The Government's 'Future of Mobility' and 'Road to Zero' strategies outline a second UK transport revolution, characterised by rapid decarbonisation, increased automation and enhanced connectivity. This radical transformation presents both opportunities and challenges for improving air quality over the next two decades, occurring in the context of disruptive changes in transport technology, increasing public environmental awareness and evolving transport behaviours. In this context, actions taken during the emerging transition phase will influence air pollutant sources and exposure patterns across indoor (i.e. vehicle, rail/bus) and outdoor (i.e. pavement, platform, bus station) land transport environments, with profound future implications for public health. We recognise this critical opportunity for encouraging policy foresight, cultivating scientific advancement and stimulating citizen engagement at the air quality, climate and health nexus. Our vision is to establish a diverse interdisciplinary network, connecting researchers across nine UK higher education and research institutions with >20 network partners, comprising commercial, public sector and non-profit organisations. We will establish sustainable connections to undertake co-definition of issues and opportunities and co-delivery of innovative, evidence-based solutions. We will deliver a varied portfolio of network activities including TRANSITION summits, problem-solving workshops, hackathons, discovery studies, site visits, policy engagement events and creative outreach activities at transport locations. Thus the network partners will achieve the ambitious but achievable goal of directly shaping future air quality, climate and transport policy, reflecting the ambitions of the UKRI SPF Clean Air Analysis and Solutions programme.

Aerosol science, the study of airborne particles from the nanometre to the millimetre scale, has been increasingly in the public consciousness in recent years, particularly due to the role played by aerosols in the transmission of COVID-19. Vaccines and medications for treating lung and systemic diseases can be delivered by aerosol inhalation, and aerosols are widely used in agricultural and consumer products. Aerosols are a key mediator of poor air quality and respiratory and cardiac health outcomes. Improving human health depends on insights from aerosol science on emission sources and transport, supported by standardised metrology. Similar challenges exist for understanding climate, with aerosol radiative forcing remaining uncertain. Furthermore, aerosol routes to the engineering and manufacture of new materials can provide greener, more sustainable alternatives to conventional approaches and offer routes to new high-performance materials that can sequester carbon dioxide. The physical science underpinning the diverse areas in which aerosols play a role is rarely taught at undergraduate level and the training of postgraduate research students (PGRs) has been fragmentary. This is a consequence of the challenges of fostering the intellectual agility demanded of a multidisciplinary subject in the context of any single academic discipline. To begin to address these challenges, we established the EPSRC Centre for Doctoral Training in Aerosol Science in 2019 (CDT2019). CDT2019 has trained 92 PGRs with 40% undertaking industry co-funded research projects, leveraged £7.9M from partners and universities based on an EPSRC investment of £6.9M, and broadened access to our unique training environment to over 400 partner employees and aligned students. CDT2019 revealed strong industrial and governmental demand for researchers in aerosol science. Our vision for CDT2024 is to deliver a CDT that 'meets user needs' and expands the reach and impact of our training and research in the cross-cutting EPSRC theme of Physical and Mathematical Sciences, specifically in areas where aerosol science is key. The Centre brings together an academic team from the Universities of Bristol (the hub), Bath, Birmingham, Cambridge, Hertfordshire, Manchester, Surrey and Imperial College London spanning science, engineering, medical, and health faculties. We will assemble a multidisciplinary team of supervisors with expertise in chemistry, physics, chemical and mechanical engineering, life and medical sciences, and environmental sciences, providing the broad perspective necessary to equip PGRs to address the challenges in aerosol science that fall at the boundaries between these disciplines. To meet user needs, we will devise and adopt an innovative Open CDT model. We will build on our collaboration of institutions and 80 industrial, public and third sector partners, working with affiliated academics and learned societies to widen global access to our training and catalyse transformative research, establishing the CDT as the leading global centre for excellence in aerosol science. Broadly, we will: (1) Train over 90 PGRs in the physical science of aerosols equipping 5 cohorts of graduates with the professional agility to tackle the technical challenges our partners are addressing; (2) Provide opportunities for Continuing Professional Development for partner employees, including a PhD by work-based, part-time study; (3) Deliver research for end-users through partner-funded PhDs with collaborating academics, accelerating knowledge exchange through PGR placements in partner workplaces; (4) Support the growth of an international network of partners working in aerosol science through focus meetings, conferences and training. Partners and academics will work together to deliver training to our cohorts, including in the areas of responsible innovation, entrepreneurship, policy, regulation, environmental sustainability and equality, diversity and inclusion.

