Laminar Burning Velocities, Measurements and Validation

Dear Colleagues,

Burning velocity is a fundamental parameter in premixed combustion, describing the rate at which a flame front-propagates into a quiescent fuel–oxidizer mixture. Among its forms, laminar burning velocity (often denoted as Sl) is the most fundamental because it reflects the intrinsic chemical kinetics and transport properties of the mixture, independent of turbulence or flow disturbances (unstretched and adiabatic). Laminar burning velocity represents a balance between chemical heat release, the diffusion of heat and radicals, and molecular transport within a flame structure. In classical combustion theory, this balance is captured in the thermal–diffusive model, where Sl scales approximately with the square root of the product of thermal diffusivity and the global reaction rate.

Laminar burning velocity is essential for understanding flame structure. A laminar premixed flame consists of a preheat zone, where conduction raises reactants to ignition temperature, and a thin reaction zone, where radical chemistry drives rapid heat release. Flame thickness and speed directly emerge from molecular transport coefficients and reaction rate constants. Because these processes strongly depend on temperature, pressure, equivalence ratio, and fuel and oxidizer composition, laminar burning velocity is highly sensitive to operating conditions, making it a powerful diagnostic for validating chemical kinetic models.

From an engineering perspective, laminar burning velocity serves as the baseline for turbulent flame propagation. Turbulent flame speed correlations typically scale with Sl, meaning that accurate predictions of engine or burner performance rely on accurate laminar values. This is particularly important for lean-burn technologies and high-efficiency combustion systems, where flame stability margins become small. In spark ignition engines, for example, Sl influences flame kernel growth, combustion duration, and ultimately efficiency and emissions.

Laminar burning velocity also plays a critical role in safety and explosion risk assessment. A higher Sl indicates greater mixture reactivity, often correlating with higher explosion pressures and faster deflagration development. Parameters such as minimum ignition energy, flashback propensity in premixed burners, and deflagration to detonation transition (DDT) likelihood all depend on laminar flame speed. Because measurements are performed under controlled, turbulence-free conditions, Sl provides a reliable benchmark for comparing fuels and quantifying their hazard potential.

Furthermore, experimentally derived laminar burning velocity serves as a basis for validation chemical kinetics models. This is an important tool for numerical methods to evaluate different phenomena of flame propagation for laminar, as well as turbulent cases.

Finally, laminar burning velocity is indispensable in evaluating alternative and emerging fuels, such as hydrogen, ammonia, bio-derived gases, synthetic e-fuels, and even metal (powder) fuels. These fuels exhibit distinct diffusivities, ignition characteristics, and flame structures. Since Sl captures the interplay of molecular transport and chemical kinetics, it is widely used to assess whether such fuels can be safely and efficiently used in existing combustion infrastructures.

In summary, laminar burning velocity is a scientifically grounded and foundational quantity linking microscopic reaction kinetics to macroscopic combustion performance, safety, and fuel innovation.

Dr. Rob Bastiaans
Dr. Roy Hermanns
Dr. Ayman M. Elbaz
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fire is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• laminar burning velocity
• flame propagation
• unstretched flame speed
• adiabatic
• premixed combustion
• model validation
• alternative fuels