Combustion Process Research Articles

Thermokinetic study of tannery sludge using combustion and pyrolysis process through non-isothermal thermogravimetric analysis

Sludge from the tannery is produced in enormous amount. This work has investigated the thermal analysis behaviour of the tannery sludge by use of the thermogravimetric analysis (TGA). The TGA experiments is carried out in both air and nitrogen environment at the varied heating rates of 5, 10, 20 and 40 °C/min from the temperature range of 30–900 °C. In the assessment of kinetic parameters, the model fitting (Combined kinetics) method was employed. It was investigated that thermal degradation of the tannery sludge sample occurred in three stages. Majorly the conversions were observed in stage II for both in air and nitrogen environment. The activation energy (Ea) value for the combustion is 165.9 kJ/mol while for the pyrolysis the Ea value is obtained as 65.2 kJ/mol from the conversion range between 0.2 and 0.8 which is a promising approximation supported by a strong R2 value of 0.9719 and 0.93 for combustion and pyrolysis respectively. It is estimated from the master plots that six ideal models A1/2, A1/3, A1/4, F3, F4 and D5 were probably in approximation with the linear fitted data for both air and nitrogen. Various thermodynamic parameters which include the ΔH, ΔG and ΔS are also complimented that indicates the formation of activated complex and non-spontaneity of the reaction. The detailed thermokinetic study of the tannery sludge in combustion and pyrolysis offers a novel approach to understanding how this waste material decomposes under different temperature conditions. This holistic perspective contributes valuable insights into waste management practices, environmental impacts, resource recovery, and process optimization within the leather industry. Furthermore, the optimization of leather production processes on a large scale can minimize waste generation and enhance energy efficiency, strengthening the competitiveness and sustainability of the leather industry.

Experimental study on the discharge characteristics of high-voltage nanosecond pulsed discharges and its effect on the ignition and combustion processes

Non-equilibrium plasma has been proven to expand ignition limits and enhance combustion. This paper uses high-voltage nanosecond pulsed discharge (NPD) to generate non-equilibrium plasma and experimentally studies the discharge characteristics at different parameters in a constant-volume combustion bomb. NPD is used to ignite the methane-air mixture, and the effects of pulse power output voltage and pulse interval (PI) on ignition and combustion processes are studied. In addition, the minimum ignition energy (MIE) at different ignition methods (Transistor coil ignition (TCI) and NPD) is also studied. The results show that the first pulse of NPD discharge has a higher breakdown voltage and discharge energy when using multi-pulse discharge. After the second pulse, the highest breakdown voltage and current tend to stabilize, and the discharge energy remains unchanged. As the PI increases, the breakdown peak voltage and the peak current increase slightly. The study on the MIE of NPD shows that at different mixture concentrations, the MIE of NPD is smaller than that of TCI, and NPD can expand the lean burn limit. An increase in initial temperature can significantly reduce MIE. In addition, when the discharge energy is near the MIE, the combustion stability begins to decrease, and the combustion cycle fluctuates wildly. When the ignition energy is increased, the stability improves, and the combustion fluctuation rate can be maintained within 5%.

Municipal Solid Waste Management and Health Risks: Application of Solid Waste Safety Plan in Novi Sad, Serbia

Inadequate solid waste management (SWM) can cause environmental contamination and health risks. Minimizing the health risks from SWM practices requires the identification of linkages between potential sources of exposure, environmental transport pathways, and adverse health outcomes. A safety planning approach can represent an innovative tool for reducing such risks. In previous research, we introduced the solid waste safety plan (SWSP) concept, only focusing on the health risk ranking assessment matrix. Here, we demonstrate the application of the SWSP framework in a case study of the municipal landfill of Novi Sad, Serbia. We identify potential hazards and assessed the likelihood and severity for them, using a combination of quantitative and semi-quantitative approaches to estimate risk levels for each identified hazard. Hazards deemed high and very high risks for the community and workers include groundwater contamination from leachate, airborne contaminants from combustion and non-combustion processes, and worker injuries associated with waste combustion. Control measures for each are identified, together with a corresponding cost analysis. Adding a final top cover to the landfill and introducing a collection, transport, and treatment system for the biogas would address hazards presenting high health risks but are also among the highest costs. While we demonstrate the approach and utility of an SWSP in a research context, future work is needed to assess the use of the SWSP by local communities or SWM utilities.

