Felix Leach DPhil (Oxon) MEng CEng MIMechE FHEA

Felix Leach is an Associate Professor of Engineering Science, and Fellow and Tutor in Engineering Science at Keble College. Felix is a Chartered Engineer, a Fellow of the Institution of Mechanical Engineers, a Fellow of the Higher Education Academy, and a Member of the Society of Automotive Engineers (SAE).

His research interests are in thermal propulsion systems, air quality, and noise pollution. He runs projects on hydrogen as an energy vector, green ammonia for propulsion, air (NO₂ and PM) and noise pollution, life cycle analysis, advanced instrumentation, and hybrid propulsion systems. 

He is the author of two prize-winning books, the first, with Kelly Senecal, Racing Toward Zero: The Untold Story of Driving Green, is about decarbonising cars rapidly. The second, with Nick Molden, Critical Mass: The One Thing You Need to Know About Green Cars, is about how to simply assess the environmental impact of vehicles.

Felix’s previous projects have included a long collaboration with JLR in two centres of excellence using world-leading measurement capabilities to develop high-efficiency, low-emission engines. He has also worked on advanced measurement techniques for engine diagnostics and the influence of fuels on emissions. Felix has a significant engagement with public policy on environmental impact, emissions, and air quality. He has run projects with Cambustion, Convergent Science, Energenics, Formula 1, Oxford Bus Company, Oxford City Council, Oxfordshire County Council, and Siemens and is frequently consulted on the link between policy and pollution.

Felix is an Associate Editor of the ASME Journal of Engineering for Gas Turbines and Power, Chair of the SAE International Fuels and Lubricants committee, and Secretary of the Universities’ Internal Combustion Engines, Electrification and Energy Group.  

Felix won the 2014 Richard Way memorial prize, the 2018, 2019 and 2024 SAE Excellence in Oral Presentation awards, the 2021 ASME ICED Most Valuable Technical Paper Award, the 2022 Independent Press Award (Environment category), the 2022 SAE Forest R. McFarland Award, the 2024 SAE International Myers Award, and the 2025 APEX Award (Climate & Environmental Sustainability category).

Proudly, he won a 2023 Department of Engineering Science Gold Teaching Award.

My research is in thermal propulsion systems, air quality, and noise pollution. Specifically, I am running projects in the following areas at the moment:

Green Ammonia for Propulsion

Ammonia (NH3) is a promising zero-carbon fuel for future transportation. Today transportation emits around 8.9 billion tonnes of CO2 annually. Whilst some sectors (e.g. cars) can be decarbonised using batteries, heavier transport (marine or freight) is less likely to use batteries due to their cost and energy density.

Ammonia is a hydrogen carrier, and (by volume) contains 50% more hydrogen than liquid hydrogen (which alone is extremely energy intensive to liquefy and store). Ammonia has among the highest energy densities of any non-hydrocarbon (traditionally fossil) fuel. Ammonia is particularly attractive because it can be made using the well-established Haber-Bosch process, which today is used to make 230 million tonnes of ammonia per year. Ammonia production can be 100% renewable when powered by solar and wind. This means that ammonia production can be scalable and can be undertaken repurposing a large amount of existing infrastructure.

My research has been supplying data to enable the design of energy conversion systems specific to ammonia. This has included fundamental data on liquid ammonia sprays into nitrogen. This data obtained included spray break-up (how liquid ammonia breaks up and evaporates upon injection) and how ammonia and air mix under realistic conditions including spray particle size, cone angle, and penetration length. In addition, significant advances have been made in safe handling and disposal of ammonia under laboratory conditions. A new spray rig has been designed, built and commissioned, which can handle ammonia at up to 220 bar / 110°C and background (nitrogen) conditions up to 15 bar.

The rig is modular enabling a wide variety of different ammonia injectors to be tested. The chamber has optical access along three axes, facilitated by five 80 mm viewable diameter fused silica (quartz) windows, two pairs on the side and one at the bottom. Spray images are recorded by a high-speed camera at 10,000 FPS using shadowgraphy by back-illuminating the spray with a white (i.e., broadband) LED shining through a diffusing screen giving a uniform backlighting to the images. Spray particle size is measured using a Malvern Spraytec device, which uses the laser diffraction technique. It provides a spatial measurement on the bulk behaviour of the spray at a given time - all the droplets within the measurement region (defined as the intersection between the laser beam and the plume) at the time when the measurement was taken would contribute to the final droplet size distribution. It provides measurement of droplet size ranging from 0.1−900 μm, most often reported as the Sauter Mean Diameter (SMD).

This experimental approach is complemented with parallel modelling activity - using the experimental data to improve models. The data obtained have been used to code new models into commercial modelling software (computational fluid dynamics (CFD)) provided by project partner, Convergent Science. Its CONVERGE CFD software is used by companies globally. The focus has been on both evaporation and breakup models used with ammonia sprays.

