THERMAL SCIENCE

International Scientific Journal

NUMERICAL MODELLING AND SIMULATION OF HYDROGEN AND AIR MIXING TO PREVENT IGNITION DELAY AND FLASHBACK

ABSTRACT
Practically all residential and commercial gas appliances installed within the EU today were designed for operation with natural gas. A clean and efficient solution for heating and hot water generation is the combustion of hydrogen in case of a gas condensing boiler. Safe and stable combustion of hydrogen is a complex issue, and several influence parameters must be understood for the safe design of hydrogen capable gas condensing boilers. In premixed hydrogen-air combustion, there are two physical problems that should be avoided at all costs: flashback through the burner to the premixing duct and ignition delay in the combustion chamber. Well mixing of reactants is therefore, very important to achieve stable and efficient hydrogen combustion. To evaluate the influence of commercialized mixing stages (fan-venturi combination), the impact of the rotational velocity on the degree of mixing in case of a venturi-fan combination used in domestic gas condensing boilers is presented in this paper. Transient, 3-D simulations with different turbulence modelling approaches were performed to assess the degree of mixing upstream the hydrogen capable multi-hole burner. It is shown that the lower angular velocities produce better mixing. It can also be assumed that a local variation of up to 17% in the adiabatic flame speed can be expected due to the mixing processes as the consequence of the local air-fuel equivalence ratio variation.
KEYWORDS
PAPER SUBMITTED: 2023-05-29
PAPER REVISED: 2024-09-04
PAPER ACCEPTED: 2024-10-17
PUBLISHED ONLINE: 2024-11-09
DOI REFERENCE: https://doi.org/10.2298/TSCI230529250J
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2025, VOLUME 29, ISSUE Issue 2, PAGES [1015 - 1032]
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2025 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence