Combustion Properties Research Articles

Hydrogen as Fuel of Tomorrow

As well know that carbon-based fossil fuels are a non- renewable resource and these are depleting at an alarming rate. The unmonitored explicit usage of fossil fuels certainly demands for an alternate type of fuel which could replace it in the future because not today but in the near future there will come a time when we will be short on carbon based fuels and need for an alternative type of fuel will the demand of the day. The increasing global demand for sustainable and clean energy sources has finally demanded the exploration of alternative fuels. Hydrogen, with its high energy density and zero carbon and greenhouse gas emissions during combustion, has emerged as a promising fuel of the future. Hydrogen is a potential fuel which can change our fossil fuel based dependency for energy generation to hydrogen economy. The various properties of hydrogen make it excellent alternative and soon to be primary source of fuel in the future. The various techniques of hydrogen production such as electrolysis and coal-based extraction will be discussed as well as the storage methods. Hydrogen is a better fuel in every term. There will be comparative study as well which compares the versatility, the combustion properties, electrical generation efficiency, thermal usage efficiency and also that it’s extraction methods are certainly more eco friendly as compared to other fossils fuels. Researchers are still going to make hydrogen as feasible as fossil fuels are today and soon in the upcoming years, we will see hydrogen economy booming. Keywords—Hydrogen, electrolysis, fuel, efficiency, fuel cell

Combustion characteristics of refuse-derived fuel pellets having varying plastic compositions.

The plastic fraction of refuse-derived fuel (RDF) pellets influences fuel's physico-chemical, and mechanical properties, which in turn might affect the combustion behavior of RDF. In the present study, the combustion behavior of different plastic fraction-simulated RDF pellets is reported. The simulated pellets were prepared based on the Indian commercial RDF composition. Initially, the plastic content varied from the existing fraction in Indian commercial RDF, i.e., 35% (RDF-1), to a lower plastic content of 5% (RDF-2). Physico-chemical characterization showed that a higher plastic fraction in RDF-1 reduces its pellet density by 25% as compared to RDF-2. The changes in RDF physico-chemical properties due to plastic variation are reflected in the RDF conversion process. Single-particle and packed-bed studies concluded that the lower density for higher plastic RDF-1 leads to lower conversion times (36%), and higher flame front speed (11%), which are desirable conditions for faster conversion. However, packed-bed studies also showed limitations regarding the utilization of high plastic RDF as RDF-1 has a narrow range of operating air mass flux due to the early advent of convective cooling of the bed. Finally, considering the constraints associated with the utilization of high plastic fraction (~ 35%) RDF and to maximize the effective utilization of plastic in RDF, a workable plastic fraction of 15% in RDF was proposed and tested for its combustion properties. RDF with 15% plastic showed faster conversion, higher flame front speed, and a wider range of operating air mass flux before the advent of convective cooling of the bed.

Combustion and impact performance of DEGDN propellants under different size conditions

DEGDN propellant plays an important role in the use of large-caliber artillery, and its combustion and mechanical properties determine the power of large-caliber artillery. In order to study the combustion performance and mechanical properties of DEGDN propellant, four kinds of single-hole propellant with different pore diameters were prepared from DEGDN raw material ZY-11 pellets, with pore diameters of 3mm, 4mm, 5mm, and 6mm, which were recorded as 45/1-3mm, 45/1-4mm, 45/1-5mm, and 45/1-6mm, respectively. Analyze its combustion performance using closed bomb and test its impact resistance using a pendulum impact tester. The experimental results show that in the combustion process, the combustion pressure of the propellant in the higher temperature conditions, the faster its growth rate, while the whole combustion process is also faster; combustion process combustion speed will not change with the change of the aperture, only the different temperature conditions will make the combustion speed change, the higher the temperature of the maximum combustion speed it can achieve the larger. When the pore diameter is 4mm, the impact strength reaches a maximum of 30.6KJm-2, which is nearly 40% stronger than 45/1-3mm and 45/1-6mm.

