Mass Burning Research Articles

The Impact of COVID-19 Patient Surges on the Burn Care System

Introduction:Burn mass casualty incident (BMCI) planning efforts have been in practice and publication for 40+ years. While COVID-19 has no direct connection to burn injuries, the impact of COVID-19 on the healthcare system including burn care was and remains significant.Method:A retrospective analysis of data was conducted voluntarily submitted to the American Burn Association from March 2020 to June 2021 which generally coincides with the first three waves of the pandemic. We focused on the self-reported data specific to the three critical components in managing a surge of patients: staffing, space, and supplies (to include pharmaceuticals and equipment).Results:Staff: These data were collected over a period that coincided with the first three waves seen in the USA. Staffing shortages were noted during each of the surges but were most excessive when a regional surge paralleled surges in other parts of the country (November-December 2020).Space: Late November and early December 2020, space was in short supply with the surge of patients for more of the region than at any other time during the 28 weeks of reporting. While single facilities reported other episodes of limited space or supplemented with temporary structures, the peak was early December.Supplies: As the first surge began to subside, the supply shortages were abated. However, as additional surges occurred; the supply chain had not recovered. Supply shortages were reported in greater numbers than either space or staffing needs through the multiple waves of the pandemic.Conclusion:The COVID-19 pandemic directly led to a diminished available capacity for burn care in such a way that it compromised the ability to confront a surge of burn-injured patients. Future BMCI planning efforts must consider this aspect of the process. Crisis Standards of Care may come into play during such an event.

Effects of turbulence–heat loss interactions on detonation development in end gas and its resulting knock intensity

The main objective of the present work is to investigate the end-gas autoignition and detonation development in a confined space with the presence of wall heat loss by two-dimensional numerical simulations with a hydrogen/air mixture. The effects of turbulence–heat loss interactions, initial temperature, equivalence ratio, and wall temperature on end-gas combustion modes are analyzed in detail. The results show that with the presence of wall heat loss, end-gas autoignition takes place in the hot core regions away from the walls, and the autoignition fronts touching the wall can lead to a much larger wall heat flux than that induced by main flame–wall interactions. In the base cases, increasing the turbulence intensity promotes the end-gas autoignition mode transition from thermal explosion-detonation to thermal explosion-deflagration and finally to no-autoignition, whereas detonation takes place in all cases regardless of the turbulence intensity after the initial temperature or equivalence ratio is raised. However, in these cases with a low equivalence ratio, the detonation propagation is unstable, which can be easily decoupled spontaneously after it encounters the cold flow. It is further found that for the cases with unstable detonation propagation, the burned mass fraction (BMF) dominates the knock intensity, whereas for the cases with stable detonation propagation, the maximum pressure in a chamber will extremely depend on the local and instantaneous interactions between the pressure/shock waves, but the effect of BMF becomes minor.

Integrating Response Plans for Burn Mass Casualty Incidents

Introduction:Across the United States (US), there are approximately 2,000 burn beds in 133 burn centers, only 72 of which are verified by the American Burn Association (ABA). As such, many areas in the US are hundreds of miles from the closest burn center. Eight states do not have a burn center, and another 11 do not have an ABA-verified center. Further, the average center has 15 beds, and, on average, there are 90 available beds across the US. Therefore, in addition to patient care complexities, the broader infrastructure for burn patients is severely limited. These constraints suggest the burn healthcare system is particularly vulnerable to disasters, where the needs will exceed the resources available.Method:A literature review was conducted of available burn mass casualty incident (BMCI) plans from stakeholders in each level of a response. These response partners included prehospital agencies, hospitals (those with and without trauma center designations), emergency management agencies (local, state, and federal), healthcare coalitions, public health (district, state, and federal), regional coordinating burn centers, and the ABA.Results:The amalgamation of the BMCI plans yields a tripartite infrastructure not unfamiliar to emergency management professionals. The burn care agencies integrate into a response, similar to the way in which public health integrates into the emergency management infrastructure. The local to state to federal escalation of assets is reflected by an escalation from the local burn center to the regional coordinating burn center to the ABA. However, gaps remain in the communication between response partners. Few plans, particularly at the local level, reflect the integration of the burn system response.Conclusion:The burn healthcare infrastructure in the US is constrained and therefore is particularly vulnerable to a BMCI. Emergency responders should preemptively examine their plans and systems to specifically integrate the burn care and response infrastructure.

