable efficiency factor and sustainability index are calculated to be 1.2487 and 0.2487, respectively. On the other hand, the environmental effect factor and ecological effect factor are found to be 4.0202 and 5.0202, respectively. The sustainable aviation metrics of the JT15D turbofan engine are illustrated in Fig.2. System Description The JT15D-4B model turbofan engine produces 11.24 kN maximum thrust at take-off operation mode and is used on Cesna Citation II/S-II in Turkish Air Forces.The major parts of the engine are shown in Fig.1. Under the sea level condition (To=288.15 K. Po=101.325 kPa), the technical and calculated data of the whole engine is given in Table 1. Table 2. The sustainable aviation metrics of the JT15D turbofan engine Fig.1. The cutaway of JT15D-4 engine Conclusion Some sustainability metrics based on the analyzing methods of energy, exergy, environmental and sustainability are suggested for sustainable aviation. The proposed metrics are applied on the JT15D-4 turbofan engine to measure the sustainability level of engine. The results indicate that the methodology can be used to investigate and compare the gas turbine engines used on aviation sector. Table 1. Technical and calculated data of the engine References Aydın, H.,2013, Exergetic sustainability analysis of LM6000 gas turbine power plant with steam cycle. Energy 57: 766-774. Balli, O., 2017, Exergy modeling for evaluating sustainability level of a high by-pass turbofan engine used on commercial aircrafts. Applied Thermal Engineering 123: 138-155. Boyaghchi ,F.A., Molaie , H. ,2015, Advanced exergy and environmental analyses and multi objective optimization of a real combined cycle power plant withsupplementary firing using evolutionary algorithm. Energy 93:2267-2279. EASA .European Aviation Environmental Report 2016. Prepared by the European Aviation Safety Agency (EASA), the European Environment Agency (EEA) and EUROCONTROL. ISBN: 978-92-9210-197-8, doi: 10.2822/385503, Catalogue No.: TO-01-15-323-EN‑N, www.easa.europa.eu/eaer Saravanamutto, H.I.H., Rogers ,GF..C., Cohen ,H., Strazincky, P.V. , 2009,Gas Turbine Theory, 6th ed., Pearson Education Limited, ISBN: 978-0-13-222437-6.