Lower Heat Release Rate Research Articles

Investigations on performance of gasifier engine integration using three different biomasses as feedstocks

The integration of a downdraft gasifier with modified internal combustion engines presents a feasible solution for heat and power production, such as off-grid areas. This study conducted an experimental analysis to evaluate combustion in a modified engine. The morphological characteristics of the agricultural residue used in the gasifier were analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM), along with an examination of the slagging inorganic constituents. The engine used in the experiments was a modified single-cylinder design paired with a downdraft gasifier. Three types of biomass feedstocks—eucalyptus, corncob, and pearl millet in pellet form —were tested. The performance of the downdraft gasifier was stabilized, and the engine was run independently on each type of producer gas at a constant speed under different loads to determine the optimum load. Cylinder pressure measurements were taken to estimate the heat release rate.The study found that power generation was lower than typical woody biomasses due to the lower calorific value of the producer gas from the tested feedstocks. Additionally, lower cylinder pressures and heat release rates were recorded, along with longer combustion durations. The varying proportions of producer gas affected combustion stability. Among the studied ashes, pearl millet corncob (PMC) exhibited the highest slagging tendency, followed by corncob (CC). Morphological analysis indicated that the eucalyptus residue's increased porosity was caused by the volatiles changing, forming pores and tube-like structures. An aliphatic C–H peak (3000–2500 cm⁻1) is absent from the residue, indicating that the aliphatic structure was disturbed during thermochemical conversion. During the gasification process, the residue's crystallinity reduced as it split down.

Experimental research on the flow field and flame geometry of free buoyant diffusion flames with low dimensionless heat release rates

The flame geometry of turbulent diffusion flames is dominated by the turbulent mixing between the gaseous fuel and the entrained air. The significant variations of the power law for the mean flame height regarding the dimensionless heat release rate (Q˙*) in different Q˙* ranges implied that the turbulent mixing characteristics would change greatly among these Q˙* regimes. This paper presents a combined experimental and analytical study to reveal the turbulent transport properties and flame shape of free turbulent buoyant diffusion flames of relatively low Q˙* prevalent in large-scale fires. The instantaneous velocity fields of free buoyant methane diffusion flames (burner diameter: d = 0.30 m, Q˙*= 0.22–0.40) were measured by the stereo particle image velocimetry (SPIV) technique. The results indicate that the radial profiles of the time-averaged axial velocity, axial normal stress, radial normal stress, shear stress, and turbulent kinetic energy exhibited self-similarity at different heights under all the heat release rates. The turbulent flow in the buoyant flame was found to be anisotropic. Based on the gradient transport approximation, the mean turbulent viscosity within the mean flame height (νt=) was scaled by g1/2d3/2, where g is the gravitational acceleration. The semi-physical correlations for the mean flame height and width were derived based on the concepts of turbulent mixing and equal axial convection and radial diffusion times, respectively. The two correlations agreed reasonably with the experimental data of this work.

Visualization study on the flame propagation and distribution characteristics and exploration of optimal injection strategy in ammonia/diesel dual direct injection mode

With the increasing shortage of fossil fuels and the worsening carbon emission problems, ammonia has been attracted widely to alleviate the current challenges faced by internal combustion engines. Igniting direct injection of liquid ammonia by diesel may be a measure to achieve effective ammonia application, while the research on the characteristics of combustion and the unburned ammonia emission is little. Therefore, this paper studies the effects of ambient parameters and injection parameters on the characteristics of diesel ignition and flame propagation and distribution based on a constant volume combustion chamber, through the shadow method. The results indicate that the premise to ensure that ammonia can fully participate in combustion is that the flame can backpropagate to the junction of the two sprays. The current optimal injection strategy is the simultaneous injection of diesel and ammonia combined with a complete ammonia injection before the maintained flame. At a low temperature and high diesel injection pressure, ammonia will participate in combustion after a delay, which may result in a relatively low heat release rate and high unburned ammonia emissions. Overall, the paper can provide important references for professional researchers which is of great significance for the development of diesel/ammonia engines.

