Optical and numerical investigation of global equivalence ratio effects on combustion and flame propagation in active pre-chamber methanol turbulent jets

Geometric characteristics and radiative heat flux at the downstream centerline and lateral ground for propane and methane diffusion flames under strong wind environments

Investigation of flame propagation behavior and heat release characteristics of ammonia/methane/air with pre-chamber jet ignition

Potential improvement in hydrogen spherical flame propagation by ultrasonic-fed implementation under lean-burn conditions

Cool flame propagation velocities of DEE: Determination in an ozone-seeded stagnation plate burner configuration

This study presents a detailed numerical analysis of impinging propane flames within confined enclosures using the Fire Dynamics Simulator (FDS, v6.5.3). Two archetypal configurations were examined: (i) free buoyant plumes in unconfined environments, and (ii) ceiling-impinging flames under both open and confined conditions. The investigation encompassed a range of heat release rates (0.5–18.6 kW) and five degrees of ventilation confinement. The simulation results confirm that FDS reliably reproduces flame height evolution under free plume conditions, exhibiting strong consistency with Heskestad’s empirical correlation and available experimental benchmarks. Under ceiling impingement, confinement markedly influences the thermal field, the distribution of major gas species (O2, CO2, C3H8), and the accumulation of unburnt gas. Distinct from previous works primarily centered on unconfined plume dynamics, the present study systematically characterizes the onset of auto-ignition through combined lower flammability limit (LFL) and auto-ignition temperature (AIT) criteria for confined propane combustion. The highest auto-ignition risk was identified in partially confined configurations (Conf. 2 and Conf. 3) at an HRR of 18.6 kW, where unburnt propane concentrations locally exceeded the LFL (≈0.2%) and ceiling temperatures surpassed the AIT of propane (455 °C). The findings elucidate critical trade-offs between ventilation and safety. They also contribute to a validated FDS-based methodology for evaluating fire-induced flow structures, combustion behavior, and ignition hazards in confined spaces.

Achieving a green transition in the energy structure and reducing reliance on traditional fossil fuels has become a global imperative for addressing climate change and promoting sustainable development. The search for clean energy alternatives to traditional fossil fuels has emerged as a critical challenge in the energy and power sector. Ammonia (NH3) shows great potential as a zero-carbon fuel in the energy sector, but issues such as its low flame propagation speed, high ignition energy requirements, and elevated NOx emissions limit its widespread industrial application. To address these issues and enhance ammonia combustion, plasma-assisted combustion technology has gained widespread attention in recent years as an effective solution. The plasma-assisted technology enhances combustion stability and efficiency of ammonia, and effectively suppresses NOx emissions. Additionally, the high-energy electrons and intense chemical reactions in plasma help to decompose and crack ammonia fuel, increase flame propagation speed, and thus improve ammonia combustion performance. This paper provides a comprehensive review of the latest research advancements in plasma-assisted technology in ammonia combustion. It covers the fundamental principles of plasma generation, the mechanisms of combustion enhancement, industrial application status, and development trends. The aim is to assess the potential of plasma-assisted combustion technology in achieving efficient, stable, and low-carbon ammonia combustion, and to explore its future prospects for industrial application.

Abstract The use of plasma as an innovative solution to enhance combustion has been the focus of intense research for the past two decades. Plasma-Assisted Ignition and Combustion (PAI/PAC) has emerged as a potential solution for numerous industrial applications. This Foundation paper consists of two parts. Part 1 introduces the context and is followed by a brief summary of the reviews done over the last two decades to show the continued relevance of the topic. We then focus on the fundamentals of combustion and introduce the main concepts of the field. In particular, we discuss combustion kinetics, flame propagation modes, and numerical modeling. Following this, a more in-depth description of plasma physics, specifically non-equilibrium plasma, is provided. As in the previous section, the main concepts are highlighted and defined. We discuss electron energy distribution functions, electron-impact cross-sections, and reaction rates, with a focus on dissociation and fast gas heating which are of particular relevance in the field of plasma-assisted combustion. Finally, elements of numerical modeling are provided. Part 2 of the article will describe the topic of plasma-assisted combustion from the description of fundamental mechanisms to novel combustion systems of importance for the energy transition.