Due to their high fuel economy, diesel engines are widely used in on-road applications. The need to maintain efficiency and performance while meeting increasingly stringent emissions regulations is forcing engine developers to design advanced in-cylinder combustion strategies tailored to minimize emissions and maximize performance at specific operating conditions. These strategies are currently limited by high emissions and poor performance as the engine's speed and load change during transient operation. Even under a wide range of steady-state combustion conditions, there is a shortage of fundamental understanding of the effects of the engine load, charge conditions and charge composition on the combustion process.Transient tests provide information on the effects of a change in the operating mode of an engine. The results of such tests are highly specific to the engine, air exchange, and control system used; it can also be difficult to identify cause and effect relationships relating to the combustion event. As a result, while such tests are necessary for engine development, they do not provide the information needed to develop the improved fundamental understanding being sought in this project. Therefore, this project will adopt well controlled steady-state engine tests with the operating conditions selected to be representative of the charge conditions encountered by individual engine cycles during transient operation. Cycle-to-cycle variability in the composition of the air in the intake and exhaust streams will be measured and will be compared to the observed variability in the combustion event. A variety of tests, including the use of an ignition promoter, will permit evaluation of the principal causes of combustion instability.Combustion instability leads to poor engine performance and high unburned fuel emissions. It is one of the key barriers to the application of high EGR strategies to control diesel engine emissions. Many new diesel engine injection systems have the potential to inject fuel several times within one combustion cycle. This project will use the newly developed fundamental understanding of high-EGR operation to identify novel injection strategies that can improve combustion performance. An optimization process will be used to identify the most promising potential strategies over a range of engine operating conditions similar to those encountered during transient operation. This project will involve two PhD research students (one of whom will be funded by Loughborough University) working under the close supervision of the PI. An advisory panel composed of experienced academic and industrial engine researchers will provide guidance for the project. Technical support will be provided by skilled research technicians. The research will be conducted on a newly installed, state-of-the-art automotive-sized single-cylinder research engine. The overall project methodology will involve first identifying the operating conditions which will be encountered during a transitional mode-shift between low temperature (high EGR) and conventional (low EGR) diesel combustion. Then, steady-state engine tests will be conducted over a range of conditions which are representative of the charge composition and EGR levels encountered during transient operation. Based on these experimental results, those operating conditions which demonstrate high emissions and/or poor combustion stability will be investigated in more detail, including optical in-cylinder evaluation and cycle-resolved emissions measurements. A combustion enhancer will be used to investigate the effects of kinetic limitations at high EGR levels. Finally, a range of multiple-injection strategies will be evaluated to identify techniques for controlling emissions under high-EGR transient operation.

Recent studies have indicated that nanoparticles (NPs) may have greater negative impacts than coarser particles (PM10 or PM2.5 i.e. mass concentrations of particles with aerodynamic diameters <10 or 2.5 um, respectively) on human health, urban visibility and global climate change. Here, NPs are referred to as particles of size <300 nm as this size range includes nearly all particles (>99% of total number concentrations) in the urban environment. Road vehicles emit most particles within this size range. Current air quality regulations are based on PM10 and PM2.5 and therefore do not control particle number concentrations (PNCs). In contrast, ultrafine fraction (<100 nm) of NPs contribute little to particle mass concentrations but significantly higher (~80%) to total PNCs. It means that existing air quality regulations are ineffective to control a major part of road vehicle particle emissions. Recently, the UN-ECE Particle Measurement Programme has taken a step forward by proposing emission limits for particles (covering 10-300 nm size range) on a number basis for light and heavy duty diesel vehicles; these have been included in Euro 5 and 6 emission standards. Such initiatives are also required for ambient NPs that will allow regulatory authorities to design effective mitigation strategies for controlling urban NPs on a number basis. However, this progress has been hampered due (in part) to the lack of standard guidelines and instrumentation to measure NPs, the limited knowledge of their dispersion at various spatial scales and the complex particle dynamics involved. Today nearly half of the global population lives in urban areas where probability of human exposure to vehicle-emitted high PNCs is considerably higher. Therefore, it is a matter of public and scientific concern to examine emissions from individual vehicles under real world driving and dilution conditions. However, the situation becomes complex when fine spatial scale studies are contemplated (e.g. in a vehicle wake). This is because the distribution