Lightweight, high-strength and fireproof borax-crosslinked graphene/hydroxyethyl cellulose hybrid aerogels fabricated via ice template method

In recent years, there has been a growing interest in fireproof nanomaterials due to their broad applications in fire-safety and environmental preservation. In this study, one kind of lightweight fireproof hybrid aerogel with low thermal conductivity (0.039 W/m•K) was prepared through a facile ice template method, where the graphene nanosheets and hydroxyethyl cellulose (HEC) are combined with borax crosslinkers. It was found that this aerogel can be not only recyclable and repairable, but also possesses excellent compressive strength and stiffness, owing to the interfacial van der Waals adsorption, ionic crosslinking and hydrogen bonding interactions. Remarkably, it has excellent flame retardancy performance (an extremely low peak heat release rate (PHRR) was measured to be 37.44 kW/m2, reduced by 88.6 % comparing to that of graphene/HEC aerogel). To further explore the fire resistance mechanism of this aerogel, the molecular dynamics simulation was performed. It reveals that the borax can effectively wrap and hinder the graphene and HEC molecules from decomposition. Besides, the borax can compact graphene and HEC closer, thereby further isolating heat and oxygen, realizing the fireproof property. This study offers valuable insights for designing advanced fireproof nanomaterials and applications in shipbuilding or construction.

Experimental investigation on the combustion characteristics of electrolyte jets containing flame retardant tris (2-chloroethyl) phosphate

Abstract It is critical to well understand the combustion characteristics of the electrolytes inside lithium-ion batteries for safety concerns, particularly the electrolyte jet flames after thermal runaway. An electrolyte jet fire setup is developed in this study to investigate the combustion characteristics of electrolyte jets with the flame-retardant additive tris (2-chloroethyl) phosphate (TCEP) under high-temperature circumstances. Jet and ignition delay times and flammability are defined to characterize the flame-retardant effects. The fundamental parameters of self-extinguishing time and propagation rate are also measured for a comprehensive comparison. The experimental results show that the propagation of electrolyte flame at ambient temperature can be entirely stopped with 40 wt % of TCEP additives and 50 wt % can make the electrolyte nonflammable. Owing to the high boiling temperature and vaporization enthalpy of TCEP, more heat is required for the decomposition of electrolytes and TCEP mixtures, resulting in lower decomposition reaction rates and heat release rates. Thus, both the jet delay times and the ignition delay times significantly increase with the TCEP additives. Moreover, analyses on the spectrum of electrolyte jet flame reveal that the suppressing effects of TCEP on the combustion of electrolyte jets are operated by scavenging the OH radical and heat release.

A zinc-embedded multicomponent copolymer customized for polypropylene and its synergistic flame-retardant effect and outstanding mechanical properties

The poor compatibility between the common polar intumescent flame-retardant system (IFR) and the nonpolar polypropylene (PP), as well as the high additive amount, seriously impacts the mechanical properties of the composites. This study introduced collaborative flame-retardant technology to construct block copolymer flame retardants and prepared a zinc-embedded multicomponent copolymer (PM-Zn2+) customized for PP composites. In the PM-Zn2+ system, zinc oxide was embedded into the copolymer composed of piperazine phosphate oligomer and melamine phosphate. PM-Zn2+ exhibited an amorphous structure with extremely low crystallinity and demonstrated specific morphological adaptability. The PM-Zn2+ were well dispersed in the PP matrix and changed their morphology during processing. When applied to PP, excellent flame retardancy and mechanical properties were obtained by using a minimal amount of flame retardants (20 %). PM-2 %Zn2+ gave PP an LOI value of 31.5 %, and achieved a UL94 V-0 rating (1.6 mm thick), exhibiting a lower heat release rate and smoke release. The flame-retardant mechanisms of PM-Zn2+ mainly involved the synergistic and aggregative effects. Transition metal zinc synergistically interacted with polyphosphate groups to create a charring barrier effect and enhance synergistic smoke suppression, leading to a significant reduction in combustion intensity. In comparison to the Mix-Zn/PP composites, the mechanical properties of PM-Zn2+/PP were significantly enhanced due to the specific morphological adaptability and improved compatibility. The elongation at break increased significantly from 15.6 % to 627.9 %, marking a remarkable improvement of 40-fold improvement, while the impact strength rose from 23.7 kJ/m2 to 54.3 kJ/m2, representing a 129 % enhancement. Finally, the zinc-embedded multicomponent block copolymer offers a promising approach to developing high-performance flame-retardant polypropylene materials.