Preparation and properties investigation of flame‐retardant rigid polyurethane foam composites based on alkylphosphate oligomer

AbstractIn this work, FR‐PNX, an alkylphosphate oligomer was introduced into rigid polyurethane foam (RPUF) to fabricate FR‐PNX/RPUF composites. The flame retardancy, thermal stability, and combustion properties of composites were investigated by limiting oxygen index (LOI), thermogravimetric (TG), microcalorimetry (MCC), scanning electron microscopy (SEM), et al. The flame retardancy tests demonstrated that the incorporation of 50 phr of FR‐PNX yielded composites that the highest LOI of 23.6 vol% and achieved a V‐0 rating in the UL‐94 test. TG results indicated that FR‐PNX promoted the decomposition of FR‐RPUF in the process, but enhanced the high‐temperature stability of the composites. MCC analyses revealed that the addition of FR‐PNX suppressed the heat release during combustion, and FR‐PNX50/RPUF exhibited the lowest total heat release of 17.3 MJ/m2, a 35% reduction compared to the pure sample. Moreover, the peak heat release rate was decreased to 83.1 W/g, representing a 46.9% reduction compared to pure RPUF. SEM and Raman analyses of the char residue demonstrated that the incorporation of FR‐PNX facilitated the formation of a dense and continuous char layer in the FR‐RPUF, with increased graphitization degree of the char layer, thereby enhancing the composite's fire resistance through the development of a more stable fire barrier.

Optical observation and combustion properties during paper sludge fast heating

Optical observation and combustion properties during paper sludge fast heating

Delineating the effects of ignition propensity and Markstein number on deflagration-to-detonation transition

Although the process through which a deflagration transitions to a detonation (DDT) has been studied for over a century, it is not well-understood how the propensity for DDT varies among different combustible mixtures. We investigate the effect of two fundamental mixture properties, ignition delay (τign) and Markstein number (Ma), on this stochastic process. Experiments were conducted in a smooth cylindrical tube, and the critical state (characterized by the velocity of the reacting front) at which a detonation formed from an accelerating deflagration was measured. The novelty of the study lies in the selection of mixture compositions that enabled changing only one relevant combustion property at a time and hence isolating the sensitivity to that property. Experiments with mixtures with similar deflagrative properties but different τign revealed that the critical state is not measurably sensitive to ignition propensity. Mixtures studied with different thermo-diffusive properties revealed that Ma has a strong effect on the critical state. Specifically, thermo-diffusively-unstable mixtures (with low Ma) underwent DDT at significantly lower velocities. Furthermore, experiments were performed with and without a spiral to isolate the effect of flame wrinkling and turbulence. The spiral-affected flames underwent DDT at lower velocities, similar to thermo-diffusively-unstable mixtures. This observed effect of thermo-diffusive nature of the mixture and turbulence on DDT propensity is not predicted by existing models.

Combustion Behavior of Cellulose Ester Fibrous Bundles from Used Cigarette Filters: Kinetic Analysis Study.

This study is focused on the detailed examination of the combustion properties and kinetic analysis of a cellulose acetate fibrous bundle (CAFB), separated from used cigarette filters. It was shown that the faster rate of CAFB heating allows a large amount of heat to be supplied to a combustion system in the initial stages, where the increase in heating rate has a positive response to ignition behavior. The best combustion stability of CAFB is achieved at the lowest heating rate. Through the use of different kinetic methods, it was shown that combustion takes place through two series of consecutive reaction steps and one independent single-step reaction. By optimizing the kinetic parameters within the proposed reaction models, it was found that the steps related to the generation of levoglucosenone (LGO) (by catalytic dehydration of levoglucosan (LG)) and acrolein (by breakdown of glycerol during CAFB burning-which was carried out through glycerol adsorption on a TiO2 surface in a the developed dehydration mechanism) represent rate-controlling steps, which are strongly controlled by applied heating rate. Isothermal predictions have shown that CAFB manifests very good long-term stability at 60 °C (which corresponds to storage in a sea shipping container), while at 200 °C, it shows a sudden loss in thermal stability, which is related to the physical properties of the sample.

