Ignition Characteristics Research Articles

Insight into the ignition characteristics of dust layers by mechanical friction sparks

Frictional sparks resulting from malfunctions pose a potential hazard for the accidental ignition of combustible materials in the processing industry. Ignition experiments revealed that mechanical friction sparks generated by TC4 titanium alloy, Q235 steel or 304 stainless steel were unable to ignite corn starch, PMMA, or wood powders. However, friction sparks generated by those materials at a pressure of 3.75 N/mm2 and a disc speed of 12 m/s could ignite a cotton fibrous dust layer. The release of frictional sparks is accompanied by energy dissipation. As friction pressure and rotational speed increase, the initial energy of the friction spark increases. Thus, the possibility of igniting the cotton fibrous dust layer increases, while the ignition time decreases. In terms of the ability to ignite the fibrous dust layer under identical friction conditions, the ranking is as follows: TC4 titanium alloy > Q235 steel >304 stainless steel. Moreover, TC4 friction sparks demonstrate weak ignition capability for dust layers with humidity levels of 2% and 10%. The susceptibility of the cotton fibre dust layer to ignition diminishes with increasing humidity. The distinctive flocculation structure of fibrous dust makes it more prone to ignition by mechanical friction sparks compared to traditional spherical dust. These findings imply that when employing metal alloys as mechanical equipment or tools in fibrous processing, the possibility of mechanically generated sparks serving as an ignition source should be taken into account.

Synthesis of novel carbon dots based combustion catalysts and their effects on thermolysis and laser ignition of 1,1′-dihydroxy-5,5′-ditetrazolium dihydroxyammonium salt (TKX-50)

The carbon dots (CDs) were prepared by the oxidation etching method. On this basis, the composite materials of CDs and Cu (CDs/Cu) were synthesized by the hydrothermal method. The elemental composition, morphology and structure were analyzed by TEM, SEM, EDS, XRD and XPS. The effects of CDs and CDs/Cu for thermal decomposition of TKX-50 pyrolysis were studied by DSC-FTIR-MS and in-situ solid FTIR. The CDs and CDs/Cu reduced the low-temperature decomposition peak temperature of TKX-50 by 10.1 ℃ and 16.1 ℃ respectively (10 ℃·min−1), and the second decomposition peak almost disappeared. This is because CDs and CDs/Cu can effectively facilitate the thermal decomposition of TKX-50 into NH2OH and 1,1′-ditetrazole diol (BTO). The CDs can promote the direct decomposition of BTO into small molecule gases and stable polymers at the initial pyrolysis stage. And they inhibit the combination of BTO and NH3 into 5,5′-bistetrazole-1,1′-didiolate (ABTOX), which is more difficult to decompose. So, the HCN and N2/CO were increased obviously during pyrolysis while NH3 and H2O content were decreased. On the other hand, the CDs/Cu promotes the decomposition of NH2OH in the first reaction. It manifested as the increase of NH3 and H2O. At the same time, the CDs/Cu facilitates the transition of difficult to decompose ABTOX losing NH3 to BOX to accelerate thermal decomposition reaction, playing a synergistic catalytic effect. Thus, in-situ solid FTIR signal of ABTOX was significantly weakened and the total content of NH3 was raised, especially the significant expansion of NH3 in the second stage. Finally, the influence of the catalysts in ignition characteristics was contrasted and discussed. Under the lower-power density region, the CDs and CDs/Cu decreased the ignition delay time of TKX-50. The CDs/Cu caused the flame propagation velocity of TKX-50 faster. Therefore, the CDs and their composites, as another new lightweight carbon material, are expected to be applied in the catalytic combustion of energetic materials.

