• Aleksandar Ribnishki

  • Theme:Chemical Energy Converters
  • Project:Combustion Mixture Preparation in a Direct Injection Hydrogen Internal Combustion Engine
  • Supervisor: Sam Akehurst
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Alex recently graduated from the University of Bath with an MEng in Mechanical with Automotive Engineering, during which he undertook a three-month placement at Horstman Defence Systems Limited and a year-long placement at Mammoet. It was during these placements that he developed an interest towards the research and development of low carbon and carbon neutral systems. Alex’s passion for internal combustion engines led him to join the university’s ICE Formula Student team – Team Bath Racing, during his penultimate year. During his time with the team, Alex conducted engine simulations of the team’s KTM 500 engine and designed the intake system. For his final year project titled ‘Analytical and Numerical Modelling of the Surface-to-Volume Ratio of a Two-Stage Wankel Engine’ and supervised by Dr Aaron Costall, Alex investigated the effects that the geometrical parameters of a two-stage Wankel engine have on its surface-to-volume ratio and proposed an optimised engine design for reduced thermal losses and improved thermal efficiency.


  • My go-to comfort-binge TV series is Friends
  • I collect LEGO sets
  • I have been skiing since I was 12
  • I am afraid of heights

Combustion Mixture Preparation in a Direct Injection Hydrogen Internal Combustion Engine

The internal combustion engine (ICE) has been the ‘silver bullet’ in powering machinery for the transportation, mining and construction industries. However, with existing and upcoming regulations on CO2 emissions, the industry is exploring the viability of fuelling ICEs with hydrogen as a carbon neutral alternative – notable examples include BMW, Toyota, Yamaha and JCB.

Current hydrogen combustion research focuses on achieving high brake thermal efficiency (≥45%) while keeping NOx emissions levels low by utilising direct injection fuelling strategies. This results in increased volumetric efficiency and allows for a more precise control of abnormal combustion events compared to port fuel injection. Nevertheless, topics such as combustion irregularities, turbocharger design for hydrogen-specific operation and injection strategy optimisation for efficiency, emissions and power density remain under-researched.

This research project will explore air-fuel mixture preparation techniques in a reciprocating hydrogen internal combustion engine utilising 3D CFD models validated using empirical data. These models will be used to study different hydrogen direct-injection strategies under lean operating conditions (λ < 0.6) and to investigate advanced ignition and combustion modes under distinct intake conditions (i.e., intake charge temperature, pressure, humidity, etc.). The aim is to identify injection and mixing strategies that promote efficient mixing of the air-fuel mixture and result in lean hydrogen flames with suppressed emissions, improved combustion stability and increased thermal efficiency. This work will provide more accurate requirements for turbochargers for hydrogen engines and a better picture of the in-cylinder effects at diverse engine operating points. Ultimately, it will fulfil gaps in the understanding of fundamental hydrogen combustion and identify regimes for high efficiency, zero-carbon zero-emission operation.

As an extension, the project activities will be preceded by a detailed one-dimensional simulation study in GT-POWER of a hydrogen ICE operating under lean conditions as part of the MRes Summer Project activities. The aim of this study will be to compare the 1D simulation findings and assess their accuracy and robustness against experimental data and previous 3D simulation studies. The variables of interest are brake thermal efficiency, NOx emissions, in-cylinder pressure and temperature.

© Copyright 2021 AAPS CDT, Centre for Doctoral Training in Advanced Automotive Propulsion Systems at the University of Bath