A flame‐retardant, dendrite‐inhibiting sandwich separator prepared by electrospinning for high‐performance and safety lithium batteries

AbstractAs the “safety switch” of lithium batteries, the separator controls the electrochemical performance and safety performance of lithium batteries. However, highly flammable and easy to induce lithium dendrite generation of commercial polyolefin pose a huge safety hazard for current commercial lithium‐ion batteries. Therefore, developing a flame‐retardant, lithium dendrite‐inhibiting separator can achieve further leap in the lithium battery industry. A “sandwich” separator (SPS‐B) is designed by integrating silk fibroin (SF), decabromodiphenyl ethane, and polyvinyl alcohol through electrospinning. SPS‐B shows excellent flame‐retardant properties through a free radical trapping mechanism. Moreover, the SPS‐B demonstrated satisfactory capability of suppressing lithium dendrites by constructing Li3N‐SEI with high ionic conductivity and high strength, and the secondary structure β‐sheets of SF can inhibit the “tip effect” of lithium dendrites, which enables efficient lithium plating/stripping in Li//Li and Li//Cu cells. In addition, the enhanced porosity, electrolyte affinity of SPS‐B promotes excellent electrochemical performance with enhanced discharge capacity and reduced concentration polarization. Finally, fire risk of soft‐pack batteries are evaluated by continuous external heating. Compared with commercial separator, soft‐pack batteries with SPS‐B show much lower heat release rate, peak temperature and flue gas release rate, further confirming the effectiveness of SPS‐B in reducing fire risk. Overall, the SPS‐B provides a satisfactory way to develop high‐performance and superior safety lithium batteries.

Diphenylphosphoryl Azide as a Multifunctional Flame Retardant Electrolyte Additive for Lithium-Ion Batteries

Graphite anode materials and carbonate electrolyte have been the top choices for commercial lithium-ion batteries (LIBS) for a long time. However, the uneven deposition and stripping of lithium cause irreversible damage to the graphite structure, and the low flash point and high flammability of the carbonate electrolyte pose a significant fire safety risk. Here, we proposed a multifunctional electrolyte additive diphenylphosphoryl azide (DPPA), which can construct a solid electrolyte interphase (SEI) with high ionic conductivity lithium nitride (Li3N) to ensure efficient transport of Li+. This not only protects the artificial graphite (AG) electrode but also inhibits lithium dendrites to achieve excellent electrochemical performance. Meanwhile, the LIBS with DPPA offers satisfactory flame retardancy performance. The AG//Li half cells with DPPA-0.5M can still maintain a specific capacity of about 350 mAh/g after 200 cycles at 0.2 C. Its cycle performance and rate performance were better than commercial electrolyte (EC/DMC). After cycling, the microstructure surface of the AG electrode was complete and flat, and the surface of the lithium metal electrode had fewer lithium dendrites. Importantly, we found that the pouch cell with DPPA-0.5M had low peak heat release rate. When exposed to external conditions of continuous heating, DPPA significantly improved the fire safety of the LIBS. The research of DPPA in lithium electrolyte is a step towards the development of safe and efficient lithium batteries.

Experimental study of flame extension lengths and fire pattern lengths induced by the turbulent jet fire impinging on inclined wooden boards

The safety of producing and transporting flammable gas may be compromised by the occurrence of jet fires resulting from pipeline leakage. During such incidents, combustible obstacles can impede the development of vertical jet fires, leading to impingement. Wood, a typical building material, was chosen as a combustible solid for the experiment due to its ability to produce regular fire patterns on its surface when heated, making it useful for fire investigation. A series of experiments were conducted to examine the flame extension length and fire pattern length resulting from a jet fire impinging on inclined wooden boards with different nozzle diameters, inclination angles, and heat release rates. This work showed that, unlike non-combustible boards, the rate of increase in flame extension length beneath a wooden board continues to rise as the heat release rate increases. Additionally, the boards' ability to absorb heat during the initial stages of combustion affects the flame extension length at low heat release rates. This work introduces a new correlation that can predict the length of flame extension under wooden boards, addressing a gap in research on jet fire impingement on combustible ceilings. For the regular fire patterns left by jet fires impinging on wooden boards, a new correlation of fire pattern length with flame extension length for different inclination angles of wooden boards is proposed. Considering the characteristics of turbulence, a novel model for fire pattern length is introduced, incorporating the Karlovitz flame stretch factor, nozzle inner diameter, and fire source-wooden board spacing.