Development of Prepositioned Burn Care-specific Disaster Resources for a Burn Mass Casualty Incident

Disaster preparedness for a burn mass casualty incident (BMCI) must consider the needs of the first responders and community hospitals, who may be the first to receive those patients. Developing a more comprehensive statewide burn disaster program includes meeting with regional healthcare coalitions (HCCs) to identify gaps in care. Quarterly HCC meetings, which link local hospitals, emergency medical services (EMS) agencies, and other interested parties, are held around the state. We rely on the HCC's regional meetings to serve as a platform for conducting focus group research to identify gaps specific to a BMCI and to inform strategy development. One of the deficiencies identified, particularly in rural areas that infrequently manage burn injuries, was a lack of burn-specific wound care dressings that could support the initial response. Relying on this process, a consensus was created for equipment types and quantities, including a kit for storage. Furthermore, maintenance, supply replacement, and scene delivery processes were developed for these kits that could augment a BMCI response. The feedback from the focus groups reminded us that many systems report having infrequent opportunities to provide care for patients with burn injuries. Additionally, several types of burn-specific dressings are expensive. With the infrequent occurrence, EMS agencies and rural hospitals reported that it was doubtful their agency/hospital would have more than a minimal stock of burn injury supplies. Therefore, developing supply caches that can be quickly mobilized and deployed to the impacted area was one of the deficiencies we identified and addressed through this process.

Influence of Immersed Conductive Objects on Quasi-Steady Burning Behavior of Fuel Slick in Turbulent Waters

ABSTRACT In situ burning (ISB) is an effective technique for burning oil spills that occur in oceans. The need for enhancing the burning characteristics and advancing the technique of burning fuels on the water sublayer has been identified. Following this, the study analyzes the steady burning behavior of a fuel layer floating on a turbulent water surface. The turbulent water surface is generated using an experimental platform comprising an axisymmetric upward-pointing submerged jet, an approach used in studies of free-surface turbulence. The turbulence is isotropic in the horizontal plane and bulk-flow free, with a turbulence intensity equal to 1.7 cm/s comparable to water turbulence in a calm ocean. The turbulent boundary condition causes an increase in heat extraction from the bottom of the fuel layer, thereby reducing the mass burning rate by 45% compared to a case with no turbulence. To improve the burning under turbulent water sublayer condition, a 10 mm conductive object is immersed at different depths in the fuel. The copper rod collects the flame’s heat and transmits it into the fuel layer via conduction, thereby increasing the burning rate by more than 1.4 times. A heat transfer model shows that the case with a small rod immersion depth (~10 mm) in a 40 mm fuel layer is best at improving burning because the heat losses from the object to the water sublayer are the lowest. The model also shows that the heat from the flame transmitted by the rod is primarily distributed in a region close to the surface of the fuel, where nucleate boiling is observed around the rod surface. As more of the rod is immersed in the fuel layer, the heat dissipation to the turbulent water increases nearly five times, thereby reducing the bubbling around the rod surface and the burning rate. The implications of burning fuel slicks for fast, slick cleanup during in-situ burning in turbulent water conditions are espoused.