Experimental study on knock suppression by direct water injection and direct ammonia-water injection based on low-flow injector under high load

Under the appropriate injection strategies, both direct water injection and direct ammonia-water injection can effectively suppress the knock, but the effect of the knock suppression is slightly different. In this paper, water and ammonia-water were respectively injected directly into the cylinder of a high performance port gasoline injection engine by modified low-flow direct injectors. The effects of direct injection timing and injection ratio on knock, combustion and emission were investigated. Both water and ammonia-water can effectively suppress knock in SI mode. Compared to water, ammonia-water exhibits a more prominent inhibitory effect on knock at lower DI ratios. However, when the ratio was further increased, the difference between the effects of ammonia-water and water on the inhibition of knockdown became less pronounced. Water and ammonia-water DI affect the knock through different mechanisms due to their unique chemical properties. While water predominantly influences the later combustion phases due to its rapid vaporization and high specific heat capacity. Ammonia-water primarily impacts the early combustion phase because of its complex combustion process and lower laminar flame speed.

Enhancement of aluminum powder reaction behavior at high temperatures—Aluminum powders with “sea urchin structure” coated by AP

To solve the problem of high ignition temperature of aluminum powder and easy to burn into blocks at high temperatures, “sea-urchin-structured” aluminum powders (μAl@nAl) obtained by electro-explosion were coated by ammonium perchlorate (AP) on its surface. AP in a high-temperature environment has a rapid decomposition, then the gas production will promote the dispersion of aluminum powder into micro-clusters, thus preventing the aluminum powder agglomeration during the combustion process. The micro-nano composite aluminum powder (μAl@8 %nAl) and physical mixed aluminum powder (μAl + 8 %nAl) coated by AP were completed by solvent volatilization method. The coating surface was observed by scanning electron microscopy. The heat of combustion and pressure curves for different AP contents were tested using a chamber with a constant volume, and the ignition and combustion performance of the AP samples were investigated using a carbon dioxide (CO2) laser ignition device. The AP samples shortened the ignition delay time and improved the combustion performance in the fixed-volume combustion and laser ignition tests. Under atmospheric air, taking into account the theoretical calorific value, pressure curve, and combustion performance, the optimal AP content is 10 %. The thermal decomposition process of two samples was further analyzed using the thermogravimetric and differential scanning calorimetry (TG-DSC) method. The decomposition of AP advanced the first oxidation peak of aluminum powder; however, in the second step oxidation peak, the peak temperature of μAl@8 %nAl@10 %AP sample was delayed compared to μAl + 8 %nAl@10 %AP sample. High-voltage electrical explosions and high-energy laser-induced air shock waves were created to simulate the high-temperature environment of the detonation reaction zone, and pictures of the reaction process and pressure change curves of the “sea urchin structure” aluminum powder coated by AP at high temperatures were recorded. The results showed that the “sea urchin structure” aluminum powder coated by AP exhibited better combustion performance, and the reaction degree of the aluminum powder had been deepened.

Synthesis of ZnO and NiO nano ceramics composite high-performance supercapacitor and its catalytic capabilities

NiO and ZnO mixed nanocomposites were manufactured using the solution combustion process. As-prepared samples were analyzed using XRD. The XRD shows an average crystallite size of 35–40 nm. The elemental composition determined by EDS indicates a nearly equal proportion of Ni and Zn, with an atomic ratio of Ni/Zn = 0.96. The specific capacitances of NiO is 295.5 Fg-1, ZnO is 117.3 Fg-1 and ZnO/NiO nanocomposites is 561.75 Fg-1 which are more than NiO and ZnO alone. This study shows that constructing binary oxide nanocomposites is an approach for developing high-performance supercapacitor electrode materials. Experimental observations on catalytic activity revealed that NiO/ZnO increased catalytic activity. Furthermore, adding NiO to ZnO in the composite increased the overall amount of oxygen vacancies in the samples. Our research lays the door for a simple, inexpensive, nontoxic, and quick technique to synthesize binary transition metal oxide-based electrode materials for high-performance supercapacitors.