The chemical structure of triple flames in laminar blue whirls

The blue whirl is a conical, near-limit flame with a bright, blue ring, occurring at low heat-release rates that can stabilize over a pool of liquid fuel. This unique structure forms following suppression of soot formation in a laminar fire whirl under the influence of vortex breakdown. Recent literature on the blue whirl has hypothesized and predicted the existence of a triple flame at the blue ring. In this work, we explore the distribution of various chemical species in the flame to quantitatively establish a map of equivalence ratio around the flame. Using high-speed chemiluminescence and planar laser-induced fluorescence, the distribution of OH, PAH and CH radicals were measured. The OH*/CH* ratio was used to estimate the local equivalence ratio. Results show that the blue ring is mostly stoichiometric, but there is a small rich region below it, towards the fuel layer, and a lean region above it, towards the wake of the vortex breakdown bubble. This structure provides experimental evidence that a triple flame exists in the blue whirl. The time scales of flow within the recirculation zone are estimated using soot traces that are observed occasionally, and then used to estimate a range of Damköhler numbers that can lead to stable blue whirl formation, providing an important scaling factor to design clean, practical burners using the blue whirl regime.

Manufacture and Combustion Characteristics of Cellulose Flame-Retardant Plate through the Hot-Press Method.

This study focuses on the increased risk of high heat release and asphyxiation (toxic gas poisoning) in the event of a fire involving polyurethane (PU)- and MDF-based building materials, which are commonly used in buildings. Among them, polyurethane (PU) building materials are very commonly used in buildings, except in Europe and some other countries, due to their excellent thermal insulation performance. Still, problems of short-term heat release and the spread of toxic gases in the event of a fire continue to occur. To overcome these problems, researchers are actively working on introducing various flame retardants into building materials. Therefore, in this study, we produced a laboratory-sized (500 mm × 500 mm) plate-like flame-retardant board that can be utilized as a building material with a lower heat release rate and a lower toxicity index. The material was made by mixing expanded graphite and ceramic binder as flame retardants in a material that is formulated based on the cellulose of waste paper, replacing the existing building materials with a hot-press method. According to the ISO-5660-1 test on the heat release rate of the plate-like flame-retardant board, the Total Heat Release (THR) value was 2.9 (MJ/m2) for 10 min, showing an effect of reducing the THR value by 36.3 (MJ/m2) compared to the THR value of 39.2 (MJ/m2) of the specimen made using only paper. In addition, the toxicity index of the flame-retardant board was checked through the NES (Naval Engineering Standards)-713 test. As a result, the test specimen showed a toxicity index of 0.7, which is 2.4 lower than the toxicity index of 3.1 of MDF, which is utilized as a conventional building material. Based on the results of this study, the cellulose fire-retardant board showed the effect of reducing the heat release rate and toxicity index of building materials in a building fire, which reduces the risk of rapid heat spread and smoke toxicity. This has the potential to improve the evacuation time (A-SET) of evacuees in fires. It is also important to show that recycling waste paper and utilizing it as the main material for building materials can be an alternative in terms of sustainable development.

Experimental investigation on mechanical properties and fire performance of innovative wheat straw-gypsum composites as building sheathing panels

