Further investigation of engine performance loss, in particular exhaust gas temperature margin, in the CF6-80C2 jet engine and recommendations for test cell modifications to record additional criteria

Abstract

The exhaust gas temperature (EGT) of civil jet engines is a major parameter to monitor and ensure safe engine operation and longer lifetime. Therefore EGT is limited to avoid damage to engine components. The di erence between actual measured EGT and the de ned limit is called EGT margin. Since the end of 2008 General Electric CF6-80C2 jet engines which have been overhauled at LTQ Engineering achieve low EGT margin without recognising any reasons. Therefore engines overhauled before and after that date are compared in order to identify di erences in performance. By analysing data of an engine performance estimation software and recorded data at the test cell as thrust speci c fuel consumption, rotor speeds, thrust, fuel

ow and pressure ratios, the problem is narrowed down to the fan and low pressure turbine. After isolating the problem, the blade tip to shroud clearance and the quantity of repair procedures of the fan module are analysed to order to detect any di erences and possible reasons for low EGT margin. Both do not reveal any relationship to low EGT margin. Finally recommendations are given at which engine stations additional test cell instrumentation should be implemented for subsequent test runs. The aim is to gain better knowledge of the performance of fan and low pressure turbine module. Therefore additional probes should be integrated in the secondary air ow behind the fan and in the exhaust nozzle behind the turbine. Hence a modi cation of the exhaust nozzle is necessary as no ports are available.