Faster Burning Rate Research Articles

Conductive chitosan/polyaniline hydrogel: A gas sensor for room-temperature electrochemical hydrogen sensing

Hydrogen (H2) has been deemed a source of energy for both stationary and mobile applications to contribute to lowering carbon emissions due to its abundance (which can be extracted from various compounds), environmental friendliness, and high energy density. However, H2 gas is highly flammable and has a fast burning rate. Consequently, the need to ensure human safety and environmental preservation necessitates the development of hydrogen sensors that exhibit heightened sensitivity, a reduced detection threshold, and quick response times. Herein, we present the synthesis of a ternary hydrogel composite, chitosan-crosslinked poly(acrylic acid)-based polyaniline hydrogel (Cs-cl-pAA/PANI), which was developed to function as a cathode material in hydrogen sensing applications. The structural and optical properties of ternary cathode materials were evaluated using various analytical techniques, and hydrogen sensing was studied using electrochemical techniques. The electrochemical sensing characteristics of the hydrogel matrix were improved by including polyaniline (PANI) as a result of the overlapping of localised π-electrons in the p-orbitals. The sensitivity of the Cs-cl-pAA/PANI hydrogel was determined to be 48.7845 μA M, with a reaction time of 0.6s, recovery time of 2s, and detection limit of 3.682 μM. The sensor also exhibited outstanding restoration and repeatability.

Virtual experiments about hydrogen explosions with linear propagation

The dangers associated with hydrogen mainly come from its wide flammability range, it’s extremely fast burning rate (having much more aggressive explosive properties than methane gas) and the considerable amount of energy released when it burns or explode. The development of new applications that use hydrogen as clean energy is constantly increasing, thus, hydrogen can be used on a large scale. This paper presents the use of computational fluid dynamics techniques, regarding the linear propagation of the explosion of air and hydrogen mixture in closed spaces, the main purpose being the determination of the overpressures to which a test stand of this processes is subjected.

Potential of Coffee and Cocoa Shell Waste as An Energy Source: Analysis of Characteristics of Briquettes From Coffee and Cocoa Shell Waste Through The Carbonization Process

This research aims to compare the characteristics of briquettes as an energy source produced from coffee shell waste and cocoa waste. The briquette-making process involves carbonization to produce charcoal as the primary raw material for briquettes. Carbonization time varies, influenced by the type of waste and size of the material. After that, the charcoal is reduced and sifted into fine and coarse powder. Briquette molding uses pressure using a pipe as a mold. The characteristics of briquettes are analyzed through water content, density, burning rate, and ash content. The research results show differences in characteristics between coffee and cocoa waste. The carbonization process affects the time and mass difference of raw materials. Cocoa pod shells require the longest (±35 minutes), while cocoa bean shells require the shortest (±17 minutes). Next, making briquettes involves molding and pressing using a pipe as a mold. The results showed that waste cocoa pod shells and cocoa bean shells produced more briquettes than waste coffee pod shells and coffee bean shells. The moisture content of briquettes from all types of waste meets the standards, but the density of the raw material for coffee husk waste is low, while the briquettes have a high density. The burning rate of briquettes varies, with cocoa bean shell briquettes having the fastest burning rate and producing much smoke. The ash content of cocoa pod husk briquettes exceeds the standard, while cocoa bean husk briquettes have low ash content. The density of the raw material is correlated with the moisture content of the briquettes. The highest burning rate occurs in cocoa bean shell briquettes, influenced by low density and high water content. The ash content of the briquettes meets standards, except for cocoa shell briquettes. This research proves that cocoa and coffee shell waste can be processed into briquettes with different characteristics.

