Work

Characterizing the Instability Limits of Turbulent, Premixed Combustion Using CO 2 -diluted, Oxy-Hydrogen Mixtures

Year: 2026

Type: article

Abstract: The transition toward carbon-neutral energy systems motivates the development of combustion strategies that can eliminate NOx emissions while maintaining high efficiency. CO2-diluted oxy-fuel combustion of hydrogen is one potential approach, yet the use of CO2 as a diluent introduces strong quenching effects that may compromise combustion stability. To address this challenge, the present study investigates the combustion instability limits of CO2-diluted oxy-H2 mixtures in a spark-ignition reciprocating engine using a combination of experiments and reduced-order modeling. Two experimental campaigns were carried out at constant fuel mean effective pressure and maximum brake torque spark timing: in the first, the CO2 concentration was held constant, while N2 in the oxidizer was gradually replaced by CO2; in the second, the O2 concentration was increased during the substitution of N2 with CO2 to partially mitigate the inhibitory effect of CO2. The results show that the pronounced thermal quenching of CO2 alters the cyclic energy balance, reducing thermal efficiency while distributing proportionally more heat to the in-cylinder gases. This shift suggests that combined heat and power applications, which can exploit the increased gas-phase energy while achieving zero NOx emissions, may be the most suitable implementation of the concept. The experimental findings were then utilized in a predictive model, extending the theory of premixed turbulent combustion into the CO2-diluted oxy-fuel regime. A strong correlation was observed between theoretical dilution limits and experimentally measured combustion instability, even under operating conditions that depart from the canonical flamelet regime.

Source: Combustion Science and Technology

DOI: 10.1080/00102202.2026.2652426

Authors: Mauro Daese, Joshua Lacey, Francesco Contino

Institution: KU Leuven

Language: English

Topic: Combustion and flame dynamics

Subfield: Computational Mechanics

Field: Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action

Open Access status: green

Funders: Agentschap Innoveren en Ondernemen, Moonshot Research and Development Program, Federale Overheidsdienst Economie, K.M.O., Middenstand en Energie