Efficient Gas Turbine Modeling for Low Emission Aircraft Preliminary Design Workflows

A major issue, which has prevented aircraft manufacturers from implementing efficient and cost-effective design processes, is the loose integration of engine models into iterative aircraft design workflows. Modern civil transport aircraft involve several subsystems which are designed, in general, to have the lowest possible weight and the highest possible energy efficiency, so as to minimize their impact on the overall aircraft performance. This same criterion applies to the powerplant system of a modern aircraft, which needs to be specifically designed and built, to meet all the necessary requirements and constraints in terms of performance (thrust and fuel consumption), emissions, noise and costs. Actually, an effective integration between the design of the aircraft and that of the engines is something which has started to be radically implemented only in recent years. Traditionally, the design of a new aircraft has always been decoupled from the engine design. Even for supersonic military applications, for which the matching between the two designs represents a crucial aspect, an integrated approach supported by dedicated tools has started to be adopted only from the 1990s. For civil transport aircraft, this radical change in the overall design process has been effectively put into practice only for the latest development programs, such as the ones for the Boeing 787 or the Bombardier C Series (now Airbus A220), during which the engine manufacturers, Rolls-Royce/GE and Pratt & Whitney respectively, have been directly involved in the overall design process of the aircraft since the earliest stages. Based on these observations, the work described in this thesis addresses the following research question: how to improve preliminary design workflows focused on the optimization of low-emission aircraft by including detailed effects related to changes to the propulsion system? In order to enable a radical change, aircraft designers should be supported by dedicated tools, allowing to easily and promptly perform, even at conceptual and preliminary design stages, trade-off studies involving information related to the behaviour of the powerplant system in terms of performance, emissions, dry mass, main dimensions, environmental noise, and costs, by linking these changes to key engine design parameters, such as the overall pressure ratio, the bypass ratio, and the burner exit temperature. This type of approach, from one side, would allow aircraft designers to have, since from early design stages, more precise figures on the powerplant, significantly increasing the number and the quality of information available on the aircraft-engine integration process. On the other side, aircraft designers would be allowed to provide important indications to engine designers on which set of design input variables should grant the matching of aircraft requirements, while minimizing mission fuel burn, emissions, noise, or costs. The generation of a tool with these characteristics, supporting aircraft preliminary design phases, was the main objective of the collaboration between UNINA and MTU Aero Engines AG for a three-month internship, involving the author of this thesis and engine design experts from MTU. This work was carried out within the context of the Clean Sky 2 project ADORNO (call H2020-CS2-CFP07-2017-02, project number 821043). The activities related to the tasks of ADORNO served as proving ground of the capabilities in terms of powerplant system modelling of JPAD, a preliminary aircraft design tool designed at UNINA, in whose development the author of this thesis was directly involved. Observations on the gaps and on the margins for improvement related to the implemented modelling of the powerplant characteristics, that emerged during the execution of the project tasks, motivated even further the need for a new tool accounting specifically for the engine. For this reason, the first section of this thesis is dedicated to the description of the activities carried out by the author for ADORNO. A second section is dedicated to illustrating the work performed for GENESIS, another Clean Sky 2 project (call H2020-CS2-CFP11- 2020-01, project number 101007968), for which the author had the possibility to set up a first version of this new tool for preliminary engine design, specifically dedicated to turboprop engines. A detailed description of the implemented methodology is provided in this section. The last chapter of this thesis is dedicated to a generalization of the previously mentioned methodology for preliminary design to the case of turbofan engines, and to a description of its implementation in JPAD. Finally, several examples of application are provided, for an aircraft similar to the Airbus A320neo.