Study of combustion and emission of a SI engine at various CR fuelled with different ratios of biobutanol/hydrogen fuel

The global requirement is shifting to territorial independence of energy sources, and the introduction of alcohols and biofuels are the primary sectors. Recently agriculture products-based ethanol has replaced a larger portion of gasoline. Butanol is another impressive fuel in the same chain, much better than ethanol in many parameters. Butanol has certain limitations, too, such as higher latent heat and low heating value. Therefore, biobutanol/hydrogen is tested experimentally at various compression ratios (CR) in the present study. Brake thermal efficiency was not significantly changed by CR at 90% butanol, while CR is more impressive with increasing hydrogen. The flame development period was reduced by 34%, while the flame propagation phase was reduced by 29% by increasing CR to 15 and hydrogen to 25%. Peak pressure and heat release rate surged by 12.89% and 12.32% and advanced by 6°CA. The coefficient of variations is also reduced by 21% by increasing CR to 15 and hydrogen to 30%. Higher hydrogen faced combustion difficulties due to increasing stratification and heterogeneity during combustion. Unlikely to trend, Tmax (peak cylinder temperature) and NOx were continuously increased with CR and hydrogen due to increased fuel quantity and larger mass burning before TDC. However, CO and HC emissions were reduced by CR due to increased BTE (brake thermal efficiency) and reduced by hydrogen due to less HC supply. A slight increase in HC and CO was noticed for higher hydrogen due to local heterogeneity and disassociation at high temperatures.

Optimizing biodiesel blends with green hydrogen fuel: A study on combustion duration, fuel mass burnt, engine performance and emissions

Although the combustion of petroleum-based fuels currently satisfies the majority of our energy needs, rapid industrialization has spurred the utilization of alternative energy sources to meet the growing demand for electricity. With the global population on the rise and increasing awareness of the dangers of climate change, there is a greater need to find sustainable and eco-friendly fuels. Utilizing biodiesel derived from non-edible sources is the most efficient and appealing option for meeting energy needs while mitigating environmental impacts. This paper focuses on the preparation and experimental analysis of biodiesel from Karanja oil. Various blends of Karanja biodiesel and regular diesel were produced and stirred to create KB10 (Diesel 90% + Karanja Biodiesel 10%) and KB20 (Diesel 80 % + Karanja Biodiesel 20%). Hydrogen was incorporated into the biodiesel to enhance fuel characteristics, delivered at a rate of 5 L per minute. The emissions and combustion results of the biodiesel blends were compared to those of pure diesel. At full load condition, KB10H5 reported the minimum combustion duration of 25.8°CA with mass fraction burnt of 17.8%. However, the biodiesel blend with 10% and 20% reported the reduced BTE. Highest brake power has been observed at 4.95 kW. The combination of Karanja biodiesel and hydrogen improves fuel quality and reduces the harmful gases emissions such as carbon monoxide and carbon dioxide. It is crucial to ensure that the operation is both efficient and comfortable, and this approach achieved both objectives. In addition, hydrogen energy can also be applied to the railway transportation industry, as a new direction for the green and low-carbon development of intercity transportation, driving the virtuous cycle and innovative development of the hydrogen energy-related industrial chain.

Comparative evaluation of combustion, performance, exergy and emission characteristics in hydrogen-biodiesel dual fuel engine under RCCI mode

The present work focuses on the impact of combustion phase shifting from CDC (conventional diesel combustion) to RCCI (reactivity controlled compression ignition) mode of operation under various premixed ratios of hydrogen on the combustion, performance and exhaust emissions of a partially modified CI (compression ignition) engine. The hydrogen premix ratios are varied from 10% to 60% with 10% increment and the engine is tested at 0.9 kW, 1.8 kW, and 2.7 kW. The experimental results have shown that the hydrogen participation up to 40% premixed ratio improves the homogeneousness and stability of the combustion, resulting in 8.19% increase in cylinder pressure and 27.81% increase in heat release rate (HRR) at 2.7 kW brake power. It is also observed that the premix phase of combustion is faster with up to 40% hydrogen participation as the 50% mass burn is found to shift towards TDC. At the same operating point, the combustion is also found to be more stable with 72% reduction in COVIMEP. The brake thermal efficiency (BTE) increases by 10.07% when operating at 2.7 kW brake power with a 40% premix ratio, compared to diesel CDC operation. The unburned hydrocarbon (UHC), carbon monoxide (CO), and PM emissions are reduced by 9.17%, 21.68%, and 9.51%, respectively, for the hydrogen premixed ratio of 40%, with a marginal increase in the oxide of nitrogen (NOX) emissions.