An innovative and high-performance wheat straw-gypsum composite (SGC) was developed to solve the problem of cracking and separation caused by water release when exposed to high temperature of gypsum board (GB) on the fire side of a wall. Compatibility between wheat straw and gypsum crystal was improved by combined pretreatment (i.e., sodium hydroxide and coupling agent) and adding magnesite. The mechanical properties of SGC were investigated and its fire performance determined by cone calorimetry and fire tests. The results indicated that the modulus of rupture, modulus of elasticity, and internal bond strength of SGC were 53.7%, 115.9%, and 173.9%, respectively higher than the traditional GB. The improvement in strength was attributed to the fact that alkali-treated wheat straw was well combined with gypsum crystals through magnesite to form a compact structure, as evidenced by scanning electron microscopy. SGC had extremely low heat and smoke release rate, ignition point at > 1200 s, and mass retention increased by 17.1%, compared with the literature results of gypsum-based bio-composites. Under a 60-min duration exposure, the charring depth of the wood studs of light frame walls sheathed with GB was 27 mm higher than that of SGC wall, and the bearing capacity retention rate of SGC wall 65.4%, while that of GB wall was lost. Errors between the calculation of bearing capacity proposed in this study and test values were < 6%. SGC with superior thermal insulation and mechanical properties could beneficially replace GB as fire-resistant panels in buildings.

Ammonia as a Fuel for Gas Turbines: Perspectives and Challenges

The paper addresses the prospects and challenges associated with the use of ammonia in gas turbine plants. The complexity of the chemical kinetic mechanisms of ammonia combustion and the insufficient amount of experimental data that can confirm the results still require a lot of scientific research. In this sense, this application is even less technologically mature than other sectors such as the marine engine one. From the point of view of combustion in gas turbines, the techniques in use and being perfected to deal with flame instability, low laminar burning velocity (about 20% of that of methane-air flames), the long ignition delay time and low volumetric heat release rate. In particular, the use of ammonia blended with other combustion enhancers such as hydrogen, methane and alcohols has been analyzed. Mild combustion is also being analyzed as a valid technique for dealing with the difficulties of ammonia combustion. The combustion of ammonia generates significant quantities of nitrogen oxides, both for the thermal mechanism and for the “fuel” one, which must therefore be mitigated, together with the emission of unburnt ammonia. Even in this case, blending with other fuels allows for improved emissions performance. The paper compares the different techniques and the relative advantages both in terms of combustion efficiency and emissions. Finally, the perspectives for the use of ammonia in gas turbines are outlined, highlighting the challenges still to be overcome, in a panorama of energy transition towards an increasingly decarbonized future, with the aim of mitigating climate change as much as possible.

Fabrication of expandable graphite and soybean oil-based synergistic modified polyurethane foam with improved thermal stability and flame retardant properties

Abstract Biomass soybean oil-based polyol rigid polyurethane foam (RPUF) was modified and prepared by expandable graphite (EG). The effects of EG on the thermal stability and flame retardant properties of soybean oil-based polyol RPUFs were investigated by thermogravimetric analysis, pyrolysis kinetic analysis, conical calorimetry and flue gas toxicity analysis. The results showed that modified RPUF (RPUF-4) with EG content of 20 wt% had the highest initial and end temperatures, the highest activation energy E, the lowest Ds (17.6), and the highest light transmittance (73.6 %). At the same time, RPUF-4 had the lowest heat release rate (10.1 and 16.5 kW/m2), the lowest total heat release (1.5 and 2.1 MJ/m2), and the lowest average toxic gas emissions. The current study indicated that RPUF-4 had better thermal stability and flame retardant performance, which provided a useful reference for subsequent biomass flame retardant modified RPUFs.

Fabrication of soybean oil-based polyol modified polyurethane foam from ammonium polyphosphate and its thermal stability and flame retardant properties

Abstract Rigid polyurethane foams (RPUFs) were prepared using biomass soybean oil-based polyol and ammonium polyphosphate (APP) as raw materials. The effects of APP on the thermal stability and combustion performance of soybean oil-based polyol-modified RPUFs were investigated by thermogravimetric analysis, pyrolysis kinetic analysis, limiting oxygen index (LOI) test, cone calorimetry (CONE), scanning electron microscopy (SEM), and smoke density (Ds). The results showed that the modified RPUF with 20 wt% APP (RPUF-S3-20) had the lowest mass loss, the highest integrated programmed decomposition temperature and the highest activation energy. In addition, RPUF-S3-20 had the lowest Ds (30.9), the highest light transmittance (61.4 %), the lowest heat release rate (602.7 kW/m2, 506.8 MJ/m2, and 847.3 kW/m2) and the total heat release (18.3 MJ/m2, 21.4 MJ/m2, and 31.4 MJ/m2), which showed that RPUF-S3-20 had good thermal stability and flame retardant performance. The current results can provide an effective reference for the preparation of environmentally friendly RPUF by bio-based modification.

