Net-Zero Aircraft Design Optimisation

Although aircraft fuel efficiency improved by around 50% over the past three decades, rising demand for air travel led to a 34% increase in CO2 emissions just over the past five years. Hydrogen fuel cell aircraft offer the opportunity for truly net-zero flight over much longer distances than battery-electric aircraft. They are particularly suited for the European aviation market, which has an average range of 983 km, but is currently dominated by the Airbus A320 and Boeing 737 with design ranges above 4000 km.
The fallacy of prior hydrogen aircraft concepts was that they followed established kerosene aircraft design practices, as summarised in the works of Torenbeek, Roskam, and Raymer. As a result, existing airframes were reused, current mission trajectories were considered, novel aerodynamic technologies were retrofitted, and wrong design objectives were applied. Hence, there is a need for a physics-based, multi-level sizing method giving an unprejudiced view of the design space.
This will allow the following three questions to be answered: Which are the fundamental design parameters governing the optimum size of a fuel cell? How should current aircraft operating practices be modified to play to fuel cells' strengths? Could a synergistic propulsion airframe integration close the weight and drag gap between hydrogen and kerosene aircraft?
The preliminary work conducted during the MRes phase of the CDT demonstrated the power of a whole-system approach, where the impact of design decisions taken at aircraft level could be tracked down to powertrain component level and vice versa. The purpose of the first year of the PhD is to further the understanding of the physical nature of the FC aircraft sizing problem. An important interim goal of this project is to identify the non-dimensional groups governing the FC aircraft design space; this is important insofar as the conclusions drawn by current studies heavily depend on the assumed technology levels, with the risk of imposing false constraints on the multi-dimensional design space. The remainder of the PhD will likely be built on three pillars: higher-fidelity modelling, experimental design, and collaboration with other institutions, however, a detailed plan is yet to be developed.

In summary, this project aims to strike a balance between realism and minimum climate impact, starting with a clean slate, yet keeping to the laws of physics, in order to realise short- to medium-haul net-zero air travel; not by 2050, but by 2035 as HRH The Prince of Wales challenged the global aviation community in 2020.

1. Impact on the UK Aero-Propulsion and Power Generation Industry
The UK Propulsion and Power sector is undergoing disruptive change. Electrification is allowing a new generation of Urban Air Vehicles to be developed, with over 70 active programmes planning a first flight by 2024. In the middle of the aircraft market, companies like Airbus and Rolls-Royce, are developing boundary layer ingestion propulsion systems. At high speed, Reaction Engines Ltd are developing complex new air breathing engines. In the aero gas turbine sector Rolls-Royce is developing UltraFan, its first new architecture since the 1970s. In the turbocharger markets UK companies such as Cummins and Napier are developing advanced turbochargers for use in compounded engines with electrical drive trains. In the power generation sector, Mitsubishi Heavy Industries and Siemens are developing new gas turbines which have the capability for rapid start up to enable increased supply from renewables. In the domestic turbomachinery market, Dyson are developing a whole new range of miniature high speed compressors. All of these challenges require a new generation of engineers to be trained. These engineers will need a combination of the traditional Aero-thermal skills, and new Data Science and Systems Integration skills. The Centre has been specifically designed to meet this challenge.

Over the next 20 years, Rolls-Royce estimates that the global market opportunities in the gas turbine-related aftercare services will be worth over US$700 billion. Gas turbines will have 'Digital Twins' which are continually updated using engine health data. To ensure that the UK leads this field it is important that a new generation of engineer is trained in both the underpinning Aero-thermal knowledge and in new Data Science techniques. The Centre will provide this training by linking the University and Industry Partners with the Alan Turing Institute, and with industrial data labs such as R2 Data Labs at Rolls-Royce and the 'MindSphere' centres at Siemens.

2. Impact on UK Propulsion and Power Research Landscape
The three partner institutions (Cambridge, Oxford and Loughborough) are closely linked to the broader UK Propulsion and Power community. This is through collaborations with universities such as Imperial, Cranfield, Southampton, Bath, Surrey and Sussex. This will allow the research knowledge developed in the Centre to benefit the whole of the UK Propulsion and Power research community.

The Centre will also have impact on the Data Science research community through links with the CDT in Data Centric Engineering (DCE) at Imperial College and with the Alan Turning Institute. This will allow cross-fertilization of ideas related to data science and the use of advanced data analytics in the Propulsion and Power sectors.

3. Impact of training a new generation of engineering students
The cohort-based training programme of the current CDT in Gas Turbine Aerodynamics has proved highly successful. The Centre's independent Advisory Group has noted that the multi-institution, multi-disciplinary nature of the Centre is unique within the global gas turbine training community, and the feedback from cohorts of current students has been extremely positive (92% satisfaction rating in the 2015 PRES survey). The new CDT in Future Propulsion and Power will combine the core underlying Aero-thermal knowledge of the previous CDT with the Data Science and Systems Integration skills required to meet the challenges of the next generation. This will provide the UK with a unique cohort of at least 90 students trained both to understand the real aero-thermal problems and to have the Data Science and Systems Integration skills necessary to solve the challenges of the future.