Evaluation of hydrogen/ammonia substitute fuel mixtures for methane: Effect of differential diffusion

One strategy for utilizing ammonia as an energy vector is to replace conventional hydrocarbons with hydrogen-enriched ammonia in existing or retrofitted combustors. However, the strong differential diffusion effect of hydrogen can significantly alter the combustion properties and cause challenges in combustor operability. Therefore, this numerical study performs a systematic investigation on the effect of differential diffusion on fundamental combustion properties of ammonia/hydrogen fuel blends. The investigated combustion properties span from the initiation of combustion, i.e., ignition, to stretched flame propagation and ultimately to flame stabilization mechanisms. The objective is to evaluate the feasibility of hydrogen/ammonia/air mixtures as substitutes for methane/air particularly considering the implications of differential diffusion effects. To this end, four fuel blends with similar unstretched burning properties are selected: fuel lean ammonia/hydrogen (AH-L), fuel rich ammonia/hydrogen (AH-R), fuel lean methane (M-L) and fuel lean methane/hydrogen (MH-L). First, the forced ignition and stretched flame propagation are evaluated. It is found that the AH-L (AH-R) mixture has a large negative (positive) Markstein length, and thereby among the selected fuel blends, AH-L (AH-R) has the lowest (highest) minimum ignition energy. Then flame stabilization mechanisms are investigated. For a stable flame, AH-L (AH-R) has an intensified (weakened) flame base and a weak (strong) flame tip, which shows a higher flashback (blow-off) propensity. Based on the critical gradient theory, a novel stability regime diagram is proposed. With the regime diagram, the flame stabilization limits (central flashback, boundary layer flashback, stable, and blow-off) and flow conditions can be determined for burners of different sizes.

Comparative study of the combustion properties of briquettes produced from blends of mung beans shell, uncarbonized and carbonized sawdust

In this research, the combustion properties of the briquette produced by blending mung beans shell (MBS) with carbonized danta wood sawdust was compared with that of the briquette produced by blending MBS with uncarbonized danta wood sawdust. The briquettes wereproduced atdifferentsawdust to biomass ratios (100%:0, 70%:30%, 50%: 50%, 30%: 70% and 100%:0). Cassava starch was used as a binder. Proximate analysis (moisture content, ash content, volatile matter and fixed carbon) and combustion properties (calorific value, ignition time, burning time, burning rate, specific fuel consumption and thermal efficiency) were calculated using standard methods. The results of the analyses showed that 100% sawdust briquette samples had the lowest moisture content, 4.74±0.00 for carbonized sawdust and 6.76±0.02 for uncarbonized sawdust.100% uncarbonized and carbonized sawdust briquette samples had a fixed carbon of 68.93±0.02 and 87.46%, Ash content:3.70±0.00% and 2.18±0.04%,volatile matter: 20.61±0.00 and 5.61±0.04 and calorific value: 29.401±0.0 MJ/Kg and 32.532±0.05 MJ/Kg respectively.The ignition time increase with increase in biomass load for uncarbonized sawdust samples and decrease with increase in biomass load for carbonized sawdust briquette samples. The burning time decreased from 86±0.57mins (70% sawdust + 30% biomass) to 70±0.57mins (100% biomass) for the carbonized sawdust briquette samples and for the uncarbonized, it ranged from 68±0.00 (70% sawdust + 30% biomass) to 71.6±0.57 mins (30% sawdust + 70% biomass) and then dropped to 68±0.57(100% biomass load). The burning rate decreased in carbonizedbriquette samples and increased in uncarbonized briquette samples with increase in biomass load. The specific fuel consumption for carbonized and uncarbonized sawdust briquette sample decreased with increase in MBS load. 100% carbonized and uncarbonized sawdust briquette samples had a thermal efficiency of 8.78 and 16.47 respectively. It can be concluded that blend of carbonized sawdust and mung beans shell will make a better fuel due to better combustion properties than the uncarbonized sawdust samples.

Reduced erosion and its erosion reducing mechanism of gun propellants by octaphenylsilsesquioxane

Low erosion high-energy propellant is one of the research directions to extend the weapon's life and improve the weapon's capability. In this study, energetic propellants containing different corrosion inhibitors were designed and prepared. Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants. The mechanism of erosion-reducing of titanium dioxide (titania, TiO2), talc, and octaphenylsilsesquioxane (OPS) on the propellant was comparatively analyzed. The results show that OPS has the lowest burning rate and the longest burning time, and a minimized loss of fire force, with the best effect of explosion heat reduction. The erosion reduction efficiency of OPS is twice that of TiO2 and talc. The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion, and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO2 protective layer. This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.