Chicken feather protein for the thermal stability and combustion performance of rigid polyurethane foam

Abstract Rigid polyurethane foams (RPUFs) were synthesized with chicken feather protein using the “one-step method” of all-water foaming. Thermogravimetry, pyrolysis kinetics analysis, Cone calorimetry and smoke density (Ds) were used to investigate the effects of chicken feather protein on thermal stability and combustion performance of RPUFs. The results showed that the modified RPUFs with 2.5 wt% chicken feather protein (RPUF-CF1) had the lowest mass loss, the highest integrated program pyrolysis temperature, the highest activation energy, the lowest Ds (13.3), the highest light transmittance (79.3 %), the lowest heat release rate (22.0 kW/m2 and 30.6 kW/m2) and total heat release (2.4 MJ/m2 and 2.8 MJ/m2), which indicated that RPUF-CF1 had better thermal stability and combustion performance. The current research results provide a useful reference for the preparation of RPUFs with good thermal stability by bio-based modification.

Auto-ignition and knocking combustion characteristics of iso-octane-ammonia fuel blends in a rapid compression machine

Ammonia has attracted much attention because of its carbon-free nature. Ammonia also has a high research octane number (RON), making it a promising anti-knock additive for conventional engine fuels. In this study, to investigate the effects of ammonia addition on the knocking combustion of iso-octane, a series of spark ignition experiments were conducted in an optical rapid compression machine. And compression ignition experiments were also carried out to measure the ignition delay times. The molar fractions of ammonia in iso-octane-ammonia blends were set as 80% (A80), 40% (A40), and 0% (A0), and the initial thermodynamic conditions were 630–840 K and 8–25 bar. Chemical kinetics analysis of the end-gas was also performed with a blended reaction mechanism obtained by directly merging the LLNL iso-octane mechanism and the Glarborg ammonia mechanism. The experimental results showed that the ignition delay time increased with increasing ammonia fraction, but this trend could only be qualitatively predicted by the blended mechanism. At the same initial pressure and temperature conditions, the knock intensity (KI) decreased with increasing ammonia fraction, but the inhibitory effect was less pronounced at high initial temperature conditions. At the same initial energy density and high-temperature conditions, the KI of A40 and A80 was higher than A0, which was ascribed to the higher pressure requirement for the blended fuels with higher ammonia fractions to achieve the same energy density as those with lower ammonia fractions. At low temperature and pressure conditions, the auto-ignition showed a two-stage characteristic. With the increasing fraction of ammonia, the first-stage auto-ignition shifted from supersonic to subsonic, and the second-stage detonative auto-ignition gradually disappeared. The weakened auto-ignition with increasing ammonia fraction was attributed to the less reactive end-gas, as evidenced by the lower mole fraction of OH radical and lower heat release rate in the end-gas at the auto-ignition timing. When using the ε- ξ diagram to examine the auto-ignition mode, the experimental detonation cases were well distributed in the detonation peninsula, but the non-detonation and critical detonation cases were scattered irregularly.

Effects of Waste Cooking Oil Biodiesel on Performance, Combustion and Emission Characteristics of a Compression Ignition Engine