Impact of mixing low-reactivity gases on the mechanism of hydrogen spontaneous combustion: A ReaxFF MD study

The phenomenon of spontaneous combustion during the release of high-pressure H2 is critical to the safe storage and transportation. Besides physical methods to suppress self-ignition, the approach of mixing low-reactivity gases has gained increasing attention. Previous work has mainly focused on the flow, physical heating effects, and boundary conditions of self-ignition in mixed gases, while the intrinsic chemical reaction mechanisms of spontaneous combustion remain underexplored. To clear this issue, this work uses the ReaxFF MD simulation method to study the spontaneous combustion process of H2/CO and H2/CH4 mixtures with various concentrations. The results indicate that: (1) in pure H2, H2/CO, and H2/CH4 systems, the primary initial reaction mechanism is H2+O2HO2+H. Additionally, in some mixed systems, CO + O2CO2+O and CH4+O2CH3+HO2 may also serve as initial reaction mechanisms. (2) Under fuel-lean combustion conditions, the RIDTs of the systems decrease, supporting the viewpoint that self-ignition typically occurs first in fuel-lean regions. The addition of CO and CH4 increases the RIDTs, which helps inhibit the development of self-ignition. (3) In H2-rich environments, CO combusts to CO2 through the formation of HOCO, while CH4 undergoes dehydrogenation and oxidation processes through intermediates such as CH3, CH3O, and HCHO, leading to the formation of CO and CO2. The combustion of H2 is also influenced by these processes. (4) The addition of CO and CH4 increases the activation energy of H2 combustion, raising the reaction energy barrier that must be overcome for spontaneous combustion. This effectively helps to suppress the occurrence and development of self-ignition during the release of high-pressure gases.

Hydrogen combustion analysis via infrared and visible optical diagnostics combined with CFD in a dual fuel engine at low load

Dual Fuel (DF) combustion concept has demonstrated to be a valid solution to ensure the utilization of diesel engines in heavy duty and naval applications. The substitution of part of diesel fuel with a cleaner gaseous one can reduce among others: carbon dioxides (CO2), nitrogen oxides (NOx) and surely particulate matter (PM). Nevertheless, the difficulties encountered by the reduced pilot liquid jet to reach out the furthest areas of the combustion chamber, especially at partial load, lead to unburned emissions of the premixed charge. They can be a serious issue to overcome when the premixed fuel is represented by a carbonaceous fuel like natural gas (NG). For this reason, hydrogen, that is carbon-free, represents the new progression to clean mobility. This work aims at deepening the in-cylinder phenomena through a synergetic methodology that involves experimental optical diagnostics and 3D numerical investigations. The experimental activity is carried out on a single cylinder research engine (SCRE) equipped with an optical apparatus allowing the visualization of the combustion process, later processed via high speed visible (VIS) and infrared (IR) imaging. Several filters applied on the IR camera permit to detect specific species such as CO2. Subsequently, these outcomes are used to validate numerical models, and in turn, the numerical results help to validate the species detected qualitatively via optical diagnostics and to identify which ones majorly affect the physical and chemical processes. Numerical simulations are performed with ANSYS Forte ® code on a geometry which accurately reproduces the shape of the combustion chamber. Combustion models include a turbulent-kinetic interaction model with a mechanism of 124 species and 660 reactions to deal with the autoignition phase and diesel surrogate oxidation, while to account for the flame propagation through the premixed charge the G-equation is considered. The reference test cases are characterized by two different engine speeds, 1500 and 2000 rpm, and a low load level, corresponding to 2 bar of brake mean effective pressure (BMEP) on light-duty vehicle. The hydrogen energy shares are between 83.2 and 81.8%. Results demonstrate that IR images and OH radical are key for the detection of ignition process of both diesel and hydrogen. The flame propagation in the air/H2 charge can be observed with the help of CFD elaborations. Finally, emission levels are adequately predicted by the chosen oxidation models.

The Impact of Catastrophic Forest Fires of 2021 on the Light Soils in Central Yakutia

This paper presents the results of studying changes in the main parameters and properties of soils in larch and pine forests growing on sandy soils of the Lena-Vilyui interfluve of Central Yakutia, where catastrophic forest fires occurred in 2021. According to the remote monitoring information system of Rosleskhoz, in 2021, almost 8.5 million hectares of forests burned in Yakutia, which is considered as one of the largest forest fires in Russia and in the world in that year. After the fire passes through the forest floor, the content of organic matter decreases as a result of combustion processes. The acidity of the soil changes towards its alkalization due to the entry of combustion products. Changes in soil profiles occur; turbation processes begin more intensively, which in turn change the natural distribution of soil indicator values such as the organic carbon content, the pH, and the number of exchangeable bases. Due to the sharp increase in heat supply after a fire, the depth of seasonal thawing in the soils of burnt larch forests increases by a quarter and by twofold in pine forests. With the beginning of the thawing of the seasonally frozen layer, all the soils experience waterlogging, and ground water occurs above the permafrost.