Experimental Research and Numerical Analysis of Marine Oil Leakage and Accidental Ignition in Fishing Vessels

The hazard of highly combustible marine oil leakage greatly increases fishing vessel operation risks. This research integrates an experiment to explore the coupling mechanism of a typical heated surface of an engine room as a source to ignite marine oil. A numerical model is established that depicts the dynamic process of and variations in the combined effects regarding multiple factors of oil ignition under actual experiment. The leaked marine oil is ignited with a heated surface, relevant models are applied to reproduce the results, and the influences of specific parameters of a fishing vessel’s engine room are analyzed. The results indicate that the leaked oil boils violently on the heated surface, and a vapor film forms on the oil surface. Increased heated-surface temperatures lead to a significant difference in the initial ignition occurrences of marine oil, and the distance between the ignition height and oil is closely related to the engine room environment. The ignition probability of marine oil shows a gradually increasing trend with elevated heated-surface temperatures. The ignition height presents a downward trend with the increase in the heated-surface temperature, while the engine room’s humidity in air inhibits the upward transfer of heat; however, the degree of inhibition is limited accordingly. The results evidence that this comparative work can be an effective approach to reveal the impacts of marine oil, heat source, ventilation velocity, and humidity on initial ignition characteristics. Additionally, this work provides a basis for setting up emergency planning with appropriate monitoring equipment and further preventing vessel fires due to oil–thermal ignition.

Effect of accelerated weathering on pyrolysis kinetics and ignition characteristics of typical thermal insulation materials

Thermal insulation materials are widely installed on external walls because of their excellent properties. However, thermal insulation materials are often exposed to air and sunlight as external facades fall off, which can lead to weathering and potential fire risk. Especially, weathering may cause changes in pyrolysis and combustion characteristics of thermal insulation materials, which is of great significance for understanding fire. To simulate real exposure conditions, typical thermal insulation materials (expanded polystyrene) were weathered by accelerated weathering for 25, 45, 90, 135 and 180 days. Pyrolysis characteristics of unweathered and weathered materials were researched by thermogravimetric analysis, Fourier transform infrared (FTIR) spectrometric technique and cone calorimeter experiments. The kinetic parameters were estimated and optimized using Coats-Redfern and Shuffled Complex Evolution methods. Subsequently, the correlation between weathering time and kinetic parameters was obtained. The functional groups were detected by FTIR. Finally, the ignition time was measured. The results showed that the color of materials changed and the chalking appeared as accelerated weathering increased. Activation energy decreased from 324.44 kJ/mol to 91.04 kJ/mol, and pre-exponential factors reduced from 52.31 lns−1 to 10.72 lns−1. The intensity of vibration bands was strengthened. Ignition time was shortened by 119 s, indicating that weathered EPS is more easily ignited.

Comparison on the ignition and combustion characteristics of single Al-Li alloy and Al fuel microparticles in air

To address the resistance effect of protective oxide shell on the ignition of micron-sized aluminium (Al) and the particle agglomeration and residue deposition of Al-based fuels, aluminium-lithium (Al–Li) alloy by introducing tiny elemental Li could have a promising potential in substituting for Al. The paper presents a comparative study on the surface structure and the ignition and combustion characteristics between single Al-Li alloy and pure Al fuel microparticles in air. The Al-Li alloy with the content of 1.0 wt.% Li was prepared by gas-atomized method and characterized by multiple methods. The characterization of the surface morphology, elemental distribution, and residues of incomplete combustion show the dendritic structure of eutectic compounds like veins at the surface and interior of the Al-Li alloy microparticles. Compared to the dense oxide shell of Al, the oxide shell of Al-Li alloy provides many more pathways like cracks/openings for the Al and O2 contact as inductively heated by a highly-focused laser beam, resulting in a reduction of ignition delay. The difference of ignition delay between the two demonstrated that the addition of Li element shortened the ignition delay, especially, over 80% for the particle size of > 45 µm. The ignition delay can be reduced by minimizing the particle size or enhancing the ignition power density. Owing to the variations in reactivity, melting, and boiling points compared to pure Al, the Al-Li alloy particles exhibit distinct gas-phase flame and micro-explosion behaviour. These differences result in considerably higher flame temperatures and more intense radiation. Finally, a sequence of reaction mechanisms that potentially control the ignition and combustion of single Al-Li alloy particles (as distinct from pure Al) is proposed, the physical and chemical properties of highly reactive Li are crucial to improve the combustion performance of Al.

