Powertrain Innovation Requires Accelerated Learning To Deliver Revolution

Jon Lawson

The Institute for Advanced Automotive Propulsion Systems (IAAPS) at The University of Bath in the West of England is benefiting from a £70 million investment. Sam Akehurst, Professor of Advanced Powertrain Systems, outlines his vision of the future.

Powertrain innovation is at the heart of the transport sector’s response to the environmental imperative, but the industry is discovering that processes that are finely tuned to ensure reliable evolution are not well placed to deliver revolution. Throw in the need to accommodate trends such as mobility-on-demand, model fragmentation and the growing diversity of global markets and you have unprecedented demand placed on already stretched engineering resources.

Recognising this challenge, The University of Bath is developing a new type of innovation and education centre. International Transport Manufacturer spoke to Professor Sam Akehurst about the new approaches he feels are needed and how these align with the fast-changing automotive powertrain technology roadmap.

Does the engineering industry need to change?

For a hundred years, innovation has been a double-edged sword: on one hand, it allows us to meet challenging new regulations and to increase competitive advantage; on the other, it is expensive to deliver and even more costly if the research is not adopted or an error in development results in anything from a late-stage tooling change to a major recall. Accelerating innovation exponentially increases these risks and can also have unwelcome impacts on costs and timescales.

Engineering challenges to be addressed through a new powertrain research and innovation centre

A vital addition to the technology roadmap is, therefore, a fresh understanding of how these innovations are going to be delivered without affecting our industry’s outstanding achievements in quality and reliability.

The second part of the answer is that whatever process is used, it will need more flexible and transdisciplinary skills. The constraints on advanced engineering departments are not only cost, timescales and risk: there is also a lack of skills across our industry. On every continent, we are still educating too few engineers with the breadth of understanding needed to work in teams developing complex, highly integrated designs. We are just beginning to see the potential of electric powertrains designed as one system, yet the skill sets needed to develop them are in short supply.

These are the challenges that we are addressing with IAAPS, a new powertrain research and innovation centre that will focus on collaboration between our academics and companies of all sizes, and on educating engineers to have ‘T-Shaped’ skills: that is a depth of expertise in their field, augmented by broad expertise in complementary fields and also collaboration and team leadership skills.

Powertrain innovation

The University of Bath has more than 40 academics working on powertrain innovation and leads the development of the UK government’s Thermal Propulsion Systems automotive technology roadmap. Our view is that there are two possible pathways: ideally, engines will be optimised for the best possible fuels, but realistically, at least into the medium term due to variability in world markets, they will have to remain flexible and able to work efficiently with a wide range of fuels.

What alternative fuels are there?

Fuels are so key to reducing emissions that we feel more profile should be given to this area of research, especially with regulators and governments, as the consistency of supply is a key limiting factor. In the short term, reducing the carbon intensity of conventional fuels would deliver a substantial reduction in CO2, straight into the existing vehicle fleet, a fact recognised by fuel suppliers who are now making welcome investments in this area.

In the five to seven-year timeframe, there are already dual- and bi-fuel systems that show great promise, such as lean burn direct injection CNG/LNG with gasoline. In the medium term (seven-15 years) we may see higher bio content made not from virgin agricultural crops, but from waste products. I can see great potential for hydrotreated vegetable oil (HVO) and biomass to liquid (BTL) low carbon fuels, which may be mixed with conventional fuels to reduce their carbon content. In the longer term, there is great potential for alternative thermodynamic cycles such as fuel cells and combustion engines co-developed with ‘sun-to-liquid’ fuels for near-zero emissions.

The commercial availability of these fuels revolves around a number of complex decisions, so the continuing development of global energy systems analysis tools are vital to inform the fuel pathway choices and therefore also engine development priorities. Research must be focused on an objective with commercial viability, which means taking the time to understand the global picture right from the beginning.

How much more efficient can piston engines become?

Taking a mid-point between diesel and gasoline, a typical new engine would have a peak engine system brake thermal efficiency of around 42%. We expect that to increase to around 48% by 2025 and 53% by 2035, with Heavy Duty vehicles then up to 60%. Initially, this will be highly efficient, very dilute, low-temperature combustion and heat recovery, then potentially through new combustion cycles. NOx and PM will be essentially solved by 2025, regardless of fuel: with appropriate combustion management and aftertreatment, exhaust levels can be below the ambient levels found in most zero-emissions zones.

The term ‘piston engine’ includes a lot of novel architectures, but they are all a decade or more from volume production. While researching the UK Government’s automotive technology roadmap, we were given compelling cases for many approaches, including split cycle concepts and linear piston generators. When ICE evolves to a point where it is the junior partner in an electrified powertrain system, it could be any of these or it could be rotary, or even something that has not yet been proposed. There are great synergies between electrification and ICE in hybrid vehicles. When the level of hybridisation is high enough, then the engine can be much more effectively optimised around a more constrained operating envelope.

How are advances in modelling aiding engine design?

Unlocking new powertrain designs

This is a great question as new modelling and simulation tools are crucial to unlocking new powertrain designs and their development will be a key focus of IAAPS. Virtual prototyping and testing will enable more efficient, lighter vehicles to be developed more quickly, but only if we can ensure our models accurately reflect the real world and our test protocols are representative of how vehicles are used.

One of our objectives is to focus not just on more sophisticated models that provide more detailed insights, but also on closing the gap between the simulation and the real world.