CHARACTERISTICS OF AMMONIA COMBUSTION AND MODERN GORENJE STABILIZATION STUDIES

In the light of current problems such as difficulties with ammonia ignition, low combustion stability and high NOx emissions, the features of basic ammonia combustion are considered and the available stabilization technologies are summarized. Gorenje gorenje. Among these technologies, the mixed combustion of ammonia, hydrogen and methane stands out, as well as methods of enhancing heat transfer, such as high oxygen pressure, and external assistive technologies, including plasma. Gorenje The aspects of ammonia combustion stability in various types of engines such as internal combustion engines, gas turbines and boilers are discussed. Gorenje The need for future research in the field of ammonia fuels, including the development of gorenje gorenje stabilization technologies, mixed combustion of ammonia with hydrogen, ammonia with solid fuels, and others, is emphasized. The importance of adapting various gorenje stabilization technologies gorenje depending on specific application areas to optimize the ammonia combustion process is noted. The prospects of ammonia-hydrogen mixed combustion systems are discussed, and the need for further research and development in this area is emphasized. Gorenje It is also noted that there is limited experimental data on the mixed combustion of ammonia with solid fuels, which provides potential for research in this direction. Gorenje Achieving a carbon peak and carbon neutrality is an essential strategic course in the context of countering global warming and is becoming an internal necessity to stimulate high-quality economic development. This prospect will necessarily entail significant transformations in the energy structure of Russia.

Experimental study on combustion instability characteristics in a pre-chamber natural gas engine under lean burn conditions

Pre-chamber jet ignition is a key technology for future high-efficiency natural gas (NG) engines. It can achieve fast and stable combustion through excellent ignition performance. However, there are still some challenges, such as high combustion instability near the lean burn limit and the narrow engine operating range. Therefore, this paper investigates the combustion instability of a pre-chamber NG engine under ultra-diluted conditions by experimental method. At two engine loads, experiments are carried out with different jet ignition intensity schemes to study the effect of jet ignition intensity on the cyclic combustion variations. Then, the combustion instability characteristics of the pre-chamber NG engine are studied by cyclic variation analysis and phase space reconstruction. The results show that with the increase in the jet ignition intensity, the cyclic combustion variations decrease, and the cyclic variation coefficient of the indicated mean effective pressure decreases to below 2%. The lean burn limit of the pre-chamber natural gas engine is extended to an excess air ratio of 2.0. The operation instability of the pre-chamber NG engine is mainly due to cyclic variations in the ignition and combustion process. The nonlinear dynamic analysis shows that the combustion process in the lean burn pre-chamber NG engine behaves with chaotic characteristics under the operating conditions of low jet ignition intensity. As the jet ignition intensity increases, the combustion stability is improved and the cycle-to-cycle variations change from fairly deterministic to more stochastic behavior. The chaotic characteristics of the combustion process become weaker. In conclusion, it is of great importance to generate stable and high ignition intensity jets for reducing combustion instability and improving combustion efficiency in lean burn pre-chamber NG engines.

Novel THAI well arrangements for improving heavy oil recovery rate in comparison to that achievable in the conventional THAI in situ combustion technology