Thermal propulsion systems

An EPSRC Prosperity Partnership between Oxford, Siemens, JLR, and Bath is developing a Thermal Propulsion System (TPS) that, combined with a matched hybrid energy recovery system, will be capable of powering an EV from hydrogen at the same or lower economic and environmental cost than would be incurred by importing electricity to the vehicle from the grid.

By utilising a globally established refuelling network of proven capacity, the TPS technology that will be delivered by this partnership will enable the widespread adoption of zero-emissions capable, electrically driven, vehicles suitable for some of JLR’s applications.

This work is of substantial national importance to the UK's manufacturing sector. The research will protect the role of the TPS, and the UK's well-established engine manufacturing expertise, within the rapidly growing low-emission vehicle sector of the automotive market. The UK government predict that the global market for these low-emissions vehicles could be worth £1.0-2.0 trillion per year by 2030, and £3.6-7.6 trillion per year by 2050. The UK's automotive supply chain as a whole would benefit from the world leading technology that this Partnership seeks to provide.

This Partnership combines the industry knowledge, design and manufacturing resources of Jaguar Land Rover (JLR), with the academic expertise of two of the UK's leading TPS research groups. The University of Oxford are world-leaders in the development of optical diagnostics and the study of in-cylinder phenomena, combustion and emissions. The University of Bath are similarly expert in the study of air handling, waste heat recovery and the systems-level analysis and modelling of vehicle powertrain.

The research is divided into interrelated "Grand Challenges". Jaguar Land Rover will lead the TPS concept design and evaluation. The University of Oxford will perform fundamental experimental studies on mixing, ignition, combustion and emissions formation under conditions relevant to hybrid-focused TPS operation. The data from these experiments will be used at Oxford to develop and validate new predictive models in Siemens software that, in turn, will feed back into concept design process at JLR and systems models at the University of Bath. Oxford will also develop new and improved measurement tools and methods for the experiments. The University of Bath will investigate low-grade and high-grade heat recovery, air-handling and boosting systems--demonstrating and evaluating concepts on a prototype multi-cylinder TPS and feeding back into JLR's concept design process. Bath will also perform extensive systems and vehicle modelling of the TPS system (using models validated against Oxford's data) in a hybrid powertrain to optimise system-level energy balance and demonstrate the target systems-level energy recovery in a virtual environment.

A particular focus for Prof Leach is on hydrogen heat transfer – using thin film gauges to measure wall heat flux of hydrogen flames, which behave substantially differently to traditional hydrocarbon fuel flames.

Air quality

Poor air quality poses a significant public health risk in the UK and worldwide. I have had a significant interest, working alongside Public Health specialist, and UK Clean Air Champion Dr Suzanne Bartington at the University of Birmingham, in projects assessing air quality in Oxford and further afield. The OxAria project enabled a robust evaluation of the positive and negative impacts of introduction, maintenance and removal of COVID-19 measures in Oxford City on air quality (primarily NO2 and PM2.5). The data assimilated generated a series of AQ control scenarios and predicted health benefits, thereby informing and redefining council-led AQ policy and climate strategy. We spend most of our time indoors, yet our focus is almost always on outdoor air pollution. I think that needs to change. I have undertaken careful measurements of NO2 and PM2.5 in a fully instrumented domestic house as well as fast (of order 10 ms) measurements around common household activities such as cooking on a gas hob, lighting a candle, or using a toaster.

Noise pollution

Similar to my air quality work, aligned with this I have a growing interest in urban noise pollution. Previous work has taken place looking at the impact of introducing a Low Traffic Neighbourhood scheme on urban noise. Now I am interested in the impact of the switch to electric buses (from diesel ones) on noise and also on electrification of rail on noise.

Public policy

I have had significant engagement with public policy around transport and air pollution. This has included interviews on the radio and television, report writing for organisations such as the National Engineering Laboratory and Formula One Management. I have written two books aimed at policy makers (Racing Toward Zero and Critical Mass), both of which won awards. I have written sections of reports that went to cabinet at local authority level to inform policy decisions – I work closely with both Oxford/shire councils. I have presented to the European Parliament and representatives of the Welsh and Scottish governments and given keynote and invited talks all over the world.

• Ammospray Fundamental ammonia spray data and model development for zero-carbon propulsion
• Centre of Excellence for Hybrid Thermal Propulsion Systems Working alongside JLR, Siemens and Bath in reducing emissions and increasing efficiency in hybrid engines.
• ZEBRA Measurement of air and noise pollution across Oxford using a network of low-cost sensors
• Indoor air quality Careful measurements of air pollution (particularly NO2 and PM) in the indoor environment
• Public Policy Engagement with the public and media influencing the discourse on future mobility

I am always interested to hear from people interested in doing a DPhil. Projects would be in the general area of thermal propulsion, ammonia, and air quality / noise pollution, but please get in touch to discuss specific projects and ideas.