AN INVESTIGATION INTO PERFORMANCE MODELING OF A SMALL GAS TURBINE ENGINE

A small gas turbine performance modeling and testing project has been completed as part of a DSTO research program. The main objective of the program was to enhance capability in understanding and modeling the thermodynamic and performance characteristics of gas turbine engines. The secondary objective of the program was development of a simple, low-cost test apparatus for basic thrust augmentation technologies and infrared suppression studies. Engine performance modeling was conducted using commercial software (Gasturb) and an in-house developed code. Various techniques were used in predicting component performance which included scaling of published performance data, use of standard empirical performance models, mean-line and through flow codes and detailed Computational Fluid Dynamics (CFD) analysis. A comparison of the advantages and disadvantages of each method was made and compared with engine test data. The AMT Olympus HP turbojet engine was used as the test engine. The engine was instrumented using a bell mouth to measure mass flow rate, load cell to measure thrust, tachometer to measure engine rotational speed, thermocouples to measure flow total temperature and pressure transducers to measure wall static pressure at various stations along the engine. A pair of Olympus engines were tested for comparison during baseline testing, with consistent results between the two. The first engine was fully instrumented and used in all of the tests. This engine was used to test the engine standard operating line tests to determine bulk performance and establish compressor operating line. Tests were repeated and error analysis conducted to ensure repeatability and validity of the data. The second engine was used as a control engine with only the OEM supplied instrumentation, thrust and bell mouth used for benchmarking purposes. The data from both engines have been compared with the engine performance model and OEM data. A number of other tests were completed to "stress" the engine and shift its operating line closer to the compressor stall line. This was accomplished through various types of exhaust blockage. Stall behaviour was clearly evident in the initial commissioning tests where a large nozzle blockage resulted in engine stall and incomplete start-up. Engine performance and compressor map results from the tests have been compared to the engine performance model with good agreement.