Future Platforms and Propulsion Systems is a key theme in the University of Sheffield AMRC’s strategic vision. But what is it, why does it matter and how is the AMRC using its capabilities to address some of the grand challenges?  James Hunt, future propulsion lead at the AMRC, writes. 

In the simplest of terms, propulsion systems comprise the various components that contribute towards providing the motive force of a vehicle, aircraft, train or boat. This encompasses everything from the onboard storage of fuel or energy, such as a petrol tank or battery pack, and the conversion of that energy into power via an engine, electric motor or gas turbine, though to propelling the vehicle forward via a gearbox, driveshaft and wheel, or by the thrust generated from a jet engine or propeller.

For the majority of the transport sector, these propulsion systems have been heavily reliant on fossil fuels for more than a century, whether that was burning coal in steam-powered trains and ships, to petrol and diesel for cars and trucks, or kerosene for aviation.

The pressing need to address the climate crisis places the spotlight on those sectors that are significant contributors to CO2 emissions and other global warming effects. According figures from 2021, the transport sector accounts for approximately 24 per cent of global greenhouse gas emissions, primarily driven by this heavy reliance on fossil fuels, compounded with a thirst for increased mobility and global connectivity of people and goods.

Future propulsion systems is a catch-all term for technologies that transition the transport sector away from fossil fuels, hence reducing emissions to either zero or net zero. These technologies include battery electric, hydrogen fuel cell, hydrogen burning engines, sustainable/synthetic fuels and hybrid systems. 

The best solution for any single application will depend on many factors, such as the availability of the fuel, or charging points in the case of battery, range i.e: how far the vehicle needs to travel before refuelling, power and duty cycle requirements, purchase cost, running costs etc. Clearly the solution for a small passenger car commuting short distances and only carrying one or two people will be very different to that required for a large articulated lorry travelling long distances. 

There is no silver bullet solution to all applications. The pros and cons of competing technologies are not easy to define and lockdown as the landscape is constantly evolving with the development of new battery chemistries, more advanced fuel cells and greater access to sustainable fuels. 

The relative sustainability of these technologies can also be contentious, with issues around mining critical elements for batteries, magnets or catalysts, or how landmass use for bio-fuels competes with food production being played off against the potential CO2 benefits they bring.  It is not the role of the AMRC to pick a winner amongst these technologies, nor provide a view on which solutions are more viable than others. Our role is to support the industrialisation of the key technology elements and ensure UK manufacturing companies are equipped with the knowledge and capability to exploit them.

What excites me, as an engineer, is that there are lots of clever technology solutions being developed in the UK and beyond, and many of these will provide at least part of the answer as to how we can carry on using cars, buses, trucks and aeroplanes - but in a much more sustainable way. 

Why is this of interest to the AMRC? Well, beyond the engineering development phase, all of these solutions will need a viable method of manufacture to produce them at the scale and rate required by the transport sector, and companies are experiencing significant challenges along this industrialisation journey. The AMRC is well placed to address these challenges, with strong alignment between our core competencies and the needs of industry. 

Across the AMRC we have been building specialist capability and expertise to address some of these specific challenges, these include:

• The Hydrogen Electric Propulsion Systems Testbed at AMRC Cymru. This facility is dedicated to carrying out research and development on the assembly of fuel cell stacks, to improve the quality and repeatability, allowing industry to de-risk production scale up. This capability, established via the High Value Manufacturing Catapult funding, and led by our future mobility lead, Lee Wheeler, has already attracted interest from several companies across aerospace and automotive, and has resulted in landing a project with Toyota UK, backed by the Welsh Government-administered Ford Low Carbon Vehicle Transformation Fund.
• At AMRC North West, our technical fellow for batteries and automation, Richard Heggie, has been developing a facility to assist during the development and prototyping phase of electric vehicle battery modules and packs. Technologies such as laser welding, wire bonding, ultrasonic and resistance welding, are utilised to join individual cells into connected modules. Our focus is on automation of battery assembly, with emphasis on greater intelligence and flexibility. In-process monitoring and testing is used to ensure quality and reliability, while also providing data to create digital passports which can be used to monitor the health of the batteries through production and during use. This will enable greater optimisation of the manufacturing processes and provide a pathway to the re-use and recycling of batteries at the end of life.
• The AMRC is one of the collaborating research institutes in the EPSRC Future Electrical Machine Manufacturing (FEMM) Hub. Lloyd Tinkler, our senior technical fellow for electrical machines, works closely with the FEMM Hub director and vice president of the advanced manufacturing group, Prof Geraint Jewell, to establish credible manufacturing solutions for the production and assembly of electric motors. This ranges from laser cutting of sheet steel laminations used to produce motor stators or the machining of stator stacks to produce more complex geometries which could incorporate cooling channels - through to investigating different approaches to the forming of coils, including robot assisted winding, form winding and even the use of additive manufacturing, allowing greater coil packing efficiency to improve the power density of the motor.