Influence of the Composition and Particle Sizes of the Fuel Mixture of Coal and Biomass on the Ignition and Combustion Characteristics

The work determines the characteristics of the processes of thermal decomposition and combustion when heating coal, cedar needles, and their mixtures with different fuel particle sizes. Based on the results of thermal analysis, the following characteristics were determined: the temperature at which the coke residue ignition occurs, the temperature at which the combustion process is completed, and the combustion index. An analysis was carried out of the interaction between the fuel mixture components on the characteristics of their combustion for compositions (50% coal and 50% biomass) with a particle size of 100–200 μm and 300–400 μm. The combustion kinetic parameters of individual solid fuels and their mixtures containing 50% coal and 50% biomass are compared. The activation energy for coal combustion was 60.3 kJ mol−1, for biomass 24.6 kJ mol−1, and for mixture 42.5 kJ mol−1. The co-combustion of coal and biomass has a positive effect on the main combustion characteristics of solid fuels. Fuels with particle sizes of 100–200, 200–300, and 300–400 μm were studied at temperatures of 500–800 °C under heating conditions in a heated airflow. Using a hardware-software complex for high-speed video recording of fast processes, the ignition delay times were determined, the values of which for the considered fuels vary in the range from 0.01 to 0.20 s. Adding 50 wt% biomass with particle sizes of 100–200, 200–300, and 300–400 μm to coal reduces the ignition delay times of mixtures by 55, 41, and 27%, respectively. The results obtained can become the basis for the conversion and design of modern power plants operating on solid fuel mixtures to co-combust coal with biomass.

Controlling the combustion and agglomeration characteristics of solid propellants via new micro-unit composite fuel Al@AP

New micro-unit composite fuels Al@AP with different mass ratios of Al and AP are designed, prepared, and added to solid propellants in place of the original aluminum powder. Through Thermogravimetric Analysis- Differential scanning calorimetry- Mass Spectrometry (TG-DSC-MS), laser ignition experiment, thermocouple temperature measurement, burning rate test, and combustion diagnostic, we study how Al@AP affects the ignition, combustion, and agglomeration properties of solid propellants. The results indicate that the increase of Al content of Al@AP can promote the advance of thermal decomposition of AP. As the AP content increases in Al@AP, the ignition delay time of Al@AP decreases by three times, and the mass burning rate increases by almost five times. At the same time, Al@AP significantly improves the burning rate and temperature gradient. When compare to the baseline propellant, Al@AP-containing propellants present a maximum increase in burning rate of 33% at low pressures and 19% at high pressures. In terms of agglomeration reduction, the number of large-size agglomerates in the CCPs of propellants containing Al@AP is reduced, the average particle size decreases by 78%, and the combustion efficiency increases to 99.34%. A mechanism is proposed to explain how the micro-unit composite fuel Al@AP alters propellant combustion and agglomeration. In summary, Al@AP provides excellent control over ignition, combustion, and agglomeration characteristics. This study provides guidance on the application and development of new aluminum-based composite fuels used in solid propellants.

Ozone-assisted combustion and emission control in RCCI engines: A comprehensive study

This paper presents an investigation into the combustion and emission characteristics of reactivity-controlled compression ignition (RCCI) engines using ozone seeding, which is known as one of the most highly oxidizing chemical species. The study aims to address challenges pertaining to combustion control and emissions deterioration. Therefore, the current work investigates the RCCI mode of operation in a single-cylinder diesel engine with intake air that has been seeded with ozone by introducing conventional diesel fuel as a high-reactivity fuel using a high-pressure direct injection method and iso-octane as a low reactivity fuel using a low-pressure port injection method. In the experimental study, different ozone concentrations up to 300 ppm and three different energy-based premixed ratios of low reactivity fuel from 0% to 45% with a 15% rise rate were examined under various engine loads and constant engine speed. The methodology used in this research provided for simultaneous decreases in unburned hydrocarbon (HC) emissions and smoke opacity for RCCI engines. According to the experimental findings, simultaneous utilization of RCCI mode and ozone seeding led to a decrease of up to 36% in HC emissions and a reduction of up to 98.7% in smoke opacity. Moreover, nitrogen oxides (NOx) emissions were reduced by up to 39.5% at 20% engine load, whereas carbon monoxide (CO) emissions exhibited a decrease of up to 46% at 60% load. The RCCI mode also yields significant reductions in pollutant emissions and notable increases in brake thermal efficiency (BTE) when compared to the conventional diesel mode (CDM). In conclusion, this experimental study presents a promising solution for addressing emissions deterioration in RCCI engines while simultaneously achieving reductions in pollutant emissions.

