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An investigation was conducted to perform study of small turbojet engine testing and analysis. This program was mainly to investigate the current steady and dynamic performance of a 12-pound thrust turbojet engine. As a result, we can establish the basis for future small turbojet engine design guidelines. This program involved the bench testing of the small turbojet engine at both design and off-design conditions, in order to establish the baseline performance of the engine. Using the PC based data acquisition system, we will be able to test the engine for both steady and dynamic performance and record data for different operating conditions, especially, during very rapid acceleration and deceleration of the engine at different rates. Also, a compressor map testing was conducted to provide the compressor map data to be used by the performance analysis. With the above testing, this program will establish a useful database for the 12-pound thrust turbojet engine. A performance analysis using GASTURB cycle analysis software was performed for performance prediction of the small turbojet engine for both steady state conditions and dynamic transient conditions. Both performance predictions agreed reasonably well with actual performance of the engine.

It is very common for aircraft engines to have dual rotor or even triple rotor designs. Due to the complexity of having multiple rotor design, the transfer matrix methods have used in the past to deal with multiple rotor-bearing systems. However, due to transfer matrix method’s assumptions, sometimes resulted in numerical stability problems or root-missing problems. The purpose of this paper is to develop a systematic theoretical analysis of the dynamic characteristics of turbomachinery dual rotor-bearing systems. This dual rotor-bearing system analysis will start with a finite element (FEM) rotor-bearing system dynamic model, then using different methods to verify the analysis results including critical speed map and bearing stiffness. In an inertia coordinate system, a general model of continuous dual rotor-bearing systems is established based on a lagrangian formulation. Gyroscopic moment, rotary inertia, bending and shear deformations have been included in the model. From a point of view of the systematic approach, a solution of the finite element method is used to calculate the critical speeds by several different methods, which in turn can help to verify this dual rotor-bearing system approach. The effects of the speed ratio of dual rotors on the critical speed will be studied, which in turn can be used as one of the dual rotor design parameters. Also, both critical speeds are in effect functions of dual rotor speeds. Finally, the bearing stiffness between high speed and low speed shafts not only affect the critical speeds of the dual rotor system, but also affect the mode shapes of the system. Therefore, the bearing stiffness in between is of even greater importance in turbomachinery dual rotor or multiple rotor design.