Large Eddy Simulation of Hydrogen/Natural Gas/Air Premixed Swirling Flames and CIVB Flashback Risks

The desire to develop gas turbines (GTs) that can utilise natural gas (NG) blended with hydrogen (H2) often encounters operability challenges related to combustion-induced vortex breakdown (CIVB) flashback issues. Hence, a detailed Large Eddy Simulation (LES) was employed in this study to examine the impact of H2-NG co-firing on central recirculation zones (CRZs), combustion properties, and the risk of CIVB flashback in a pilot-scale swirl burner facility. The LES model successfully replicated the swirling component of the flame observed in the experiment with reasonable accuracy. The findings revealed that the introduction of H2 into the burner increased the velocity and temperature of the burned gases. The higher reactivity of H2 resulted in faster burning rates and a shift in the reaction zone, indicating that NG-H2 firing burns more rapidly than pure NG firing. Additionally, H2 was found to enhance the velocity gradient, pushing the CRZ upstream. Changes in the location of the CRZ can disrupt density and velocity gradients, affecting the generation of vorticity by the baroclinic torque and potentially increasing negative axial velocity, thereby increasing the risk of CIVB flashback. Further research is necessary to comprehensively assess the CIVB flashback risk, particularly when the proportion of H2 exceeds 30 %.

The Influence of Different Ratio of Goat Dung and Lontar Shells (Borassus Flabellifer Linn) Charcoal on the Biochar Briquettes Properties

Research goals was to determine the physico-chemical and burning propersties of biochar briquettes with different ratios between goat dung and lontar shell charcoal. Material used were goat dung, lontar shell, tapioca as binder and water. The equipment were kiln drum (pyrolysis drum), grinding machine, hydraulic pressor, briquette stove, infrared digital thermometer, digital hanging scales, digital sitting scales. Variables measured were density, moisture, ash, volatile matter, fixed carbon, calorific value, burning rate and burning resistance. Analysis of variance was applied to determine the influence of treatment on the variables measured. Result of analysis showed that treatment had a very significant (P<.01) on moisture, ash, volatile matter, fixed carbon, calorific value, burning rate and burning resistance, but no significant (P>.05) on density of biochar briquettes. More proportion of goat dung charcoal generated the biochar briquettes with properties more ash content, lower fixed carbon, higher volatile matter, reduced calorific value, faster burning rate, shorter burning resistance. It can be concluded that the physico-chemical and burning properties of the biochar briquettes generated in this study did not meet the standards according to SNI 01-6235-2000. In this case, however, the best ratio is 25% of goat dung charcoal and 75% of lontar shell charcoal.

Influence of injection strategies on ignition patterns of RCCI combustion engine fuelled with hydrogen enriched natural gas

The depletion of fossil fuel and the concerns for harmful emissions and global warming has instigated researchers to use alternative fuels. Hydrogen (H2) and natural gas (NG) are attractive fuels for internal combustion engines. The dual-fuel combustion strategy is promising to reduce emissions with efficient engine operation. The concern for using NG in this strategy is the lower efficiency at low load conditions and the emission of exhaust gases like carbon monoxide and unburnt hydrocarbon. Mixing fuel with a wide flammability limit and a faster burning rate with NG is an effective method to compensate for the limitations of using NG alone. Hydrogen (H2) is the best fuel added with NG to cover NG limitations. This study investigates the in-cylinder combustion phenomenon of reactivity-controlled compression ignition (RCCI) engines using hydrogen-added NG as a low-reactive fuel (H2 addition to NG on a 5% energy basis) and diesel as a highly reactive fuel. The numerical study was done on a 2.44 L heavy-duty engine using CONVERGE CFD code. Three low, mid, and high load conditions were analyzed in six stages by varying the diesel injection timing from −11 to −21 O after top dead centre (ATDC). The H2 addition to NG had shown deficient harmful emissions generation like carbon monoxide (CO) and unburnt hydrocarbon with marginal NOx generation. At low load conditions, the maximum imep was achieved at the advanced injection timing of −21OATDC, but with the increase in load, the optimum timing was retarded. The diesel injection timing varied the optimum performance of the engine for these three load conditions.

