Experimental study to verify oil loss through the vent line of the aero-engine lubrication system
Creators: name:  L. LI 
name:   M. DI.MATTEO 
name:   P. HENDRICK 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: AERONAUTICS
FUTURE DESIGN

description: With the increase in flights and air routes and the growing concern for air pollution, airplanes have become a source of air pollution that cannot be ignored [1]. Oil loss through the vent line of the lubrication system of modern aero-engines will pollute the atmosphere, in particular the TCP, the anti-wear additive present in lubricating oil, which is harmful to humans. Aerotoxic syndrome is mainly caused by it, people suffering from this disease in a severe state have multiple and/or chronic symptoms [2]. And more, the oil leak takes a significant place in the oil consumption, causing oil wastage. The aim of this research is therefore to understand whether or not there are operating conditions in the engine oil system that could potentially increase (cause/avoid) the emissions of oil vapors. Many researchers have focused on this topic, from different points of view. They focused on improving the efficiency of the cyclone separators by studying the geometry. Their outcomes are several theoretical models to calculate the efficiency of these separators by knowing their geometries and/or designing the separator geometry to have a desired efficiency [3]. The efficiency of the separator could be approached towards 100%, but leakage is still possible [4]. Our study is focused on the analysis of the impact of the operating conditions. Some models remain effective for any operating conditions [5], so, if we could prove that the operating conditions (especially transients) have an impact on oil leakage, on the basis of these efficiency-enhancing separators, we can further prevent oil losses by adjusting the operating conditions. We noticed that we were able to use water at room temperature, which is cheaper, less dangerous and dirty and not very corrosive, instead of oil at 150C thanks to their similar viscosity in these temperature conditions. The temperature of the oil during flight is about 150 C [6], at this temperature, the jet oil type 2 has a similar viscosity and density to that of water at 20 C according to oil data sheet and viscosity-temperature relationship [7]. In this study, the studied fluids are therefore air and water. The tests have been carried out in a test bench developed by the ATM department of ULB. We made the tests to measure the water leakage rate at the air outlet of the separator under different operating conditions, with changing water flow rate, air/water volume ratio, separator level and operating air pressure limit. The results show the following behaviors. No leaks are observed at lower flow rates, despite high air water ratios or high air pressure limits. When no air is introduced in the system no water leakage is observed, even at high water flow. The leakage, at higher water flow rate, starts at a certain air/water volume ratio and increases with the increase of this ratio. Figure 1 shows that the leakage increases with the water flow, keeping constant the air/water ratio. We observe that the operating pressure inside the oil line has a non-negligible influence on the leak. Figure 2 shows that the oil leak increases with the operating pressure. This result opens up a new possibility to control oil leakage by managing the operating conditions of the oil/air circuit. References [1] V. Pardee, Up in the air, how airplane carbon pollution jeopardizes global climate goals, Center for Biological Diversity, December 2015. [2] A. Picot, J. Ducret, S. Pasqualimi, Connaissez-vous le Syndrome Aerotoxique ?, ATC Association Toxicologie-Chimie, France, 18 June 2018. [3] S. Altmeyer, V. Mathieu, S. Jullemier, P. Contal, N. Midoux, S. Rode, J.-P. Leclerc, Comparison of different models of cyclone prediction performance for various operating conditions using a general software, Chemical Engineering and Processing, Volume 43, P. 511522, April 2004. [4] S. Sadighi, M. Shirvani, M. Esmaeli, R. Farzami, Improving the Removal Efficiency of Cyclones by Recycle Stream, Chemical Engineering Technology, No. 10, 1242-1246, October 2006. [5] J. Gimbun, T. G. Chuah, Th. S. Y. Choong, A. Fakhrul-Razi, A CFD Study on the Prediction of Cyclone Collection Efficiency, International Journal for Computational Methods in Engineering Science and Mechanics, 6:3, 161-168, 17 August 2006. [6] P. Ricco, Le coeur du SR-71 Blackbird : le puissant reacteur J-58, Conference Pilatre de Rozier, France, 20 December 2003. [7] M. Milou, J. D. Wurtz, J, Kessous, Viscosimetre a bille, Departement denseignement de Physique, Universite Montpellier 2.