of NPs changes rapidly after emission from the tailpipe in the wake of a moving vehicle due to the competing influences of a number of transformation (i.e. coagulation, condensation, deposition and nucleation) and dilution processes. Information on the time scales for these rapid processes is essential for the modelling of NPs in the tailpipe-to-road region but is not available because of the inadequate sampling frequencies of available instruments.The proposed work aims to deploy a recently commercialised fast response differential mobility spectrometer (DMS50) for measuring particle number and size distributions in the 5-560 nm size range at a sampling frequency of 10 Hz. The DMS50 has not been applied ever for ambient measurements yet. The objectives are to study the change in NP distributions due to competing influences of dilution and transformation processes over the travel time from tailpipe to roadside and to model the fate of these particles at a fine spatial scale (i.e. the near and the main/far wake regions of a moving vehicle). These objectives will be achieved (i) by performing field measurements of NP number and size distributions using a DMS50 in the wake of vehicles (a diesel-engined car and a van) moving at various speeds, (ii) by mimicking the field experiments using wind tunnel simulations for investigating the flow and dispersion characteristics in the wake regions of vehicles, and (iii) by analysing the data obtained from field experiments and wind tunnel simulations to develop the basis for predicting NP concentrations in vehicle wakes.Findings from this work will assist the scientific community and regulatory authorities in better understanding the science behind the NP dynamics involved in the tailpipe-to-road region and in doing so provide a link between studies targeting either roadside or engine measurements separately.

An aerosol consists of solid particles or liquid droplets dispersed in a gas phase with sizes spanning from clusters of molecules (nanometres) to rain droplets (millimetres). Aerosol science is a term used to describe our understanding of the collective underlying physical science governing the properties and transformation of aerosols in a broad range of contexts, extending from drug delivery to the lungs to disease transmission, combustion and energy generation, materials processing, environmental science, and the delivery of agricultural and consumer products. Despite the commonality in the physical science core to all of these sectors, doctoral training in aerosol science has been focussed in specific contexts such as inhalation, the environment and materials. Representatives from these diverse sectors have reported that over 90% of their organisations experience difficulty in recruiting to research and technical roles requiring core expertise in aerosol science. Many of these will act as CDT partners and have co-created this bid. We will establish a CDT in Aerosol Science that, for the first time on a global stage, will provide foundational and comprehensive training for doctoral scientists in the core physical science. Not only will this bring coherence to training in aerosol science in the UK, but it will catalyse new collaborations between researchers in different disciplines. Inverting the existing training paradigm will ensure that practitioners of the future have the technical agility and confidence to move between different application contexts, leading to exciting and innovative approaches to address the technological, societal and health challenges in aerosol science. We will assemble a multidisciplinary team of supervisors from the Universities of Bristol, Bath, Cambridge, Hertfordshire, Imperial, Leeds and Manchester, with expertise spanning chemistry, physics, biological sciences, chemical and mechanical engineering, life and medical sciences, pharmacy and pharmacology, and earth and environmental sciences. Such breadth is crucial to provide the broad perspective on aerosol science central to developing researchers able to address the challenges that fall at the boundaries between these disciplines. We will engage with partners from across the industrial, governmental and public sectors, and with the Aerosol Society of the UK and Ireland, to deliver a legacy of training packages and an online training portal for future practitioners. With partners, we have defined the key research competencies in aerosol science necessary for their employees. Partners will provide support through skills-training placements, co-sponsored studentships, and contribution to taught elements. 5 cohorts of 16 doctoral students will follow a period of intensive training in the core concepts of aerosol science with training placements in complementary application areas and with partners. In subsequent years we will continue to build the activity of the cohort through summer schools, workshops and conferences hosted by the Aerosol Society, virtual training and enhanced training activities, and student-led initiatives. The students will acquire a perspective of aerosol science that stretches beyond the artificial boundaries of traditional disciplines, seeing the commonalities in core physical science. A cohort-based approach will provide a national focal point for training, acting as a catalyst to assemble a multi-disciplinary team with the breadth of research activity to provide opportunities for students to undertake research in complementary areas of aerosol science, and a mechanism for delivering the broad academic ingredients necessary for core training in aerosol science. A network of highly-skilled doctoral practitioners in aerosol science will result, capable of addressing the biggest problems and ethical dilemmas of our age, such as healthy ageing, sustainable and safe consumer products, and climate geoengineering.