A positional isomer of LLM-116: N—NO2 moiety enhancing the laser ignition combustion performance of nitrogen-rich energetic materials

It has long been a driving force in the development of energetic materials to hunt for novel energetic materials (EMs) with high energy and low sensitivities. Recently, the combination of nitrogen-heterocycles and NNO2 moiety could generate novel energetic derivatives with high energy content and low sensitivity benefiting from the high heat of formation and abundant hydrogen bonding interactions. The critical role of isomerism strategy in tuning the laser ignition combustion performances of EMs is rarely mentioned in the chemical enterprise, although some researches reveal that isomerism strategy has significant effects on their thermal behaviors, mechanical sensitivity and detonation performance. In this work, the positional isomerism of nitramine-pyrazole was investigated, and 3-nitramine-4-nitropyrazole and a series of energetic derivatives were synthesized and well characterized. Their physical properties, energy performance, as well as laser-ignited combustion performance, were further explored. The experimental results showed that all compounds possess excellent detonation pressure, and detonation velocity (P: 26.5∼30.4 GPa, D: 7876∼8377 m·s−1), which were much better than those of trinitrotoluene (TNT) (P: 19.5 GPa and D: 6881 m·s−1). Moreover, all of the resulting energetic derivatives exhibited low mechanical sensitivities (IS>40 J). Interestingly, they also had excellent laser ignited combustion properties owing to the NNO2 moiety attached to nitropyrazole backbone.

A novel spectral model for prediction of nongray radiative properties in gaseous combustion

Radiative heat transfer during gaseous combustion displays very strong spectral or “nongray” behavior, which is both very difficult to characterize and to evaluate. A novel spectral model based on the full-spectrum correlated k-distribution (FSCK) method combined with the multilayer perceptron (MLP), i.e., NFM model, is developed for the prediction of nongray radiative properties in gaseous combustion. Followed by the nature of FSCK method, the NFM model is designed as a simple MLP structure that has only two outputs to directly give both correlated k-value and corresponding ka-value. This not only avoids on-the-fly calculations of a-values but also saves storage by the simple structure. Moreover, by constructing training data with a number of small mole fractions, the errors caused by nonlinear effects are found to be mitigated during the use of NFM model. Several test cases have been carried out to compare the developed NFM model and other spectral tools including FSCK look-up tables and traditional FSCK MLP (TFM) model. Results show that the NFM model can achieve excellent accuracy that is even better than FSCK look-up tables at a tiny computational cost that is far less than that of TFM model.

A novel dynamic simulation method for investigating the hygroscopicity of Ammonium perchlorate

Ammonium perchlorate (AP) is a widely used oxidizer, extensively employed in solid propellants with excellent combustion properties. Ultrafine AP has better combustion properties, but its strong hygroscopicity and high sensitivity hinder its application. To safely and efficiently explore the hygroscopicity of ultrafine AP, this paper proposes a novel molecular dynamics (MD) simulation approach. By analyzing the movement of water molecules, fluctuations in average hydrogen bond strength, and the influence of non-covalent intermolecular forces throughout the moisture absorption process, this study presents a comprehensive overview of the hygroscopic properties of ultrafine AP across relative humidity (RH) levels spanning from 10 % to 100 %, and temperatures ranging between 273 K and 373 K. It was found that temperature has a more significant impact on the hygroscopicity of AP compared to RH. During the hygroscopic process of AP, Van der Waals interactions hindered the water absorption of AP, while electrostatic forces promoted its hygroscopic properties. The hygroscopicity of AP reached a maximum when the temperature exceeded 333 K, and plateaued as the increase of RH. The proposed moisture simulation method facilitates the secure and effective forecasting of moisture absorption in AP-based materials across various temperature and RH environments, thereby greatly expediting research on enhancing the moisture resistance of ultrafine AP.