Optical Study on Spark Plug Gap in Extending Methane Lean Combustion Limits under High Ignition Energy Conditions

<div>Lean combustion has the potential to achieve high thermal efficiency for internal combustion engines. However, natural gas (NG) engines often suffer from slow burning rates and large cyclic variations when adopting lean combustion. In this study, the effects of spark plug gaps (SPGs) on methane lean combustion are optically investigated under high ignition energy conditions. Synchronization measurements of in-cylinder pressure and high-speed photography are performed for combustion analysis. The results show that large SPGs with high ignition energy exhibit great improvement in engine combustion stability and power capability. Under ultra-lean conditions, a large SPG with a high ignition energy of 150–200 mJ can extend the lean limit to 1.55. Combustion images indicate that this is contributed by the enlarged initial flame kernel, which promotes early flame propagation. Besides, an empirical criterion is adopted to quantify the underlying mechanism, and the results confirm that a more stable early flame development with a faster burning rate can be obtained by a larger SPG and higher ignition energy under lean conditions. Therefore, a large SPG is an effective way to improve combustion stability and thermal efficiency for NG engines.</div>

Laser ignition of solid propellants using energetic nAl-PVDF optical sensitizers

Laser ignition of propellants could provide better control of the ignition process and improve safety. However, sustained laser ignition of solid propellants is often challenging in practice due to a lack of optical absorptivity at convenient wavelengths. Common optical additives, i.e., opacifiers, improve the absorption characteristics but are typically inert and fail to contribute to the reactivity of the propellant. In this work, ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellants are optically sensitized by adding reactive nano-aluminum (nAl)/polyvinylidene fluoride (PVDF) particles (ranging from 600 to 1000 µm). These propellants are compared with neat (no additive) AP/HTPB, and other AP/HTPB propellants with carbon black or nano-aluminum (nAl) additives. The nAl/PVDF additives enable sustained ignition with relatively low laser energy levels (< 5 J/cm2) at common wavelengths (1064 nm). Only the propellant with added nAl/PVDF exhibited sustained ignition. The ignition delays of the nAl/PVDF propellant ranged from 2 to 5 ms, depending on the energy density of the laser. We propose that the sustained ignition in nAl/PVDF propellants is due to the lower critical energy needed for nAl/PVDF composites (estimated 0.5 J/cm2 compared to 15 J/cm2 needed for AP/HTPB based propellant). The propellant's calculated critical energy is similar to the reported values of nAl/PVDF composites. The nAl/PVDF based propellant has a faster burning rate and increased pressure dependence due to the PVDF's gas generation and rapid burning of aluminum particles near the surface. Potential applications for this propellant, such as flash ignition and subsurface ignition, are also explored.

Combustion Behavior and Microstructure of TC17 Titanium Alloy under Oxygen-Enriched Atmosphere

TC17 titanium alloy is widely used in the aerospace industry, but its combustion behavior and microstructure after combustion are rarely investigated. Herein, the ignition critical oxygen pressure, combustion velocity, and microstructure after the combustion of TC17 titanium alloy were investigated by promoted ignition combustion tests under an oxygen-enriched environment. The results indicated that there were three stages, ignition, splash, and flame propagation, for the combustion process of the TC17 alloy. As compared to TC11 titanium alloy, the TC17 titanium alloy exhibited a similar ignition critical oxygen pressure with the same size, but an obviously faster burning rate, which followed a power law relationship with the oxygen pressure. The segregation of Cr, Mo, and Al was observed in the interdendritic phase of the melting zone and the interface between the melting zone and the heat-affected zone. The segregation of Cr at the liquid/solid interface can be responsible for accelerating the burning kinetic of the TC17 alloy by decreasing the interfacial temperature.