Kinetic studies of ignition of coal char particle suspension in hot air

Coal ignition has been a focal point in the pursuit of improved energy efficiency and reduced emissions. This study focuses on investigating the kinetic characteristics of char ignition within a closed reactor. The combustion process is modeled using a one-step global reaction in a quiescent air environment. The results show that particle ignition time increases with equivalence ratio and particle size, while decreases with gas initial pressure and initial temperature. Particle ignition temperature is minimally affected by the particle size, slightly influenced by the gas initial pressure and initial temperature, but substantially influenced by the equivalence ratio. In the fuel-rich condition, the coal char combustion exhibits a thermal runaway stage, primarily driven by the escalating particle temperature, followed by a decaying stage, mainly influenced by the depleting oxygen mass fraction. The dominant kinetic factors affecting the heat release rate (HRR) peak are detailly investigated: the HRR peak shows an initial increase and subsequent decrease with the equivalence ratio, which is mainly controlled by the total particle number and particle temperature; Particle size affects the HRR peak through altering the total particle specific surface area, i.e., the product of the particle number and the particle diameter squared; the gas initial pressure and temperature all affect the HRR peak through directly altering the gas density. Additionally, larger retention coefficient leads to faster particle ignition and higher HRR peak. These findings provide valuable insights into the regulations of coal combustion processes, particularly in scenarios involving elevated pressure and temperature, such as coal/mine explosions.

Performance and emission characteristics of a CI engine with post-treated plastic pyrolysis oil and diesel blend

Conversion of waste plastics into energy products is an effective waste management technique as they constitute a considerable portion of solid waste at present. In this study, distilled diesel fraction of Plastic Pyrolysis Oil (PPO) named Distilled Plastic Diesel (DPD) was hydrotreated named hydrotreated plastic diesel (HPD) and blended with commercial diesel fuel by 15:85 ratio (wt%), defined as HPD15, to experimentally investigate the performance and emission characteristics of a compression ignition (CI) engine. The experiment was done in 4-cylinder, 4-stroke diesel engine with an eddy current dynamometer testbed at full load (100 % engine load) and an engine speed of 1200–2400 rpm with 300 rpm intervals. The results are compared with neat diesel fuel data at the same operating conditions. This study found that HPD15 performed better or comparable with diesel fuel. Overall, the brake power (BP) and brake thermal efficiency (BTE) of HPD15 were higher than diesel fuel by a maximum of about 4.77 % and 3.77 %, respectively. Brake specific fuel consumption (BSFC) of HPD15 was lower at all operating speeds (by a maximum of about 4.66 %) and brake specific energy consumption (BSEC) was lower in most of the operating speeds (by a maximum of about 3.77 %). This study also revealed that CO2 at some operating speeds and NOx emission at all operating speeds for HPD15 are lower than diesel fuel. However, CO and unburnt hydrocarbon (UHC) emission are slightly higher for HPD15 than diesel at all speeds. Overall, HPD15 can be recommended as a suitable alternative for diesel fuel without any engine modification.

High-temperature interaction mechanisms of typical igniting pyrotechnics with cellulose as the packing material

In order to study the effect of cellulose shell on the thermal behavior including pyrolysis gaseous products, ignition and combustion characteristics of typical pyrotechnics, three composites of pyrotechnics/cellulose were prepared in this paper. Various characterization techniques were used to investigate the prepared composites and their combustion condensed products (CCPs), including scanning electron microscopy (SEM), simultaneous thermal analysis (DSC-TG-FTIR), X-ray diffraction (XRD), bomb calorimetry, and home-made combustion diagnostic system. The results showed that the overall heat release of the black powder and Mg/PTFE decreased from 3108 J·g−1 and 1157.4 J·g−1 to 1045.4 J·g−1 and 810.4 J·g−1 in the presence of 33.3% cellulose, respectively. Moreover, the FTIR spectra showed that the cellulose did not change the reaction pathways of black powder and Mg/PTFE, which mainly include H2O, CO2, NO2 for the black powder, and HF, H2O, CO2, CF2 for Mg/PTFE. However, the condensed products of cellulose would interact with B/KNO3 at a higher temperature, so that the heat release was largely increased by 339%. The cellulose has obviously impact on the energy release rate of Mg/PTFE in comparison to the other two composites. Moreover, the negative impact on ignition of Mg/PTFE composite is significant, when the content of cellulose reaches over 33.3%, resulting in difficult self-sustainable combustion at ambient pressure. The cellulose can largely reduce the maximum flame temperature of the black powder and Mg/PTFE, whereas it has little effect on B/KNO3. The CCPs of the involved igniting pyrotechnics and their cellulose-based composites have different phases due to their strong thermal interactions with cellulose.