The toe-to-heel air injection (THAI) is an environmentally friendly process for in situ upgrading of heavy oils and bitumen via in situ combustion (ISC). Unlike the conventional ISC that uses a vertical producer, the THAI process uses a horizontal producer (HP) well to produce the upgraded oil to the surface. Recent field data has shown that the THAI process is a relatively low-oil-production-rate technology. These considerations call for innovative solutions so that the oil production rate is improved, whilst propagating a stable, efficient, and safe combustion front. Consequently, this work has provided those solutions. Through numerical reservoir simulations, using CMG STARS, five completely new THAI well configurations, which have been labeled A01, A02, A03, A04, and A05, have been developed and studied, and their performances are compared against that of the conventional THAI process which has wells arranged in a classic SLD pattern (i.e. the best-performing conventional THAI process) and against each other. The THAI arrangements A02-A04, however, assume a horizontal air injection well, which currently is not used in field practice but may be developed in the future. In field practice, THAI is applied in a line drive configuration starting up-dip and going down on the structure whilst taking advantage of the contribution provided by the drainage due to gravity; the expansion is made one way only (by drilling new patterns in one direction only). For this reason, the classic SLD pattern refers to the case where the dip of the reservoir is significant (>2-3 degrees). However, when the dip of the reservoir is not significant (“flat” reservoirs) there is a possibility to expand the process in both opposing directions. This is the case dealt with in this work. All configurations A01-A05 assume expansion of the THAI commercial operation in both directions. Selection criteria have been developed and used to determine the two best performing processes. For example, in terms of long-term stability, safety, and efficiency of the combustion process, a process named model A01 is the best, as it achieved 99.8% oxygen utilization when compared with any other model. It also achieves oil recovery, due to two years of combustion only, of 30.78% OOIP, which is greater than that in the base case model. Overall, based on the weighted selection criteria, which are developed from the deepest analyses of the quantitative 1-dimensional time-dependent parameters and from thorough analyses of the qualitative 2-dimensional profiles of temperature, the combustion zone in the form of oxygen mole fraction, and the oil-flow dynamics inside the reservoir in the form of oil saturation, then model A01 is the best and is followed by model A03. The overall performance of each of these two novel methods outweighs that of the conventional THAI process. However, model A03 uses a horizontal well for injection, which is not current field practice. Therefore, future developmental work should concentrate on the novel method A01 for upgrading and recovery of heavy oils and bitumen, especially since this is low-carbon, efficient, wastewater-free, and provides upgrading inside the reservoir and hence it has a low surface footprint.

Stability of THAI in situ combustion process in reservoirs with layers of grading permeabilities and porosities: Detailed qualitative investigations

The world-wide reserves of heavy oil, tar sand, and bitumen, etc., outweigh those of conventional oil by a factor of 7/3. Given that the conventional reserves are being rapidly depleted, the need to develop and produce the unconventional resources has never been so critical. However, the proven most efficient and environmentally-friendly technology, namely the THAI process, still requires further study, and it has no documented design procedures that factor in the non-ideal geological features of heavy oil and bitumen reservoirs. Throughout the literature, there is little reported on the effects of gradations in reservoir petro-physical parameters on the performance of the THAI process. Consequently, this work reports the results of numerical simulations for four different kinds of reservoirs, each having progressive gradations in permeabilities and porosities. The major findings from this in depth study include:(i) In terms of the temperature distribution, regardless of the permeability and porosity gradations, the high temperature zone is always skewed towards the highest permeabilities and porosities zone. Furthermore, it is found that, in any model in which the shoes of the VI wells have no direct communication pathway with the highest permeabilities and porosities zones of the reservoirs, the high temperature zones occur in two chambers, otherwise, there is one high temperature zone.(ii) It is found that generally, the combustion front tends to be lopsided in favour of the most permeable and porous zone. In the case of a bottom-up progressive increase in permeabilities and porosities (model L1), the single combustion front has greatest advance horizontally at the top and axially in the middle of the reservoir, while in model L2 (the converse of model L1), the combustion fronts propagated in two chambers before the chambers overlapped in the toe region of the HP well where it advanced fastest. Therefore, the combustion zone in model L1 was far more stable than in model L2.(iii) It is found that the combustion fronts in model L3, with the lowest permeabilities and porosities at the centre in the longitudinal direction, propagated in two chambers that overlapped each other around the toe region of the HP well and advanced greatest in the HP well and on either lateral edge of the reservoir. In model L4, which has lateral gradation in permeabilities and porosities, however, the thinner edge of the wedge-shape combustion front had advanced fastest along the vertical mid-plane where the HP well was located. Thus, the combustion zone in model L3 was far more stable than that in model L4.(iv) It is found that in all the models except model L4, there exist rich oil saturation zones in the most permeable and porous regions located ahead of the mobile oil zone (MOZ) of each reservoir. These are formed due to restrictions in the pathways via which the mobilised oil can drain into the HP well. In model L4, the HP well is already in the most permeable zone and consequently, the fluids that favourably reach there are rapidly gravity-drained into the HP well.