Enhancing the combustion and propulsion performance of Al/CuO via introducing AlH3 as fuel substitute

The research on nanothermites mainly focuses on formulation and structural modification, performance optimization and application research. Whereas, the few gaseous products of nanothermites limit the practical applications, especially in microthrusters. Here, various contents of AlH3 was introduced in typical nanothermites (Al/CuO) to replace Al as fuel. The characteristics of Al/AlH3/CuO were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The ignition and combustion performance such as burning rate, unconstrained combustion, ignition temperature and delay time, pressurization and propulsion properties was investigated. Results revealed that when AlH3 content was 20%, Al/AlH3/CuO had the fastest burning rate (189 m/s), the lowest ignition temperature (441.4 °C), the shortest ignition delay time (5.32 ms), the maximum Pmax (1141.3 kPa), the highest pressurization rate (75.06 kPa/μs) and the maximum microthrust (1.61 N). In short, replacing Al with AlH3 in the Al/CuO provides an innovation for creating nanothermites with completely new metal fuels, and also enhances the combustion and propulsion performance.

Combustion model for thermite materials integrating explicit and coupled treatment of condensed and gas phase kinetics

Nanothermites are interesting energetic systems as their combustion driven by the oxidation of the metallic fuel associated with the reduction of the oxidizer, can produce extremely fast burning rates exceeding hundreds of m s−1. In addition, by changing the reactant (composition, stoichiometry) geometry and compaction conditions, the control of the burning rate can be achieved, allowing the designer to customize the chemical energy for each application. To date, only rough combustion models exist, most restricting the combustion mechanisms to only condensed phase processes, thus providing an approximative prediction of structure-combustion performance relationships. This work presents a tri-phasic model for the combustion of Al/CuO powder considering 9 gaseous species (Al, Cu, O2, O, Al2O, Al2O2, AlO, AlO2, N2) and 4 condensed species (Al, Cu, CuO, Al2O3) that can be liquid or solid. The reactionnal scheme involves 12 heterogeneous reactions and 2 phase changes based on diffusional kinetics, while gaseous reactions are considered through a chemical equilibrium. A detailed description of the theoretical formulation and numerical method is presented, followed by a discussion of a closed-bomb simulation. This work highlights the great impact of the Al particles initial diameter on the pressure development in the chamber. After the initiation stage, the decomposition of CuO releases gaseous O2, which is spontaneously absorbed on the surface of submicronic Al particles and diffuses through alumina to react with pure Al. At high temperature, gaseous copper, aluminum sub-oxides and aluminum condense on both particle types. By contrast, Al particle micron-size limits the quantity of O2 absorption and gaseous species surface condensation, leading to the formation of a pressure pre-peak 4 times higher than the final chamber pressure.

Bio‐modified pyrotechnic composite materials for firefighting application

SummaryThe traditional aerosol‐forming composites are a mixture of potassium nitrate/chlorate and synthetic resins like phenol‐formaldehyde, melamine‐formaldehyde, polyurethane, and epoxy resin. Though these synthetic organic resins have excellent adhesion and mechanical properties, their high flammability and associated life‐threatening occupational hazard have limited their application. Such compositions' combustion flame may reach up to 2100°C and cause secondary fire risk in an explosive atmosphere, especially ship engine rooms and oil‐producing platforms. This study aimed to investigate the ability of natural flame‐retardant tannic acid, which is a natural phenolic compound abundant in many plants, to reduce the exothermicity of potassium nitrate/chlorate‐based pyrotechnic composite. In the present work, we newly developed a pyrotechnic composition that employed tannic acid as a reducer instead of synthetic resin. Its combustion behaviour, thermal properties, and fire extinguishing performance were comparatively evaluated against phenolic resin‐based traditional pyrotechnic composition. Though both the new and traditional pyrotechnic composition has shown similar fire extinguishing efficacy, the newly developed composition showed 57% lower combustion flame temperature, faster burn rate, and lower calorific value than the traditional composition. The physical and chemical characteristics of the discharged aerosol were characterized by a series of techniques viz; high‐resolution X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive X‐ray analysis to understand the fire extinguishing mechanism.