In this study, to reveal the changes in explosion pressure and flame propagation characteristic, a 12 L cylindrical explosion device was used to conduct experiments on the explosions of two-phase mixtures of paper powder and volatile organic compounds (VOCs) at varying concentrations. The findings indicate that, at a constant paper powder concentration, increasing the VOCs concentration initially causes minor fluctuations in the maximum explosion pressure (Pmax), followed by an increase. At a constant VOCs concentration, as the paper powder concentration rises, the Pmax also increases, while the time to reach peak explosion pressure initially decreases before increasing. Additionally, under the two-phase concentration range produced in the production process, higher concentrations of paper powder and VOCs significantly enhance flame brightness, combustion intensity, heat release rate, and flame duration. These insights provide data support for determining the alarm limit values of VOCs concentration detection, provide a scientific basis for evaluating and predicting explosion risks associated with paper powder and VOCs, offering significant practical implications for fire and explosion prevention in the printing industry.

<div>This study investigated the combustion processes in hydrogen dual-fuel operation using hydrotreated vegetable oil (HVO) and diesel fuel as pilot fuels. The visualizations of hydrogen dual-fuel combustion processes were conducted using hydroxyl radical (OH*) chemiluminescence imaging in an optically accessible rapid compression and expansion machine (RCEM), which can simulate a compression and expansion stroke of a diesel engine. Pilot injection pressures of 40 and 80 MPa and injection quantities of 3, 6 mm<sup>3</sup> for diesel fuel and to match the injected energy, 3.14, 6.27 mm<sup>3</sup> of HVO were tested. The total excess air ratio was kept constant at 3.0. The RCEM was operated at a constant speed of 900 rpm, with in-cylinder pressure at top dead center (TDC) set to approximately 5.0 MPa. Results demonstrated that using HVO as pilot fuel, compared to diesel fuel, led to shorter ignition delay and combustion duration. OH* chemiluminescence imaging revealed that longer ignition delays observed with diesel fuel resulted in pilot mixture ignition downstream near the piston bowl wall, followed by flame propagation into the hydrogen–air mixture. In contrast, the shorter ignition delays characteristic of HVO caused the pilot mixture to ignite between the injector and the piston bowl wall, with subsequent flame propagation into the hydrogen premixture.</div>

Theoretical prediction model for dust explosion pressure and flame propagation in vessel–pipeline systems under airflow transport conditions

ABSTRACT In the aircraft engine, auxiliary power unit and other areas, hot surfaces are generated due to fuel combustion, power transmission and other reasons. Meanwhile, these areas may have the potential for oil leakage. When the leaked oil contacts these hot surfaces, it may be ignited to form a fire, threatening the aircraft’s safety. In this paper, evaporation and ignition experiments of oil leakage on a flat hot surface were carried out, and the vapor plume movement and flame propagation characteristics were investigated. Furthermore, the relationship between the hot surface temperature and the ignition core height and ignition delay time was studied. By the PIV technique, the velocity distribution of the vapor plume was studied. The flame transient development process and the flame propagation speed were quantitatively analyzed. The results show that the vapor plume velocity increased rapidly with height, then remained relatively stable, and eventually decreased gradually. Overall, the plume velocity shows a “cap-shaped” horizontal distribution. After ignition, the flame first expands in a spherical shape and then propagates in the vertical direction. The vertical upward propagated flame velocity is greater than the downward, and the corresponding velocities are 100.6 ~ 496.42 cm/s and 66.71 ~ 192.51 cm/s, respectively.

Effect of the ignition location on ignition and flame propagation characteristics in a gas turbine model combustor

Understanding the flame propagation in confined methanol active Pre-chamber with structural converging and spray impinging

Thermal runaway and flame propagation behaviors of NCM batteries under varying heights: An experimental study

Influence of the scale effect on the flame propagation dynamics during premixed stoichiometric hydrogen/air deflagration

Study on the suppression of spontaneous flame propagation from high pressure hydrogen venting by porous media

An integrated open-source CFD workflow for gas distribution and flame propagation analysis in nuclear reactor safety

Study on the Coupled Flame Propagation Dynamics of Hydrogen/Air Deflagration in Interconnected Vessels

Explosion flame propagation and characteristics of coordination hydride hydrogen storage materials under concentration effects: A case study of LiAlH4