Nox Emissions Assessment of a Multi Jet Burner Operated with Premixed High Hydrogen Natural Gas Blends

Abstract Decarbonization of gas turbine combustion creates a pressing demand for new technical solutions for the combustion process. While switching to hydrogen fuels may solve the problem of carbon emissions and associated pollutants it can also lead to stability issues for swirl-stabilized combustors due to its increased reactivity. However, with jet flame burner systems, the required flashback safety can be achieved with high axial flow velocities even for premixed combustion of 100% hydrogen fuel. The development of such an engineering solution, however, requires significant effort to reach the maturity of today's swirl burners. This study examines the capacity of a premixed multi-tube jet burner to manage the chemical reactivity change over a range of volumetric blends from pure natural gas to pure hydrogen fuel. NOx emissions are measured and analyzed for atmospheric tests. The changes in emissions originate not only from altered combustion chemistry but also from changes in flame shape and turbulence intensity. To get a deeper understanding of the NOx formation process, a low-order model is designed and compared to the experimental data of technically and perfectly premixed combustion tests. Parameter variations of the low-order model are conducted to assess the influences on the NOx emission production of the multi jet burner. The information on the combustion process required for the model is obtained computationally and experimentally. Therefore, flame images are recorded and analyzed.

266 nm Laser-Induced Fluorescence Reference Spectra of Ketones and Aromatic Compounds

ABSTRACT Laser-induced fluorescence (LIF) is an established noninvasive measurement method to determine temperature distributions and local gas concentrations in combustion processes with high spatial and temporal resolution. This work presents high-precision LIF spectra of acetone and other tracers at ambient conditions. By using a large UV-sensitive sCMOS camera instead of an image intensified camera, many issues like nonlinearity, varying sensitivity, vignetting, limited resolution etc. could be minimized or eliminated. Particular care was taken to remove residual stray light and to calibrate the spectra with metrological traceability to the International System of Units SI.

Study on carbon emission characteristics and its influencing factors of energy consumption in Sichuan Province, China

Clarifying the key sectors and influencing factors of carbon emissions from energy consumption is an important prerequisite for achieving the “carbon peaking and carbon neutrality” goals. This study calculated the carbon emissions of fuel combustion in 7 major departments and regional electricity trading of Sichuan Province from 2000 to 2021, and empirically analyzed the impact of energy structure effect, energy intensity effect, industrial structure effect, economic development level effect, and population size effect on the carbon emissions of energy consumption based on the LMDI model. The main research conclusions are as follows: (1) LMDI model has the advantages of no residual and high interpretation. By refining the multi-departments of energy consumption and different types of fuel, it is helpful to improve the accuracy of empirical analysis results. (2) The carbon emissions of energy consumption mainly come from the fuel combustion process. Specifically, the industry sector composed of steel, building materials, chemicals and machinery is the key emission sector, and transportation and residential life are also vital. Regional electricity trading can indirectly reduce the intensity of carbon emissions while ensuring the safety of energy supply. (3) From 2000 to 2021, the energy intensity effect and the economic development level effect were key factors in slowing down and promoting the carbon emission growth of energy consumption in Sichuan Province, respectively. The population scale effect mainly played a positive role in driving carbon emissions, but the impact is small and almost negligible. Before 2012, the energy structure effect and the industrial structure effect were mainly positive driving effects, and after 2012, they all turned into negative inhibitory effects. This was mainly due to the low-carbon transformation of energy structure and the optimization of industrial structure.

The Influence of Pre-Chamber Parameters on the Performance of a Two-Stroke Marine Dual-Fuel Low-Speed Engine

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity.

Direct and Indirect Measurements of the 19F(p,α)16O Reaction at Astrophysical Energies Using the LHASA Detector and the Trojan Horse Method

Fluorine is one of the most interesting elements in nuclear astrophysics. Its abundance can provide important hints to constrain the stellar models since fluorine production and destruction are strictly connected to the physical conditions inside the stars. The 19F(p,α)16O reaction is one of the fluorine burning processes and the correction evaluation of its reaction rate is of pivotal importance to evaluate the fluorine abundance. Moreover, the 19F(p,α)16O reaction rate can have an impact for the production of calcium in the first-generation of Population III stars. Here, we present the AsFiN collaboration efforts to the study of the 19F(p,α)16O reaction by means of direct and indirect measurements. On the direct measurements side, an experimental campaign aimed to the measurement of the 19F(p,α0,π)16O reaction is ongoing, taking advantage of the new versatile arrays of silicon strip detectors, LHASA and ELISSA. Moreover, the Trojan Horse Method (THM) was used to determine the 19F(p,α0)16O reaction S(E)-factor in the energy range of astrophysical interest (Ecm≈ 0–1 MeV), showing, for the first time, the presence of resonant structures within the astrophysical energy range. THM has been also applied for the study of the 19F(p,απ)16O reaction; data analysis is ongoing.

