Session: 07-02 Educational tools

Paper Number: 123953

123953 - Teaching Aero-Engine Performance: From Analytics to Hands-on Exercises Using Gas Turbine Performance Software 

In this paper, we present an approach for teaching aircraft engine performance that combines mathematical analysis with the use of gas turbine performance software to provide students with a comprehensive and in-depth understanding of engine performance and how it is affected by design parameter choices.

In the first part of the paper, we present the derivation of a universally valid analytical model describing the performance of turbojet engines, which is the basis of the aircraft propulsion courses at RWTH Aachen University. The derivation for the turbojet is the logical basis for a later extension to turbofan and turboprop engines, which will be presented in a future paper. The analytical model is developed starting from the first law of thermodynamics and by introducing a number of reasonable simplifications, including uniform flow, constant gas properties, and an ideal nozzle with perfect expansion to ambient pressure. The model takes into account compression and expansion efficiencies. It allows for the calculation of specific thrust, thermal and propulsive efficiencies as a function of pressure ratios and burner exit temperature. These are all expressed as differentiable functions. Their mathematical extremes form a basis for examining the intricate relationships in turbojet engine performance. Most importantly, with a constant burner exit temperature, it is demonstrated that distinct, predictable pressure ratios yield the highest specific thrust, optimal thermal efficiency, and lowest thrust-specific fuel consumption. The underlying relationships are illustrated graphically for an exemplary cycle, a turbojet at cruise conditions at 11 km altitude and Mach 0.9. The derivations, formulas, and plots will be presented in the full paper.

In the second part of the paper, we move from theory to practice. We utilize the GasTurb software for gas turbine performance analysis, computing turbojet engine performance over a wide range of cycle design parameters, including compression pressure ratios and burner exit temperatures. The analytically derived trends are validated and errors introduced by simplifications are assessed: Differences between the analytical approach and software-based performance simulations, like temperature-dependent gas properties and secondary air systems, are emphasized and discussed, thus providing a bridge to real-world applications. With its graphical interface and versatile plotting capabilities, the GasTurb software enables students to explore the complexities of turbojet engine design and performance analysis themselves. We will provide a comprehensive overview of the practical exercises used at RWTH Aachen University for this purpose in the full paper.

In summary, this paper describes a twofold approach to teaching aircraft engine performance using analytics and gas turbine performance software.  Each approach alone can be used to enrich and extend existing engine performance courses. Combining the approaches has significant benefits, improving understanding and inspiring students to pursue further research in the field of jet engines. In future publications, we will present the analytical model derived for off-design behavior and the extension of the approach to turbofan and turboprop engines.

Presenting Author: Peter Jeschke Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University

Presenting Author Biography: 1988 – 1993: General Mechanical Engineering, TU Darmstadt (Technical University)
1991 – 1992: Master Aerospace Engineering, Cornell University, USA
1993 – 1998: Member of scientific staff, Technical Thermodynamics, TU Darmstadt
1998 – 2000: Siemens AG, Power Generation (KWU), steam turbines, Mülheim, Germany, Process development for designing steam turbine blading Project management
2000 – 2005: MTU Aero Engines, Munich, Director of development for the PW6000 high-pressure compressor
2005 – 2007: LEISTRITZ AG, Nuremberg, Director central development and innovation
2007 – today: RWTH Aachen University, Head of the Institute of Jet Propulsion and Turbomachinery (IST), University Professor

Authors:

Peter Jeschke Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Wolfgang Koschel Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Christian Klumpp Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Daniel Weintraub GasTurb GmbH