Burning of fuel layers on a turbulent water surface with an immersed conductive object

This study experimentally investigates the burning dynamics of dodecane and heptane with a vertical-immersed copper rod on a turbulent water surface. The water surface turbulence is isotropic across the pool area created by an upward-directed axisymmetric submerged jet, with turbulence intensity ranging from 0.017 to 0.033 m/s. The copper rod (dr= 10 and 20 mm) is placed at the burning zone where the bottom section is immersed in both the fuel and water sublayer. The experiments reveal a strong dependence on burning behavior with the fuel type (heptane and dodecane are used) and the presence of turbulence. In quiescent conditions, the copper rod causes the burning rate to decrease by 28% for dodecane and increase by 13% for heptane because of the differences in nucleate boiling behaviors observed on the immersed section of the copper rod. With turbulence in the water sublayer, the nucleate boiling reduces, and the burning rate for both fuel types decreases because of the heat losses caused by the portion of the rod immersed in water. A mathematical model for the mass burning rate, including the effects of the immersed rod and turbulent water sublayer, is developed and validated using the experimental results. A parametric study using the model shows the influence of multiple immersed rods and the corresponding implications to a practical application of oil spill clean-up by burning.

Waste-to-Energy Recovery from Municipal Solid Waste: Global Scenario and Prospects of Mass Burning Technology in Brazil

Inadequate disposal of Municipal Solid Waste (MSW) is one of the greatest environmental issues confronted nowadays. One of the techniques used for its final disposal is incineration, otherwise known as mass burning. Although this procedure remains very controversial in Brazil, some recent studies published in Europe reveal a large amount of misinformation about it. It has been widely used in European countries, Japan, and a few U.S. cities and has been increasingly and significantly adopted in China. Therefore, this article aims to carry out a literature review on the evolution of waste-to-energy recovery from Municipal Solid Waste (MSW) worldwide and the progress of mass-burning technologies, particularly in the Brazilian context. For such a purpose, global scientific databases were selected and some of their results allowed us to present how the main WtE recovery technologies function, as well as their benefits and impacts. Moreover, it was possible to systematize the main regulatory frameworks on the theme in Brazil and to reveal the country’s electricity generation capacity, in addition to depicting the progress of Waste-to-Energy Plants (WtEPs) undergoing licensing processes in the state of São Paulo.

Образование токсичных газов при горении мягких игрушек в многофункциональных торгово-развлекательных комплексах

Introduction. Stuffed children’s toys in children’s entertainment areas at multifunction shopping malls are among the most dangerous combustible materials. However, flammable properties of stuffed toys, especially the qualitative and quantitative composition of resulting toxic gases, have not been studied. Goals and objectives. The aim of the work is to identify specific coefficients of generation and partial density of toxic gases released during the combustion of stuffed toys. To achieve the goal, a small experimental unit was upgraded and experimental studies of the above parameters were carried out to learn more about the most dangerous toxic gases released during the combustion of specimens of staffed toys made in China. Methods. An experimental method was used to study the generation of toxic substances during the thermal decomposition of specimens of staffed toys in a small experimental unit. The results of the experiment were analyzed. Results and discussion. The small experimental unit was upgraded so that it could measure concentrations of nitrogen dioxide and phosgene. Dependences between time and the specific mass burn up rate, the average volumetric partial density, as well as carbon monoxide, hydrogen cyanide, phosgene, and nitrogen dioxide generation coefficients were obtained for the period starting from the launch of the experiment. It was found that only partial densities of hydrogen cyanide and phosgene reached their critical values. In this case, the partial density of hydrogen cyanide exceeded its critical value by 2.5 times, and that of phosgene by 17 times. Therefore, it is necessary to calculate the time for blocking evacuation routes for hydrogen cyanide and phosgene to determine fire risks in children’s play areas. Conclusions. When stuffed children’s toys are in combustion, highly toxic gases as carbon monoxide, hydrogen cyanide and phosgene are released in concentrations dangerous to human life and health. This fact must be taken into account when fire risks in children’s play areas are analyzed.