Disproportionate collapse of steel-framed gravity buildings under travelling fires

Observations from realistic fires have revealed that a fire tends to “travel” across the floors rather than burning simultaneously for the duration. However, the collapse mechanism and mitigation measures of structures under travelling fires are still not well understood. This paper investigates the disproportionate collapse behaviour of three-dimensional steel-framed gravity buildings subjected to travelling fires. The effect of fire curves (burning rate) and fire spreading speeds on the collapse behaviour is first studied. The effectiveness of using fire protections and bracing systems in preventing collapse is examined. It is found that the duration of the heating phase has a great effect on whether a building collapses or not, and the building may collapse during the cooling phase. A “long-cool” fire curve (slow burnig rate) is more dangerous than mild (average burning rate) and “short-hot” fire curves (fast burning rate) since the former causes a higher temperature in the structure. The fire travelling speed significantly affects the failure sequence of columns, range of damage and collapse mode of structures. For the structure analysed, a slow travelling fire (e.g. 2.5 mm/s) may lead to a partial collapse mode confined around the fire-affected region, but a global collapse in a wider range may occur in a fast travelling fire (e.g. 10 mm/s). A higher level of fire protection may prevent the collapse of structures, but may also lead to collapse in the cooling phase due to the delayed increment of temperatures in the heated members. The collapse time of a protected structure under a travelling fire is longer than the fire-resistance rating of its components (up to 130 min). Application of bracing systems (horizontal, vertical or combined) can prevent collapse of structures under a slow travelling fire, but not for a fast travelling fire. It is recommended to consider the possible fire scenarios when determining the fire-resistance rating, and increase the fire-resistance rating of components to 3 h to prevent collapse under a travelling fire with a “long-cool” fire curve. The beam-to-column connections should possess a sufficient tension and compression resistance, which may be equal to 100% and 50% of the yielding capacity of beams, respectively.

A Benchmark Study of Burning Rate of Selected Thermites through an Original Gasless Theoretical Model

This paper describes a kinetic model dedicated to thermite nanopowder combustion, in which core equations are based on condensed phase mechanisms only. We explore all combinations of fuels/oxidizers, namely Al, Zr, B/CuO, Fe2O3, WO3, and Pb3O4, with 60 % of the theoretical maximum density packing, at which condensed phase mechanisms govern the reaction. Aluminothermites offer the best performances, with initiation delays in the range of a few tens of microseconds, and faster burn rates (60 cm s−1 for CuO). B and Zr based thermites are primarily limited by diffusion characteristics in their oxides that are more stringent than the common Al2O3 barrier layer. Combination of a poor thermal conductivity and efficient oxygen diffusion towards the fuel allows rapid initiation, while thermal conductivity is essential to increase the burn rate, as evidenced from iron oxide giving the fastest burn rates of all B- and Zr-based thermites (16 and 32 cm·s−1, respectively) despite poor mass transport properties in the condensed phase; almost at the level of Al/CuO (41 versus 61 cm·s−1). Finally, formulations of the effective thermal conduction coefficient are provided, from pure bulk, to nanoparticular structured material, giving light to the effects of the microstructure and its size distribution on thermite performances.

Effects of high ignition energy on lean combustion characteristics of natural gas using an optical engine with a high compression ratio

Natural gas engines often suffer from slow-burning rate and large cyclic variations, which significantly affects engine performance and thermal efficiency. In this study, using an optical spark-ignition engine with a high compression ratio, the role of high ignition energy in lean combustion characteristics of natural gas was investigated. Synchronization measurement of in-cylinder pressure and visualization images were performed to analyze the correlations of engine performance and combustion characteristics. The results show that elevating ignition energy can improve combustion instability and thermal efficiency, manifesting more concentrated heat release and greater influences on the combustion duration from 10% to 50% in burned mass fraction than that of 50%–90% range. The combustion visualizations show that ignition energy mainly affects initial flame kernel formation and early flame development, and improved flame speed and combustion instability can be observed even when excess air coefficient reaches 1.4 at sufficiently high ignition energy. Furthermore, an empirical criterion based on burned mass fraction and combustion visualizations was adopted to quantify early flame development. The shortage of ignition delay time and the acceleration of initial flame propagation are observed with the increases of ignition energy, which leads to lower cyclic variations and a faster burning rate at the early combustion stage.