Within our composites team, the existing capability in filament winding is ideally suited to the manufacture of lightweight pressure vessels that are needed for the onboard storage of gaseous hydrogen for passenger cars or trucks. We are building expertise in the design, simulation, manufacture and testing of such vessels. Working alongside our HVM Catapult colleagues at the National Composites Centre (NCC), we will develop and demonstrate a viable and scalable process for the manufacture of type IV pressure vessels that can be exploited by UK supply chains.

To fully embrace the benefits of some of the future propulsion technologies, the vehicle platforms will also need to evolve and adapt, as such future generations of cars, trucks, buses and aeroplanes will require new designs and new methods of manufacture. 

For example, vehicle manufacturers have expressed a desire to have adaptable architecture that could either accommodate a large battery pack or, within the same volume, house the pressure vessels for a hydrogen fuel cell. Similarly, for aerospace, current designs are based on the principle of kerosene being stored within the wings and large gas turbine engines installed on pylons under the wing. The adoption of liquid hydrogen and distributed propulsion will force future designs to look very different. Programmes such as the ATI’s FlyZero and Airbus ZEROe have indicated the direction these may take, with concepts such as belly tanks or more radical blended wing configurations.

The AMRC also has a role to play in future platforms, whether that is making efficiency improvements to existing designs, enabled by lightweighting technologies such as composites and topology optimised castings, or in developing the new methods of manufacture and assembly for truly novel aircraft concepts.

Our vision is to establish the AMRC as the UK’s leading centre for manufacturing development of high-performance future platforms and propulsion systems. Supporting the transition away from fossil fuels and creating a more sustainable future for transport solutions.

A great example that showcases the AMRC’s combined strengths is ROTATOR, a project funded via the EU programme Clean Sky2, that is developing a novel solution for the pitch control mechanism of an open rotor aeroengine. Safran is developing a new engine concept based around an open rotor design; these engines provide the thrust and performance of a turbofan engine but with the enhanced fuel efficiency of turboprop engines. To maximise the thrust and efficiency of these engines for take-off and cruise, a complex pitch control mechanism (PCM) is required. 

This £4m project, led by Sheffield based company Magnomatics a spin-out of the University of Sheffield, and involving AMRC partner Hexagon, is developing a solution based around Magnomatics’ pseudo-direct-drive (PDD), this is a fault tolerant design that eliminates the hydraulic mechanism of conventional PCMs. 

The AMRC is contributing by seeking opportunities to lightweight key components in the system to provide further efficiencies. This includes the use of composites for the PDD rotor, topology optimisation of the blade hub produced as a titanium casting, and additive manufacturing of the blade lever arms. This requires close cooperation across various AMRC groups including design and prototyping, machining, composites and castings, as well as working alongside our colleagues at the University of Sheffield, who are providing input on the design and sizing of the electric drive system.

Over the next 12 months, we will further enhance our capability and offerings in this theme both in terms of platforms and propulsion. We have a strong programme of HVM Catapult projects and will continue to collaborate with industry to address their specific challenges: from battery packs to electric motors, hydrogen storage to fuel cells, turbines and gearboxes, to high rate composites manufacture of aerostructures to deliver on our vision for a tomorrow, done better.