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Spotlight: Professor Felix Leach

One of the main objectives of #HugYourEngine is to shine a spotlight on individuals who are helping make internal combustion engines cleaner and more efficient. This spotlight is on Felix Leach.

Felix Leach is an Associate Professor of Engineering Science, and Fellow and Tutor in Engineering Science at Keble College. Felix is a Chartered Engineer (MIMechE), a Fellow of the Higher Education Academy, and a Member of the Society of Automotive Engineers. His research interests are in combustion, and specifically emissions and efficiency in internal combustion engines. He works in the Jaguar Land Rover Centre of Excellence for Combustion Research at Oxford using world-leading measurement capabilities to develop an engine for the 21st Century. Felix won the 2014 Richard Way memorial prize, and 2018 & 2019 SAE Excellence in Oral Presentation awards. Felix works on particulate emissions from GDI engines, diesel engine emissions and efficiency, advanced instrumentation, real driving emissions (RDE) as well as a growing profile of public engagement on combustion and air quality.

Some of the Oxford engines group, in Prof Richard Stone’s 1922 Vauxhall 14-40. (Note from Kelly: I was fortunate enough to get a ride in that car!)

Kelly Senecal (KS): When and why did you get started in combustion research?

Felix Leach (FL): It was all through Professor Richard Stone, head of our group here in Oxford and author of the bible for engines research “Introduction to Internal Combustion Engines”. He got in touch with me towards the end of my undergraduate degree, asking if I would be interested in doing a DPhil (as Oxford calls a PhD) in engine research with Jaguar Land Rover. It sounded like an excellent opportunity – and it was! I’m still here!

KS: What are you working on now?

FL: Today my activities split into five streams: particulate emissions from GDI engines, emissions and efficiency in diesel engines, advanced instrumentation, transient RDE emissions from vehicles, and “combustion and public policy”. Here are more details of the five streams:

1. I first started measuring particulate emissions from GDI engines as part of my DPhil, where I developed an equation (the PN index) which linked fuel composition to particle number (PN) emissions from GDI engines. That work continues today – with interests in gasoline compositions, and biofuels and their influence on PN emissions – the field has also expanded substantially since I first became involved, with a global interest in particulate indices today.

2. My work on diesel engines is in close collaboration with Jaguar Land Rover, investigating combustion system design, and fuel and air handling parameters further to improve emissions and efficiency in JLR’s “ingenium” family of diesel engines.

High speed Coriolis fuel flow test rig in the lab at the University of Oxford.

3. As our modelling capabilities get better, the data which we input into the models needs to improve at a similar rate (rubbish in, rubbish out) – so I am working on a variety of new instrumentation techniques not only to improve the models, but (one day) to provide additional control information to ECUs. Nick, one of our DPhil students, has developed a very fast thermocouple technique for obtaining crank angle resolved temperature data from the exhaust port. I am also leading a project aiming to provide direct injector mass flow measurement using Coriolis flow meters (Fast NGC) – although at an early stage (and sometimes I feel all we’ve discovered is how hard the problem is) this technique is showing real potential and will provide a step-change in capability – particularly for digital rate shaping.

Live NOx emissions from an in-service bus.

4. Recently I have started high spatio-temporal RDE measurements from vehicles in collaboration with Cambustion. This technique, combining their very fast analysers (~2ms) combined with very accurate differential GPS (~0.1cm) means that we can identify emissions from a vehicle to around 10cm, and understand what caused it – for example a speed-bump or set of traffic lights. There is a huge interest in local air quality in Europe at the moment, and this technique is a valuable way for the “engines” community to interact with the “air quality” community to try and improve AQ for everyone.

Felix hugging a GM 1.6L BIN 125.

5. In a sense, the most important thing I do is “combustion and public policy”. I sometimes feel that the combustion community needs an advocate like Elon Musk for BEVs. I do not claim to be that advocate, but consider trying to advocate for our community vital, unless I can communicate my message effectively, its impact will remain consigned to unread pdfs. I have written an article for and published letters in (UK) national newspapers, had a letter published in The Economist, and given national radio interviews. I make an effort to talk to school groups such as those visiting Oxford, and have discussions with policy makers throughout the UK - advocating for evidence-based policy around combustion.

Overview of the single cylinder diesel engine test cell in the lab at the University of Oxford – part of the Jaguar Land Rover Centre of Excellence for Combustion.

KS: Describe your lab facilities.