The auto-ignition behaviors of HMX/NC/NG stimulated by heating in a rapid compression machine

In this work, we have for the first time, applied a rapid compression machine (RCM) to generate initial uniformly high temperature environment to investigate the auto-ignition behaviors of solid energetic material (HMX/NC/NG). Pressure evolution recording and high speed visualization were synchronized to reveal the response of energetic material to thermal stimulus in a time scale of the order of 100 ms. Results show that at sufficiently high end of compression (EOC) pressure and temperature, auto-ignition of solid energetic material is observed after certain period of induction time upon EOC. The ignition delay time defined by the first flame spot observation from high speed imaging (IDTI) is smaller than defined by the maximum pressure rise rate instant (IDTP). However, both IDTI and IDTP decrease with the increase of EOC pressure and temperature. In addition, the burning duration also decreases, indicating a faster burning rate. By tuning the EOC pressure and temperature, the critical thermodynamic condition that separates the auto-ignition region and the non-ignition regime is obtained. The present method of thermal stimulus generation is believed to provide a new approach for evaluating the thermal stability of energetic materials, beyond the literature on cook-off test approaches.

Preparation of charcoal briquette from palm kernel shells: case study in Ghana

In Ghana, the potential of palm kernel shells as renewable energy in charcoal production has not been exploited adequately. Using a low-cost instrument (kiln and compressor box) built from local resources, we produced charcoal briquette from palm kernel (Elaeis guineensis) shells. Further, we measured and compared its efficiency using starch as a binder to traditional charcoal and commonly used fuelwood (Acacia) in Cape Coast. Following the American Standards for Testing and Materials (ASTM), the proximate analysis was conducted for all fuels with results indicating that palm kernel shell (PKS) briquette produced had a moisture content of 1.08 %, as compared to 9.25 % in charcoal and 16.00 % in fuelwood. The volatile matter, ash content and fixed carbon recorded were 71.80 %, 0.06 %, and 27.07 % in PKS briquette, 86.00 %, 0.78 %, and 3.97 % in charcoal and 80.50 %, 2.04 %, 1.46 % in fuelwood respectively. The calorific values for charred PKS increased after binding to form the PKS briquette with the highest value among the other fuels. The calorific value for the other fuels were 17.5 MJ/kg for charcoal, 18.72 MJ/kg for charred PKS, and 18.72 MJ/kg for PKS briquette. We also conducted an ignition test, combustion test, fuel burning rate (FBR), and specific fuel consumption (SFC) on PKS briquette and charcoal to determine their suitability as cooking fuels. Charcoal readily ignited as compared to PKS briquette with respective fuel mass of 5.08 g and 25.5 g. The resultant briquette possesses desirable combustion characteristics such as no smoke emissions and ash formation. The FBR and SFC in PKS briquette recorded the highest in comparison with charcoal. The values recorded were 2.84 g/min and 20.05 g/ml respectively while that of charcoal was 0.42 g/min and 3.48 g/ml respectively. PKS briquette produced from this study showed high calorific value, low moisture content, and a fast burning rate amongst other excellent properties. These properties are potential indicators that the proper utilization and production of PKS briquette as renewable energy in Ghana would contribute to solving the existing energy crisis. Additionally, reduce climate change impacts, via the reduction in the over-dependence on fuelwood and charcoal for domestic and commercial heating.

Investigation on performance and combustion of compression ignition aviation piston engine burning biodiesel and diesel