Numerical study on forced ignition and flame propagation in a counterflow of nitrogen-diluted hydrogen versus air

Hydrogen is widely perceived as the next generation of clean energy due to its zero carbon emissions. However, there is an escalating concern regarding hydrogen safety. A deeper understanding of the ignition characteristics of hydrogen in inhomogeneous environments is imperative for enhancing our physical comprehension and conducting accurate risk assessments. The purpose of this study is to delve into the ignition phenomena of hydrogen and air in a non-premixed counterflow. Transient two-dimensional simulations are performed, considering detailed chemistry and transport. The focus is placed on the effects of strain rate, mixture stratification, and ignition position on ignition and flame propagation. The first part studies the ignition process at varying strain rates while the ignition position is fixed at the stagnation point. The results show that a low strain rate has a minimal impact on ignition outcome, whereas a high strain rate hinders ignition by reducing mixing layer thickness and residence time. As a result, the minimum ignition energy (MIE) barely changes at a relatively low strain rate but rises rapidly as the strain rate approaches the extinction limit. Subsequently, ignition is studied at different positions along the symmetry axis, where the flow field and mixture composition vary simultaneously. It is demonstrated that ignition is more feasible on the lean side than on the stoichiometric and rich sides, and a high strain rate can expand the ignitability limit of the mixture fraction under extreme off-stoichiometric conditions. The separate contributions of forced convection and mixture inhomogeneity are further assessed through simulations with and without counterflow and stratified mixture. The results suggest that the significance of the forced convection is contingent upon the timescale competition between flow and ignition, while the mixture stratification determines the evolution of the ignition kernel into either an outwardly propagating premixed flame or a triple flame. The MIEs at premixed and non-premixed conditions are examined, and the influence of fuel stratification is analyzed. In the end, a regime diagram is presented, illustrating the comprehensive roles of strain rate and mixture fraction during ignition. This study provides invaluable insights into the non-premixed ignition of hydrogen in complex flow conditions.

Enhancement of the energetic performance of solid fuels with metal-fluoropolymer additives

Aluminum (Al) holds a pivotal role in augmenting the energetic potential of solid fuel formulations. Its incorporation can notably amplify the energy yield upon combustion. Nevertheless, challenges such as ignition delay and incomplete combustion have hindered its optimal utilization. In the context of hybrid rocket propulsion, where reignition and high regression rates are sought, a promising solution lies in harnessing the potential of metal-fluoropolymer combinations. This paper explores the influence of polytetrafluoroethylene (PTFE) and Viton fluoropolymer additives on the combustion and regression rates of hydroxyl‑terminated polybutadiene (HTPB)-based solid fuels loaded with nano-aluminum (nAl). To comprehensively address these objectives, binary composites of nAl-PTFE and nAl-Viton were prepared using high-energy ball-milling, and the resulting mixtures were incorporated into hydroxyl‑terminated polybutadiene (HTPB)-based fuel through a vacuum-casting technique. The ignition and combustion characteristics of the solid fuels, as well as the post-combustion products, were examined using an opposed flow burner setup to gain insights into their oxidation and combustion mechanisms. The findings demonstrate that the inclusion of PTFE and Viton in nAl has a positive impact on the ignition delay time, combustion behavior, and regression rates of the solid fuels. The HTPB-nAl-PTFE(S3) sample exhibited the shortest ignition delay time of 108 ms, outperforming the other tested samples (S1: 227 ms, S2: 182 ms, S4: 122 ms). Furthermore, the addition of nAl to pure HTPB resulted in an average regression rate of 0.3–0.6 mm/s for HTPB-nAl (S2), representing a two fold improvement compared to pure HTPB-based samples. Compared to the baseline HTPB fuel, HTPB-nAl-PTFE(S3) demonstrated a significant increase in regression rate by approximately 178%, while HTPB-nAl-Viton(S4) exhibited an increased regression rate of 122%. These results highlight the positive influence of fluoropolymers on combustion behavior, ultimately enhancing the overall performance of the fuel. Additionally, the study observed gas-phase reactions during the combustion process, including the reaction between nano-aluminum (nAl) and fluoride, the intermediate product of Al oxidation, and the decomposition products of fluoride. These reactions resulted in the faster fracture of the alumina (Al2O3) shell, leading to improved heat release and regression rate performance.

