Thesis work - 30hp - Effect of O3 (Ozone) on Promoting the Self-Ignition and Combustion of H2

Introduction
Thesis work is an excellent way to get closer to Scania and build relationships for the future. Many of today's employees began their Scania career with their degree project.

Background 
Achieving carbon-free combustion in heavy-duty engines is one of the major technological frontiers in sustainable transport. Hydrogen (H2) is a promising candidate due to its high energy content and zero CO2 emissions. However, its high auto-ignition temperature and long ignition delay complicate its use in compression ignition (CI) engines. Conventional HPDI (High-Pressure Direct Injection) concepts rely on small diesel pilots to initiate combustion, an approach that still emits CO2 and constrains the system’s green potential.

A potential breakthrough involves using oxidizing radicals such as ozone (O3) to promote hydrogen self-ignition. Ozone is a powerful oxidizer that can decompose into atomic and molecular oxygen, generating reactive species such as •O and •OH radicals, which in turn reduce ignition delay times and stabilize the combustion process. Preliminary CFD work performed with CONVERGE indicates that introducing trace amounts of ozone into the intake air dramatically accelerates hydrogen ignition even at moderate temperatures.

Given the increasing onboard availability of electric power in modern trucks, onboard ozone generation becomes feasible using compact corona-discharge or dielectric barrier discharge (DBD) systems. Experimental studies have also shown that even ppm-level ozone concentrations can promote self-ignition of high-octane fuels and hydrogen mixtures, making it a promising route for eliminating diesel pilots altogether.

Objective 
The purpose of this master thesis is to develop and validate a CFD methodology in STAR-CCM+ to simulate hydrogen combustion in the presence of ozone and to evaluate ozone’s effect on ignition delay, combustion stability, and thermal efficiency under CI-relevant conditions.

The study will build on prior work conducted in CONVERGE but migrate to STAR-CCM+’s In-Cylinder module, enabling future integration with ongoing Scania in-cylinder simulation frameworks. A specific focus will be on quantifying the minimum ozone concentration required to achieve reliable ignition without diesel assistance in an HPDI system.

Job description 

• Literature Review: Review experimental and numerical studies on hydrogen–ozone ignition and combustion. Summarize reaction mechanisms involving ozone dissociation and radical formation (•O, •OH). Analyze previously reported effects of ozone on ignition delay times and flame propagation
• Method Development in STAR-CCM+: Establish an in-cylinder simulation setup replicating prior CONVERGE results. Implement detailed or reduced chemical mechanisms including O3 decomposition pathways (e.g., Jian et al. mechanism). Calibrate boundary conditions (fueling, ozone concentration, injection timing) for heavy-duty hydrogen operation.
• Simulation Campaign: Conduct parametric studies on ozone concentration, initial temperature, and injection parameters. Evaluate their influence on ignition delay time, in-cylinder pressure, and heat release rate (HRR). Investigate ozone decomposition dynamics and radical production at engine-relevant time scales.
•  Analysis and Optimization: Identify threshold ozone levels enabling stable self-ignition of hydrogen without pilot fuel for different engine loads. Assess potential efficiency trade-offs and quantify energy requirements for onboard ozone generation. Evaluate combustion uniformity, NOx sensitivity.
• Validation and Recommendations: Compare simulated ignition delays and HRR trends with available experimental data. Provide recommendations for feasible ozone concentrations and generator designs compatible with Scania’s HPDI platform.
• Safety Measures: Explore residual ozone at exhaust valve opening.

Additional considerations

•    Evaluate feasibility of onboard ozone generation using available electrical power (~? kWh/kg O₃).
•    Explore the half-life of ozone in the intake manifold, i.e., the time required for ozone to decompose (or dissociate) under engine-relevant pressure and temperature conditions.

Education
MSc in Mechanical Engineering, Engineering in physics,Chemical Engineering, or similar 
Number of students: 1
Start date for the thesis work: January 2026
Estimated time required: 20 w

Contact persons and supervisors
Supervisor: Darius Gohari, darius.gohari@se.traton.com
Co-Supervisor: Louise Olsson, louise.olsson@chalmers.se

Application:
Your application must include a CV, personal letter and transcript of grades 

A background check might be conducted for this position. We are conducting interviews continuously and may close the recruitment earlier than the date specified.