Industry R&D needs in hydrogen safety

Hydrogen's unique physicochemical and combustion properties make it stand out among fuels as new hydrogen production technologies, means of transportation, and consumers emerge. The future viability of these technological solutions will depend on numerous factors, including safety, environmental, regulatory, and economic considerations. Safe deployment of these technologies requires additional research and development activities. These range from an improved quantitative understanding of hydrogen leaks, material limitations due to embrittlement, very large-volume liquefied hydrogen storage and transport, to equipment- and usage-specific considerations as is the case for gas turbines and electrolyzers.

Changes in the state of matter of KCIO4 to improve thermal and combustion properties of Al/MoO3 nanothermite

To improve the thermal and combustion properties of nanothermites, a design theory of changing the state of matter and structural state of the reactants during reaction was proposed. The Al/MoO3/KClO4 (Kp) nanothermite was prepared and the Al/MoO3 nanothermite was used as a control. SEM and XRD were used to characterize the nanothermites; DSC was used to test thermal properties; and constant volume and open combustion tests were performed to examine their combustion performance. Phase and morphology characterization of the combustion products were performed to reveal the mechanism of the aluminothermic reaction. The results show that the Al/MoO3/Kp nanothermite exhibited excellent thermal properties, with a total heat release of 1976 J·g− 1, increasing by approximately 33% of 1486 J·g− 1 of the Al/MoO3 nanothermite, and activation energy of 269.66 kJ·mol− 1, which demonstrated higher stability than the Al/MoO3 nanothermite (205.64 kJ·mol− 1). During the combustion test, the peak pressure of the Al/MoO3/Kp nanothermite was 0.751 MPa, and the average pressure rise rate was 25.03 MPa·s− 1, much higher than 0.188 MPa and 6.27 MPa·s− 1 of the Al/MoO3 nanothermite. The combustion products of Al/MoO3 nanothermite were Al2O3, MoO, and Mo, indicating insufficient combustion and incomplete reaction, whereas, the combustion products of Al/MoO3/Kp nanothermite were Al2O3, MoO, and KCl, indicating complete reaction. Their “coral-like” morphology was the effect of reactants solidifying after melting during the combustion process. The characterization of reactants and pressure test during combustion reveals the three stages of aluminothermic reaction in thermites. The excellent thermal and combustion performance of Al/MoO3/Kp nanothermite is attributed to the melt and decomposition of Kp into O2 in the third stage. This study provides new ideas and guidance for the design of high-performance nanothermites.

Enhancing liquefied petroleum gas production through debutanizer column optimization

Debutanizer columns are important in natural gas processing as they are crucial in generating Liquefied Petroleum Gas (LPG). LPG is well recognised for its environmentally benign combustion properties, making it a desirable fuel option for cooking, heating, and transportation. The optimisation of debutanizer units has significant relevance in improving the efficiency of LPG separation. This study aims to enhance the separation efficiency of a butane removal tower by modelling and optimising its operation using HYSYS software. The research aims to introduce innovation in this field. A series of comprehensive simulations were carried out to achieve this goal, resulting in outcomes that nearly corresponded to the findings obtained from natural gas units. Moreover, a thorough examination was conducted to examine the impact of temperature, pressure, feed flow rate, and reflux ratio on the production yield of n-butane. The study reached this conclusion by optimising tower conditions, with a particular emphasis on improving the performance of the condenser during the hot summer season. In ideal circumstances, the distillate demonstrated a butane concentration ranging from 70% to 74%, while all overhead gas is condensed in all instances. This study highlights the importance of optimising the debutanizer column in enhancing the quality and efficiency of LPG production in the natural gas processing sector.

Combustion and mechanical properties of pellets from biomass and industrial waste

Experimental research findings are reported on the impact of industrial waste additives on the mechanical properties of pellets, their ignition and combustion. The compositions under study consisted of wood sawdust with coal slime/peat/a mixture of straw and rice husk. Composite pellets exhibited high moisture resistance and durability when subjected to vibration. The respective coefficients were 6–32 % higher than for sawdust without additives. The ignition characteristics of wood pellets tended to worsen when additional components were used in their composition. The ignition delay times increased by a factor of 3–4. In most cases, the use of additives increased the combustion duration of pellet fuels. The greatest environmental benefits in terms of carbon oxides were gained from mixtures of straw with rice husk and coal slime. СО2 and СО emissions decreased by 10–20 % and 10–54 %, respectively. A high nitrogen content in peat, coal slime and straw led to 5–94 % higher emissions of NOx for composite pellets. Using plant biomass and peat reduced the concentrations of sulfur oxides almost 3-fold. The results of multi-criteria analysis covering 13 energy, operational, economic and environmental components suggest that the difference in the relative efficiency indicator of wood pellets and compositions with industrial waste additives is 4.4–6.5 %.