Scoping Studies for a Lead-Lithium-Cooled, Minor-Actinide-Burning, Fission-Fusion Hybrid Reactor Design

A feasibility study of a subcritical fission-fusion hybrid reactor using lead-lithium eutectic as a coolant and minor actinides (MAs) as fuel is presented. Such a reactor could support the fission community by transmuting MAs and the fusion community by breeding tritium. The feasibility of such a reactor for the burnup of MAs is assessed in terms of burnup performance, tritium breeding, and safety characteristics. Tandem mirrors are a promising neutron source technology, and a deuterium-tritium tandem mirror is considered here for the neutron source with power Psource = 1.13 MW assumed for scoping purposes. Subcritical reactivities from keff = 0.9800 to keff = 0.9950 were considered, representing the initial reference for subcritical reactivity and the assessed upper limit, respectively. Stability analyses indicated the reactivity would be stable under perturbations of fuel, coolant, and inlet temperatures, with a positive reactivity insertion expected during reactor shutdown. This range corresponded to nuclear heating values of 150 to 650 MW and mass burn rates of 53 to 216 kg/year. The upper mass burn rate limit would require 1110 reactor years with a capacity factor of 0.9 to fission the global supply of MAs and could offset the annual U.S. MA production with eight reactors. Tritium breeding was assessed for keff = 0.9800 and 3.795% 6Li enrichment in the coolant, and a tritium breeding ratio of 1.602 0.017 was tallied, suggesting the reactor could, without elevated 6Li enrichment, produce tritium to both sustain operation and supply tritium for other fusion devices. Time-series modeling of fuel burnup was conducted for a four-batch loading scheme and three different fuel residence times at keff = 0.9800, which showed system performance would drop with burnup, and that the rate of this drop was lower for longer fuel residence times, motivating a means of reactivity control. Last, changes in fuel composition with burnup were assessed for relative concentrations of MAs, transmutation products, and fission products. The breeding of plutonium in the blanket was calculated and found to be of minimal proliferation concern.

Flame Flickering can Cease Under Normal Gravity and Atmospheric Pressure in a Horizontally Moving Dual Burner System

This paper provides a feasible way to suppress flame flickering under normal gravity and atmospheric pressure without changing the fuel mass burning rate, thus promoting steady-state combustion. By periodically reciprocating one burner horizontally in a dual burner system, a death mode (namely, amplitude death of flame height oscillation) is generated around the critical burner separation distance, which is a transition point between in-phase and antiphase flickering modes of the two flames. The criterion to obtain a complete death mode region in a general dual burner system (with horizontal movement function) is defined by two dimensionless parameters, which respectively quantify the burner configuration and its dynamic performance.

Determination of Unstretched Laminar Burning Velocity by Simultaneous Measurements of Flame Radius and Pressure-Time Trace Using Constant Volume Method

ABSTRACT Values of laminar burning velocity obtained by the constant volume method suffer from the inaccuracies introduced by the semi-analytical burned gas mass fraction model and flame stretch. A cylindrical combustion chamber with full optical access was developed in the present study, enabling the photography of the flame until the flame touches the inner wall of the combustion chamber. This enables direct visualization of the flame, thus eliminating the dependency on burned gas mass fraction models. The values of laminar burning velocity obtained by simultaneous measurement of flame radius and pressure-time data using the constant volume method are not stretch-free. This paper also develops a methodology for stretch correction based on the determined laminar burning velocity. Experiments were performed on mixtures of methane and air at initial pressures (0.8–1.05 bar), initial temperatures (293–320 K) and equivalence ratios (0.8–1.2). Stretch-corrected laminar burning velocity for lean, stoichiometric, and rich methane-air flames has been obtained in the present study, and the results obtained are validated against available experimental data and 1-D flame computations. It is expected that the proposed method significantly reduces the inaccuracies in laminar burning velocity obtained by the constant volume method.

