Abstract

The Fuel cooled oil coolers (FCOC) in an aero gas-turbine engine plays a critical role in the aero-thermal management of hot oil in the lubrication circuit and cold fuel of the engine. The extremely low operating temperatures of the flight environment sometimes induce the congealing of oil and related loss of cooling.  In order to ensure the process safety and loss of cooling, a Bypass Valve (BV) is installed in the cooler. Because the failure of the BV might lead to uncontained injuries, it is necessary to understand the detailed characteristics of the de-congealing process related to the BV under various operating and boundary conditions. This study has experimentally investigated the effects of the different BV passage conditions and boundary conditions of pressure and temperature on the FCOC de-congealing mechanism. For the BV passages, tests with fully open and closed bypass passages were conducted. The re-routing of the oil or fuel paths as well as the variation of the temperature and the pressure conditions of the oil and environment, were considered. The time variation of the mass flow rate of each working fluids, temperature, and pressure are monitored and summarized in quantitative manners. Moreover, a detailed methodology to undertake de-congealing studies in practical applications is provided in this study.