Evaluation of the Combustion Properties and Catalytic Activity of MgAlB Energetic Ternary Particles

ABSTRACT Boron powder possesses significant potential for use as a combustible agent in energetic materials, owing to its superior combustion thermodynamic properties. However, the powder’s tendency to form an oxide layer on its surface results in delayed ignition, reduced combustion efficiency, and compromised energy advantage. To enhance the ignition and combustion properties of boron powder, we prepared boron-based energetic composites containing flammable metals (MgxAl1-xB2) through high-temperature sintering. These were then characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS). The combustion heat of these alloy powders were measured using an oxygen bomb calorimeter, while their catalytic performance on the thermal decomposition of ammonium perchlorate (AP) was analyzed using differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The results indicate that compared with boron, the MgxAl1-xB2 powders are more flammable, require less oxygen, exhibit a higher combustion efficiency and exothermic advantage. Especially, the Mg0.9Al0.1B2 and MgB2 alloy exhibit optimal combustion heat values of 39,094.92 and 37,693.90 J·g−1, respectively. They significantly enhance the thermal decomposition of AP and reduce the activation energy by over 20%.

High-Performance Aluminum Fuels Induced by Monolayer Self-Assembly of Nano-Sized Energetic Fluoride Vesicles on the Surface.

Surface modification is frequently used to solve the problems of low combustion properties and agglomeration for aluminum-based fuels. However, due to the intrinsic incompatibility between the aluminum powder and the organic modifiers, the surface coating is usually uneven and disordered, which significantly deteriorates the uniformity and performances of the Al-based fuels. Herein, a new approach of monolayer nano-vesicular self-assembly is proposed to prepare high-performance Al fuels. Triblock copolymer G-F-G is produced by glycidyl azide polymer (GAP) and 2,2'-(2,2,3,3,4,5,5-Octafluorohexane-1,6-diyl) bis (oxirane) (fluoride) ring-open addition reaction. By utilizing G-F-G vesicular self-assembly in a special solvent, the nano-sized vesicles are firmly adhered to the surface of Al powder through the long-range attraction between the fluorine segments and Al. Meanwhile, the electrostatic repulsion between vesicles ensures an extremely thin coating thickness (≈15nm), maintaining the monolayer coating structure. Nice ignition, combustion, anti-agglomeration, and water-proof properties of Al@G-F-G(DMF) are achieved, which are superior among the existing Al-based fuels. The derived Al-based fuel has excellent comprehensive properties, which can not only inspire the development of new-generation energetic materials but also provide facile but exquisite strategies for exquisite surface nanostructure construction via ordered self-assembly for many other applications.

Aspects of Ammonia as Green Fuel for Propulsion Systems of Inland Water Vessels

Ships are a crucial backbone of the transport system for goods and people. However, the currently utilized fossil fuels require a green replacement. Ammonia produced from green hydrogen is an interesting, carbon‐free green fuel, which has been demonstrated to be promising for maritime applications. Its application under the specific boundary conditions of river ships and other inland water vessels still deserves a closer evaluation. In this work, ammonia as a green fuel for propulsion systems of inland water vessels is evaluated regarding several technological aspects. These include onboard decomposition for hydrogen release, combustion of ammonia–hydrogen mixtures in internal combustion engines and the thermal integration of the different components. To achieve favorable combustion properties of the fuel, a certain share of the ammonia has to be decomposed in an ammonia cracker to produce a mixture of hydrogen and ammonia. First single‐cylinder engine tests show that the combined combustion of ammonia and hydrogen allow an efficient and reliable process for the investigated high‐speed engine concept. Efficiency values of nearly 40% at part load already are achieved. With proper system integration, it is possible to reasonably operate small‐ and medium‐sized ships with ammonia as a green fuel.