Mass Thermal Injuries in Perspective of Safety of Patients in the European Union

Mass disasters with multiple thermal injuries are an actual topic of safety management of patients in an actual safety situation in Eastern Europe. Availability of highly specialized burn centers complies with geographic borders of countries, but from an international perspective it is reasonable usage of nearby burn centers in neighboring countries. The aim of the report is to describe the actual needs of coordinating national programs for mass burn disasters. Actual situation reflects recommendations of WHO and European Union authorities and allows to ratify them to national plans. But it is also needed step-back coordination of individual national plans to set the highest possible safety of management of burned patients in the European Union despite geographical borders of countries.

Scalable recycling of feldspar slime into high-quality concentrates by removal of colored minerals using the combined beneficiation processes

Feldspars are the main raw materials for glass and ceramics. The feldspar slime generated during beneficiation processes contains a high content of colored iron-bearing minerals, which is an obstacle to its utilization. In this study, dishwashing liquid is used as the flotation collector and frother, and combined beneficiation processes, including wet ball milling, froth flotation and magnetic and gravity separation, are employed to remove the iron-bearing minerals from feldspar slime in order to achieve high-quality concentrates. In the milling process, slime particles are pulverized to liberate fine impurity minerals, which are gradually separated and removed by the subsequent processes with the assistance of anionic surfactants in the collector. The mass recovery of feldspar concentrates decreases with increasing milling time and first decreases and then increases with increasing collector dosage. While the burnt whiteness of feldspar concentrates first increases and then decreases with increasing milling time and collector dosage, it continuously decreases with the prolongation of gravity sedimentation. When feldspar slime is milled for 2 h, floated with a 2% collector dosage and settled for 10 h in gravity separation, the resulting feldspar concentrate contains 12.6% Na2O + K2O and 0.21% Fe2O3, with a mass recovery and burnt whiteness of 58.0% and 53.6%, respectively. This feldspar concentrate meets the requirements of the glass and ceramics industries. The scalable and environmentally-friendly recovery of feldspar slime represents a promising route for the sustainable utilization of feldspar minerals.

European Burns Association guidelines for the management of burn mass casualty incidents within a European response plan

BackgroundA European response plan to burn mass casualty incidents has been jointly developed by the European Commission and the European Burn Association. Upon request for assistance by an affected country, the plan outlines a mechanism for coordinated international assistance, aiming to alleviate the burden of care in the affected country and to offer adequate specialized care to all patients who can benefit from it. To that aim, Burn Assessment Teams are deployed to assess and triage patients. Their transportation priority recommendations are used to distribute outnumbering burn casualties to foreign burn centers. Following an appropriate medical evacuation, these casualties receive specialized care in those facilities. MethodsThe European Burns Association’s disaster committee developed medical-organizational guidelines to support this European plan. The experts identified fields of interest, defined questions to be addressed, performed relevant literature searches, and added their expertise in burn disaster preparedness and response. Due to the lack of high-level evidence in the available literature, recommendations and specially designed implementation tools were provided from expert opinion. The European Burns Association officially endorsed the draft recommendations in 2019, and the final full text was approved by the EBA executive committee in 2022. RecommendationsThe resulting 46 recommendations address four fields. Field 1 underlines the need for national preparedness plans and the necessary core items within such plans, including coordination and integration with an international response. Field 2 describes Burn Assessment Teams' roles, composition, training requirements, and reporting goals. Field 3 addresses the goals of specialized in-hospital triage, appropriate severity criteria, and their effects on priorities and triage. Finally, field 4 covers medical evacuations, including their timing and organization, the composition of evacuation teams and their assets, preparation, and the principles of en route care.