FL: Underground! At Oxford, the engines lab is two floors underground, which has some unique challenges, such as getting equipment in and out through constrained lifts and floor hatches. In addition, getting heat and exhaust out of the lab is also more complicated than in many other places, but we have very good systems. We have six engine dynamometers hosting a variety of single- and multi-cylinder engines as well as spherical combustion vessels, three spray rigs, and a host of other smaller rigs. The lab is the home to the Jaguar Land Rover / University of Oxford Centre of Excellence for Engine Combustion Research. This centre, now in its sixth year, hosts both gasoline and diesel activity today on both optical access and thermal single cylinder engines. Researchers at Oxford work right alongside those from Jaguar Land Rover in developing the latest technologies and ideas, which can go straight into the Jaguar Land Rover production pipeline (which can be hugely satisfying!). As a post-doc, I designed and built the test cell, which houses the thermal engine six years ago, and today it is satisfying to see it continue to give such excellent results. During design and build there was a particular focus on data quality and accuracy, and I think it is among the most accurate Single Cylinder Engine test cells in Europe (and I’m only a little biased!). The single cylinder optical engine gives us some extraordinary capabilities, from flame imagine to developing our innovative temperature measurement technique Laser Induced Thermal Grating Spectroscopy (LITGS) – which is being developed by Prof Paul Ewart and Prof Ben Williams. Outside of the lab we have a growing CFD activity (OpenFOAM, Star-CD, and CONVERGE) using both local machines and Oxford’s supercomputer facilities; although this part of our work is relatively new (5 years or so) – it is hugely important and definitely the future!

Gin combustion in an optical engine.

KS: What’s your favorite type of flame?

FL: This one! (picture to the left) – this is a flame image taken using gin as a fuel in our optical engine. In 2012 I undertook a project with a Masters student looking at aqueous ethanol. One problem with making ethanol is that ethanol forms an azeotrope at 95.63% ethanol and 4.37% water (by mass). What this means is that it is not possible to remove that last 4.37% water by distillation. Techniques such as molecular sieves are used, which are very energy intensive. Therefore we conducted a study to see what the influence of water content on ethanol’s performance in engines was. To take this to an extreme, I wondered if say 53% water / 47% ethanol would run in an engine – which is gin! Sure enough, it ran (just) and gave this unusual red colour to the flame – probably as a result of all of the water present. I wouldn’t recommend it as a practical fuel – not least gin is a lot more expensive than gasoline!

KS: What’s your favorite fuel?

FL: Gin! No, but seriously, I think future fuels are a real opportunity for the combustion community. Higher octane numbers and a better understanding of how fuels interact with engines (such as the co-optima project). Low carbon fuels such as biofuels and e-fuels are also a possible route to a low carbon, sustainable future for combustion. At this point, I would not like to pick a favourite, but look forward to the progress! For now, I’ll stick with Gin!

KS: What advice would you give students thinking about going into combustion research?

FL: Go for it! I cannot think of a more complex, exciting challenge to investigate. It is a wonderful blend of physics and chemistry. My Engineering background meant I was fairly strong on the physics and thermodynamics required, but I really wish I had more chemistry – I feel like I am always catching up on that front! If you are interested, combustion research is maybe a little more “underground” than it was five years ago, but there is a lot going on. Get involved – the SAE and IMechE (in the UK) have all sorts of events – go along to one – it will probably be fun!

Felix hugging a GM LF3 3.6L twin turbo V6.

KS: Is the IC Engine dead?

FL: No! Indeed I am a passionate advocate for continued investment in the ICE, this is a focus of my strand of work above “combustion and public policy”. Indeed, this is how I first met Kelly (founder of HYE) - I had published a letter ( also signed by a large number of other British academics in the Economist, which Kelly had read. Part of my work today continues to be advocacy for combustion as a future energy source, we have made so many amazing steps in the last century, and I am confident we have many more ahead of us. The advantages offered by future fuels, combustion technologies, and electrification, mean there is a lot of opportunity out there, and a lot more work to be done! It is also important to listen very carefully to government pronouncements, as often the details of the terminology used can make a big difference – for example an electrified vehicle is not the same as an electric one ( It is also important to remember that all technologies have their advantages and disadvantages – and we should not hide from the disadvantages of combustion. But given that in many places on the planet we struggle to get electricity into people’s homes, I am confident that the combustion engine will be around long into the future; and as a result we have an obligation to keep improving it! The internal combustion engine has transformed the world over the last 100 years – bringing substantial benefits to billions of people. Given it will be on our roads and rails for at least the next 50 years—can we afford not to keep improving it?

KS: How is your work helping improve fuel efficiency or reduce emissions?

FL: All of my work is focused around this goal; my DPhil work influenced (a very small part of) European law around emissions, the work on RDE emissions is being taken seriously by policy makers around road design. The diesel work continues to influence future JLR engines. Other projects are more speculative, but the potential rewards are huge! Finally, one of the pleasures of my job is that I get to teach such talented students. The Oxford system means that I have close oversight of just over 40 undergraduates who end up specializing in a wide variety of fields. I don’t know what they’re going on to do, but I’m confident that a lot of them will make the world better through engineering – and I hope I’ve played a small part in that too.

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