Development of Methods for Analysis and Optimization of Complex Jet Engine Systems

Doctoral thesis, 2000

This thesis describes the development of GESTPAN (GEneral Stationary and Transient Propulsion ANalysis), a generalized system for the design, steady-state and transient simulation of gas turbine systems. Some of the main achievements in the thesis are related to the development of new algorithms or integration of existing numerics tailored to simplify the structure and use of generalized gas turbine simulation systems. In particular, a method for performing system design utilizing the analysis equations, i.e. an inverse design method, has been developed. Furthermore, attention is drawn to a number of advantages of using an implicit high order differential algebraic system solver for transient gas turbine system analysis. The simulation studies carried out with the GESTPAN system have focused on the performance optimization of the Selective Bleed variable cycle engine. In particular, a method for controlling the engine during mode transition was developed. Work with the implementation of a hybridized optimization method suitable for mission optimization of variable cycle engines is also described. The method couples the cycle selection and the control optimization of the engine variable geometry. Simulations performed with the method indicate that previously published designs of the Selective Bleed Variable cycle engine can be downsized considerably. Early work carried out in the research project concentrated on developing a method for optimizing the performance of variable geometry compressors integrated in gas turbine systems. Although the method was limited to subsonic operation of compressors, it was successfully used to simulate the core driven fan stage of the double bypass variable cycle engine.