Experimental study on ignition and blowout characteristics of dual combined flame stabilizers in scramjet

The ignition and blowout characteristics have a significant impact on the performance and operating limit of the scramjet. In this study, direct-connected ground tests of a typical scramjet combustor have been conducted to simulate the high-altitude flight condition of Mach 6. The incoming air has a total temperature of 1689 K and a dynamic pressure of 30 kPa. The ignition and blowout characteristics of the dual strut/cavity combined flame stabilizers in the scramjet are obtained. The immediate response of pressure at key positions is used to analyze the forward propagation characteristics of pressure during the ignition process and the pressure variation during the flame blowout process. The flame distribution and temperature variation during the ignition and blowout processes are obtained by high-speed photography, OH⁎ spontaneous radiation photography, spectrometer and multispectral imaging equipment. Results indicate that the process from local ignition to global ignition successfully has durations lasting for hundreds of milliseconds, comprising four stages with two pressure lift stages. The flame diffusing forward and upstream cavity igniting successfully are the main processes, constituting 60% and 30% of the duration, respectively. During the ignition process, the pressure response time of the two-stage cavity differs by several milliseconds. And the flame is transmitted forward to the upstream cavity through combustor walls. As the ignition process progresses under high equivalent ratio (ER) conditions, flame stabilization mode shifts from stabilizing flame in the recirculation zone of the cavity to stabilizing flame in the shear layer of the strut. Upon completion of global ignition, the flame temperature at the shear layer of the cavity upstream exceeds 2700 K, but decreases to 2125 K as the core reaction zone is shifted from the top of the strut to the tail and bottom of the cavity when the ER decreases. Two pressure drops occur during the flame blowout process, and the critical ER of the global blowout is approximately 0.33. The primary shear layer flame is blown out during the first pressure drop, and the intensity of the cavity flame decreases. Finally, the second pressure drop occurs as the flame in the cavity moves downstream and extinguishes.

Effects of K2SiF6 on Ignition and Heat Release Characteristic of Nano-Sized Aluminum Powders

ABSTRACT This study investigates the effect of potassium fluosilicate (K2SiF6) on the ignition and heat release characteristics of n-Al50, n-Al100, and n-Al800. It is found that K2SiF6 can effectively improve the ignition and heat release characteristics of nano-aluminum powder (n-Al). This is because K2SiF6 effectively increases the reaction rate. The heat release characteristics of the n-Al/K2SiF6 mixture are improved as the particle size of aluminum powder decreases and the heating rate increases. However, when the particle size reaches a certain level, the enhancement effect will become smaller and smaller. The study revealed that the addition of K2SiF6 influences the ignition delay time, reaction, and combustion products of the n-Al/K2SiF6 mixture. A small amount of K2SiF6 can greatly reduce the ignition delay time of nano-aluminum powder. With the increase of K2SiF6 content, the ignition delay time of n-Al50 decreases first and then increases, while the ignition delay time of n-Al100 and n-Al800 decreases continuously but the extent of this reduction progressively diminishes. The morphology and composition of the combustion products were analyzed. This paper found that K2SiF6 fluorinates the oxidized shell of aluminum, thereby promoting its ignition and combustion. The influence mechanism of K2SiF6 on n-Al ignition in air is discussed.