Purpose This study aims to contrastively investigate the effects of biodiesel and diesel on the power, economy and combustion characteristics of a compression ignition aviation piston engine for unmanned aerial vehicles. Design/methodology/approach Biodiesel used as alternative fuel will not be mixed with diesel during experimental study. Pure diesel fuel is used for the comparative test. Same fuel injection strategies, including pilot and main injection, are guaranteed for two fuels in same test points. Findings The engine-rated power of biodiesel is lower than diesel, which results in higher specific fuel combustion (SFC) and effective thermal efficiency (ETE). Biodiesel has the faster burning rate, shorter combustion duration. The crank angle of 50% mass fraction burned (CA50) is earlier than diesel. The ignition delay angle of biodiesel and diesel in the pilot injection stage is almost the same at high engine speed. As the speed and load decrease, the ignition delay angle of biodiesel in the pilot injection stage is smaller than diesel. At 100% high load conditions, the fuel-burning fraction of biodiesel in the pilot injection is the same as diesel. The peak heat release rate (HRR) of biodiesel is slightly lower than diesel. At 20% part load conditions, the fuel-burning fraction of biodiesel in the pilot injection stage is lower than diesel. Because of the combustion participation of unburned pilot injected fuel, the peak HRR of biodiesel in the main injection is equal to or even higher than diesel. Originality/value The application feasibility of alternative fuel and its effects on aviation engine power, economy and combustion characteristics will be evaluated according to the “drop-in“ requirements and on the low-cost premise without changing the aviation engine structure and parameters.

The role of alkali metal and alkaline metal earth in natural zeolite on combustion of Albizia Falcataria sawdust

The combustion process of Albizia falcataria (AF) sawdust with the addition of natural zeolite (NZ) was observed experimentally using PT 1600 LINSEIS Simultaneous thermal analyzer (STA). The results showed that alkali metal and alkaline metal earth in NZ play an essential role in the process of decomposing the Hemicellulose AF molecule. The results of the molecular analysis show that the chemical balance of the mixture determines the combustion temperature. Excess NZ becomes a thermal burden which slows down the combustion reaction because heat does not sufficiently activate alkali metal and alkaline metal earth in NZ. In a small amount, NZ is less involved in the AF decomposition process. It shows that a mixture of AF and NZ can increase combustion kinetic in the right mix. Addition of 15–20% of NZ decreases the ignition temperature within faster burning rate. Activated alkali metal and alkaline metal earth decompose hemicellulose faster so that they burn completely in minimizing pollutant and maximizing LHV. Greater NZ completes the decomposition much earlier so that at the resting time of the process NZ slightly absorbs heat sinking LHV. The drastic reduction of Ca due to NZ make the fuel is suitable for boiler because Ca is responsible for agglomeration and corrosion.

A comparative study on the combustion and emissions of dual-fuel engine fueled with natural gas/methanol, natural gas/ethanol, and natural gas/n-butanol

• Primary alcohol fuels support faster flame development and flame propagation. • Primary alcohol fuels reduce total hydrocarbon and nitrogen oxide emissions. • Methanol has advantages over ethanol and n-butanol in increasing η et . • Adding methanol produces smaller regulated emissions than ethanol and n-butanol. The effects of the addition of primary alcohol fuels (methanol, ethanol, and n-butanol) on the combustion characteristics and performance of natural gas engines are examined by experimentation with a dual-fuel test engine, followed by a comparative analysis of the test results. The test engine was operated under a light load, at a fixed speed of 1600 rpm, and with a brake mean effective pressure of 0.387 MPa. The air-fuel ratio was held constant at the stoichiometric equivalent ratio. The engine performance was analyzed for different natural gas/alcohol fuel mixtures by using four alcohol fuel energy substitute ratios (AESRs): 0% (pure natural gas), 19%, 44%, and 60%. The experimental results indicate that faster burning rates can be obtained by mixing any of the three alcohol fuels with natural gas, compared with pure natural gas. Further, by increasing the AESR, faster flame development and flame propagation times can be obtained, and the crank angle when 50% of the mass is burned approaches the top dead center position. These outcomes lead to an advance in combustion phasing. The addition of primary alcohol fuels in the dual-fuel mode can also reduce total hydrocarbon and nitrogen oxide emissions. Moreover, the brake thermal efficiency of natural gas can be improved significantly by adding methanol, whereas negligible improvements in this aspect are obtained by adding ethanol and n-butanol. The comparative analysis indicates that methanol addition has advantages over ethanol and n-butanol additions in increasing the brake thermal efficiency and reducing the regulated emissions of natural gas engines.