Decarbonised Clean Marine: Green Ammonia Thermal Propulsion (MariNH3)

Battery electrified power is predicted to become the dominant mode of propulsion in future light duty transport.

For sustainable heavy duty applications challenges remain around practical range, payload and total cost. Currently there is no economically viable single solution.

For commercial marine vessels the problem is compounded by long service lives, with bulk carriers, tankers and container ships the main contributors to greenhouse gases.

Ammonia (NH₃) has excellent potential to play a significant role as a sustainable future fuel in both retrofitted and advanced engines. However, significant uncertainties remain around safe and effective end use, with these unknowns spanning across fundamental understanding, effective application and acceptance.

The multi-disciplinary programme Decarbonised Clean Marine: Green Ammonia Thermal Propulsion (MariNH₃) seeks to overcome the key related technical, economic and social unknowns through flexible, multidisciplinary research set around disruptive NH₃ engine concepts capable of high thermal efficiency and ultra low NOx.

The goal is to accelerate understanding, technologies and ultimately policies which are appropriately scaled and "right first time".

The University of Brighton contributes work on Fuel Definition (Theme 2: Work Package 4).
Dr Steven Begg, Dr Angad Panesar, Dr Guillaume de Sercey and Dr Vikas Sharma work with partnering industries and institutions: BP, Clean Air Power,  Infineum, University of Birmingham, Cardiff University, University of Nottingham.

Their focus is on advancing the fundamental understanding of the mechanisms by which pilot fuels or combustion promoters interact with selected additives, with the aim of identifying optimum combinations that deliver high combustion efficiency, fuel flexibility and significant reductions in carbon-based emissions.

A key aspect of this research considered the Injection of Liquid Ammonia Sprays in Net-Zero Carbon Applications.

The research focused on developing and applying direct injection liquid ammonia spray strategies to achieve zero-carbon emissions in marine and broader combustion applications. It built on the support provided by MariNH3 and other ongoing EPSRC research programmes in ammonia and hydrogen combustion for marine applications, the University of Brighton secured further funding by the Royal Academy of Engineering (RAEng) via the Transforming Systems through Partnership (TSP) scheme:

> Phase I (TSP-2325-5-IN\145): November 2023-January 2025

> Phase II (TSP-2526-7110): October 2025-January 2026

In Phase I, an integrated experimental and simulation methodology was developed to investigate various ammonia delivery methods into engines, either indirectly via the intake port or by direct injection into the combustion chamber. 

In Phase II, the research emphasised experimental characterisation of liquid ammonia spray injection at engine-

relevant conditions using a Rapid Compression Machine (RCM). This work explores how air entrainment and phase-change properties of liquid ammonia influence spray dynamics, air-fuel mixing and vaporisation, aiming to enhance overall combustion efficiency.

The MariNH₃ project has identified key barriers to adoption. Findings have been widely disseminated through leading journals and international conferences.

Researcher development is a key focus, with several now leading spin-out projects. MariNH3 is also contributing knowledge directly to the Clean Maritime Research Hub.

The project has advanced ammonia engine knowledge. Remaining challenges include effective cold start and safe operation. Ongoing work will explore advanced engine cycles and develop a published roadmap to guide future ammonia propulsion research.

University of Brighton

As MariNH₃ partners, the University of Brighton have successfully developed the MariNH₃ Fuel Definition Matrix which optimises combustion performance, anti-corrosion behaviour and anti-wear characteristics using fuel and lubricant additives. The matrix encompasses various fuels and their blends, particularly focusing on ammonia, hydrogen, methane, methanol and diesel.

The evaluation considers thermodynamic, kinematic and kinetic properties, as well as factors such as material compatibility, fuel handling, lubricant performance and combustion outcomes. The specification of the matrix has been informed by Life Cycle Assessment results (Work Package 3) and existing end-use experience drawn from both the public domain and project partners, incorporating data from dual-fuel, jet ignition and split-cycle operation studies.

Key outputs from the University of Brighton have included :
> Optimised combustion strategies: development and evaluation of advanced ammonia/hydrogen fuel blends for marine applications - such as Reactivity-Controlled Compression Ignition (RCCI) engines - culminating in a roadmap for the sector to improve efficiency and reduce emissions.

Life Cycle Assessment (LCA): comprehensive environmental and economic analysis of the ammonia/hydrogen life cycle - from production to end-use, providing evidence-based guidance for sustainable energy policy.

Training and knowledge transfer: capacity building through training early career researchers and students in clean energy technologies, alongside knowledge exchange and dissemination with industry stakeholders and policymakers via workshops and publications.

The first international workshop on Ammonia Combustion (22 Nov. 2024) took place and included presentations from University of Brighton by Dr Angad Panesar & Dr Steven Begg

Challenges and solutions
During the project, several technical and operational challenges have been identified
and addressed:
> Combustion: a detailed combustion reaction mechanism for a liquid ammonia/gasoline fuel blend has been developed and validated using experimental data characterising laminar burning velocity and a more detailed
investigation was proposed using the RCM to achieve deeper insights into the ignition delay of
ammonia/hydrogen.
> Engine modifications: successful implementation to accommodate dual-fuel ammonia/hydrogen combustion experimental activities using liquid ammonia in a dual-fuel mode were conducted to support ongoing computational fluid (CFD) modelling. These modifications represent a key milestone in demonstrating the
technical feasibility of ammonia-based RCCI combustion.
> Engine application: adapting ammonia/hydrogen combustion technology to practical marine engines introduces additional complexities for these fuels due to factors such as larger bore sizes, slower engine speeds and specific maritime operating conditions. Understanding these effects is paramount for the successful
adoption of net zero fuels, a topic currently underexplored.
> Storage and handling: compliance with safety regulations and addressing the challenges of safe storage and handling of liquid ammonia during experimental work has highlighted the need for further research into ammonia liquefaction, fuel integration and safety aspects in future projects.

The projects have already delivered significant impact across international collaboration, research capacity, technological development, and environmental awareness.
> Enhanced collaboration and knowledge transfer through exchange visits (two from India and two from the
UK) which facilitated the sharing of knowledge and expertise between the partner institutions, with a focus on advanced engine technologies including the Recuperated Split Cycle Engine (RSCE) and RCCI systems.
> Joint international workshops both online and in-person.
> Researcher mobility: two PhD students from IIT Bombay and NIT Agartala visited University of Brighton where they undertook a shared experimental programme.

2. Capacity building in advanced combustion research
> Training and skill development: practical training in state-of-the-art facilities at the University of Brighton and IIT Bombay has enhanced the skills and expertise of early career researchers, PhD students and research scholars in combustion.
> Model development has included the creation of a merged kinetic model for ammonia/gasoline combustion has improved scientific understanding of alternative fuel blend behaviour in engine systems.

3. Technological advancements in fuel combustion
> Experimental infrastructure: the externally heated diverging channel rig at IIT Bombay enables experiments with both liquid/gaseous fuels, supporting detailed combustion studies essential for validating zero-dimensional simulations of laminar burning velocity and optimising fuel blend ratios.
> RCCI engine development: the successful installation and commissioning of the RCCI test engine at NIT Agartala has expanded the project’s experimental capability. Ongoing dual-fuel combustion experiments are contributing to the development of sustainable engine technologies, marking a vital step toward
the adoption of net-zero fuels.

4. Environmental impact and awareness
> The research has advanced understanding of how ammonia/hydrogen fuel blends can be used as sustainable fuels to reduce emissions and improve energy efficiency in RCCI and RSCE engines.
> Findings highlight strategies for reducing NOx emissions and minimising ammonia slip, thereby supporting the project’s environmental goals.