CFD and RSM Assist in Reducing the LPG Consumption of Burners for Agarwood Oil Production in Thailand

ABSTRACT This research aimed to optimize LPG consumption in Thai commercial burners used in agarwood oil production, specifically focusing on the KB-10, S-10, and EB-10 burners. Enhancing burner efficiency is crucial due to rising energy costs and environmental concerns. A dual approach using Response Surface Methodology (RSM) and Computational Fluid Dynamics (CFD) was employed in order to achieve the best burner. Central Composite Design (CCD) within the RSM framework determined the optimal swirl and inclination angles combinations. Modified burners with variant combination angles, as suggested by RSM, were numerically investigated. CFD simulations with Ansys Fluent, utilizing the k-ε turbulence and discrete ordinates (DO) radiation models, provided detailed insights into the combustion and heat transfer processes of those modified burners. The modified burners, SB10–1, SS10–3, and SEB10–7, demonstrated significant improvements. Laboratory and field tests indicated energy savings of 16.15%, 23.74%, and 20.75%, respectively. Statistical analysis confirmed these savings with p-values < .05. The 95% confidence intervals for LPG savings were 31.31 ± 0.8%, 33.42 ± 0.7%, and 31.84 ± 0.6%, corresponding to payback periods of approximately 2.99, 4.21, and 8.95 months. Additionally, CO and NOx emissions were kept below 350 ppm and 100 ppm, respectively. The novelty of this study lies in the combined use of RSM and CFD to optimize burner performance, leading to significant energy savings and emission reductions. These findings highlight the potential of these methods for burner optimization, offering both economic and environmental benefits. This research underscores the importance of integrating advanced modeling techniques to achieve sustainable and cost-effective industrial processes.

Emission Spectra of Ammonia Laminar Flames in Spherically Propagating Flames and a Modified McKenna Burner

ABSTRACT Ammonia (NH3) has received significant attention recently as a promising carbon-free, low-cost, and safe candidate as a chemical energy storage element and/or fuel alternative. As for any new fuel, fundamental aspects of the combustion process, such as the detailed chemical kinetic pathways of NH3 oxidation, flame propagation and stability, and emissions, are to be understood to predict its combustion behavior in practical systems. One aspect of improving our understanding of the combustion behavior of NH3 is to explore the emission spectra of spherically expanding and/or Bunsen-type flames under controlled laboratory conditions. In this study, flame spectra from NH3-containing mixtures were obtained utilizing two different experimental flame configurations, namely a spherically propagating flame and a modified Mckenna burner flame. Two different fuel mixtures were investigated. The first was an oxy-ammonia mixture consisting of NH3 + (25% O2 +75% N2) with the goal of studying neat ammonia. The second mixture consisted of H2:NH3:N2 with a ratio of 45:40:15 by volume. Several excited-state species within the UV-visible spectral region were identified. For instance, NO* emission features were found between 220 and 280 nm. In addition, OH* emission was detected around 310 nm, and an NH* feature was seen around 337 nm. Moreover, a broadband intensity was reported over the visible range (400 ~ 800 nm), where several NH2* features were also detected. The effect of the mixture on the flame spectra was investigated by examining the two different mixtures utilizing the same experimental apparatus (spherical flame in this case), and it was shown that the mixture has an effect on the presence of NH2* features, which was also backed by chemical kinetics predictions for the NH2* mole fraction profiles. It was shown (from kinetics) that the oxy-ammonia mixture produced more NH2* than the H2:NH3:N2 mixture by up to 113%. Additionally, the effects of the flame configuration were also investigated by studying the same mixture (the H2:NH3:N2 mixture in this case), and it was revealed that the spectra produced using the modified Mckenna burner had less noise, and all features were easily identified. Lastly, laminar flame speeds of the oxy-ammonia mixture were measured using the spherical flame apparatus. The laminar flame speed followed the expected pattern, peaking near a 1.1 equivalence ratio with a measured flame speed of 22.7 cm/s.