Analysis and testing of debris monitoring sensors for aircraft lubrication systems

In an aircraft engine, some pieces are describing a rotating movement. These parts are in contact with rotating and non-rotating parts through the bearings and gears. The different contact patches are lubricated with oil. During the lifetime of the engine mechanical wear is produced between the contacts. This wear of the bearings and gears will produce some debris in the oil circuit of the engine. To ensure effective operations of the aircraft engines, the debris monitoring sensors play a significant role. They detect and collect the debris in the oil. The analysis of the debris can give an indication of the overall health of the engine. The aim of the paper is to develop, design and model an oil test bench to simulate the oil lubrication circuit of an aircraft engine to test two different debris monitoring sensors. The methodology consists of taking inspiration of the oil lubrication system of the aircraft engine. The first part is to build the oil test bench. Once the oil test bench is functional, the tests of the two debris monitoring sensors are performed. A test plan is followed, 3 sizes of debris, like the type and sizes of debris found in the aircraft engine oil, are injected in the oil. The test parameters are the oil temperature, the oil flow rate and the number or mass of debris injected. Each time debris are injected, they are detected and caught by the two sensors for a temperature and a flow rate for which the sensors have been optimized. The test results given by the two sensors are similar to the mass and number of debris injected into the oil circuit. The two sensors never detect the total mass of debris injected in the oil. In average 55 to 60 % of the mass injected are detected and caught by the two sensors. The sensors are very efficient to detect the debris which size correspond to the design range parameters of the sensors, but their efficiencies fall in detecting debris which size lies outside this range.