Modeling study of the ignition characteristics of directly injected 1,3-Cyclohexadiene in surrogate Gasoline/Air under RCCI combustion conditions

In this work a validated chemical kinetic model of the combustion of multicomponent gasoline surrogate fuels containing 680 reactions of 152 species has been used to simulate conditions reminiscent of those of Reactivity Controlled Compression Ignition (RCCI) in order to evaluate 1,3-cyclohexadiene (CYC6H8) as the high reactivity directly injected fuel and a gasoline surrogate fuel as the low reactivity premixed fuel. A single-zone modeling approach was adopted using a modified Cantera example describing the simulation of a gaseous Diesel-type internal combustion engine. The adaptable chemical structure of CYC6H8 to cis-1,3,5-hexatriene (lC6H8), load, start of injection and premixed fuel mass fraction were varied in order to analyze the potential of CYC6H8 as an ignition enhancer. Results have been compared to n-heptane and show that CYC6H8 and its isomer lC6H8 have the potential to be used as the high reactivity directly injected fuel in dual-fuel RCCI combustion, especially at high load conditions. For increased load, the ignition promoting effect is more pronounced at lower premixed fuel mass fractions and less affected by a delayed start of injection. The ignition promoting effect of lC6H8 is more pronounced than CYC6H8 for a decreasing premixed fuel mass fraction. Results from the kinetic analysis indicate that at increased concentrations of lC6H8, the thermal effects are becoming more significant.

Enhancing Performance and Emission Characteristics of Biodiesel-Operated Compression Ignition Engines through Low Heat Rejection Mode and Antioxidant Additives: A Review.

Depending on the heat content and compression ignition (CI) engine combustion, biodiesel is a viable substitute fuel. Biodiesel is an oxygenated, safe, sulfur-free, biodegradable, and renewable fuel. It may be utilized in CI engines in any combination with diesel fuel without requiring the engine to be significantly modified. Many research studies have been made with several biodiesels as diesel substitutes, including Pongamia pinnata, Jatropha curcas, Mangifera indica, and Madhuca longifolia. The topic of the current review is the potential of renewable fuels to outperform diesel fuel in terms of performance, combustion, and emission characteristics. In the present study, CI engines are fueled with biodiesels made from Man. indica, Mad. longifolia, and pongamia seed oil. Adopting low heat rejection (LHR) mode CI engines and adding an antioxidant agent in addition to the biodiesel blends may resolve the issue of these biodiesels' poorer performance and increased NO emission. Both these additions may provide positive approaches in both performance and emission.

Experimental research on ignition characteristics of hot jet matched with single-channel wave rotor combustor

An experimental system employing hot jet ignition was used to investigate the effects of hot jet equivalence ratio, jet flow rate, and premixture equivalence ratio on the ignition and flame propagation characteristics of a single-channel wave rotor combustor. The study revealed that the hot jet equivalence ratio and jet flow rate exert a notable influence on the initial flame front position. The ignition delay time for the wave rotor combustor remains approximately 4 ms within the tested parameter range, regardless of variations in the jet conditions. The stable flame propagation velocity primarily depends on the premixture equivalence ratio within the wave rotor channel, with optimal flame propagation achieved at a specific ratio. Additionally, the premixture equivalence ratio inside the wave rotor channel significantly impacts the shape of the flame front.

Ignition characteristics and alkali metal release behaviors of single-particle coal in O2/CO2 or O2/N2 atmospheres using optical diagnostic technology

In this study, the ignition characteristics of and alkali metal release behaviors of single-particle coal were investigated using single-particle coal combustion system coupled with optical diagnostic technology. Furthermore, the effects of coal types (Yangchangwan bituminous coal (YCW), and Naomaohu lignite (NMH)) and oxygen concentration in different atmospheres (i.e., O2/CO2 and O2/N2) were analyzed. The results show that since the specific heat capacity of CO2 is higher than that of N2, the flame temperature in the O2/CO2 atmosphere is lower in the combustion process of coal particles, resulting in a longer ignition delay and combustion time for both coals than in the O2/N2 atmosphere. The maximum flame area of the YCW is twice as long as that of the NMH coal in the different atmospheres. The Na* and K* radiation intensity of coal particles in the O2/N2 atmosphere is stronger than in the O2/CO2 atmosphere, and due to the influence of the volatile matter content of NMH. However, the Na* radiation intensity in the O2/N2 atmosphere is more likely to show a bimodal distribution with increasing oxygen concentration, i.e. the boundary between the volatile reaction phase and the coke combustion phase is clearer.

Optical Study on Spray and Two-Stage Ignition Characteristics for Diesel Spray Under Low Ambient Temperature and Density Conditions

Optical Study on Spray and Two-Stage Ignition Characteristics for Diesel Spray Under Low Ambient Temperature and Density Conditions