There are, for example, still significant challenges around the fundamental science of combustion and battery degradation modelling. Even when the system can be modelled, the resource and time requirements for complex multiphysics CFD including chemistry can be too great, even with advanced HPC resources, so with today’s systems, complex system-level validation is still required.

What about the use Of VR & AR?

Virtual and Augmented Reality will be part of this, but largely for different reasons. The main benefit of these tools is to enhance collaboration, allowing ideas to be explored in dispersed global teams with different areas of expertise. At IAAPS we are entering an agreement with one of the world leaders in powertrain test systems and VR will be an important part of the work we do together, not just as a tool for the engineers working at the facility, but also to help us understand how best to use, and hence evolve, these exciting new techniques.

VR will – and indeed already does – help to accelerate the design of manufacturing systems. In our field, we have seen it used to plan the manufacture of an electric derivative of an existing model, developing supply lines through the factory to the cell, optimising assembly processes and ensuring seamless integration with the existing lines.

We also see it as a useful tool in simplifying end-of-life recycling. Regulations will rightly become more demanding, requiring vehicles that can be more easily disassembled and separated into their constituent materials. VR has a role to play here as there will be substantially less capital and automation available to dismantlers, who have to work across a vast range of vehicle types and ages. VR will help ensure that vehicle designs enable cost-effective disassembly and materials recovery using appropriate, low-cost techniques.

Where is turbo design going?

The University has developed a core competence in turbocharging and works with most of the UK vehicle manufacturers in this area. We focus not so much on turbocharger technology but on the tools needed for the development and evaluation of turbochargers and downsized turbocharged engines. The behaviour of a turbocharger and its interaction with the engine’s combustion dynamics is highly complex, particularly when aggressive transients have to be considered as they do when optimising emissions for real-world driving. Our focus is therefore on understanding what’s going on in that interaction and building simulation tools that help specialists develop better products more quickly.

Electrically assisted turbochargers

This is another area of research where the constraints change dramatically when we start looking at engines optimised for future hybrid propulsion systems as the transients can then be supported by the electrification. Although this simplifies the demands on the turbocharger, it also greatly expands the range of possible system options to be investigated.

We see considerable potential for electrically assisted turbochargers as they can improve transient response without any parasitic losses to the engine while also providing energy recovery to increase overall system efficiency. With 48-volt mild hybridisation now well established, the ideal electrical infrastructure is in place to develop a highly synergistic, highly integrated electrified combustion powertrain. Research at the University has shown that the implementation of a motor-generator electric turbocharging system, even on an otherwise largely standard engine, can contribute to reducing the response time of the engine by up to 90% while improving its thermal efficiency and generating up to 1kWh of energy. These technologies may also find applications in fuel and air supply systems for fuel cells.

What are the trends with battery and hybrid?

Lithium-Ion Batteries and electrically assisted turbochargers

Existing lithium-ion (Li-ion) batteries are likely to dominate the market throughout the current vehicle cycle and the next, but will require significant improvements to cell chemistry, battery management and manufacturing processes to increase the usable power density and the charging rate. There are also question marks over the supply chain for some battery materials, so the development of techniques for battery pack refurbishment and then end-of-life materials recovery are equally vital.

There is still a lot of progress possible in battery management, particularly around increased data from individual cells, improved thermal management and more sophisticated control strategies. We also expect battery packs with mixed cell chemistries, allowing characteristics that are optimised for opposing requirements such as power and energy. The trend to higher voltages is inevitable, but bigger technical challenges are battery chemistry and battery management.

There is much work to be done on optimising cathode materials and structures within Li-ion chemistries, both to reduce costs and improve energy density, although there is a balance here. For example, increasing the nickel and cobalt content offers improved energy density, but raises costs and leaves vehicle manufacturers (or their suppliers) exposed to raw material price and availability. For further developments in energy density, new chemistries such as lithium-sulphur, metal-air and multivalent chemistries could be required.

There is also significant progress required at a battery component level, for example in reducing the proportion of binders used in the electrode manufacturing process and the development of separators that are thinner, dissipate heat more quickly and are more resilient to chemical breakdown. Careful design here could also reduce manufacturing process steps and remove harmful solvents.

Does our industry have the relevant skills?

The short answer is no. As you can see from the discussion above, the development of these technologies requires skills that have not traditionally been part of an engineer’s training. It also needs the ability to understand colleagues with very different specialist skills that have not previously been part of our industry (so often don’t have a full grasp of the quality/reliability imperative) and to collaborate in cross-disciplinary teams, probably distributed around the world. It also requires an entirely new set of test and development tools, from simulation through to physical test rigs.

The facilities at IAAPS are designed around these new requirements, including high transient propulsion system and chassis dynamometers, laboratories for combustion research and pressure charger research, and a substantial investment in systems for the development and testing of

electrification technologies. IAAPS will be one of the first independent research facilities to include research cells designed specifically for high-voltage battery packs and energy storage at a systems level.

How can universities improve?

The answer in my view is to reach a standard in teaching and research where the academic team offers real value to the industry. You can then build research facilities such as IAAPS that bring large companies together with small companies and academics, which introduce students to real projects and teach new skill sets that create the young professionals that our industry needs.

 

The Institute for Advanced Automotive Propulsion Systems will open in 2021. Keep any eye here for updates