With their higher sustainability index, biofuels, environmentally-friendly and renewable nature is a viable alternative energy source in the transportation sector. This study presents the effect of waste cooking oil (WCO) biodiesel on performance, combustion, and emission from a compression ignition engine. The biodiesel was blended with diesel in varying proportions of 5% biodiesel and 95% diesel (designated as B5), 10% biodiesel in diesel (B10), 15% biodiesel in diesel (B15), 20% biodiesel in diesel (B20), 50% biodiesel in diesel (B50), and 85% biodiesel in diesel (B85). Simulation of a 2-cylinder diesel engine fueled with diesel, biodiesel blends and pure biodiesel was carried out using Ricardo Wave software and the results obtained were validated. The engine speed was varied from 1200 rpm to 3200 rpm at full load condition using a positive valve overlap of 32°. Performance results showed that WCO biodiesel blends at 1200 rpm produce brake-specific fuel consumption of, 0.240109 kg/kWhr, 0.241996 kg/kWhr, 0.244331 kg/kWhr, 0.24661 kg/kWhr, 0.26089 kg/kWhr, 0.27947 kg/kWhr and 0.28798 kg/kWhr for B5, B10, B15, B20, B50, B85 and B100 respectively, as compared to 0.239383 kg/kWhr of diesel fuel while the brake power and torque reduced at full load with varying speed. Combustion analysis showed similar trends between diesel and biodiesel blends whereas biodiesel blends produced shorter ignition delay, shorter combustion duration, and lower heat release rate. Emission levels of CO, reduced by 1%, 10%, 15%, 22%, 48%, 68% and 74% with B5, B10, B15, B20, B50, B85 and B100 respectively at 1600 rpm when compared to diesel fuel. HC emission was reduced by 9% with B100. NO&lt;sub&gt;x&lt;/sub&gt; levels slightly increased when B5, B10, B15, and B20 at 1200 rpm and B10 and B15 at 1600 rpm were fueled in the engine. The exhaust gas temperature (EGT) of B5, B10 at 1600 rpm was higher than diesel fuel and B5, B10 at 2400 rpm to 3200 rpm EGT was higher than diesel fuel. Generally, biodiesel blends showed better emission levels and other combustion and performance levels are within acceptable limits.

Seashell-Inspired Switchable Waterborne Coatings with Complete Biodegradability, Intrinsic Flame-Retardance, and High Transparency

Inspired by the "brick-and-mortar" structure and the whole lifecycle eco-friendliness of seashells, we have constructed a proof-of-concept and environmentally friendly coating with switchable aqueous processability, complete biodegradability, intrinsic flame retardance, and high transparency, via using natural biomass and montmorillonite (MMT). We first designed and synthesized cationic cellulose derivatives (CCD) as the macromolecular surfactants, which effectively exfoliated MMT to obtain nano-MMT/CCD aqueous dispersions. Subsequently, via a simple spray-coating process and a post-treatment process with a salt aqueous solution, the transparent, hydrophobic, and flame-retardant coating was fabricated with a "brick-and-mortar" structure. The resultant coating exhibited an extremely low peak heat release rate (PHRR) of only 17.3 W/g, which is 6.3% of cellulose PHRR. Moreover, it formed a lamellar and porous structure once ignited. Thus, this coating could effectively protect combustible materials from fire. In addition, the coating had a high transparency (>90%) in the range of 400-800 nm. After use, the water-resistant coating was converted into a water-soluble material by using a hydrophilic salt aqueous solution, which then could be easily removed by water. Furthermore, the CCD/nano-MMT coating was completely degradable and nontoxic. Such a switchable and multifunctional coating with whole lifecycle environmental-friendliness exhibits huge application potential.

Knock Mitigation and Power Enhancement of Hydrogen Spark-Ignition Engine through Ammonia Blending

Hydrogen and ammonia are primary carbon-free fuels that have massive production potential. In regard to their flame properties, these two fuels largely represent the two extremes among all fuels. The extremely fast flame speed of hydrogen can lead to an easy deflagration-to-detonation transition and cause detonation-type engine knock that limits the global equivalence ratio, and consequently the engine power. The very low flame speed and reactivity of ammonia can lead to a low heat release rate and cause difficulty in ignition and ammonia slip. Adding ammonia into hydrogen can effectively modulate flame speed and hence the heat release rate, which in turn mitigates engine knock and retains the zero-carbon nature of the system. However, a key issue that remains unclear is the blending ratio of NH3 that provides the desired heat release rate, emission level, and engine power. In the present work, a 3D computational combustion study is conducted to search for the optimal hydrogen/ammonia mixture that is knock-free and meanwhile allows sufficient power in a typical spark-ignition engine configuration. Parametric studies with varying global equivalence ratios and hydrogen/ammonia blends are conducted. The results show that with added ammonia, engine knock can be avoided, even under stoichiometric operating conditions. Due to the increased global equivalence ratio and added ammonia, the energy content of trapped charge as well as work output per cycle is increased. About 90% of the work output of a pure gasoline engine under the same conditions can be reached by hydrogen/ammonia blends. The work shows great potential of blended fuel or hydrogen/ammonia dual fuel in high-speed SI engines.