The Burning Characteristics of Transformer Oil Spill Fire on Horizontal and Inclined Substrate Under Continuous Leakage Condition

Abstract Spill fire is a typical fire type that endangers industrial safety. This work systematically investigates the burning characteristics of transformer oil spill fire under different fuel leakage rates and substrate tilt angles, and the fuel flow hydrodynamic parameters. According to the flame spread behavior and substrate temperature distribution, the spill fire spread process is divided into four stages and the substrate is divided into three zones. The relative difference between max burning length and stable burning length is positively correlated with the substrate tilt angle. The increase of fuel flow velocity contributes to the flame spread velocity, but the increase of fuel flow velocity and the decrease of fuel layer thickness weaken the accelerating effect of surface flow on flame spread, which leads to a decreasing trend of flame spread velocity increase. The spill fire mass burning rate is 0.161–0.358 times of pool fire, and the increase of heat loss due to fuel flow and the radiant heat loss through the fuel layer dissipated through the substrate are the main reasons for the lower mass burning rate than pool fire. The research results provide basic data and references for further research on the formation mechanism of heavy oil spill fire and the prevention and control of small-scale spill fire.

Influence of longitudinal wind on mass burning rate of rectangular heptane pool fire with different aspect ratios

Fire is one of the primary disasters that threaten the safe operation of tunnel and underground space. Mass burning rate is a significant parameter in characterizing the behavior of pool fire which is related to thermal feedback, pool shape and ambient wind. Five convection-controlled heptane pool fires are examined inside a longitudinal wind tunnel with aspect ratio of 1, 2, 4, 8, and 16. The variation of burning rate with longitudinal wind is divided into increasing regime at v < 0.96 m/s, decreasing regime at 0.96 ≤ v < 1.98 m/s, and slightly-fluctuating regime at 1.98 ≤ v < 2.49 m/s. The effect of longitudinal wind on burning rate is attributed to heat feedback, flow disturbance and oxidizer supply around the flame. The increment of burning rate with wind speed is proved by the liquid evaporation theory. The heat transfer analysis proves that the enlargement rate of burning rate is linearly proportional to a coupling factor of longitudinal air flow speed and aspect ratio in a unified mathematical correlation Δṁ″/k′=(2n+1n)v which is fully consistent with measurements. The results provide guidance for tunnel fire protection design and prediction of fire development under the condition of vehicle tank leakage inside a tunnel.

Ignition behaviors of primary reference fuels in a rapid compression machine under vortex-existing/minimized conditions

Knock is one of the main obstacles to improving the thermal efficiency of spark-ignition internal combustion engines. Although knock has been widely studied and accepted as a result of end-gas auto-ignition, the fundamentals regarding auto-ignition behaviors are still not fully revealed. In this study, the ignition behaviors of primary reference fuels were investigated in an optical rapid compression machine equipped with a quartz combustion chamber allowing for visualizing the combustion process from the lateral view. By combining both the lateral view and the top view photography, ignition behaviors under vortex-existing conditions with a creviced piston and vortex-minimized conditions with a flat piston were comprehensively analyzed to reveal the impact of the vortex on the ignition behaviors of PRF fuels. The influence of fuel reactivity was also investigated. The results showed that mild ignition was prevalent under large Da* numbers. The occurrence of mild ignition was closely related to the ignition delay time of the mixture, and the critical ignition delay time was not fixed but decreased with increasing initial temperature. The propensity of mild ignition could be boosted under vortex-existing conditions due to the increasing hotspot formation probability. Vortices were demonstrated to be capable of mitigating knock intensity via 1) the buffer effect of surrounding burned regions on the shock waves generated from surrounded unburnt pockets; 2) a larger burned mass fraction at the instant of the final ignition under vortex-existing conditions. The results also showed that strong ignition was more likely to occur under vortex-minimized conditions. Besides, higher fuel reactivity also could increase the probability of strong ignition occurrence. Compared with the creviced piston, the use of the flat piston could shift the ignition regime towards regions with higher Ret and lower Dat in the Dat-Ret diagram, where the strong ignition is less pronounced.