Session: 01-12 Whole Engine Performance and Novel Concepts III

Paper Number: 103505

103505 - Advanced Hydrogen Cycles to Help Decarbonize the Aviation Industry. Part 1: Development of Simulation & Modelling Toolsets. 

Hydrogen has been identified as a key fuel to enable decarbonization of fundamentally challenging industrial sectors such as the aviation industry. However, the poor volumetric energy density of this element imposes severe challenges on inflight energy storage when it is directly employed as a fuel. This becomes particularly relevant for high payload middle-to-long range missions, typical of regional and long-haul markets, where the combination of fuel burned plus reserve represents a large fraction of the total aircraft weight. While storing hydrogen as a high-pressure gas (GH2) is an option, in this study it is assumed that liquid hydrogen (LH2) is the more likely storage solution to be adapted by the aviation industry.

Historically, the aircraft fuel delivery system, including fuel tank and low-pressure delivery pumps, has remained within the aircraft manufacturer design domain. The engine is expected to receive fuel at a pre-established interface point, typically located at the engine mount (pylon) or after the low-pressure pumps. LH2 imposes additional energy storage and fuel conditioning challenges which need to be addressed at system level from early conceptual design stages. In particular from an engine perspective, fuel delivery pressure and temperature need to be appropriately set at the engine combustor interface throughout the whole flight envelope to ensure correct engine operations in design and off-design mode. Furthermore, as LH2 represents an ideal onboard heat sink, given its extremely low storage temperature, it offers important cycle level advantages when the fuel delivery system is fully integrated within the engine cycle design, allowing for effective engine waste heat utilization towards active fuel conditioning.

Consequently, the capability to model the hydrogen fuel management and conditioning systems integrated with the gas turbine cycle is becoming more essential. This allows the simulation of the full liquid hydrogen delivery system as part of the preliminary engine cycle design, allowing exploration of not only the effect that hydrogen combustion products have on optimal engine performance and core size definition, but also help in assessing the more advanced cycle architectures that LH2 would enable. This complex topic is elaborated into a two-parts paper which aims to cover hydrogen cycle model development (Part 1) as well as its application to support advanced hydrogen cycle definition and performance evaluation of the chosen cycles (Part 2). More specifically, Part 1 is intended to cover fundamental aspects of steady-state hydrogen cycle simulations by taking an existing preliminary engine design tool build in NPSS (Numerical Propulsion System Simulation) for kerosene applications, and adapting it to being able to simulate hydrogen fuel properties from its liquid storage temperature and pressure to the combustion injector interface; thus being able to model the effects that a fully integrated fuel delivery system has on the cycle design. The engine sizing tool allows for a sufficiently detailed design and off-design analysis, including primary and secondary air systems to enable overall cycle optimization. The combination of higher fuel heating value and larger exhaust water content associated to changing in fuel from kerosene to hydrogen, is reflected in the model logic, improving cycle SFC (Specific Fuel Consumption) and resulting in smaller engine core sizes for equivalent engine thrust. The paper will show that these fundamental cycle level advantages due to the hydrogen fuel switch are affected by the fuel conditioning requirements, which are modelled within the engine cycle definition, leading to the need for the exploration of more advanced hydrogen cycle arrangements.      

Part 2 further elaborates on these cycle implications by showing variants of the baseline hydrogen cycle, represented by a simple engine integrated fuel preheating unit. Among these more advanced cycles, alternative configurations of recuperation as well as fuel turbine concepts are considered, and results will be shown for a mid-size single aisle aircraft class application and an UltraFan engine arrangement.         

Presenting Author: Jacopo Tacconi Rolls-Royce Plc.

Presenting Author Biography: Jacopo Tacconi was born in Tradate, Italy, in 1993. He received the BSc degree in aerospace engineering from Politecnico di Milano, Milan, Italy, in 2015, and his MSc degree in aerospace engineering with specialization in Flight Performance and Propulsion at TU Delft, Delft, the Netherlands, in September 2018.

In June 2016, he joined Rolls-Royce plc. for his engineering internship in Derby, United Kingdom, until January 2017. At Rolls-Royce, he was dedicated to the aftermarket customer service support of the Trent 1000, a large turbofan engine. Held responsible for engine manual publications, engine overhaul and off-wing maintenance management and after testing engine component inspections.

Between 2017 and 2018 he performed his MSc final research project at the University of Sydney (USYD), Sydney, Australia. The program represented a research cooperation between TU Delft and USYD for the obtainment of his MSc diploma. His research area was related to the development of a numerical tool capable of thermodynamic analysis, preliminary sizing and optimization of conventional open and semi-closed cycles for high altitude UAV propulsion systems.

In 2019, he joined Rolls-Royce for his graduate development program which is currently undergoing. He supported different project within the R&D department and he is currently employed as applied researcher working in the area of novel gas turbine cycles, hydrogen and fuel cells.

Authors:

Jacopo Tacconi Rolls-Royce Plc.
Nicholas Grech Rolls-Royce Plc.